Monster Media 1993 #2/Image.iso/internet/cld9audi.zip/CLD9AUDI.TXT

Text File | 1993-06-08 | 197KB | 4,099 lines

Archive-name: AudioFAQ/part1
Last-modified: 1993/6/4
Version: 1.5

1.0 Contents:

    Part 1:
 1.0 Contents
 2.0 Organization
 3.0 Purpose
 4.0 Omissions
 5.0 Credits
 6.0 Errors and Corrections
 7.0 Disclaimer
 8.0 Copyright Notice
 9.0 Speakers
 10.0 Amplifiers
    Part 2:
 10.13 Amplifiers (continued)
 11.0 CD Players, CDs, Turntables, and LPs
    Part 3:
 12.0 High Fidelity Systems
 13.0 Listening Rooms and Houses
 14.0 Recording
 15.0 Mail Order
    Part 4:
 16.0 Wire
 17.0 The Press
 18.0 Retail
 19.0 Miscellaneous
 20.0 Net Protocol

2.0 Organization:

This FAQ is divided into a preamble and a list of subjects.  Each
subject is described by a list of questions and answers.  Some
questions have no answers yet.  That's life.

This FAQ is split into four individual postings.  This FAQ also
references a frequent posting of sources for audio via Mail Order.
That list is maintained by [e-mail] (William R. Nau).  Contact
Mr. Nau directly for information or corrections to that posting.
The list is also available via FTP in the pub/rec.audio directory
of SSESCO.com.

Lines beginning with "|" are new since the last version of the FAQ.

3.0 Purpose:

The purpose of this FAQ is to address frequently-asked questions as
a whole, so that rec.audio volume can be reduced.  Towards this end,
we assembled a list of common questions, and some general answers to
these questions.  Audio is part science and part art, so some of the
answers are objectively correct, while others try to open-mindedly
present both sides of a subject.

4.0 Omissions:

Many valuable things have been left out of the FAQ.  In part this is
because there is just too much to say about audio.  In part, this is
because the general reader doesn't need that much detail.  Also, some
things were omitted because they are too controversial or inflammatory.

5.0 Credits:

This FAQ is the work of many people.  Allow me to thank everyone who
helped now.  We appreciate all of your contributions.  However, all
blame and criticism should go to Bob Neidorff at [e-mail].
Some of the contributors to this FAQ are listed below.  Others have
made great contributions, but are no less appreciated.

 [e-mail] (Andrew Hume)
 [e-mail] (jj)
 [e-mail] (Bob Neidorff)
 Rick Oakley (no internet access)
 [e-mail] (Richard d Pierce)
 [e-mail] (Paul Smee)
 [e-mail] (Gabe M. Wiener)

6.0 Errors and Corrections:

Some errors are intentionally included in this FAQ.  (It's easier to say
that and later admit we were wrong, than to claim that this is a best
effort).  If you have a correction to the FAQ, additional information,
or a new topic for the FAQ, please send e-mail to [e-mail]
describing your thoughts in detail.  Please include your e-mail address
in your submission, so that we can stay in touch.  Every submission will
be considered for inclusion in the next release of the FAQ.  This FAQ
will be reposted every month.

7.0 Disclaimer:

Everyone's human.  Nothing is perfect.  The people who wrote the
information here put varying amounts of research into their work.
To the best of my knowledge, no one made any contribution or
comment because of a vested interest.

Audio is a very lucrative and competitive industry, filled with
honest companies, aggressive marketing people, people who stretch the
truth very thin, excellent products, and lousy products.  We tried
hard to screen the hype from valuable data.  If we insulted, omitted,
or otherwise disturbed you, your company, your product, or something
you feel strongly about, please let me know.

The information here attempts to paraphrase a large portion of the
information exchanged on rec.audio.  At times, people will make
recommendations or suggestions to others on rec.audio.  Some of these
statements are included here because we have been asked to include
statements of that sort.  These statements, and everything in this
document is the opinions of various people.  Nothing here is intended
as recommendation or suggestion.

Further, no matter how it is worded, nothing here should be taken as
fact.  The authors take no responsibility for any use of this
information.

8.0 Copyright Notice:

The information contained here is collectively copyrighted by the
authors.  The right to reproduce this is hereby given, provided it is
copied intact, with the text of sections 1 through 8, inclusive.
However, the authors explicitly prohibit selling this document, any
of its parts, or any document which contains parts of this document.

9.0 Speakers:

9.1 What should I listen to when evaluating speakers?
 The most important thing is to listen to recordings that
 you *know*.  Any good salesman will play you recordings
 that highlight that particular speaker.  Do not be embarrassed
 about bringing a stack of CDs with you to the hi-fi shop.

 Do not spend your valuable listening time switching between a
 dozen pairs every 3 seconds.  If you are shopping at a quality
 store, the dealer will, from the description of your room, your
 size requirements, your musical tastes, and your budget, be able
 to show you a couple of pairs that will be close to what you
 want.  Spend several minutes listening to each.  When you think
 you're close, don't be embarrassed about spending half an hour
 or more listening to the speakers.  You're going to have them in
 your home for a lot longer, and many speakers will cause
 "listening fatigue" after a short time.  Make sure you really
 like them before you hand over money.

 One thing to try is well recorded "Spoken Word" records; most
 people have a very good ability to tell when a speaking voice
 sounds unnatural, even if they've never heard the person
 speaking live.  If you play an acoustic instrument, find
 something that features that instrument solo, or in a small
 group; make sure it really sounds like it should.  Almost
 everyone has heard a live piano.  Piano can be very revealing.

 Blues, jazz, folk, or 'easy listening' music with simple
 instruments and a female vocalist is also revealing.  Well done
 female singing voices provide a very good test of a system's
 response.  Try something simple and soft, which will let you
 hear any noises coming from the system; and something complex,
 with lots of instruments all happening at once, to make sure the
 system doesn't go muddy when things get complicated.  And, of
 course, try a few of your favorites, and see if you like what
 happens with them.

 If a sales person suggests some music to listen to, the odds are
 that it isn't the most revealing.  Sales people tend to suggest
 things which sound great.  Anything you own and like is good,
 because you know it and are happy to listen to it carefully.  No
 matter how good the recording, if you don't like Opera, you
 won't listen to it as carefully as your favorite, scratchy,
 1940's rhythm and blues.

 Most important is to listen to something you are familiar with.
 Even if a recording is flawed (and what ones aren't?), how is it
 different from your normal setup?  Some of the most important
 differences are "Gee, I never heard that instrument before!"

9.2 What should I listen for when evaluating speakers?
 When comparing two speakers side-by-side, doing an AB
 comparison, be extremely careful to match the levels before
 evaluating.  A slight level difference can make one speaker
 sound better, even though the difference may not be perceived
 as a level difference.  Some claim that you will be influenced
 by a difference of less than 1/2 dB!

 First and foremost, the sound should be natural.  If you listen
 to vocals, close your eyes and try to picture someone singing in
 the same room with you.  Does it sound realistic?  Likewise with
 instruments.  You selected recordings of instruments that you
 like and have heard live.  Do they sound like what you remember
 them sounding like live?

 Your very first impression should be something like "what nice
 sound".  If your initial gut reaction is "gosh, what a lot of
 detail", the system is likely to be heavy in the treble (often
 interpreted by beginners as "more detailed") and you'll probably
 find that annoying after a while.  If your first reaction is
 "hey, what powerful bass", then the system is probably
 bass-heavy, rather than ideal.  The most common mistake for
 beginners is to buy a system with REALLY powerful bass, because
 it sounds "impressive" at first.  After a while, though, you'll
 get tired of being thumped on the head by your music.

 Not to say that good bass and treble aren't important.  But your
 first realization should be that the music is all there, and
 that it comes together as good music, without one particular
 part trying to dominate it.  Sit back and listen to it for a
 bit.  You should be able to pick out the individual instruments
 if you want.  They shouldn't force themselves on you, and you
 should also be able to hear the music as a single piece, the sum
 of its parts, without feeling like each of the instruments is
 trying to grab your attention away from the others.

 You should check how things sound with the amp turned up, and
 also with it turned down to a fairly low volume level.  Some
 speakers which sound very nice at low levels begin to sound
 confused, like they can't cope, when turned up.  On the other
 hand, some sound nice loud, but sound thin and bodiless when you
 turn them down a bit.  With the spoken word or female vocalist,
 listen for "sibilance", a pronounced 'hiss' at the end of 's'
 and 'z' sounds.  It shouldn't be there.  Most planar speakers
 just can't play very loud.  Whatever you hear, do some
 auditioning at the maximum volume you anticipate ever wanting.

 It is acceptable and sometimes desirable to switch the stereo to
 mono to evaluate naturalness.  Mono is a good test of both the
 room and the speakers.  The image should be rock-solid dead
 center, and not move with signal or level.  If it isn't perfect
 mono, it will be nearly impossible to create a good stereo.

 A speaker in a large box is capable of producing low frequencies
 at higher volumes with more efficiency than a small box, but
 that doesn't mean that a small box can't have great bass, it
 just won't be as efficient and can't play as loud.

 Good speakers can "recreate a natural stereo sound stage",
 placing some instruments to the left of the left speaker, some
 sounds in the middle, and some to the right of the right
 speaker.  Poorer speakers make it harder to localize voices.

9.3 Why use a subwoofer?  Will it help?  One or two?
 One reason to get a subwoofer is to add bass to a feeble system.
 A second reason is to move the lowest frequencies to a separate
 driver, and thereby reduce a particular kind of distortion
 caused by the nonlinear mixing of different sounds, called
 "intermodulation distortion". A third is to increase the power
 handling ability of the system and the overall reliability.  All
 are valid reasons, but it isn't so simple.

 To improve the sound of a good speaker system, a subwoofer must
 "integrate smoothly" into the system, extending the bass without
 causing peaks or dips.  Many subwoofers have a crossover that
 goes between your amp and your main speaker which sends the lows
 to the subwoofer and sends the higher frequency signals to the
 main speakers.  This may damage the perfect sound of a good
 system, it may sound similar, or it may sound better.

 Most good small speaker systems have a bass peak at resonance,
 which attempts to compensate for the absence of lower bass.
 Like it or not, this is the only way to make a small system
 sound realistic. If the small system is done well, the
 improvement you will get from a subwoofer will be small, but
 still real and, to many, significant.

 Correctly done, a good subwoofer will enhance the sound of a
 good small-box system.  Done wrong or haphazardly, anything is
 possible.  Even a fine large speaker system might benefit from
 careful addition of a subwoofer.  However, the better the
 original system, the more likely it will be that a modest
 subwoofer will do more harm than good.

 Low frequencies travel less directionally than high frequencies,
 so many people say that only one subwoofer is required for good
 sound.  This is true to some extent, but not completely true.

 There are a few reasons for getting two subwoofers.  Some feel
 that you need two subwoofers to accurately reproduce the stereo
 image, no matter how little low-frequency stereo information
 there is.  Others feel that two subwoofers are much easier to
 set up in a room, less likely to excite standing waves in the
 room, and give smoother sound.

 A third reason is that two subwoofers can produce twice the
 sound of one.  Finally, even though subwoofers produce very low
 frequency sound and very low frequency sound is non-directional,
 subwoofers also have output at 100 Hz, and sound at 100 Hz is
 directional, so two subwoofers will give a slightly better
 stereo image than one.  Assuming, of course, that the two are
 separated by at least two feet.

 Finally, even though original source signals rarely contain any
 music with stereo components below 50Hz, there may be some noise
 component with low-frequency out-of-phase noise.  This unusual
 noise might add a sense of space to a recording if it is
 reproduced by a system in which the woofers are very far apart.

 It is still true that a single good subwoofer, correctly added
 to a system will help the sound but two will probably help more.

9.4 How do you connect a subwoofer to a stereo?
 Many subwoofers contain their own amplifier and crossover.
 For these, take the preamp output and feed it into the subwoofer
 amp input and also into the main amplifier.

 For other subwoofers, just run them in parallel with your main
 speakers, or combine them into your system with your own bass
 amplifier and crossover.

 Some A/V receivers contain a splitter specifically for use with
 subwoofers.  If you have one of these, you will either want a
 separate amplifier for your subwoofer or an amplified subwoofer.

 Consult the manual which comes with the subwoofer.

9.5 What do I need for surround sound?
 "Surround Sound" has referred to a number of different products
 over the years.  Many mass-fi receivers have "Surround Sound"
 buttons that do little more than muck up the imaging.

 In recent years the term "Surround Sound" has become synonymous
 with the surround systems produced by Dolby Laboratories.  Dolby
 Surround comes in several flavors, such as passive surround
 (which simply decodes the phase information and sends it to the
 rear speakers) and the more advanced system called Pro Logic.
 Pro Logic system uses computer circuitry to route directional
 information to the appropriate speakers.

 Generally, one needs at least two more speakers beyond the main
 stereo pair.  Advanced Pro Logic systems such as the Lexicon and
 Fosgate can accommodate several more speakers beyond the two
 additional ones (usually placed in the rear).  Often one can
 find Pro Logic systems with two front, two rear, two side, as
 well as a center channel speaker for dialogue.

9.6 I was just approached (accosted?) by a couple of kids driving a van
 that said they had some GREAT speakers to sell. They are
 overstocks, used by major recording studios and DJs or even
 hot, and they normally sell for $1000/pr, but they'll let me
 have them for just $399. Am I getting ripped off?

 Yes, you most certainly are. The speakers these people sell are
 none of what they describe. They are never used in studios.
 There might be one or two DJs out there that use them because
 they can't afford anything else.  They are not overstocks, and
 in all likelihood, they are NOT HOT!.

 Are they good speakers? No, they're, at best, no better than the
 big boom boxes you find in $400 rack systems in department
 stores.  They are worth no more than what the kids paid for them
 ($100/pr).

 The speakers go under names like "Acoustic Monitor DB IV",
 "Acoustic Linear," "Pro-Poly," "Audio Reference 4350" and so on.
 They all "feature" things like "liquid cooled 3" tweeter",
 poly-cone 12" woofer, fantastic (but impossible) frequency
 response, 98 db/watt sensitivity, and so on.

 These speaker are made by a couple of manufacturers with the
 intent of being sold exactly this way.  They cost the kids in
 the van about $100 a pair, and the kids are given minimal
 training about what kinds of stories to use, what parking lots
 are the most likely to generate sales (department store parking
 lots near colleges in September is a great time for these guys).
 Anything over and above the $100 dollars the kids paid is pure
 profit (except for gas money).

 Stay away, you're getting ripped off.

9.7 What speakers should I consider in the $XXX/pair price range?
 This is probably the most commonly asked question on rec.audio,
 and also the most impossible to answer.  The market keeps
 changing, everyone has different tastes, and no one has the time
 to listen to even 10% of the products available in any country.
 Also, many good products are only available in specific regions
 or countries.

 If you really want recommendations and are willing to listen to
 the opinions of others, check the past few issues of Stereophile
 Magazine.  Although they are strongly biased towards very
 expensive gear and have their own particular other biases, they
 do steer you to some very good equipment in their
 frequently-updated list of "RECOMMENDED COMPONENTS".

9.8 Can you build better speakers than you can buy?
 Some people can build better than you can buy.  These people are
 either experts, golden ears, extremely well equipped, inspired,
 or a combination of the above.

 Some companies have plans available to entice you into buying
 their drivers: Audio Concepts, Audax, Dynaudio, Focal, KEF, and
 Scanspeak.  Your success rate with these plans will probably be
 very good IF your cabinetry skills are very good and IF you
 follow the plans precisely.  If you deviate (as everyone does),
 anything is possible.

 Stereophile has published three different plans designed by Dick
 Olsher which are similar two-way ported systems. A recent one of
 these was in Stereophile Nov '90, pages 94-127. Audio Magazine
 published a plan called "The Pitts" by Ken Kantor, in Audio, Nov
 '88 pages 65-71 continued in Dec '88 pages 73-77.  This plan is
 a two-way sealed box.

 I have built one published design and one manufacturer's design.
 I believe that both met my expectations.  They took me a long
 time to build, taught me a lot, were fun projects, and sounded
 good when finished.

 I also believe that a commercial system which cost what my parts
 cost will never sound anywhere near as good as the one I build.
 If you consider $2/hour for my time, however, building is
 financial suicide.

 Designing your own system is even more a can-of-worms, and
 should be left to those with either a strong stomach, a very
 forgiving ear, infinite resources, or excellent guidance.

9.9 Where can I read more about speaker building?
 Speaker Builder Magazine
  Audio Amateur Publications
  PO Box 494
  Peterborough NH  03458 USA
  603-924-9464
 The Loudspeaker Design Cookbook, Fourth Edition
  by Vance Dickason (C) 1991
  ISBN 0-9624-191-7-6
  $29.95 + $2.00 S&H from
  Old Colony Sound Lab
  PO Box 243
  Peterborough NH  03458-0243 USA
  603-924-9464
 High Performance Loudspeakers by Martin Colloms
 Synergetic Audio Concepts Classes and Newsletters
  Syn-Aud-Con teaches classes on Audio and Acoustics
  12370 W. Co. Rd. 100 N.
  Norman IN  47264 USA
  812-995-8212
9.10 Where can I buy speaker drivers?
 A & S Speakers (Broad line)
  3170 23rd Street
  San Francisco CA  94110 USA
  415-641-4573
 Audio Concepts (Their own kits plus drivers)
  901 South 4th Street
  LaCrosse WI  54602 USA
  800-346-9183
 Phil Baker (Surplus cabinets only)
  546 Boston Avenue
  Medford MA  02155
 Carbonneau
  609 Myrtle NW
  Grand Rapids MI  49504 USA
  616-456-9528
 Drexler Audio Systems (Bandor Speaker Distributor)
  14 Rose Lane
  Rosemont PA  19010
 Gold Sound (Broad line including pro speakers)
  PO Box 141
  Englewood CO  80151 USA
  303-789-5310
 Madisound (Broad line)
  8608 University Green
  Box 4283
  Madison WI  53711 USA
  608-831-3433
 McGee Electronics (Polydax, Pyle, Motorola, EV, MTX)
  1901 McGee Street
  Kansas City MO  64108-1891 USA
  913-491-5287 or 800-876-2433
 Meniscus
  2442 28th Street SW Ste D
  Wyoming MI  49509 USA
  616-534-9121
 Parts Express
  340 East First Street
  Dayton OH  45402-1257 USA
  513-222-0173
 Solen Electronique (Airborne, Audax, Ceratech, Dynaudio, Eton,
  Lpg, Morel, Peerless, Scan-Speak, Seas, Solen, Vifa)
  4470 Avenue Thibault
  St.-Hubert, QC  J3Y 7T9 Canada
  Voice 514-656-2759
  FAX [phone]
 Speakers Etc.
  1828 West Peoria Avenue
  Phoneix AZ  85029 USA
  602-944-1878
 SRS Enterprises (Pyle, Pioneer)
  318 South Wahsatch Avenue
  Colorado Springs CO  80903 USA
  719-475-2545
 Transducer Technology (Cabasse, Accuton, Vieta,
   Audiom by Focal, Stage, Tekton)
  4320 Spring Valley Road
  Dallas TX  75244
  214-991-6994
 Zalytron (Broad line including kits)
  469 Jericho Turnpike
  Mineola NY  11501 USA
  516-747-3515

9.11 Where can I buy loudspeaker kits?
 Audio Concepts, Inc. (Wide range of kits.  Catalog available)
  901 South Fourth Street
  La Crosse WI  54601 USA
  608-784-4570
 Fried Products (Parts kits starting $550.  Catalog available)
  (Emphasizes high-end transmission line speakers)
  (Parts kits have plan, crossover, and driver)
  Conshocken Road
  Conshocken PA  19428 USA
  215-277-9004
 Mahogany Sound (Parts kits and Woodstyle kits)
  (Parts kits have plan, crossover, and driver)
  (Woodstyle kits also have 3/4" MDF veneered boxes)
  (Prices $150/pair to $500/pair.  Catalog available)
  (Two way, three way & subwoofer kits)
  2610 Schillingers Rd #488
  Mobile AL  36695 USA
  205-633-2054
 Also see above, under suppliers for speaker drivers.

9.12 How can I improve the sound of my speakers?
 The best way to change the sound of your speakers is to change
 where you put them.  Ideally, the speakers should be located at
 ear level, in front of you, squared off between you.  It's then
 a matter of fiddling with a) the angles, b) the distance apart,
 c) the distance from you, and d) the distance from the wall.
 Just moving the speakers around in the room or putting them onto
 stands can make a major difference. For more on speaker
 placement, see 13.1 below.

 Other than that, speaker modifications can be a can of worms, or
 can produce very subtle changes, which you might prefer.  For
 example, you might improve a speaker by adding some cross braces
 of 1"x1" wood from left to right and from front to back.  This
 will stiffen the cabinet and reduce speaker cabinet wall
 vibrations, which probably hurt sound quality.  Alas, this will
 be most effective with lower-cost and poorly built speakers.

 Along similar lines, some claim success putting lead wire or
 epoxy putty on thin parts of the speaker to damp out resonances.
 You can try doing this to the thinner parts of the speaker
 "basket" or frame, or to the front "baffle" or supporting panel.

 Still another "tweak" is to add sound deadening felt pads to the
 inside walls of the speaker.  Instead of felt pads some advocate
 sand-filled latex coatings on the inside walls of speakers.
 Others advocate ceramic tiles held in place with "thinset".
 Still others rave about commercial products like AC Glop,
 Acoustic Magic, and Bostik Sheet.  However, the people who rave
 about these products tend to be the same people who sell them.

 Any change along the lines of adding felt, cross-bracing, or
 putty will have subtle effects on the sound.

 For the brave at heart, you can replace old or cheap drivers
 with better ones, but the results of this one change can be very
 dissatisfying if you happen to get the wrong type of driver for
 that application, and may never sound right, even if you use a
 similar driver. Speaker system design is still somewhat of a
 science and somewhat of an art.  Throwing paint on a canvas
 often makes a mess.

 Whatever change you try, don't "burn your bridge" home.  Be sure
 that you can undo whatever change you did, just in case.  Many
 tweaks to good speakers, no matter how well thought through,
 will correct for one flaw, but create others, or correct a flaw
 that the designer had cleverly used to his advantage.

9.13 How can I replace/re-cone my old speakers?
 The best chance of success is to buy an identical replacement
 speaker driver from the manufacturer of the system.

 Second choice is to buy the exact same driver from a
 distributor.  This is sometimes difficult because it is hard to
 learn exactly what driver the manufacturer used.  In addition,
 EVEN IF the manufacturer used stock speakers, they might have
 used matched pairs or selected speakers by hand for an exact set
 of specific characteristics.

 There are companies that rebuild drivers, but they charge quite
 a bit.  I have heard $75 per driver. This is rarely done for
 anything but very expensive commercial drivers.  Speaker
 manufacturers will often sell owners the materials that they
 need to repair a speaker.  If you are handy with delicate
 things, it is worth a try.

 In addition to speaker manufacturers, there are companies which
 sells rebuild kits for approximately $30 per pair, containing
 new foam, a special glue, and instructions.  If you have a blown
 or distorted voice coil, this still won't help. A few netters
 have used rebuild kits from this company successfully. Contact:
  Stepp Audio Technologies
  PO Box 1088
  Flat Rock NC  38731 USA
  800-747-3692

 Another vendor of speaker repair parts is:
  Simply Speakers
  P. O. Box 22673
  St. Petersburg FL  33742 USA
  800-767-4041 or 813-571-1245

 Some speaker manufacturers have very good warranties.
 Electro-Voice warranties all professional products for life.
 KEF has a similarly broad warranty on their speakers.  Contact
 the manufacturer first.

9.14 What computer programs can I use to design speakers?
 There are many useful programs available, but none are complete
 without a good knowledge of speaker design. Further, you will
 NEED to supplement any program with hand tweaking for the best
 sound.  Finally, no simulation program is ever useful without
 good model parameters, and the parameters which manufacturers
 give you are often imperfect, so many good designers strongly
 recommend your own lab measurements.  The Loudspeaker Design
 Cookbook (see 9.9) tells you how to measure a speaker, and also
 enough theory to feel confident with a good program.

 You can get a lot done with a simple spreadsheet and the
 equations in a book like The Loudspeaker Design Cookbook.

 For more information on speaker programs for speaker design
 and speaker design hardware, such as measurement systems, get
 the archive "audio.speaker" in directory "dist" on node
 "research.att.com" (also known as 192.20.225.2).

9.15 Can I magnetically shield my speakers for use near a TV?
 You probably will need to buy speakers that are made with an
 integral magnetic shield.  Magnetic shielding is usually done
 by either shielding the speaker magnet or by cancellation of the
 magnetic field very close to the magnet, or by both.  Shielded
 speakers are NOT built by lining the enclosure with metal.
 While it sounds like a good idea, it doesn't work.

 A common magnet shield is a mild steel cup around the magnet.
 This is the cheapest shield, and is usually fairly ineffective.
 It also will interfere with the speaker's critical magnet gap,
 so this type of shield can hurt speaker performance by shorting
 the magnetic field and reducing the magnetic flux density in the
 gap, which can reduce efficiency and affect the speaker's low
 frequency performance.

 Cancellation is done using a reverse-polarized magnet glued to
 the back of the main magnet.  If done right, it can almost
 completely cancel the rear stray field.  In some cases it can
 also increase the magnetic flux density in the gap, which may
 or may not be desirable.

9.16 What are all of these abbreviations people use for speakers?
 Most of these parameters are well documented in the Loudspeaker
 Design Cookbook. (see 9.9)  In summary:

 Fs    Driver free air resonance, in Hz.  This is the point at
  which driver impedance is maximum.
 Fc    System resonance (usually for sealed box systems), in Hz
 Fb    Enclosure resonance (usually for reflex systems), in Hz
 F3    -3 dB cutoff frequency, in Hz

 Vas   "Equivalent volume of compliance", this is a volume of
  air whose compliance is the same as a driver's
  acoustical compliance Cms (q.v.), in cubic meters

 D     Effective diameter of driver, in meters
 Sd    Effective piston radiating area of driver in square meters
 Xmax  Maximum peak linear excursion of driver, in meters
 Vd    Maximum linear volume of displacement of the driver
  (product of Sd times Xmax), in cubic meters.

 Re    Driver DC resistance (voice coil, mainly), in ohms
 Rg    Amplifier source resistance (includes leads, crossover,
  etc.), in ohms

 Qms   The driver's Q at resonance (Fs), due to mechanical
  losses; dimensionless
 Qes   The driver's Q at resonance (Fs), due to electrical
  losses; dimensionless
 Qts   The driver's Q at resonance (Fs), due to all losses;
   dimensionless
 Qmc   The system's Q at resonance (Fc), due to mechanical
  losses; dimensionless
 Qec   The system's Q at resonance (Fc), due to electrical
  losses; dimensionless
 Qtc   The system's Q at resonance (Fc), due to all losses;
  dimensionless

 n0    The reference efficiency of the system (eta sub 0)
  dimensionless, usually expressed as %

 Cms   The driver's mechanical compliance (reciprocal of
  stiffness), in m/N
 Mms   The driver's effective mechanical mass (including air
  load), in kg
 Rms   The driver's mechanical losses, in kg/s

 Cas   Acoustical equivalent of Cms
 Mas   Acoustical equivalent of Mms
 Ras   Acoustical equivalent of Rms

 Cmes  The electrical capacitive equivalent of Mms, in farads
 Lces  The electrical inductive equivalent of Cms, in henries
 Res   The electrical resistave equivalent of Rms, in ohms

 B     Magnetic flux density in gap, in Tesla
 l     length of wire immersed in magnetic field, in meters
 Bl    Electro-magnetic force factor, can be expressed in
  Tesla-meters or, preferably, in meters/Newton

 Pa    Acoustical power
 Pe    Electrical power

 c     propogation velocity of sound at STP, approx. 342 m/s
 p     (rho) density of air at STP 1.18 kg/m^3

9.17 What are fluid-filled (fluid-cooled, ferro-fluid) tweeters?
 These tweeters are built almost exactly the same as other
 tweeters.  They look and act almost exactly the same, too.
 The only difference is that they have a small, controlled
 amount of a special fluid inserted into the gap between the
 magnet and the voice coil.

 One big effect of adding this fluid to a tweeter (or to any
 speaker) is that it makes the voice coil capable of dissipating
 more heat.  This means that the speaker can have a lighter voice
 coil, for better performance, or a higher power rating for the
 same voice coil.  The other big effect of this fluid is to add
 mechanical damping.  The frequency response and transient
 response of the driver will change, possibly for the better.

 In addition, this fluid may help center the voice coil, may
 lubricate the voice coil, and may help keep dirt out of the gap.
 This fluid will not increase the magnetic field, concentrate the
 magnetic field or otherwise change the magnetic circuit.  Nor
 will it cushion impact if the voice coil bottoms.

 The fluid used for this purpose is often called "ferrofluid".
 It consists of sub-microscopic particles of magnetic material
 suspended in special oil.  This fluid stays in the gap because
 of the strong magnetic pull of the magnet.  There is some debate
 over whether these fluids can dry out with time.  Manufacturers
 claim that the oil used is non-volatile.

 It is possible to use ferrofluids in mid-range drivers and
 woofers.  However, as tweeters tend to have the most fragile
 voice coils, tweeters have the most to gain from ferrofluid.
 There are various different fluids on the market, some of which
 have characteristics tailored to tweeters, some to woofers, etc.

 It is very risky to blindly add fluid to a driver.  It may not
 be compatible with the adhesives used in the driver, may not be
 practical with the particular driver layout, and is impossible
 to remove.  Permanent driver damage is possible.

10.0 Amplifiers
 Note: A receiver contains an amplifier, so the following
 questions apply to both receivers and amplifiers.  In the
 following text, "amp" and "amplifier" are used synonymously.

10.1 What is Biamping? Biwiring?
 Most speakers are connected to an amplifier by one pair
 of terminals on each speaker. Within these speakers, a
 crossover distributes the signal (modified appropriately)
 to each of the drivers in the speaker.

 Some speakers are set up to be either biwired or biamped. A
 much smaller number allows triwiring and triamping.  The same
 principles apply but use three sets of wires or three amplifiers
 instead of two.  Most speakers that support biamping/biwiring
 have two pairs of terminals and some mechanism for shorting
 the two pairs together when used in the normal way. This
 mechanism is most likely a switch or a bus bar. To help
 the descriptions below, I will refer to these two pairs as
 LO and HI  (because normally one pair connects to the woofer
 and the other pair connects to the tweeter/midrange).

 Biwiring means that a speaker is driven by two pairs of wires
 from the same amplifier output. One cable pair connects HI to
 the amp, and the other cable pair connects LO to the same amp
 output that you connected the HI cable to.  Biwiring is
 controversial; some folks hear a difference, some do not. The
 most plausible explanation involves magnetic induction of noise
 in the relatively low current HI cable from the relatively high
 current signal in the LO cable.  Accordingly, Vandersteen
 recommends the two cable pairs for a channel be separated by at
 least a few inches. In any case, the effect appears to be small.

 Biamping means that the two pairs of terminals on a speaker are
 connected to distinct amplifier outputs. Assuming you have two
 stereo amplifiers, you have two choices: either an amp per
 channel, or an amp per driver. For the amp per channel, you
 connect each terminal pair to a different channel on the amp
 (for example, the left output connects to HI and the right side
 to LO). In the other configuration, one amp connects to the LO
 terminals, and the other amp is connected to the HI terminals.

 The point of biamping is that most of the power required to
 drive the speakers is used for low frequencies. Biamping allows
 you to use amps specialized for each of these uses, such
 as a big solid-state amplifier for the LO drivers and higher
 quality (but lower power) amp for the higher frequencies.
 When you have two identical stereo amps, some folks
 recommend distributing the low-frequency load by using an amp
 per channel.  In any case, whenever you use two different
 amplifiers, be careful to match levels between them.

 Biamping also allows you to use high-quality electronic
 crossovers and drive the speaker's drivers (the voice coils)
 directly, without the series resistance and non-linear
 inductance of a passive crossover.  Biamping which uses the
 speaker's crossover is therefore much less desirable.  Replacing
 a good speaker's crossover with an electronic crossover has
 advantages, but involves some very critical tradeoffs and tuning
 which is best left to those well-equipped or experienced.

 See also section 16.0 below, on wire and connectors in general.

10.2 Can amplifier X drive 2 ohm or 4 ohm speakers?
 Almost any amplifier can drive almost any load if you don't turn
 the volume up too high.  Tube amplifiers are one exception.
 Some amps clip if you play them too loud.  This is bad and
 damages speakers.  Other amplifiers shutdown if they are asked
 to play too loud.  Many will overheat, with bad consequences.
 However, in almost all cases, it takes seriously loud sound or
 low speaker resistance (less than 4 ohms) to do damage.  Running
 two sets of 8 ohm speakers at once with common amplifiers
 represents a 4 ohm load.  Four sets of 8 ohm speakers makes a 2
 ohm load.  Two sets of 4 ohm speakers also makes a 2 ohm load.
 If you stay sober and don't turn it up past the point where it
 distorts, you are PROBABLY safe with most amplifiers and most
 loads.  See 10.3 for more information.

10.3 How do I drive more than two speakers with one stereo amplifier?
 One amp can drive many speakers.  However, there are two limits
 to this practice.  The first is that you can overheat or damage
 an amplifier if you drive too low of an impedance to loud
 listening levels.  Avoid loading any amplifier with a lower
 impedance than recommended.  Adding two speakers to one amp
 output loads that output with half the impedance of one speaker.
 (See also 10.2 above)

 The second is that with tube amplifiers, which are uncommon in
 today's common system, it is important that the speaker
 impedance and the amplifier output impedance be well matched.

 When driving two or more speakers from one amp output, always
 wire them in parallel, rather than series.  Series connection,
 while safe in terms of impedance levels, can hurt sound quality
 by raising the impedance that the speakers themselves see.

 Many amplifiers have connectors for two pairs of speakers.  In
 general, these amplifiers also have a speaker selector switch.
 These amplifiers almost exclusively connect the speakers in
 parallel when both are selected.  It is common for these
 amplifiers to specify 8 ohm speakers only.  The reason that they
 specify 8 ohm speakers is because the amplifier is built to
 drive either 4 or 8 ohms, and two sets of 8 ohm speakers loads
 the amplifier as if it were one set of 4 ohm speakers.  It is
 probably perfectly safe to connect one set of 4 ohm speakers to
 an amplifier with two sets of outputs, provided that you NEVER
 use the second set for any set of speakers.

10.4 How big an amplifier do I need?
 Unfortunately, amplifier power ratings and speaker power ratings
 are almost always misleading.  Sometimes, they are factually
 wrong.  Speaker ratings are almost useless in evaluating needs.

 More importantly, human hearing is sensitive to the log of the
 power coming out of the speaker.  This means that the perceived
 difference between an 80 watt amplifier and a 100 watt
 amplifier, all else equal, is very small. (under 1 dB!)

 There is a wide variation in the "efficiency" and "sensitivity"
 of the various speakers available.  I have seen good speakers
 with under 80 dB per watt efficiency and have also seen good
 speakers with over 96 dB per watt efficiency, measured one meter
 from the speaker.  This difference of 16 dB represents a factor
 of 40 difference in power requirement!

 So the first step in determining amplifier requirements is to
 estimate relative speaker efficiency.  Other factors include how
 loud you will want to listen, how large your room is, and how
 many speakers you will drive with one amplifier.  This
 information will give you a rough starting point.  For an
 example, a typical home speaker will produce 88 dB at 1 watt.
 In an average room, a person with average tastes will be happy
 with this speaker and a good 20 watt per channel amplifier.
 Someone who listens to loud music or wants very clean
 reproduction of the dynamics of music will want more power.
 Someone with less efficient speakers or a large room will also
 want more power.

 Past that point, you will have to use your ears.  As with all
 other decisions, your best bet is to get some candidates, borrow
 them from a friendly dealer, take them home, and listen to them
 at your normal and loudest listening level.  See if they play
 cleanly when cranked up as loud as you will ever go, into your
 speakers in your room.  Of course, it is also important to be
 sure that the amp sounds clean at lower listening levels.

10.5 Do all amplifiers with the same specifications sound alike?
 Some say that they do.  Some say that they don't.  Some
 demonstrated that many amplifier differences can be traced to
 very slight frequency response difference.  Let your own ears
 guide you.  If you want to compare amplifiers, you can do it
 best in a controlled environment, such as your home, with your
 music and your speakers.  Also be very careful to match levels
 precisely.  All you need to match levels of amplifiers is a high
 input-impedance digital voltmeter set to AC volts and a test
 recording or signal generator.

10.6 Is this amplifier too big for that set of speakers?
 There is no such thing as an amplifier that is too big.  Small
 amplifiers are more likely to damage speakers than large ones,
 because small amplifiers are more likely to clip than larger
 ones, at the same listening level.  I have never heard of
 speakers being damaged by an overly large amplifier.  I have
 heard of 100 watt speakers being damaged by a 20 watt
 amplifier, however, in really abusive hands.

10.7 Where can I get a cheap low-power amplifier?
 There are very few available.  One source is to buy a cheap boom
 box and only use the amplifier.  Another source is Radio Shack.
 A third alternative is to buy a car stereo booster and get a 12V
 power supply for it.  Finally, you can build an amp pretty
 easily if you are handy, but it probably won't be that cheap.
 Mark V Electronics, for example, sells 20 watt amp kits for
 under $30 and 80 watt amp kits for under $150.  (See 10.14,
 10.15, and 10.16.)

10.8 Is the stuff sold by Carver really awesome?
 Some people really like it.  Others believe that it doesn't
 perform up to specifications.  Still others believe that it
 isn't all that it is hyped up to be. One of Carver's claims to
 fame is lots of watts per pound of weight.  As with almost
 everything else, the best policy is to listen for yourself and
 see what you think.

10.9 What is a preamplifier?
 A preamplifier is an amplifying electronic circuit which can be
 connected to a low output level device such as a phono cartridge
 or a microphone, and produce a larger electrical voltage at a
 lower impedance, with the correct frequency response.  Phono
 cartridges need both amplification and frequency response
 equalization.  Microphones only need amplification.

 In most audio applications, the term 'preamplifier' is actually
 a misnomer and refers to a device more properly called a
 'control amplifier'.  Its purpose is to provide features such
 as input selection, level control, tape loops, and sometimes,
 a minimal amount of line-stage gain.  These units are not
 preamplifiers in the most technical sense of the word, yet
 everyone calls them that.

10.10 What is a passive preamplifier?
 A passive preamplifier is a control unit without any
 amplification at all. It is a classic oxymoron, because it has
 no capability to increase the gain of the signal.  It is only
 used with line level sources that need no gain beyond unity.

10.11 Do I need a preamp?  Why?
 The tasks of a preamp are to:
  Switch between various input signals,
  Amplify any phono inputs to line level,
  Adjust the volume,
  Adjust the treble and bass if necessary,
  Present the right load impedance for the inputs, and
  Present a low source impedance for the outputs.

 If you have a turntable, you NEED a preamp with a phono input.
 This is because the turntable has an output which is too
 small for driving amplifiers and because the output of the
 turntable requires frequency response equalization.  You
 can't connect any other source to a phono input other than a
 turntable (phono cartridge).  Also, you can't connect a phono
 cartridge or turntable to any input other than a phono input.

 Microphones also require special preamplifiers. Some microphones
 also require "phantom power".  Phantom power is operating power
 for the microphone which comes from the preamp.  Microphone
 preamps are often built into tape decks and microphone mixers.

 If you only have high level inputs, such as the output of a CD
 player and the output of a tape deck, the main value of a preamp
 is selecting between inputs and providing a master volume
 control.  If you only listen to CDs, it is plausible to skip
 the preamp entirely by getting a CD player with variable level
 outputs and connecting them directly to a power amplifier.

 Some caveats apply. One, the variable outputs on a CD player are
 often lower sound quality than fixed outputs.  Two, some sources
 have high or nonlinear output impedances which are not ideal for
 driving an amplifier directly.  Likewise, some amplifiers have
 an unusually low or nonlinear input impedance such that common
 sources can't drive the input cleanly.  A good preamplifier
 allows use of such devices without sacrificing sound quality.

 Unfortunately, the only way to be sure that a preamplifier is
 of value with your sources and your amplifier is to try one.

 Almost all receivers contain a phono preamp, a volume
 control, and input switching.  Therefore, if you have a
 receiver, you may never need a preamp.

10.12 Should I leave equipment on all of the time or turn it on and off?
 Some gear draws significant electricity, so you will waste money
 and fossil fuel if you leave it on all of the time.  As an
 example, a common amplifier consumes 40 watts at idle.  High-end
 gear uses far more electricity, but ignoring that, 40 watts x
 168 hours x 52 weeks x US $0.0001 per watt hour (rough estimate)
 is $35/year.  Now add a CD player, a preamp, and a tuner, and it
 really adds up.

 High-end enthusiasts claim that equipment needs to warm up to
 sound its best.  If you care about the best sound, give your
 equipment at least 20 minutes to warm up before serious
 listening.  Warm up will allow the inside temperature to
 stabilize, minimizing offsets, bring bias currents up to their
 proper values, and bringing gain up to operating level.

 Either way, good gear will last a very long time.  Tubes are
 known to have a finite life, but good tube designs run tubes
 very conservatively, giving them life exceeding 10 years of
 continuous service.  Some amplifiers run tubes harder to get
 more power out, and thereby may be more economical to turn off
 between use.

 Filter capacitors will fail after enough time at temperature
 with voltage applied.  They will last longer if turned off
 between use.  However, like tubes, filter caps can last tens of
 years of continuous use, as can power transformers,
 semiconductors, and the like.

 Filter capacitors have a funny problem that justified a simple
 break-in or reforming when they are restarted after many years
 of rest.  It involves bringing up the power line voltage slowly
 with a variable transformer.  For tips on reforming capacitors,
 consult "The Radio Amateur's Handbook", by the ARRL.

 Semiconductors seem to fail more often because of bad surges and
 abuse than age.  Leaving gear off may be best for semiconductors
 and other surge-sensitive gear if you expect power line surges,
 as come from an electrical storm or operation of large motors.

 Fuses seem to age with temperature and get noisy, but they are
 so inexpensive that it should not bias your decision.  However,
 some are inconvenient to change, and may require opening the
 case and even voiding the warranty.
--
Bob Neidorff; Unitrode I. C. Corp.  |  Internet: [e-mail]
7 Continental Blvd.                 |  Voice   : (US) 603-424-2410
Merrimack, NH  03054-0399 USA       |  FAX     : (US) 603-424-3460
Archive-name: AudioFAQ/part2
Last-modified: 1993/6/4
Version: 1.5

10.13 What about swapping op-amps?
 Many components use ICs called op amps as audio amplifiers.
 Earlier op amps had poor sound quality, especially if misused.
 Some engineers with a strong background in ICs and op amps
 learned that they could improve sound if they replaced slow,
 noisy, low slew-rate, or otherwise bad op amps with better ones.
 Some less informed people tried doing the same thing and made
 the sound worse.

 One pitfall with op amp swapping is that some op amps are more
 prone to unwanted oscillation than others.  The faster the op
 amp, the more likely it will cause an unwanted oscillation,
 which will really damage the sound.  For that reason, Joe may
 succeed in replacing 741 op amps with 5534 op amps in his gear,
 and you may fail.  It is dependent on design, layout, etc.

 As technology and design expertise improves, audio op amps
 get better and swapping is getting less and less useful.
 Newer op amps are displacing yesterday's best, and sound
 surprisingly similar to straight wire.

 Still, there are different op amps for different purposes.
 Bipolar op amps are ideal for preamplifiers where noise is
 critical.  The OP-27, OP-37, LT1028, and LT1115 are very well
 received for phono preamps, head amplifiers, and microphone
 preamplifiers.  Bipolar op amps are also more practical for
 signals with low source impedance.

 FET devices like the OPA604 and OPA2604 have higher slew rate,
 higher bandwidth, and lower input current.  These op amps are
 better for line-level inputs and high source-resistance signals.
 Some amplifiers, like the OP-37 and LT1115 achieve higher
 bandwidth by using less internal compensation.  These amplifiers
 are not unity gain stable, and should not be used in circuits
 with low closed loop gain or large feedback capacitors.

 Some of the better op amps for audio as of today include
 (* means highly recommended):
  Single  Dual
  AD847  AD827
  AD797*  NE5535
  NE5534  NE5532
  OP-27  AD712
  LT1115*  LM833
  AD811
  AD841  AD842
  HA5112*  OPA2604*
  LT1057  OP249*
  LT1028

 With op amp part numbers, there is a lot of room for confusion.
 Here is a guide to the numbers that is often accurate:

 Op amp part numbers start with a manufacturer's prefix:
  Analog Devices uses AD
  Burr Brown uses OPA
  Linear Technology uses LT
  Motorola uses MC
  National uses LF and LM
  PMI uses OP
  Signetics uses NE and SE
  TI uses TL
 This can be confused because if TI copies a Signetics op amp,
 they may assume the Signetics prefix, or they may use their own.
 Fortunately, if the part numbers are the same, circuitry is
 almost exactly the same, as is the performance. (Note: almost)

 The next thing in the part number is two, three, four or five
 digits.  This is invariably the key to the part. If the numbers
 are the same, the parts are almost surely the same.  For
 example, an LM357N and an LM357J are electrically identical and
 sound the same.

 Next is a letter or two indicating the op amp package and
 possibly how it has been tested and what tests it passed.
 Unfortunately, manufacturers haven't standardized these letters.
 Fortunately, you almost never care.  If it is a dual-inline
 (DIP) package and you are replacing a DIP, you shouldn't have to
 worry whether or not it is ceramic or molded.  Likewise, you
 rarely care if it has 100uV offset or 4mV offset for audio.
 Finally, you don't care if it wasn't tested at elevated
 temperatures because you will use it in your house, inside well
 ventilated gear.

 So in general, an NE5532J is a TL5532N, and an AD827JN will
 sound the same as an AD827LD.  If you aren't sure about some
 detail, call or write the IC maker and ask for a data sheet on
 the parts in question.  They will always send data sheets for
 free, and these data sheets contain details on the various part
 numbers, internal circuitry, and electrical characteristics.

10.14 Where can I buy electronic parts to make an amplifier?
 There are many commercial parts distributors that sell only to
 Corporations.  Their prices are often list, their supply is
 often good, and their service varies.  Common ones are Arrow
 Electronics, Gerber Electronics, Hamilton Avnet, and Schweber
 Electronics.  See your local phone book.

 There are also distributors that cater to smaller buyers  These
 typically have only one office.  Some have lousy selections but
 great prices.  In the following list, (+) means that the dealer
 has a good reputation, (?) means that the dealer has
 insufficient reputation, and (X) means that some have reported
 problems with this dealer. (C) means they have a catalog.

 All Electronics Corporation (Surplus, Tools, Parts) (?) (C)
  PO Box 567
  Van Nuys CA  90408 USA
  800-826-5432
  818-904-0524
 Allied Electronics (Full Line of Parts) (+) (C)
  800-433-5700
 Antique Electronics Supply (Tubes, capacitors, etc) (?)
  688 First St
  Tempe AZ  85281 USA
  602-894-9503
 DigiKey Corporation (Full Line of Parts) (+) (C)
  701 Brooks Avenue South
  PO Box 677
  Thief River Falls MN  56701-0677 USA
  800-344-4539
 Maplin (European Parts) (?) (C)
  [phone] (For Orders Only)
  [phone] (Customer Service)
 Marchand Electronics (?) (Crossover kits)
  1334 Robin Hood Lane
  Webster NY  14580 USA
  716-872-5578
 MCM Electronics (Speakers, A/V Repair Parts, Etc) (+) (C)
  650 Congress Park Dr
  Centerville Ohio 45459-4072 USA
  513-434-0031
 MesaBoogie (Tubes, instrument speakers) (?)
  707-778-8823
 Mouser Electronics (Full Line of Parts) (+) (C)
  PO Box 699
  Mansfield TX  76063-0699 USA
  800-346-6873
  817-483-4422
 Newark Electronics (Full Line of Parts) (+) (C)
 Parts Express (Speakers, Cables, Connectors) (+) (C)
  340 East First Street
  Dayton OH  45402-1257 USA
  513-222-0173
 Radio Shack (Parts, Low-End Audio) (+) (C)
 Old Colony Sound (Audio parts and audio kits) (+) (C)
  PO Box 243
  Peterborough NH  03458-0243 USA
  603-924-9464
 Michael Percy (Connectors, MIT, Wonder Caps, Buf-03) (+)
  PO Box 526
  Inverness CA 94936 USA
  415-669-7181 Voice
  415-669-7558 FAX
 Tanner Electronics (Surplus Parts) (+)
  214-242-8702
 Triode Electronics (Tubes, transformers, boxes) (?)
  2010 Roscoe Street
  Chicago IL  60618
  312-871-7459
 Welborne Labs (Connectors, Linear Tech ICs, Wima Caps) (?)
  6836 South Universtiy Blvd. #70
  Littleton CO  80122 USA
  303-470-6585 Voice
  303-791-7856 FAX

10.15 Where can I buy audio amplifier kits?
 Alas, Heath is no longer making Heathkits. Alternatives:
 Audio Synthesis (Many kits from Ben Duncan designs) (?)
  99 Lapwind Lane
  Manchester M20 0UT, UK
  061-434-0126 Voice
  060-225-8431 FAX
 Old Colony Sound (+) (See 10.14)
 Hart Electronics (UK) (?)
 Hafler (+)
 Crimson (UK) (?)
 Mark V Electronics (?)
  8019 E Slauson Ave
  Montebello CA  90640 USA
  800-423-3483
  213-888-8988
 Sonic Frontiers Inc (Tube amp and preamp kits) (?)
  760 Pacific Road Unit #19
  Oakville, Ontario Canada L6L 6M5

10.16 Where can I read more about building amplifiers, preamps, etc.?
 Analog Devices Audio/Video Reference Manual
 Audio Amateur Magazine
  Audio Amateur Publications
  PO Box 494
  Peterborough NH  03458 USA
  603-924-9464
 Electronic Music Circuits, by Barry Klein
  Howard D Sams & Co ISBN 0-672-21833-X
 Electronics Australia (Magazine with audio projects)
  AUD47 per year 12 issues, often discounted
  PO Box 199
  Alexandria, Austrailia
  [phone] or [phone]
 Elektor Electronics (How it works and you-build articles)
  (no longer published in US. Still available in Europe)
  PO Box 1414
  Dorchester DT2 8YH, UK
 Enhanced Sound: 22 Electronic Projects for the Audiophile
  (Some basic projects and some "how it works")
  by Richard Kaufman
  Tab Books #3071/McGraw Hill
  ISBN 0-8306-9317-3
 Glass Audio Magazine
  Audio Amateur Publications
  PO Box 494
  Peterborough NH  03458 USA
  603-924-9464
| IC Op-Amp Cookbook, Third Edition by Walter G. Jung
|  ISBN 0672-23453-4, Howard W. Sams, Inc.
|  buy from any book store or from:
  OpAmp Technical Books 213-464-4322
 Journal of the Audio Engineering Society (Theory & Experiment)
  Audio Engineering Society
  60 East 42nd Street
  New York City NY  10165-0075 USA
  212-661-2355
 Popular Electronics
 Radio-Electronics
 Radiotron Designer's Handbook, Fourth Edition (old, tube info)
 The Technique of Electronic Music, by Thomas H Wells
  Schirmer Books ISBN 0-02-872830-0
 Vacuum Tube Amplifiers, MIT Radiation Lab series
 Wireless World

10.17 What is Amplifier Class A?  What is Class B?  What is Class AB?
 What is Class C?  What is Class D?

 All of these terms refer to the operating characteristics
 of the output stages of amplifiers.

 Briefly, Class A amps sound the best, cost the most, and are the
 least practical. They waste power and return very clean signals.
 Class AB amps dominate the market and rival the best Class A
 amps in sound quality.  They use less power than Class A,
 and can be cheaper, smaller, cooler, and lighter.  Class D amps
 are only used for special applications like bass-guitar amps and
 subwoofer amps.  They are even smaller than Class AB amps and
 more efficient, yet are often limited to under 10kHz (less than
 full-range audio). Class B & Class C amps aren't used in audio.

 In the following discussion, we will assume transistor output
 stages, with one transistor per function.  In some amplifiers,
 the output devices are tubes.  Most amps use more than one
 transistor or tube per function in the output stage to increase
 the power.

 Class A refers to an output stage with bias current greater than
 the maximum output current, so that all output transistors are
 always conducting current.  The biggest advantage of Class A
 is that it is most linear, ie: has the lowest distortion.

 The biggest disadvantage of Class A is that it is inefficient,
 ie: it takes a very large Class A amplifier to deliver 50 watts,
 and that amplifier uses lots of electricity and gets very hot.

 Some high-end amplifiers are Class A, but true Class A only
 accounts for perhaps 10% of the small high-end market and none
 of the middle or lower-end market.

 Class B amps have output stages which have zero idle bias
 current.  Typically, a Class B audio amplifier has zero bias
 current in a very small part of the power cycle, to avoid
 nonlinearities.  Class B amplifiers have a significant advantage
 over Class A in efficiency because they use almost no
 electricity with small signals.

 Class B amplifiers have a major disadvantage: very audible
 distortion with small signals.  This distortion can be so bad
 that it is objectionable even with large signals.  This
 distortion is called crossover distortion, because it occurs at
 the point when the output stage crosses between sourcing and
 sinking current.  There are almost no Class B amplifiers on the
 market today.

 Class C amplifiers are similar to Class B in that the output
 stage has zero idle bias current.  However, Class C amplifiers
 have a region of zero idle current which is more than 50% of
 the total supply voltage.  The disadvantages of Class B
 amplifiers are even more evident in Class C amplifiers, so
 Class C is likewise not practical for audio amps.

 Class A amplifiers often consist of a driven transistor
 connected from output to positive power supply and a constant
 current transistor connected from output to negative power
 supply.  The signal to the driven transistor modulates the
 output voltage and the output current.  With no input signal,
 the constant bias current flows directly from the positive
 supply to the negative supply, resulting in no output current,
 yet lots of power consumed.

 Class B amplifiers consist of a driven transistor connected
 from output to positive power supply and another driven
 transistor connected from output to negative power supply.
 The signal drives one transistor on while the other is off,
 so in a Class B amp, no power is wasted going from the
 positive supply straight to the negative supply.

 Class AB amplifiers are almost the same as Class B amplifiers
 in that they have two driven transistors.  However, Class
 AB amplifiers differ from Class B amplifiers in that they
 have a small idle current flowing from positive supply to
 negative supply even when there is no input signal.  This idle
 current slightly increases power consumption, but does not
 increase it anywhere near as much as Class A.  This idle current
 also corrects almost all of the nonlinearity associated with
 crossover distortion.  These amplifiers are called Class AB
 rather than Class A because with large signals, they behave like
 Class B amplifiers, but with small signals, they behave like
 Class A amplifiers.  Most amplifiers on the market are Class AB.

 Some good amplifiers today use variations on the above themes.
 For example, some "Class A" amplifiers have both transistors
 driven, yet also have both transistors always on.  A specific
 example of this kind of amplifier is the "Stasis" (TM) amplifier
 topology promoted by Threshold, and used in a few different
 high-end amplifiers.  Stasis (TM) amplifiers are indeed
 Class A, but are not the same as a classic Class A amplifier.

 Class D amplifiers use pulse modulation techniques to achieve
 even higher efficiency than Class B amplifiers.  As Class B
 amplifiers used linear regulating transistors to modulate output
 current and voltage, they could never be more efficient than
 50%.  Class D amplifiers use transistors that are either on or
 off, and almost never in-between, so they waste the least amount
 of power.

 Obviously, then, Class D amplifiers are more efficient than
 Class A, Class AB, or Class B.  Some Class D amplifiers have
 >80% efficiency at full power.  Class D amplifiers can also have
 low distortion, although not as good as Class AB or Class A.

 Class D amplifiers are great for efficiency.  However they are
 awful for other reasons.  It is essential that any Class D amp
 be followed by a passive low-pass filter to remove switching
 noise.  This filter adds phase shift and distortion.  It also
 limits the high frequency performance of the amplifier, such
 that Class D amplifiers rarely have good treble.  The best
 application today for Class D amplifiers is subwoofers.

 To make a very good full range Class D amplifier, the switching
 frequency must be well above 40kHz.  Also, the amplifier must be
 followed by a very good low-pass filter that will remove all of
 the switching noise without causing power loss, phase-shift, or
 distortion.  Unfortunately, high switching frequency also means
 significant switching power dissipation.  It also means that the
 chances of radiated noise (which might get into a tuner or phono
 cartridge) is much higher.

10.18 Why do I hear noise when I turn the volume control? Is it bad?
 Almost all volume controls are variable resistors.  This goes
 for rotary controls and slide controls.  Variable resistors
 consist of a resistive material like carbon in a strip and a
 conductive metal spring wiper which moves across the strip as
 the control is adjusted.  The position of the wiper determines
 the amount of signal coming out of the volume control.

 Volume controls are quiet from the factory, but will get noisier
 as they get older.  This is in part due to wear and in part due
 to dirt or fragments of resistive material on the resistive
 strip.  Volume control noise comes as a scratch when the control
 is turned.  This scratch is rarely serious, and most often just
 an annoyance.  However, as the problem gets worse, the sound of
 your system will degrade.  Also, as the problem gets worse, the
 scratching noise will get louder.  The scratching noise has a
 large high-frequency component, so in the extreme, this noise
 could potentially damage tweeters, although I have never seen
 a documented case of tweeter damage due to control noise.

 Some controls are sealed at the factory, so there is no
 practical way to get inside and clean out the dirt.  Others have
 access through slots or holes in the case.  These open controls
 are more subject to dirt, but also are cleanable.  You can clean
 an open volume control with a VERY QUICK squirt of lubricating
 contact cleaner, such as Radio Shack 64-2315.  Even better is a
 non-lubricating cleaner, such as Radio Shack 64-2322.  With any
 cleaner, less is better.  Too much will wash the lubricant out
 of the bearings and gunk up the resistive element.

 You can also clean some controls by twisting them back and forth
 vigorously ten times.  This technique pushes the dirt out of the
 way, but is often just a short term fix.  This technique is also
 likely to cause more wear if it is done too often.  Try to do it
 with the power applied, but the speaker disconnected, so that
 there is some signal on the control.

 Sealed and worn controls should be replaced rather than cleaned.
 Critical listeners claim that some controls, such as those made
 by "Alps" and by "Penny and Giles" sound better than common
 controls.  Regardless of the brand, however, it is essential
 that whatever control you buy have the same charcteristics as
 the one you are replacing.  For most volume controls, this
 means that they must have AUDIO TAPER, meaning that they are
 designed as an audio volume control, and will change the level
 by a constant number of dB for each degree of rotation.

 Badly designed circuits will wear out volume controls very
 quickly.  Specifically, no volume control is able to work for
 a long time if there is significant DC current (or bias current)
 in the wiper.  If the output of the control goes to the input of
 an amplifier, the amplifier should be AC coupled through a
 capacitor.  If there is a capacitor there, it might be leaky,
 causing undesirable DC current through the volume control.

 If you have a circuit with no blocking capacitor or a bad
 blocking capacitor, you can add/replace the capacitor when
 you replace the control.  However, get some expert advise
 before modifying.  If you add a capacitor to a device which
 doesn't have one, you will have to make other modifications
 to insure that the amplifier has a source for its bias current.

11.0 CD Players, CDs, Turntables, and LPs

11.1 What should I listen for when evaluating a turntable or CD player?
 For tape decks and turntables, beware first of speed variations
 (wow and flutter).  A good check for this is Richard Strauss'
 "Also Sprach Zarathustra" (aka: The Theme From 2001), which has
 a long, low, sustained organ note that comes in well before the
 main theme starts, and is held through the first movement.
 Concentrate on that.  Make sure it doesn't wobble or warble.
 There's also a good bit at the beginning of Pink Floyd's
 "The Wall", but it doesn't go on as long, so you've got less
 time to think about it.  Tape decks are prone to losing
 high-frequency notes, so pick something you like which has lots
 of treble, and make sure it is clear.

 The sound of a turntable is largely bound up in the kind of
 cartridge mounted on it.  Make sure to listen to a table with
 a cartridge similar to what you're buying, and not one in a
 different price bracket.  If possible, audition the turntable
 with the same arm and cartridge, so that you will experience
 potential cartridge/arm interactions, too.  Most cartridges
 work better with one arm than another.  Treat the
 tonearm/cartridge pair as a system, rather than independent
 parts.

 For CD players, try some piano music.  See if the high notes
 sound tinny.  Also, try something which has some soft parts,
 not the same as turning the volume down.  Distortion for CD
 players (as for other devices) is measured at a high output,
 but in fact in CD players (unlike others) it's likely to be
 worse in soft passages of music.  Most classical recordings
 contain a suitable soft passage.  Most rock music won't.

 Distortion in CD players, if you want to call it that, is
 a function of the granulation noise, or time-delay pre-echo that
 can come out of the filtering.  To listen for this, use material
 that is rich in high-order harmonics, such as brass music.
 Unfortunately, you can't reliably predict how a CD player
 will sound by looking at specifications, features, or the
 technology it uses.  If you want to know how a player will
 sound, you MUST listen to it.

11.2 Are some discs better than others?
 Some recordings are better than others.  Some artists are better
 than others.  Some recording engineers are better than others.
 Some microphones are better than others.  Some music is better
 than others.

 Ignoring the above, there is some difference between discs.
 Some of the very earliest discs were badly made and deteriorated
 with time.  The technical problems that caused those problems
 have been solved.

 Some "gold" discs are available which are advertised to have
 better life and quality than common "aluminum" discs.  These
 sell for an extra US $15 or more per disc over the cost of the
 same music on a common disc.  Studies have shown that there is
 an advantage to glass-encased, gold platters for archiving
 computer data that is not error tolerant and will need to be
 stored for many tens of years.  I have yet to see a similar
 comparison which justified any extra effort for storing audio
 recordings for 50 years.  Part of the reason for this is that
 audio recordings contain error correction codes.  Another reason
 is that audio recorders can effectively reconstruct badly
 damaged audio data, even if there is data completely missing.

 Some discs seem to have pinholes in the aluminum, which are
 visible when the disc is held up to a strong light.  However,
 these discs play fine and last very well, so the effect of these
 pinholes is probably nil.  Some have performed studies counting
 errors on various discs with various players.  They found that,
 in general, the error count was consistent from one player to
 another.  Also, in general, most discs have a low, consistent
 error rate which is perfectly correctable using the redundant
 data stored on the disc.  This study did find that one group of
 discs had a higher error rate than all of the rest.  This group
 was the promotional discs, also called "music samplers" given
 away by music companies to introduce you to their family of
 artists and performers.  Despite these higher error counts,
 these discs still played fine.

 If there is no abusive handling involved, I have rarely heard of
 a disc that degraded with time.  Of the few that have existed,
 they tended to be from one of the bad batches mentioned earlier.

 There is no doubt that some discs are mastered better than
 others.  Some are badly mixed.  Some are so badly recorded that
 there is noticeable clipping.  Some are made from damaged master
 recordings.  CD technology is no guarantee of good music or of a
 good recording.

11.3 Are CDs better than LPs?
 Some excellent recordings are mastered digitally, and sound
 great on LPs.  This suggests that there is nothing inherently
 bad about digital.

 Some find that LPs sound better than CDs.  Advocates of LPs
 claim that the digital to analog (D/A) converter in home CD
 players isn't up to the quality of the information on the disc.
 They also claim that the analog electronics in a home CD player
 can be poor.

 Some believe that CDs do not sound like LPs because the CD does
 not have the frequency response errors, the distortion, or the
 stereo separation problems of LPs.

 In general, though, there are good and bad CD players, just as
 there are good and bad turntables, cartridges, and tone arms.
 Any ultimate comparison would require ultimate equipment, which
 is unaffordable.  In moderately priced systems, there will be
 some signal damage from the turntable system and some signal
 damage from the CD player.

 LP lovers often learn the nuances of cartridge selection, record
 care, and even turntable and tonearm adjustment.  They have
 found that the turntable will sound different if the arm height
 is adjusted, if the cartridge angles are changed, and if the
 tonearm wire is moved.  CDs do not offer as many avenues for the
 home experimenter.

 However, Audio Amateur Magazine has published modification
 projects for CD players; particularly for Magnavox 560 and
 similar European players.  Audio Magazine has also published
 such articles.

11.4 What turntable should I buy?
 Despite improvements in motor technology, most great turntables
 use belt drive.  Rubber roller (idler) drive sounds the worst.

 Select a turntable with a very heavy platter for the least wow
 and flutter.  Give the platter a rap with your knuckle.  It
 should not "ring" like a cymbal. It should feel and sound dead.

 Also look for a turntable that has good isolation from base to
 stylus.  With the amp on and the turntable selected, but with
 the turntable motor off, put an old record on the turntable,
 lower the stylus onto the record, and then tap the edge of the
 base.  Not too hard, you don't want to send the arm flying.  At
 worst, you should hear (through the speakers) a quick 'thump'
 followed by silence; if you're lucky, you'll hear nothing at
 all.  If the sound continues beyond a quick 'thump', the
 mechanical isolation is not great, and you might want to look at
 some other make.  To perform this test with some turntables, it
 will be necessary to unplug the turntable power cord.

 If the turntable has a tonearm, try to evaluate the arm, too.
 A good arm should be adjustable in height. A good arm should
 allow cartridge adjustments. A good arm should accommodate a
 wide range of cartridges.  Despite this, some arms work better
 with high compliance cartridges, while others are at their best
 with low compliance.  Ask.

 The original AR Turntable was very well received when it was
 first made, and the current AR Turntable is still very respected
 for its price ($450 + arm).  Turntables made by Denon, Linn,
 Rega, Sota, and VPI are also recommended, but can cost more.

11.5 What phono cartridge should I buy for my older turntable?
 The $30 Grado ZTE+1 is a great value for any home user but a
 purist.  For the purist, there are still many choices, both
 moving coil and moving magnet.  Each sounds slightly different,
 and has its individual strengths.  The Sumiko Blue Point has
 been recommended at $125 along with the $125 Denon DL-160 and
 the $150 Shure V15 type V-MR.

11.6 Will phono cartridges still be around ten years from now?
 Most likely, there will still be cartridges available, but not
 in the variety available ten years ago.  They will become
 "Special Order" in some stores and unheard of in others.

 "Pro" or "DJ" cartridges will stay available in good supply,
 "Audiophile" cartridges will stay available and very expensive,
 "Mid-line" cartridges will become very scarce, and a few
 "Budget" cartridges will remain available in copious supply.
 At the same time, some makers will drop their cartridge lines
 completely.

11.7 Will LPs still be around ten years from now?
 There is a strong movement of collectors and purists who will
 keep their collections and buy good used discs.  Count on these
 people to keep the used disc market hot for 25 years longer.

| As for new music, less is being pressed today than 20 years
| ago.  Many popular artists are being released on LP in parts
| of Europe, but availability is dependent on country.  One
| person said that many new LPs are available in Spain.

 LP sales have increased recently in Japan and in the UK. Polydor
 is now re-releasing older recordings on vinyl, and will continue
 to press them as long as it is profitable.  Likewise, there are
 several re-releasing projects in Japan.  Some are for Jazz
 collectors and others are for pure analog as well as classical
 music lovers.  They are selling the LPs by subscription, with
 shipments every 2 or 3 months.  Each release includes about 20
 titles.  Japan has released over 100 LPs this way last year.

11.8 What about CD green pens?
 In a nutshell, save your money.

 A CD player "reads" information on the disc with a laser light
 beam.  Some believe that if you put a green stripe on the very
 perimeter of the disc, then the light beam will not reflect
 around inside the disc and will more clearly pick up the data.

 Scientific studies of the data coming off of the disc have
 failed to show any difference between a virgin disc and a green
 painted disc.  I have not heard of double blind listening
 comparisons that have proved that there are people who can hear
 the difference, although many have performed uncontrolled tests
 with positive results.

11.9 What about CD stabilizer rings?
 In a nutshell, save your money.

 The data coming off of the disc is a serial string of ones and
 zeros.  If this bit stream has jitter, then it may reach the D/A
 converter out of sync.  If this happens, then the actual analog
 signal recreated will have jitter, and won't be perfectly true.
 The vendors of stabilizer rings say that using these rings will
 reduce jitter and make a more perfect signal.  Vendors also
 claim that the rings can increase the mass of a disc, making it
 spin more smoothly, and reducing transient load on the power
 supply from the motor.

 Some players will not play discs that have stabilizer rings on
 them.  The clamp can't handle the thickness.  Other players play
 ringed discs, but do not play them well, because the disc motor
 was not built for the added load.

 With those exceptions, scientific studies of the data coming off
 of the disc have failed to show any improvement going from a
 virgin to a ringed disc.  I have not heard of double blind
 comparisons that prove that people hear the difference, either.

11.10 What about CD spray treatments (ArmorAll et al)?
 In a nutshell, save your money.

 Current wisdom is to avoid any disc coating or spray.  Some will
 definitely damage the disc.

 There are many theories on what ArmorAll can do to a disc.  One
 is that it reduces static which will attract the delicate head
 of the laser detector to the disc.  Another theory is that the
 cleaner will fill voids in the disc with silicone, thereby
 making it easier to read by reducing diffraction effects.

 Scientific studies of the data coming off of the disc have
 failed to show any difference between a virgin disc and a
 treated disc.  I have not heard of double blind listening
 comparisons that have proved that there are people who can hear
 the difference.

 One of the strongest proponents of ArmorAll issued a "recall" on
 his advice.  He now warns that ArmorAll can damage the disc.  He
 also advises that you can clean ArmorAll off treated discs with
 Dawn dish detergent.

11.11 Are 1-bit CD players better than multi-bit players?
 In a nutshell, they are virtually the same.

 There are some excellent sounding 1-bit players and some
 excellent sounding multi-bit players.  Some feel that the 1-bit
 technology has more future because it can be improved with the
 rapidly improving digital technology, while the multi-bit
 players improve with slowly improving analog technology.
 Multi-bit also has its advocates.

 All of the various D/A converters try to do the same thing, and
 try to achieve the exact same ideal performance.  How well they
 succeed is more a function of their skill and the quality of the
 parts that they buy than the technique that they use.  In other
 words, the architecture of a D/A converter is less important
 than the quality of its implementation.

11.12 Are three lasers better than one in CD players?
 Some players have one beam, some three.  All use one laser diode
 to generate the beam.  Three-beam is just a different method for
 doing track alignment.  Neither is better than the other.

 There are good 1-beam players and good 3-beam players.
 Manufacturers want advertising claims and "More Beams Is Better"
 sounded good to some marketing people.  Trust your ears.

11.13 Is the BMG 8-for-1 deal good?
 Yes.  You have to put up with their frequent mailings. You can
 elect the "POSITIVE OPTION" and not have to answer each mailing
 to avoid an order.  You should expect to pay approximately $2.00
 per disc for shipping and handling in the US and more elsewhere,
 but even at that price and assuming that you will buy one of
 their discs for $16.00, you still do well.  Assuming, of course,
 that you want at least eight of the discs that they are offering
 for sale.  Some states requires sales tax on BMG sales, and some
 states tax "free" discs, but the tax still is small compared to
 the discount from retail.

 The BMG collection contains over 2000 discs.  This includes
 classical, pop, jazz, and other.  All BMG discs come from the
 larger labels.  Some rumored that BMG discs are inferior to the
 discs sold in normal retail chains.  This has not been
 substantiated.  In fact, BMG distributes their discs through
 retail chains, as well as through the mail, so you may get a BMG
 disc either way.

11.14 What should I do if there is a problem dealing with BMG?
 The number to reach BMG is 317-542-0414.  Their people have been
 very cooperative with me and others.  It is always good policy
 to confirm any phone call with a letter, restating the problem
 and the resolution you were promised over the phone.  It is good
 practice to write down the name of the person you speak with.

 If BMG sends you something that you didn't order, DON'T OPEN THE
 PACKAGE.  Write REFUSED on the package and put it back in the
 mailbox.  They will accept the return and credit your account
 for any charges.

11.15 How do I get out of the BMG racket?
 If you have taken any discs from BMG, you must either return
 what you have ordered or fulfill the terms of your original
 agreement.  This often means buying one disc at full price and
 paying for the shipping on all discs you ordered and received.

 Once you have done this, you can quit the club at any time.
 Take your next order form and mark it with a bold marker in
 large letters "CANCEL MEMBERSHIP" and mail it to: BMG COMPACT
 DISC CLUB, PO BOX 91413, INDIANAPOLIS, IN  46291 USA.  It may
 take a month to fully take effect, but they will honor your
 request.  While waiting for the cancel order to take effect, be
 sure to return all future order forms marked the same way.
 Otherwise, you may wind up with unwanted discs.

11.16 How do I get the most out of BMG?
 Only buy one disc at full price, fulfilling your obligation.
 Request the "POSITIVE OPTION" so that you save on postage.  Only
 buy from special fliers.  Every month, except November and
 December, they send out a "Two for half price then one free"
 flier.  They have almost all of the stuff in the regular fliers.
 They even offer "Buy one get two free" sometimes.  Wait for
 those special deals.  You can even order discs from an October
 catalog using the order form that came in the February catalog.

 Some have said that you get the most out of BMG by signing up,
 getting 8 discs for the price of one, quitting, signing up
 again, etc.  People have done this successfully.  However, the
 terms of the BMG agreement specify that the offer of 8 discs for
 the price of one is only for new members.  Trying to get 8 discs
 for the price of one a second time may constitute fraud, so I
 strongly discourage you from trying this.  Conversely, I have
 never heard of anyone prosecuted or refused membership for this.

11.17 What is a 1-bit (Mash, Bitstream) D/A converter (CD player).

11.18 What is the best under-$200 CD player?
 Once, Magnavox (and the identical Philips) CD players were known
 for poor reliability.  They are much better today.  Some believe
 that for sound, an under-$200 Magnavox is as good as any in its
 price range.  Be sure to listen for yourself before you buy.

11.19 What is the best under-$500 CD player?
 Some recommend the Rotel 855 and 955.

11.20 What's wrong with the CD longbox?
 Some CDs are sold shrink wrapped in a square plastic storage box
 known as the "jewel" box.  This is the ideal packaging for CDs.
| It has almost no unusable components and adequately protects and
| displays the disc.  The shrink also implies that the disc is new
| and unopened, but shrink can never assure a new disc.

| Some CDs are still sold in a cardboard box that is more
 than 2X the size of the jewel box.  This "long box" is
 ecologically wasteful and useless.  It rarely contains
 additional information about the disc or the artists.  Its
 primary purpose is to discourage theft in retail stores, but
 it is even poor at that.  These boxes are BAD.

 Some stores use a reusable plastic long box.  When you buy a
 disc in one of these boxes, you take the disc and jewel box with
 you and leave the plastic long box with the cashier for reuse.
 Not perfect, but a good compromise.

11.21 How can I promote better CD packaging?
 Vote with your money.  Don't buy CDs packaged in the long box.
 If you go to a store and they have CDs in the long box, tell the
 owner that you never buy CDs in the long box.  Then find stores
| which don't use the disposable long box.  People have been doing
| this over the past few years and have made a difference in many
| stores.  (The fact that the long box costs more than simple
| shrink wrap has also helped the cause.)

11.22 How can I clean a dirty CD?
 Use a drop of dish detergent and lots of clean water.  Do not
 rub.  Never rub or wipe in a circle.  Rinse the disc in running
 clear water, shake off most remaining drops, and lightly pat dry
 with a soft, clean cloth.

11.23 Can you repair a damaged CD?
 If the disc is lightly scratched on the bottom, then you can
 polish out the scratch and probably repair the disc perfectly.
 If there are lots of scratches or deep scratches, or there is
 damage on the top, you may be facing a lost cause.  The music
 information is immediately under the label.  If you scratched
 the reflective layer, the disc is normally unrecoverable.

 Before trying any repair, try washing the disc with clear water
 and a bit of liquid dish detergent.  Do not scrub or rub hard.
 Rinse the disc with clear water and shake off as much water as
 you can.  Finally, wipe the last few drops off with a soft,
 clean cloth, in a radial direction.

 SMALL scratches can be removed with a scrufty T-shirt and
 toothpaste, such as Tom's Toothpaste.

 You may wish to try a thin coating of Johnson's Klear floor wax
 on the bottom of the CD.  Often it will cover the scratches
 enough to allow playing.  The refractive index is pretty close
 to polycarbonate, so filled scratches will be nearly invisible.

 Noteworthy Music (800-648-7972) sells CD repair kits (#CDR 200,
 $11.99, one shipping unit).  They seem to work as advertised,
 although getting the disc to the point where you can't see any
 sign of the scratch does take real care and persistence.

 You can buy professional plastic polishing compounds at many
 hobby shops.  The ones used for polishing acrylics, plexiglas,
 etc. work.  Ordinary lapidary jeweler's polishes also work.
 You'll need a rough polish to remove the scratches, then tin
 oxide to polish to a mirror finish.  Telescope lens kits also
 work.  Finally, T-Cut, a car paintwork polish, works well for
 big scratches.

11.24 Can I add digital output to a non-digital-out CD player?
 Some Magnavox CD players using the Philips chip set can be
 modified.  Look for a SAA7220 IC.  If it has one, then it can be
 modified.  If you have experience modifying electronic
 equipment, follow this procedure:

 Take pin 14 of the SAA7220 IC and remove whatever terminating
 resistor is on it.  Connect it through a 560 ohm resistor to the
 input of a wide band pulse transformer.  Tie the other end of
 the primary of the transformer to ground.  Pulse Engineering
 PE65612, Schott Corp 6712540, and Scientific Conversions
 SC916-01 all will work.  Bypass the primary through a 620 ohm
 resistor.  Connect the output of the transformer to an RCA jack.
 Do not ground either side of the RCA jack. This output is now
 S/PDIF compatible. (Thanks for the tip to Positive Feedback)

11.25 What can I get in the way of a CD test disc?
 Many use the Hi-Fi News & Record Review test discs.  So far,
 these have received only positive comments.

 Chesky produces 2 test discs.  The first, "Chesky Jazz Sampler
 Volume I" contains some excellent imaging test signals (called
 LEDR), some well-recorded acoustic jazz, and other test signals.
 The second, "Chesky Jazz Sampler Volume II" has similar music &
 different tests.

 Stereophile produces two test discs.  The first seems of limited
 value.  The second just came out.

 Denon also produces two test discs.  The first, "Digital Audio
 Check" is more useful for home use.  The second, "Audio
 Technical" is more for repair shops and test-disc addicts.

11.26 How do the letters ADD on my CD relate to sound quality?
 The simple answer to this question is that there is no relation
 between the three letter code and sound quality.  Those three
 letters refer to the recording and mastering tools used in
 making the CD.

 The first letter refers to the recording process.  For example,
 a disc labeled ADD was ANALOG recorded, where a disc labeled
 DDD was DIGITALLY recorded.  Analog recording means that some
 form of conventional analog tape recorder was used, whether it
 be a two-track home-quality recorder or a very expensive
 wide-tape, high-speed, multi-track recorder.  Digital recording
 could be as simple as a two-track DAT recorder, or can be a
 much fancier multi-track digital recorder.

 The second letter refers to the "mastering" process.  Mastering
 refers to the processing which takes the initial analog or
 digital recording and mixes it down to two-track stereo,
 edits out flaws, equalizes for different sound, adjusts levels,
 and otherwise changes the signal.  All of this can be done with
 digital signal processors, and it can also be done with analog
 signal processors.  There are good machines available for this
 which are analog and good machines which are digital.

 The third letter refers to the final product, which for a CD is
 always a digital product.  I have seen discs that are labelled
 as AAD, ADD, DAD, and DDD.

 Future releases may not have this three letter code on them
 because they don't tell you anything that is significant. Also,
 some codes have been used incorrectly on some discs, which
 makes the information that much more meaningless.

 11.27 How can I clean LPs?
 There are expensive machines for this purpose which work very
 well.  One popular model goes by the name Nitty Gritty.  These
 machines spray cleaner onto the record, work it into the
 grooves, and then vacuum the cleaner and dirt out.  If you are
 serious about records and have lots of them, it may be a good
 investment for you.

 If you have a more reasonable collection, you might be happy
 with a good hand washing every now and then.  To give your
 records a good hand washing, start by preparing this wash:
  1 gallon distilled water
  90 ml 70% isopropyl alcohol
  1 gram Alconox (a laboratory detergent)
 Also, get a natural bristle brush and trim it to the correct
 stiffness/bristle length so that the bristles can get into the
 grooves but aren't stiff enough to scratch the record.

 Lay the LP flat and pour a thin coat of the above fluid on it.
 Brush the wash into the grooves with the bristle brush.  Brush
 in the direction of the grooves, going through all grooves.
 Flush the wash and dirt off with cool, running tap water.
 Rinse the record with distilled water and pat it dry
 with a soft, clean cotton cloth.

 11.28 How do you set the stylus pressure correctly?
 Stylus tracking force is typically adjusted at the back of the
 tonearm with a knob that is calibrated in grams at the stylus
 tip.  With the control set to zero, the stylus should sort-of
 float above the record surface.  The control is then increased
 to the number recommended by the cartridge manufacturer.

 Do not, under any circumstances, use a lower than recommended
 force, as the cartridge may lose the ability to maintain
 contact with the groove wall on passages of large amplitude.
 This WILL result in RECORD DAMAGE.

 If you want the best possible tracking and sound quality, you
 will want to fine-tune the tracking force.  Use a test record
 and listen very carefully, or get the help of a good dealer
 with a battery of instruments.

 11.29 How do you set the anti-skating on a tonearm?
 If you have a recommendation or suggestion from the
 tonearm manufacturer, follow their advice first.
 They will give you the best starting point.

 Some tonearms come with calibrated anti-skate.  The manufacturer
 of these tonearms has tried to calibrate the anti-skate control
 so that if you match the setting of the anti-skate to the
 setting of the stylus pressure, you will have nearly perfect
 anti-skate.  Read the manufacturer's recommendations to see if
 this applies to your tonearm.

 You can see gross errors in anti-skate by looking at
 the stylus.  If you shine a light on the front of the
 tonearm while playing a record, you will be able
 to see whether the stylus is centered in the stylus
 holder.  If the stylus is biased to one side or another
 while playing a record, then the anti-skate is way off.

 More subtle adjustments can be made by listening for
 mistracking.  If you can, obtain a record with equal
 left right modulation at high frequency with ascending
 modulation magnitude (volume), such as the Shure
 ERA-III, IV, or V test record.  They have five bands of
 "greensleeves" played on flute, and you fiddle until the
 audible breakup is equal in both channels, and adjust
 tracking weight until it occurs in the highest band.
 This is, like other cartridge and tonearm adjustments,
 easier for the experienced hand than the beginner.

 Some high-end dealers have electronic instruments which
 allow them to accurately adjust anti-skate and other
 cartridge and tonearm parameters.  If you can get this
 service, consider yourself fortunate.

 11.30 How else do you adjust a tonearm/cartridge/stylus?
 There are a few other critical adjustments.  Again, a good
 high-end dealer may be your best resource.  Your ear may
 also be your best test instrument.

 You need a level turntable.  Use a quality carpenter's
 level.  Some people like the Shure stylus force gage for
 setting stylus pressure accurately.  Other tools which are
 well recommended are the Geo-disk, a good protractor, and
 above all, the Cart-Align, which uses a very precise
 etched plastic mirror for cantilever alignment.

 You'll also want to set the tracking angle.  It CAN be
 done by eyeball, but is best done with test instrumentation
 and a record.  There is also the cartridge angle, tonearm
 height, etc.  Read the instructions which came with your
 tonearm for the best specific advice for that tonearm.

 Tonearm cable is more critical than any cable anywhere else in
 the signal chain.  Cable capacitance directly sets the high
 frequency characteristics of the cartridge.  In addition, the
 correct grounding of the shield is essential to minimize hum.
 It may be necessary to change preamp input capacitors so that
 the cable/preamp combination loads the cartridge with the
 right overall capacitance.  Replacing tonearm cable will have
 a similar effect, but may be harder to change tonearm cable
 than to change preamp input capacitors.  Consult the
 cartridge, tonearm, and preamp manuals for specific advice.
 Also refer to 16.6 for more information on tonearm cable.

 An excellent article on setting up a turntable is:
  Stereophile, July 1990, Pages 62-85.

11.31 Do CDs deteriorate with time?  What is their life span?
 A CD consists of a polycarbonate top layer, an aluminum (or
 gold) metal reflective layer, a polycarbonate bottom layer,
 and some miscellaneous printing ink.  Of these materials,
 polycarbonate seems to be extremely stable with time provided
 that it is well cared for.  Do not use any liquids on a CD
 that contain silicones or solvents.  Do not leave CDs in
 sunlight or other bright light.  Do not stick labels on CDs.
 Do not write on CDs.  Do not expose CDs to temperatures higher
 than normal room temperatures.  Don't leave a CD under water.
 Even the top side of a CD is critical and subject to damage.

 Some pressings from the early 1980s used ink which damaged the
 polycarbonate top layer and eventually got into the aluminum.
 These inks are not in use today.  Some earlier discs were made
 with imperfect sealing around the perimeter of the disc.  This
 was evident because the aluminum in the disc extended all of
 the way to the disc edge.  These discs were known to fail due
 to moisture getting to the aluminum and causing it to oxidize.
 Modern CD factories have solved this problem as well.

 With those cautions, modern CDs will last for more than 30
 years without deterioration.  Most of the CDs which were
 made in 1983 are still around today and still sound good.
--
Bob Neidorff; Unitrode I. C. Corp.  |  Internet: [e-mail]
7 Continental Blvd.                 |  Voice   : (US) 603-424-2410
Merrimack, NH  03054-0399 USA       |  FAX     : (US) 603-424-3460
Archive-name: AudioFAQ/part3
Last-modified: 1993/6/4
Version: 1.5

12.0 High Fidelity Systems
 People frequently use the term "Stereo" to refer to a sound
 reproduction system.  To be more accurate, we will use the term
 High Fidelity System to refer to a pile of equipment including
 at least one source, at least one amplifier, and at least one
 speaker.  Common sources are turntables, CD players, tape
 players, tuners, and receivers.

12.1 What is a receiver?
 A receiver is a tuner, power amplifier, and preamp combined.  A
 common receiver has inputs for a turntable, a CD player, a tape
 deck, and perhaps one or two other sources.  It has selector
 switch(s), tone controls, and a volume control.  A receiver may
 have outputs for two speakers, or for more.

12.2 What is a tuner?
 A tuner is a radio receiver which can not directly connect to
 speakers.  Sometimes, the radio in a tuner is higher quality
 than the radio in a receiver.  A tuner may or may not receive
 the AM broadcast band, but 99.999% will receive the FM broadcast
 band.  Some also receive short wave bands, frequencies used
| for long-distance rather than for local commercial broadcasts.

12.3 How should I go about selecting a system?
 If you're looking to buy something, the first step is to figure
 out what you can spend.  If you're looking for a whole system,
 this gets tricky, because you have to allocate amounts for the
 different components.  The most popular current rule-of-thumb
 for a single source system (speakers, amp, 1 something-player)
 is to divide the money about equally among the three parts.  If
 you want several players, you'll have to decide whether they are
 all equally important, and so deserve the same amount of money;
 or whether some are less important, in which case you can spend
 less on them and put the savings elsewhere.

 This rule isn't hard-and-fast.  It's just meant as a starting
 point so you don't have to listen to every possible combination
 of equipment.  If you are building around a CD player, you might
 spend a bit less on the player and a bit more on the speakers.
 If you are buying turntable (or something else which plays by
 physical contact) on the other hand, it might be good idea to
 put a bit extra into the player.  The reason for this is that if
 you skimp on the turntable, then when you come to buy a better
 one you may find that your records have been worn out by the
 cheap player.  If you skimp on the speakers, on the other hand,
 then when you can afford better speakers the music will still be
 there on your records.

 See also 9.1, 9.2, and 11.1 for information on what to listen
 to and what to listen for when evaluating speakers, turntables,
 CD players, tape recorders, and systems in general.

12.4 How can I improve the sound of my stereo?
 The cheapest improvement you can make, and perhaps the most
 effective, is to position your speakers carefully and correctly.
 See 13.1, below.  This will improve the frequency response
 flatness, making it easier to hear every instrument and voice.
 Setting speaker position correctly can also improve the
 three-dimensional recreation of a stereo image.

12.5 Do I want a combo system or separate components?
 Combo systems used to be cheap jokes; that's not always true
 now.  Some sound very nice; there are even some made by
 "audiophile" companies, and they sound even nicer.  They've got
 lots of advantages.  They take up less space.  The controls tend
 to be well-integrated, especially if they are remote-controlled.
 Therefore, they are easy to operate; this can be a major plus if
 some of the people who'll use it are afraid of, or not very good
 at, technology.  Also easy to set up, and don't leave millions
 of wires dangling all over everywhere.

 If you do go for a combo, get a brand name; either an audiophile
 company, or a good "consumer electronics" company.  Brand-X
 combos are generally overpriced and unpleasant.  If possible,
 buy it where you can listen to it first, such as a "real" hi-fi
 shop.  Mid-range hi-fi shops sell combos, as a way of
 introducing beginners to quality sound.

 In most good combos, the speakers are the weak link.  If you do
 go for a combo, you can almost always improve the sound
 drastically by buying a set of better speakers.  Better speakers
 start in the $100-$200 price range.  Some of the best combos
 come without speakers, forcing you to do this.  A good combo
 with replacement speakers will give you very pleasant music.

 Sounds good, you say, so why do people bother with components?
 Well, you can get better sound with a component system -- but
 usually at the expense of convenience and size.  A good
 component system will normally require a mixture of boxes from
 different makers to get the best results, so you've got to spend
 more time listening to things.  However, if you listen to your
 music seriously, then the performance of a component system is
 the reward for that extra work.

 Components are harder to set up and operate.  However, as noted,
 you can get better sound.  You also get more flexibility.  If,
 for example, you decide you want a better CD player, you just
 replace the CD player.  With a combo system, you've got to
 replace the whole system.  If your component tape deck breaks,
 you can remove it from the system and take it in for repair or
 replacement. With a combo, the whole system has to go in for
 repair or be replaced.

 When you want to add some new recording medium to your system
 (laserdisc, VCR, DAT, DCC, MD, ...), if you've got components
 you just go buy the appropriate box.  Many combo systems do not
 have places (or many places) to attach extra bits, so again you
 could be looking at replacing the whole thing.  With a component
 system, you can add a turntable; most modern combos can't cope
 with turntables any more.  Do you have a record collection?

 If you're really not sure, components are the safer bet; if
 you're going to make a mistake, that's probably the better way
 to be wrong.  But, if you're sure that a combo would be best
 for your needs, it can be a totally reasonable choice.

 Now, some people may be tempted by one-maker 'component sets',
 particularly the modern, miniature ones.  They tend to be
 equivalent to combos.  Most use non-standard connections, rather
 than the normal twin phono plug, so that it's likely you can't
 swap or add components anyway.  Even where they use standard
 interconnects, they may rely on non-standard interconnections
 for control purposes.  In a few cases, they also rely on sharing
 power, with a power supply in only one of the boxes and the rest
 taking low-voltage connections from that.  And, no one maker
 makes the best everything.  By default, assume that they will
 have the same disadvantages (and most of the same advantages) as
 combos.  If it's important for it to work with "standard"
 components from other makers, be sure to ask before you buy.

 And, if you're in doubt, go for separate components.

12.6 How can I get better FM radio reception?
 A. Use a (better) antenna. (See 12.7 and 12.8 below)
 B. Use a (more) directional antenna. (See 12.7 and 12.8 below)
 C. Aim your directional antenna.  Rhombics are ungainly to move,
  but Yagis and dipoles are small enough to point right at
  the station.  With the dipole, to tune in a station to
  the East, run the antenna North-South.  With a Yagi,
  point the individual elements North-South with the
  smallest element on the East end.

12.7 How good are these compact FM antennas?
 For receiving, small is ugly.  The bigger the antenna (all else
 equal) the better.  Of course, all else is never equal, but
 these fancy, expensive mini antennas tend to be awful.  Some
 compensate for their small receiving structure with a small
 antenna signal amplifier.  However, the quality of that
 amplifier is often no better than the quality of the amplifier
 in your tuner or receiver, so the antenna just gives you a
 stronger signal, complete with stronger noise.

 All of that said, some compact FM antennas can work better than
 a simple dipole in some situations.  They tend to have an
 internal amplifier, which helps with weak signals.  Some are
 directional.  Some aren't.  If possible, be sure that whatever
 you buy can be returned for a refund if it doesn't work out well
 for you.

12.8 What makes the best FM radio antenna?
 Although there is no "best" antenna for everyone, one of the
 most directional is the "rhombic".  Being very directional, this
 antenna can select one weak station out of many strong ones, or
 one group of stations originating from a general direction.
 This antenna is very long, and made up of four pieces of wire
 with feedline at one end for antenna connections and a resistor
 at the other for termination.  Rhombics for FM broadcast band
 use are at least 15 feet (4.5 meters) long, but can be made
 fairly narrow, less than 3 feet (1 meter) wide.  A more narrow
 antenna will be more directional. A longer antenna will give a
 stronger signal.

 Another very directional antenna is the "yagi", which looks just
 like a common TV antenna.  You can even use a common TV antenna
 as a very good FM antenna.  The FM and TV bands are very close
 together.  It has the advantages of being cheap, directional,
 and easy to rotate.

 One of the simplest and easiest to make antennas is the folded
 dipole, made from 300 ohm twin lead.  It is approx. 58" long.
 This antenna is surprisingly good for receiving signals in a
 moderately strong signal area.  Folded dipoles come with many
 tuners and receivers as a standard accessory.  They are also
 available for approximately $2 at audio and department stores.

 Whatever antenna you have, you can often get it to work better
 for specific stations by moving it.  In the case of the folded
 dipole, sometimes it works better vertically, and other times it
 works best horizontally.  Sometimes, you can get that one
 elusive station to come in perfectly if you bend the two ends of
 it at funny angles.  Don't be afraid to experiment.  One
 warning.  As atmospheric conditions change, the best antenna
 placement may also change.

 An excellent reference book on antennas is printed by the
 American Radio Relay League (ARRL).  It is called The ARRL
 Antenna Book.  Currently in its 16th edition, it is a 736
 page large, illustrated paperback.  It costs $20 plus s/h.
 It has fairly complete antenna theory, practical information
 such as charts, drawings, comparisons, and tips on construction
 and adjustment.  The ARRL is founded and chartered as a
 non-profit organization to better amateur radio, and antennas
 are a vital part of amateur radio.
  American Radio Relay League
  225 Main Street
  Newington CT 06111 USA
  203-666-1541

 Also useful:
  Practical Antenna Handbook by Joseph J. Carr
  Tab Books #3270/McGraw Hill - ISBN 0-8306-3270-3

12.9 What about power line conditioners?
 Each home and each outlet has slightly different power line
 impedance and power line noise.  Each amplifier is effected by
 power line impedance and power line noise differently.  Power
 line conditioners try to reduce this line noise.  Some also
 change the power line impedance in a way which is supposed to be
 better.  We will leave it to your ears to decide if these
 devices help the sound of your system enough to justify their
 expense.

12.10 How can I reduce vibration sensitivity?

12.11 What equipment can I buy that is 100% made in the USA?
 There are many lines of equipment that are carefully hand
 crafted in the USA.  Unfortunately, these systems are usually
 the high-end ones.  Some US companies also make gear in the
 far east. When in doubt, ask. Some US audio manufacturers are:
  Adcom (some made in Japan)
  Audio by Van Alstine
  Audio Research
  California Audio Labs (CAL)
  Carver (some made in Japan)
  Jeff Rowland
  Krell
  Mark Levinson
  McCormack
  McIntosh
  Parasound
  Proceed
  PS Audio
  Spectral
  Waida

13.0 Listening Rooms and Houses

13.1 How should I place speakers in my room?  What size room is best?
 You are after two important, distinct goals: flat frequency
 response and good three-dimensional image.  At your disposal is
 the room size, the room shape, speaker height, speaker
 placement, listening position, and room treatments.  Even though
 good speakers are essential to good sound, room effects are also
 extremely important.  In many cases, the differences in room
 effects will be more noticeable than spending twice as much on
 speakers!

 For smoothest bass response, a listening room should be as large
 as possible, have dimensions as unrelated as possible, and
 should be optimally damped.  Although nothing is ever ideal,
 there are a few room dimension ratios that are better for
 listening rooms:
  Height  Width  Length
  1  1.14  1.39
  1  1.28  1.54
  1  1.6  2.33
 If your room isn't shaped like that, don't worry.  These
 effects are not major.

 Also for smooth bass response, woofers should be at distances
 from the nearest three room boundaries that are as different as
 possible.  In some cases, the line dividing the listening room
 into left and right halves must be considered a room boundary.
 Also, for smooth bass response, the listener's ears should be
 at distances from the nearest three room boundaries that are
 as different as possible.

 All of this is essential because a wall near a speaker boosts
 the bass from that speaker at some frequencies.  If a speaker
 is the same distance from three walls, then some frequencies
 will be emphasized much more than others, rather than slightly
 more.

 For best three-dimensional image, a listening room should have
 good symmetry about the plane between the two speakers.  This
 means that if one speaker is in a corner, the other speaker
 must be in a corner.  If this symmetry is not right, the first
 reflection from the wall behind one speaker will be different
 from the first reflection from the wall behind the other speaker
 and critical parts of the stereo signal will be damaged.

 Also, no large object should block the path from speakers to
 listener or from speaker to speaker.  Speakers should be
 elevated so that tweeters are at listener ear height.  The
 distance between speakers should be no greater than the distance
 from each speaker to the listener.  Finally, the tweeters should
 be aimed at the listeners.

 A normal box-shaped listening room with bare walls will have
 "slap echo" which will reduce intelligibility.  A good cure is
 randomly-placed wall hangings consisting of small rugs spaced
 an inch or so away from the wall to increase sound absorption.
 Another cure is convex-shaped art objects on the walls to
 disperse harmful reflections.  If money is available, commercial
 room treatments such as "Tube Traps" and "RPG Diffusers" are
 also valuable, but many of the benefits of these exotic devices
 are available with simpler techniques.

 As a general rule, in a good room, speakers and listener can be
 close to room boundaries with minimal adverse effects.  In a bad
 room, a good strategy is to place both speakers and listener as
 far away from room boundaries as possible.

 An excellent starting point for speaker placement is to measure
 the listening room diagonal dimensions.  Divide that measurement
 by three.  Put each speaker that distance from a corner, on the
 room diagonals.

  I-----------------------------------I
  I                                   I
  I                 L                 I
  I                                   I
  I        S                 S        I
  I                                   I
  I-----------------------------------I

 Place your listening position midway between the two speakers
 and approximately half way from the speakers to the wall.  Be
 sure that there is nothing in the "triangle" formed by the
 listening position and the speakers.

 Try this and then move things 12" (30cm) at a time to see if
 you can improve the sound.  Your ears will be a better guide
 than any commonly-available instruments.  To keep track of
 what you are doing, take notes.  To remember exactly where
 you put the speaker on the floor, a practical trick is to
 mark the floor with a sewing needle and thread.

13.2 How do I wire a house for sound?
 A fundamental principle of physics is that the farther a signal
 travels, the more the signal will be degraded.  Translate this
 to mean that the shorter the wire, the better.  Understanding
 this, the idea of running speaker cable between  every room of
 the house isn't as attractive as it first seems.

 If you still decide to wire your house for sound, you should do
 it at the same time you're wiring for telephone and electricity.
 It is possible to wire a house after the walls are closed, but
 it becomes very difficult.

 It is economical to use common house wire (Romex, UF, NM, etc)
 for speaker wire in the walls, but this may violate building
 codes.  Check with an electrician or inspector first.  It will
 also confuse future electricians, so label the wire clearly, all
 along its length.

 If you want to make your house like a recording studio, it is
 best to use the techniques of recording studios.  When studios
 run long lengths of sound cable from one room to another, they
 drive the cable with 600 ohm line amplifiers.  They also use
 shielded, twisted-pair cable.  They only connect the shield at
 one end of the cable.  Finally, they use balanced inputs at the
 other end of the cable.

13.3 Where can I read more about listening room construction and tuning?
 "Building a Recording Studio" by Jeff Cooper
  Mix Bookshelf
 "Handbook for Sound Engineers"
 "The Master Handbook of Acoustics" by F Alton Everest
 "Sound Engineering 2nd Edition" by Don and Carolyn Davis;
  Howard W. Sams & Co. (C) 1990
 "Good Sound" by Laura Dearborn
  Introductory, but clear and accurate
 "Sound Recording Handbook" by John M. Woram
  Howard W. Sams & Co. #22583
  Excellent General Reference
 "Audio Technology Fundamentals" by Alan A. Cohen
  Howard W. Sams & Co. #22678
  Overview of Audio Theory
 "Introduction to Professional Recording Techniques"
  by Bruce Bartlett
  Howard W. Sams & Co. #22574
 "Modern Recording Techniques" by Hubar and Runstein
  Howard W. Sams & Co. #22682
 "Sound Studio Production Techniques"
  by Dennis N. Nardantonio
  Tab Books

14.0 Recording
 There are more different recording systems available today than
 ever before.  Digital and analog are both available to the
 consumer.  With the advent of consumer digital recorders, used
 pro analog recorders are becoming available for surprisingly low
 prices.  Now may be the time for you to buy a microphone and
 recorder and make your first!

14.1 What is DAT?  What is its status today?
 DAT (Digital Audio Tape) is currently the standard professional
 digital format for 2-track digital recording.  DAT had a
 short-lived consumer presence, but never "made it".  As digital
 recorders have no tolerance for clipping, using a DAT recorder
 takes a slightly different knack.  The results can be worth it,
 however, as DAT format offers the same resolution and dynamic
 range as CDs.  DATs record for up to 2 hours on a tape, and can
 run at three different sampling rates:  32 kHz, 44.1 kHz
 (for CD), and 48 kHz (the DAT standard).

14.2 What is DCC?  What is its status today?
 DCC is Philips' attempt to modernize the regular cassette.  DCC
 decks can play analog cassettes, and can record new Digital
 Compact Cassettes.  They use stationary heads (DATs use rotary
 heads as do VCR's), and although they are digital, they use
 lossy compression to fit all the data on the cassette.  Although
 DCC sound quality is far better than the 1960 standard cassette,
 the DCC does not have the sound quality present in DAT or CD.
 DCC may be a good choice for consumers who want to assemble mix
 tapes for cars or walkmans, but is not suitable for any
 professional applications.  As of December 1992, DCC is very
 new, DCC equipment is very expensive, and the ultimate future of
 DCC is not assured.

14.3 What about writable compact discs?  What is the status today?
 Recordable CD's are available, but are very expensive.  Blank
 discs sell for approximately $35 each, and the recorders start
 at around $6,000.  These units are mostly used by recording
 studios and other audio professionals.

14.4 What is the best cassette deck under $200?

14.5 What is the best cassette deck under $400?

14.6 What is PASC?  Can I hear the effects?
 PASC (Perceptual Audio Sub-band Coding) is a data-compression
 algorithm.  It increases the length of recording that can be
 stored in a given number of data bits by eliminating sounds that
 the developers' research claims can not be perceived by human
 listeners.  Its most important component is the omission of
 quiet sounds that occur at the same time and near the frequency
 of louder sounds.  It provides up to a 4x increase in the length
 of recordings a given digital medium can hold; this is essential
 to allow full-length digital recordings on DCC (and on MD, which
 uses a different compression technique).  It is not necessary
 to translate CD data to analog before compressing it using PASC,
 nor the reverse, but today's DCC decks do not have digital
 inputs or outputs.

 You CAN hear PASC, but it is very difficult, since it is not
 a distinctive noise (like a hiss) nor a consistent diminution
 (like a notch in a speaker's response), but a broad,
 uncorrelated dropout in a changing collection of sounds that
 are masked by sounds that you can hear very easily.

 Since it is lossy, repeated PASC recording will cause
 progressive loss, and this signal damage may become easily
 noticeable.  This is a side effect that recording companies
 hope will have the effect of discouraging piracy via DCC.

14.7 What is SCMS?  Can I hear the effects?
 SCMS (Serial Copy Management System) is a copy-protection system
 intended to stop rampant piracy of commercial recordings to
 digital tape.  SCMS allows the home taper to copy from a CD to a
 digital tape, but prevents anyone from digitally copying that
 new digital tape.

 You CANNOT hear SCMS.

14.8 How can I bypass SCMS?
 There are professional devices used by engineers to manipulate
 the digital bitstream, but they cost several hundred dollars and
 are not cost effective for consumers.  If you need to make
 perfect digital copies of digital copies, buy a professional
 digital recorder.  Pro models do not have SCMS, are more durable
 than consumer recorders, and may have better quality electronics
 than consumer models.

14.9 What's this about a tax on DAT?
 Every digital audio tape recorder and every blank digital tape
 sold in the USA is priced to include a "premium" or "tax".  This
 tax is collected by the US Copyright Office and distributed to
 the recording artists and record companies that own the
 copyrights to commercial music.  These fees are supposed to
 repay them for lost royalties.

 Many believe that this "tax" is illegal, because it represents
 an assumption that the buyer will use the recorder and tape to
 violate a copyright, and not to record their own works.  A
 founding principle of the USA legal system is that everyone is
 assumed innocent until proven guilty.

 If you believe that this law is unjust, write your elected
 representatives.

14.10 Is it legal to copy an LP, CD, or pre-recorded tape?
 In the US today, it may be legal to copy LP's, CD's, etc. for
 your own private use (such as to copy a CD to play on your
 walkman).  UK law specifically prohibits this, but it is almost
 never enforced.  It is definitely not legal in the US, UK, or
 almost anywhere else, to copy these sources for commercial
 purposes, or to give the copies to others.

 It is as of yet unclear whether you own the rights to sell
 or give away a copy of a recording if you made the copy on media
 which was sold with an included digital audio tax.

14.11 How do I clean and demagnetize tape heads?
 First, a caution: DAT recorder tape heads are VERY fragile.
 Before cleaning the heads on a DAT recorder, get specific
 recommendations from a very knowledgeable source that is
 intimately familiar with DAT head cleaning.  In the internet,
 a good source is the DAT-Heads-Digest FAQ.  For more information
 on DAT-Heads-Digest, see section 20.2, below.

 To clean tape heads, use pure isopropyl alcohol and lint-free
 swabs.  Wipe the metal parts of the transport with alcohol
 (DON'T wipe the rollers!) and allow them to dry.  Throw the swab
 away after use.  Be exceedingly careful when cleaning the heads
 on a DAT.  DAT heads are notoriously easy to misalign by
 incorrect cleaning.

 Practical tape head demagnetizers are available for under $10.
 Try to find one with a plastic coated tip.  If you can't find
 one which is plastic coated. you can slip a drinking straw or
 plastic tube over the tip for the same effect.  This plastic
 will prevent the demagnetizer from scratching the head.

 Before plugging in the demagnetizer, remove all tapes from your
 working area and unplug the recorder.  Hold the demagnetizer
 away from the recorder as you plug it in.  Slowly bring the tip
 of the demagnetizer up to the tape head and slide it back and
 forth across each tape head for five one-second strokes.  Then
 pull it away from the head slowly and go on to the next.  After
 demagnetizing the heads, use the tip on each metal tape guide
 with a similar five strokes.  Last, slowly pull the demagnetizer
 far away from the recorder and unplug it.  Recording engineers
 use a demagnetizer before each recording session.

14.12 How do I adjust a tape recorder for best results?
 Adjusting a tape machine for best results usually requires
 special equipment and test tapes.  Unless you know what you're
 doing, leave it for a pro.  If you are serious about doing it,
 buy the service manual for your particular tape recorder.  It
 will list a detailed procedure, as well as describe the correct
 test tape and tools.

 As for setting of record levels, it is best to experiment with
 different levels on different tape brands.  Different
 formulation will reach saturation for different levels.
 Generally speaking, the transients on a Chrome tape should peak
 at about +6 dB above 0, though some formulations can take
 significantly hotter signals.

14.13 Where can I get new pinch rollers or drive belts?
  Projector-Recorder Belt Company
  Whitewater WI USA
  800-558-9572

14.14 What is a good rubber (pinch) roller cleaner?
 Teac RC-1 available from
  J&R Music World
  59-50 Queens-Midtown Expressway
  Maspeth NY 11378-9896 USA
  800-221-8180 or 718-417-3737
 Tascam Rubber Cleaner RC-2 available from:
  Tape Warehouse
  Chamblee GA
  1-404-458-1679

14.15 How can I program a recorder to tape a radio broadcast?
 Radio Shack and Panasonic make a clock/radio/cassette that can
 be set to record at a specific time.  Radio Shack also sells 120
 minute cassettes, which can be used for 60 minutes per side.
 The recorders are not high quality, and the long tapes are
 fragile, but it works.

 You can buy "appliance timers" at hardware stores that will
 start and stop an appliance at a specific time.  Radio Shack
 sells fancier versions of the same thing for more money. Gadget
 freaks love "X-10" control systems.  These can be configured to
 do the same thing.  All require a recorder that can be left in
 RECORD mode.  Such recorders are identified by a "TIMER" switch
 on the front panel.  Many cassette decks have a TIMER switch for
 use with timers.

 Memorex sells a "CP-8 Universal Remote" with a built-in timer.
 Available for approximately $90.00 from either:
  Crutchfield
  1 Crutchfield Park
  Charlottesville VA  22906 USA
  800-955-3000 or 804-973-1811
   or
  J&R Music World
  59-50 Queens-Midtown Expressway
  Maspeth NY 11378-9896 USA
  800-221-8180 or 718-417-3737

 This can be set to start a recorder at a particular time.  As
 the recorder will be started from a remote control rather than
 by the power line voltage, no timer switch is required. Radio
 Shack has a very similar product available for $99.95, may be
 less on sale.

 Damark also sells a learning remote with a built in on/off
 timer and sleep timer. It can learn 17 commands per device on a
 total of 5 devices and should be great for taping a few shows.
 They also sell a 8 device remote with timer.  As Damark sells
 close-outs, these items may not be available in the future.
  Damark
  7101 Winnetka Avenue North
  PO Box 29900
  Minneapolis MN  55429-0900 USA
  800-729-9000 or 612-531-0066

 Use a VCR for audio-only recording.  Hook the audio in to the
 output of a radio, tuner, or receiver.  You may also have to
 connect some video signal to the VCR so that the sync circuits
 work correctly.

14.16 Will CrO2 or Metal tapes damage a deck made for normal tape?
 No.  They will work fine.  They are no more abrasive than common
 tape and may actually be less abrasive than very cheap tapes.
 Recorders which are designed for CrO2 or Metal tape have
 different bias settings and equalization settings to take best
 advantage of the greater headroom and to give flat response with
 these different types of tape.  However, they use similar if not
 identical heads as less expensive tape recorders.  Almost all
 tapes are in some way lubricated, and these lubricants minimize
 wear and squeaking.

14.17 Why do my old tapes squeak in my car cassette deck?
 One problem that will cause this is "binder ooze".  The binder
 is the glue which holds the oxide particles to the backing.
 With time, this binder can ooze forward and actually get past
 the oxide particles, so that there is sticky stuff on the
 surface of the tape.  When this sticky stuff goes past the
 heads, it can cause a slight stick, which will sound like a
 squeak.  You won't feel it with your fingers, but it is there.
 If you have a prized tape with this problem, consider baking
 the tape in a home oven at a very low temperature, like 150F.
 This might cure the problem by drying out the binder.

14.18 Is VHS Hi-Fi sound perfect?  Is Beta Hi-Fi sound perfect?
 The HiFi recording format is subject to two different problems:
 Head-switching noise and compression errors.

 To get perfect reproduction, the FM subcarrier waveform being
 played back by one audio head must perfectly match the waveform
 from the other head at the point of head switching if a glitch
 is to be avoided.  If you record and then play the tape on the
 same VCR under exactly the same conditions, you have a
 reasonable chance of this working.  But if the tape stretches
 just a bit, or you play it on another VCR whose heads are not in
 exactly the same position, or the tracking is off, the waveforms
 will no longer match exactly, and you will get a glitch in the
 recovered waveform every time the heads switch.  This sounds
 like a 60 Hz buzz in the audio, which is often audible through
 headphones even if not through speakers.

 The same glitch will occur in the video waveform too, but since
 head switching always happens during vertical retrace, you won't
 see it.

 The wonderful signal to noise ratio of VHS HiFi is achieved
 through the use of compression before recording and expansion
 after playback.  The actual signal to noise ratio of the tape
 itself is about 35 dB and a 2.5:1 compressor is used to
 "squeeze" things to fit.  Like all companders, this produces
 audible errors at certain places on certain signals, such as
 noise "tails" immediately after the end of particularly loud
 passages.

 Worse, compressors often have problems simply getting levels
 right.  That is, if you record a series of tones, starting at
 -90 dB and working up in 1 dB increments to 0 dB, and then play
 them back, you will almost invariably have level errors.  The
 trend from soft to loud will be there but the steps won't be
 accurate.  Two or three of your tones might come out at
 essentially the same level, then the next one takes a big jump
 to catch up or even overshoot.

 For music, the result will be that the relative levels of some
 instruments, passages, etc. will not be accurate.

 This doesn't matter as much for movies, which tend to have
 steady volume level.  Also, movie enjoyment is rarely hurt by
 these level errors.  VHS and Beta HiFi is fine for reproduction
 of movie and tv soundtracks.  They are also perfectly fine for
 non-critical audio applications.  But VHS and Beta HiFi are not
 serious competitors to DAT, CD, open-reel analog tape, or even a
 high quality cassette deck.

14.19 How do HiFi VCRs compare to cassette recorders?  DAT recorders?
 VHS HiFi and Beta HiFi are analog recording formats which use
 modulation techniques to record a video signal and a stereo
 audio signal on a videocassette.  The audio capabilities
 typically surpass that of the "linear" audio tracks found on all
 video recorders, thus the "HiFi" designation.  "HiFi" is
 essential for getting good sound quality on your video
 recordings and out of pre-recorded videos.

 HiFi is also touted as an excellent audio recorder for
 audio-only (no picture) applications.  On paper, the
 specifications are typically superior to analog cassette but
 inferior to DAT.  In reality, the quality of HiFi video
 recorders is better than low quality cassette recorders but not
 as good as high quality cassette recorders when they are used
 with noise reduction systems.  In no case can a HiFi video
 recorder compare to DAT.  It suffers from generational loss and
 audible noise.

 Many people use VHS HiFi for recording radio broadcasts, since
 VCRs often have built-in timers and can record for up to 9
 hours.  If you use a HiFi video recorder to record from an
 audio-only source, beware that some decks will not function
 properly without a video signal for synchronization.  If you are
 interested in very good quality sound, use a deck with manual
 level control.

14.20 What is the difference between VHS HiFi and Beta HiFi?
 VHS HiFi uses "depth modulation"; Beta HiFi uses "frequency
 modulation".

14.21 Is there any good reason to buy a HiFi VCR for common TV shows?
 If you do not own a stereo TV, the purchase of a HiFi VCR will
 give you the capability to listen to stereo TV broadcasts to
 your system.

14.22 What is the best cassette tape?
 One simple answer to this question is that the best tape is the
 tape which was used to align your tape recorder.  A second
 simple answer is that more expensive tapes are frequently
 better in terms of quality of the backing, durability of the
 oxide, accuracy of the shell and guides, and life.

 Background: When you make a tape recorder, you build electronic
 circuits which have specific, non-flat frequency response.
 These circuits correct for the non-flat response of the tape
 heads, the recording process, and the tape.  These circuits can
 be adjusted after the recorder is made, but adjustment is
 tricky, and may or may not be successful with every tape made.
 The designer of the tape recorder picked one tape as their
 standard when they did the design, and built that recorder
 to work well with that particular tape.  It may work better
 with a different tape, but it won't necessarily sound the
 best with what one person calls the best sounding tape.

 From a review of frequently given answers to this question,
 it is obvious that almost every brand of tape has its advocates.
 Many brands also have their detractors.  Maxell and TDK tend to
 have a strong following, but that is in part because they own a
 large share of the US tape distribution market.

14.23 What is the best Reel-to-Reel tape?
 See 14.22.  Just as cassette tape recorders are set up
 specifically for one type of tape, reel-to-reel tape recorders
 are equalized and biased so that they are best with one specific
 brand and model of tape.  Just as more expensive cassette tapes
 will last longer and have less noise than cheaper ones, you can
 expect fewer dropouts, better quality control, and lower noise
 from more expensive reel-to-reel tapes.

 The major brands in reel-to-reel tape include Ampex, Scotch
 (3M), AGFA/BASF, and Maxell.

14.24 What is Type I, Type II, Type III, and Type IV cassette tape?

15.0 Mail Order
 Mail order is appealing.  The general hope is that by using mail
 order, you avoid pushy sales people, you pay fixed, discounted
 prices, and you have written catalog descriptions to help you
 select your purchase.  In practice, most mail order today is
 "phone order", in that the company completes the deal with a
 phone call.  Many of the "mail order" companies don't even have
 price lists or catalogs.  They are just retailers that are
 willing to sell over the phone and ship the merchandise to
 you.  In some cases, retail store sales are better deals than
 mail order.  Don't expect the lowest price from the first place
 you call.  Also, don't expect excellent service from everyone,
 and especially not from the company with the lowest price.

15.1 Who sells brand XXX equipment mail-order?
 Consult the frequent rec.audio mail-order survey published by
 [e-mail] (William R. Nau) or contact William Nau directly.
 This survey is also available via FTP in the pub/rec.audio
 directory of SSESCO.com.  If you have any mail order
 experiences to share, please send them directly to William Nau.

15.2 Is the stuff sold by DAK really awesome?  Damark?
 DAK buys in large quantities.  They buy what they think
 they can sell.  They buy close-outs as well as new first-line
 merchandise.  They honestly represent their merchandise with
 specifications.  They offer more information on their product,
 if possible, on the phone through their toll free number.
 I know of many people who have bought from DAK and been
 happy. I personally have bought from DAK and been happy.

 Regarding Damark, opinions of people on the net are similar.
 The products are as described, they deliver what they
 say they will, and will take back or replace unsatisfactory
 merchandise.  I have not heard any unsatisfied Damark customers.

 On the other side, the catalog writers at DAK use some very
 flowery language which is intended to lead you to believe
 that they are selling gold for copper prices. In this sense,
 the words in their catalog may be deceptive.

 The DAK people have a good sense of "what the market will bear".
 They price their products to sell, but not to give away money.
 Mail order prices tend to be 10% to 20% less than discount,
 which is 10% to 20% less than retail. DAK has to compete with
 other mail order dealers, such as Damark, but they send out SO
 MANY CATALOGS that they really don't have to cut prices too far
 to sell.

 DAK has recently gone through hard financial times.  This puts
 buyers in some slight risk, because if they go out of business,
 you may get easy warranty service on their products.  I say
 easy because most DAK products are covered by a manufacturer's
 warranty, and you can often get service from the manufacturer
 as well as from DAK.  I believe that DAK is over their slump,
 but I am not sure.  For more on warranties, see 19.1, below.

15.3 Is the stuff sold by Cambridge Sound Works really awesome?

15.4 What should I watch out for when buying mail order?
 Many of the cautions mentioned in warranties (19.1) apply.
 Look for a store which has been around a long time. Look for
 friends which have dealt with the store and been satisfied.
 Look for a store which does not lie or stretch the truth.

15.5 What is gray market?
 See warranties (19.1), below.

15.6 Are there any good mail-order sources for recordings?
 Noteworthy has a good reputation among net readers as a supplier
 of CDs.  They have a range of discs available centered firmly on
 the mainstream, and are reasonable in price.  Shipping is $3.75
 for 1-5 CDs.  They offer over 14,000 different CD titles.  Their
 offerings are all from US labels.  They give a free catalog and
 also have modem software and catalog on floppy discs for $9.95.
  Noteworthy Music, Inc
  17 Airport Road
  Nashua NH  03063 USA
  800-648-7972 Voice
  603-881-5729 Voice
  603-883-9220 FAX

 BMG and Columbia also sell CDs mail-order, but have a smaller
 list of offerings and higher prices. However, BMG and Columbia
 have interesting deals to entice new customers.  Read the fine
 print before you sign to be sure that they are right for you.
 BMG and Columbia both have promotional offerings to "members"
 which allow you to buy two or three discs for the price
 of one.  These can be very good deals, if you want what they
 have.  Look at their advertisements in common magazines and
 Sunday newspapers for a better idea of what they carry.  They
 list much of their line in their ad.  Don't expect much more.

 Bose Express also sells CDs.  Their reputation so far is very
 knowledgeable people, a large collection, and high prices.
 Their catalog costs $6.00.
  Bose Express Music
  The Mountain
  Framingham MA  01701 USA
  800-451-2673 or 508-879-1916 Ext. 2008

 Tower Records has a mail order department which also sells CDs.
 Their classical catalog costs $13.45.  Their other catalog costs
 $10.45.  Tower is a large retail chain.  Many have bought from
 their retail outlets happily, but no one has expressed any
 comments on their mail order service yet.  Contact:
  Tower Records Mail Order Department
  692 Broadway
  New York City, NY 10012  USA
  800-648-4844 or 800-522-5445

 Another source is Music New Hampshire; 800-234-8458.  They sell
 many $3.79 post-paid sampler CDs and also many independent label
 single-artist discs.  Most single artist discs are $15.00 each.
 Shipping is $3 for 1-3 discs and $5 for 4-up.  Their stuff is
 mostly obscure artists.  They have Rock, Jazz, Classical, Folk,
 Country, and Children's offerings.  Affiliated with CD Review.
  Music New Hampshire - Wayne Green Inc
  70 Route 202N
  Peterborough NH  03458-1107 USA

 If you like the idea of buying CDs by Modem, consider
  The Compact Disc Connection
  1016 East El Camino #322
  Sunnyvale CA  94087 USA
  Voice 408-733-0801
  Modem 212-532-4045 New York City NY
   312-477-3518 Chicago IL
   408-730-9015 Sunnyvale CA
   510-843-1259 Berkeley CA
 They have a collection of over 58,000 CD titles.  People have
 said that their service is excellent.  Prices are fairly good.
 Shipping is $3.50 for orders under $100.00 and free for larger
 orders.  They do not stock anything, but deliver from the
 warehouses of their suppliers.  This means that some items may
 be back ordered or completely discontinued while remaining in
 their on-line data base.  They advertise 94.2% of orders in
 1992 shipped, though not necessarily immediately.  If you have
 a modem and enjoy browsing a data base, their data base is a
 a very enjoyable experience.  However, the phone bill can be
 quite prohibitive to those calling from out-of-town.

 There have been a couple of music (cd/lp) mail-order lists
 compiled on the net - one older list can be found via anonymous
 ftp to ftp.uwp.edu in the file: /pub/music/misc.mailorder.rmm
 Someone is revising this file and it should be updated or found
 in a new file name there in the future.

 Another list contains vendors that specialize in progressive
 rock, electronic and experimental music, is maintained by
 Malcolm Humes and posted sporadically to alt.music.progressive,
 rec.music.misc, & rec.music.info.  This also can be ftp'd from
 ft.uwp.edu, in the file: /pub/music/misc/mailorder.progressive

 Federal Music and Video markets "Discount Coupon Books"
 featuring two-for-one CDs and Tape deals.  They require payment
 with the order, which many consider risky.  One company that
 distributes these coupon books for Federal Music is Reed Music.
 The price from Federal or Reed Music with the two-for-one deal
 is comparable to the price from Noteworthy.  So far, no net
 user has yet related any positive or negative experience with
 Reed Music or Federal Music and Video.  Federal Music and Video
 has been in business since 1985, so is probably legit. However,
 in that they require payment in advance it is probably safer to
 avoid them completely and use a discounter like Noteworthy.

 When considering mail purchases of CDs, consider shipping costs.
 It is common for people to charge between $1 and $3 per disk for
 "shipping and handling".  This makes mail order less attractive,
 but may be equally balanced by a lack of sales tax.
--
Bob Neidorff; Unitrode I. C. Corp.  |  Internet: [e-mail]
7 Continental Blvd.                 |  Voice   : (US) 603-424-2410
Merrimack, NH  03054-0399 USA       |  FAX     : (US) 603-424-3460
Archive-name: AudioFAQ/part4
Last-modified: 1993/6/4
Version: 1.5

16.0 Wire
 More than any other topic, speaker cables and equipment
 interconnects seem to use up rec.audio bandwidth echoing the
 same theoretical arguments, testimonials, and opinions.
 Controversy can be stimulating, educational, and also amusing.
 Please try to keep postings aimed at one of those three goals,
 and avoid the insults and emotion.  Also, try to avoid
 echoing a common position or principle, as described below.

16.1 Do speaker cables matter?
 To avoid confusion and repetition, here is some terminology.
 Cables are connectors attached to wires. Wires generally
 have multiple conductors optionally surrounded by a shield and
 outer insulating covering. Cables can introduce noise into the
 signal, act as a filter (and thus change the frequency response
 of the system), and provide nonlinearities from improper
 (intermittent/loose) connections to or between the connectors.

 It is quite scientifically conceivable that some cables do
 cause a difference in sound, because of the differences in DC
 resistance, interconductor capacitance, and connector attachment
 alone.  The effects of exotic conductor weaving and materials
 are not so well established.  In general, these effects (once
 we eliminate DC resistance), seem to be small. However, if your
 system is at least fairly good, then some folks have observed
 (although not in an experimental, double-blind sense)
 significant differences in system performance with different
 cables. The effects are said to be quite system specific; the
 only real guideline is to try them and see which ones seem to
 sound better in your system.

 Roughly speaking, the price ranges for speaker cables is low
 (under $1/ft), medium (under $6-8/ft), and high (up to $100/ft
 and more). Try to arrange it so you can trial such cables; at
 several hundred dollars per set, experiments can be expensive.

 In any system or experiment, it is essential that the
 differences between cables be separated from the
 differences between connectors.

 You should have an EXTREMELY solid connection between cable and
 speaker.  Speakers operate at very low impedances, so that bad
 connections will create significant artifacts or signal losses
 at any power level.  For example, if the connection has a linear
 resistance of just 1 ohm, the speaker damping factor will be
 dramatically reduced, making bass muddy.  If the connection
 contains imperfect metal oxides, then a slightly rectifying
 junction will block the signal, producing compression,
 distortion, and other non-linear effects.

16.2 What speaker cables are available and how good are they?
 There is a wide range of speaker wire available, ranging from
 30ga zip cord (~$.10/ft) to exotic wires costing over $300/ft.
 The material used ranges from copper to oxygen-free copper
 (OFC) to silver. (There are a bunch of others as well.)

 Oxygen-free copper is probably NOT any different from common
 copper in sound.  If you hear a difference between two cables,
 it is not a difference between oxygen-free and common copper.

 Resistance may be significant for speaker cables.  The higher
 the resistance, the more the cable will affect the sound, all
 else equal.  The resistance characteristic of metals is called
 resistivity.  The resistivity of copper is 1.7 microohm-cm.
 Silver is very slightly lower, 1.6.  Gold is a bit higher, 2.4.

 Silver and gold are different from copper in other ways than
 resistivity.  Gold does not oxidize in normal environments,
 so gold contacts will not need periodic cleaning and will not
 create rectifying junctions.  Silver will oxidize, but the
 oxide of silver is conductive, so oxidized silver will still
 make good contact.  Copper oxide is a bad conductor.  Oxidized
 copper contacts may insulate, may conduct, or may rectify.
 Copper is a bad material for cable terminals, but this may or
 may not mean anything for the conductor itself.

16.3 What can I use for budget speaker cables?
 First, a few words on terminology.  Wire is sized by AWG or BS
 gauge number.  Larger numbers represent smaller wire.  AWG 40
 (also called 40 gauge) is as fine as human hair.  AWG 12 is 2mm
 or .081" diameter.  Some wire is classified as solid, because it
 contains one strand per conductor.  Other wire is called
 stranded, because it consists of many strands per conductor.
 Stranded wire is far more flexible than solid wire.  Most wire
 is made from drawn copper.  Some wire is sold that is claimed to
 be made with a process that produces oxygen-free copper.
 Oxygen-free copper has a different metallurgical structure than
 common copper and may or may not conduct current better.

 Some critical listeners have reported excellent sound from large
 diameter solid copper wire, such as home wiring "Romex 12-2".
 At least one expert has said that common 18-gauge solid copper
 hook-up wire sold by Radio Shack also works very well.  Also
 recommended on a budget is Sound King wire, a 12 gauge oxygen
 free copper stranded cable.  This is available from MCM
 Electronics for $.39/ft.

 The scientific literature indicates that small gauge wire
 generally sounds worse than large gauge.  Resistance-related
 effects of the cable can be eliminated by using at least 12
 gauge wire, particularly for long runs.  Of course, shorter
 runs are always preferred, because they come much closer to
 the ideal zero-length wire, with no resistance, no
 capacitance, no inductance, and no change in signal.

16.4 What can I use for budget speaker connectors?
 The worst connectors are push-down, or spring terminals.  Screw
 terminals with solid copper wire are much better.  Gold-plated
 binding posts and gold spade lugs are inexpensive by audiophile
 standards and are extremely stable.  Binding posts with spade
 lugs can be tightened to get a very good mechanical joint, and
 may offer the lowest electrical resistance of any connector.

 Gold plated banana plugs and jacks are very good speaker
 terminals.  Good ones are more expensive than gold spade lugs,
 however, they also provide a bigger area of contact, and are
 more convenient when you must frequently reconfigure the system.
 Banana plugs should be periodically monitored for corrosion and
 loss of spring tension.  Monster offers a banana-plug connector
 with an expanding center pin that forms an even better
 connection than common gold banana plugs.  At approximately $25
 per pair, the Monster banana plugs aren't a budget connector.

 All else equal, connectors with gold surfaces are better than
 connectors with any other surface.  This is for two reasons.
 First, gold is extremely inert, meaning that unless gold is
 exposed to very harsh chemicals or harsh vapors, it will not
 corrode or oxidize.  It will remain a pure, low-resistance
 conductor.  Second, gold is quite soft, so that if a
 gold-plated connector is squeezed between two metal
 surfaces, it will deform slightly to fill scratches and
 voids, giving a very broad, low-resistance contact area.

 Corrosion of connectors is often a problem.  Gold-plated
 terminals and connectors somewhat avoid this problem;
 problems with other connectors can be mitigated by
 unplugging and replugging the connector on a regular basis,
 cleaning the contact areas with a pencil eraser, or by
 using a contact enhancer such as Cramolin or Tweek.  When
 you use a contact enhancer, be very sure to follow the
 directions, and avoid spreading enhancer about your equipment.

16.5 What about interconnects, such as the cable between tuner and amp?
 Line-level interconnects conduct smaller signals than speaker
 cables; the typical signal ranges from -2V to +2V (the CD
 output standard) with currents in the microamps (the
 corresponding values for speaker cables attached to a largish
 power amp might be -70V to +70V and currents of many amps).
 Line-level interconnects can be divided into single-ended (or
 unbalanced), and balanced interconnects.  Home audio is almost
 always single-ended interconnects.

 Single-ended interconnects almost always use a form of the
 RCA connector (or phono plug). RCA plugs form fair to poor
 connections that degrade with time as corrosion works into the
 metal-metal contact and as the spring tension of the connectors
 relax.  Gold-plating reduces the effect of corrosion and locking
 RCA connectors solve most of the mechanical problems.  However,
 these premium phono connectors are rare and expensive.  For
 example, a gold-plated Vampire locking RCA plug costs
 approximately $23/pair.  If RCA connectors weren't a de facto
 standard, we'd recommend against them.

 Unbalanced interconnect wires vary in geometry, material and
 price.  Cheaper wires have a single conductor (normally
 stranded) and a shield and cost $.20-$2/ft. Medium (complexity
 and price) wires have two conductors (often arranged as a
 twisted pair) surrounded by a shield and cost from about
 $3-$20/ft.  Exotic wires have all sorts of geometries and
 materials (such as stranded silver conductors, or ribbon cable
 braided around a core, or in one extreme case, a tube filled
 with mercury!).  Prices may be as high as $200-$300/ft.

 Balanced interconnects have three conductors: two for the signal
 one for ground, and additionally a shield.  The standard
 connector for balanced cable is the ITT/Cannon XLR connector,
 which is quite good mechanically (they lock).  Equivalent
 connectors are also available from Switchcraft, Neutrik, and
 other vendors.  If you have to run cables longer than 12 feet or
 4 meters, the greater noise immunity of balanced interconnects
 is often a good idea. For this reason, balanced connectors are
 standard equipment in professional installations such as
 studios, public address systems, and broadcast stations.  There
 is not much variation in balanced cables.  The three brands
 mentioned above are known to be rugged, high quality and
 moderately priced. Slightly weaker imported connectors are
 available, but they aren't dramatically cheaper.

 For most systems, the most important aspect of a cable are
 the mechanical reliability of the connectors; in particular,
 the joint between connector and wire, and the joint between
 connector and socket. Typically, interconnect cables are
 short.  It is worth getting just the right length; cables
 often come in .5 meter increments.  With quite good systems,
 some people observe differences in sound between various
 interconnects. This is quite system-specific and the same
 advice as given above applies: try several brands.  Most
 good dealers will loan interconnects for home evaluation.

 In cables where the shield does not carry the signal or ground,
 the shield is normally only connected to ground at one end.
 In systems where there are significant differences between
 ground levels on various components, it may make a difference
 which way such cables are connected.  Typically, the end where
 the shield is grounded should be at the source of the signal.
 Often, such cable has arrows on it pointing in the direction of
 the signal flow.  In any case, try both orientations.

 There are many objective reasons why cables might cause
 differences in sound by interacting with the drivers in the
 signal sources as well as by providing non-linear effects in the
 RCA connector.  Most of these effects are again related to
 interconductor capacitance and resistance, and the quality of
 the shielding provided by the "shield" conductor.  In balanced
 cables the quality of the "twisted pair" inside the shield is
 also important.  One might note that a shield protects from only
 capacitively coupled interference, and not from any magnetic
 field interference.  The twisted pair in a balanced line provide
 some magnetic rejection, as does steel conduit.  However, steel
 conduit has other characteristics which make it undesirable for
 audio in general.

16.6 What about Phono Interconnects:
 Phono interconnects are part of the link between a cartridge on
 a turntable and a preamp (or head amp or receiver). They are a
 special case of line-level interconnects because the signal is
 much lower, typically 1 to 50 millivolts.  They are also
 intended to operate into a higher impedance, typically 47K ohms,
 and form part of the capacitive load for the cartridge.

 The low signal levels mean that the shielding of the cable, and
 the presence of a separate drain/shield are more important, as
 is a good ground.  A separate solid ground should come along
 with the cable as a separate lead co-routed with the cable.

 In addition, the low signal levels make a good solid connection
 to and through the connectors MUCH more important, because of
 the greater sensitivity to low-level nonlinearities.

 Wire capacitance is often ignored in line-level interconnects;
 however, in a phono interconnect, it may constitute half of the
 total capacitive load of the cartridge. Obviously, then, two
 cables with significantly different capacitances should sound
 differently.  In this sense, the "right" cable for one cartridge
 may be too low or high in capacitance for another cartridge.

 For low-impedance cartridges (most moving coil cartridges),
 the wire must have low resistance to prevent cartridge unloading
 and frequency-dependent signal loss. In addition, as the
 signal levels are quite low, shielding is important.

 Unfortunately, copper shields do not block stray magnetic
 fields, so in the case of phono cables, careful routing may be
 even more effective at reducing hum than special wire.

16.7 Is there really a difference in digital interconnects?
 There are now three kinds of digital interconnects that connect
 transports to D/A converters: coax, plastic fiber (Toslink) and
 glass fiber (AT&T ST).  In theory, these should sound EXACTLY
 the same (bits are bits).  However, this assumes good circuit
 design (in particular, the clock recovery circuits of the DAC,
 and careful consideration of electronic noise) which may be
 compromised because of cost considerations or ignorance.  Note:
 different signaling schemes are used on plastic and glass fiber.

 In any case, some people claim to hear a difference;
 of those who do, most seem to prefer the glass fiber.
 However, the technology of fast digital data transmission
 in consumer electronics is evolving very quickly now.
 Any specific recommendation should be treated with
 suspicion until the industry matures.

16.8 Can I make very good interconnects myself?
 Yes.  You will need to be the judge of whether or not they
 are as good as $100 interconnects, but it is easy to make
 interconnects that are better than the $2.00 set which comes
 with new equipment.

 There are two necessary ingredients: two-conductor shielded
 cable and RCA connectors.  There is a lot of debate over what
 is the best cable, but in general, the lower the capacitance
 per foot, the better.  Choice of insulation is harder.  There
 may be an advantage to polypropylene or teflon over polyester
 or rubber, but even that is debatable.  If you are buying wire
 from an electronics distributor, some have successfully used
 Belden 1192A microphone cable.  It is rubber insulated, so very
 flexible.  Another recommended cable is Belden 8451.  This is
 a polypropylene cable with foil shield.  Finally, consider
 Belden 89182.  This is foamed teflon insulated, so very low
 capacitance, and foil shielded.  If you plan to make a long
 cable, this low capacitance cable may be the best choice.

 There is also a variety of RCA connectors available.  A
 good connector would be gold plated and machined to tight
 tolerances.  A poorer connector will not fit as well, will
 make poorer contact as the connecting surface oxides, and
 will lose its springiness with use.

 When wiring the cable to the connector, use one wire for
 signal, (the tip of the RCA connector) and one wire for
 ground (the shell or outer conductor of the RCA connector).

 Some cables use a foil shield which is difficult to solder.
 These cables typically have a drain wire parallel to the foil
 which can be used for soldering.  Others use a braided shield.

 Regardless of which type of wire you have, connect the shield
 or the shield drain wire to ground on only ONE SIDE.  This will
 stop noise picked up by the shield from causing ground noise.

 It can be a touchy job soldering RCA connectors.  Before
 you use your new cables, check with an ohmmeter or
 a continuity tester to make sure that you have not
 accidentally sorted the signal and ground leads together,
 either with a stray drop of solder or a loose wire strand.

17.0 The Press

17.1 Which magazine should I read?
 Which ever one you like.  None are absolutely objective.
 Here's a list of some common ones:

  Audio Amateur ($20/yr 4 issues) (Do-it-yourself)
   Box 576
   Peterborough NH  03458 USA
   603-924-9464
  Audio Critic (US $24/yr 4 issues) (High-end)
   PO Box 978
   Quakertown PA  18951 USA
   215-538-9555 or 215-536-8884
  Audio Magazine (US $24/year 12 issues.  Mid-fi)
   Subscription Office: PO Box 53548
   Boulder CO  80321-2548 USA
   800-274-8808, 303-447-9330
   Editorial Office: 1633 Broadway
   New York, NY  10019
   212-767-6000
  Audio Observatory (US $15/year 12 issues)
   22029 Parthenia Street
   West Hills, California  91304
  Audiophile (High-end, High-$$$ Buying Guide,
    Blind reviews)
   Haymarket Trade & Leisure Publications Ltd
   38-42 Hampton Road
   Teddington, Middlesex, TW11 0JE,  UK
   [phone]
   US Inquiries should go to:
    Eric Walter Associates
    Box 188
    Berkeley Hts NJ  07922 USA
    201-665-7811
  Audiophile Voice
   2001 Palmer Ave Suite 201
   Larchmont, NY  10538-2420 USA
  Bound For Sound (US $18/yr 12 issues) (High-end)
   220 North Main St
   Kewanee IL  61443 USA
   309-852-3022
  Car Audio and Electronics ($19.95/year 12 issues)
   Avcom Publishing Ltd
   21700 Oxnard Street
   Suite 1600
   Woodland Hills CA  91367 USA
   818-593-3900
  CD Review (Music Reviews; all tastes, only CDs.)
   $19.97 per year 12 issues
   PO Box 588
   Mount Morris IL  61054 USA
  Glass Audio ($20/yr 4 issues) (Do-it-yourself, tubes)
   Box 576
   Peterborough NH  03458 USA
   603-924-9464
  Hi-Fi Choice (Mid-end. Comparative reviews with graphs,
    tables, and subjective commentary;
    'Buying Guide' section)
   Dennis Publishing Ltd.
   14 Rathbone Place
   London, W1P 1DE, UK
   [phone]
  Hi-Fi News and Record Review (Mid-end. Good new record
    reviews)
   Subscriptions Department
   Link House Magazines Ltd
   1st Floor
   Stephenson House, Brunel Centre
   Bletchley, Milton Keynes MK2 2EW, UK
  Hi-Fi World  (Friendly, lower-mid-end magazine)
   (reviews and "how things work" articles)
   Audio Publishing Ltd
   64 Castellain Rd
   Maida Vale
   London  W9 1EX, UK
   [phone]
  In Terms Of Music  (Emphasizes music reviews, new)
   PO Box 268590
   Chicago, IL 60626  USA
   312-262-5918
  International Audio Review (US $38/yr, 12 issues?)
   2449 Dwight Way; Box 4271
   Berkeley CA  94704 USA
  Positive Feedback (US $25/yr 6 issues) (high-end)
   Oregon Triode Society
   4106 N.E. Glisan
   Portland OR 97232 USA
   503-235-9068
  Sound Practices (US $16/yr 4 issues) (Do-it-yourself)
   Box 19032
   Alexandria VA  22320
   703-836-4382
  Speaker Builder ($25/yr 6 issues) (Speaker projects)
   Box 576
   Peterborough NH  03458 USA
   603-924-9464
  Stereophile (US $35/yr 12 issues) (High-end)
   208 Delgado
   Santa Fe NM  87501 USA
   800-238-2626 or 505-982-2366
  Stereo Review (US $6.97/yr 12 issues.  Lower end/mass
    market)
   Subscription Office: PO Box 52033
   Boulder CO  80323-2033 USA
   Editorial Office: 1633 Broadway
   New York, NY  10019
   212-767-6000
  The Absolute Sound (US $46/yr 8 issues) (High-end)
   Subscription Center: Box 6547
   Syracuse NY  13217 USA
   800-825-0061
   Editorial Office: 2 Glen Avenue
   Sea Cliff, NY  11579
   516-676-2830
  The $ensible Sound (US $20/yr 4 issues) (Mid/High-end)
   403 Darwin Drive
   Snyder NY  14226 USA
   716-681-3513 or 716-839-2199
  What Hi-Fi  (Mid-end; comparative, subjective reviews)
    (contains it's own buyer's guide with
    recommendations)
   Haymarket Trade & Leisure Publications Ltd
   38-42 Hampton Road
   Teddington, Middlesex, TW11 0JE, UK
   [phone]
   US Enquiries should go to:
    Eric Walter Associates
    Box 188
    Berkeley Heights NJ  07922 USA
    201-665-7811

17.2 Which reviews are better?
 Some reviews are so colorful and exciting, that they
 make great journalism and fun reading.  Lets ignore
 these for now, even though they have their place.

 Beware of reviews from magazines that advertise the same
 product.  The likelihood of bias is too high. Unfortunately,
 that rules out 99% of the reviews in magazines.

 Stereo Review has a bad reputation for loving everything
 made by every advertiser.  Even high-end journals such
 as Stereophile and The Absolute Sound can be influenced.

 A classic example of misleading reviews occurs with equipment
 submitted to a magazine for review.  The manufacturer may send
 the editors a carefully built, adjusted piece for review.  The
 magazine will honestly rave about it. The manufacturer will then
 send the design off-shore for more economical manufacture and
 assembly, and the quality will suffer.  Lower quality components
 will be substituted for prime parts.  Adjustments will be made
 to wider tolerances or will not be made at all.  The design may
 be completely changed to make it more manufacturable.  You will
 unknowingly get a completely different piece than reviewed.

 Home auditions with one or two candidates from each of a few
 dealers are your best guide to be sure that you get what you
 want and pay for.

17.3 Is Consumer Reports right?
 Consumer Reports is the most objective testing lab we have ever
 found.  Unfortunately, they are also the world's least
 specialized testing lab.  They market their testing to the
 average consumer.  The average consumer will not hear some of
 the subtle differences which audiophiles hear.  For that reason,
 Consumer Reports ignores issues that others feel vital.

 Consumer Reports also insists on basing their audio testing
 predominantly on lab measurements.  Although lab measurements do
 tell many differences between devices, interpreting lab
 measurements for best sound is difficult or impossible.  For
 example, it is very hard to compare two speaker frequency
 response curves and tell which will sound better.  Some $3000
 speaker frequency response curves look worse than some $600
 speaker curves, even when tested in the same setup.  On the
 other side of the issue, Consumer Reports has improved its test
 methods, and will continue to improve.  Expect the accuracy of
 their reviews to improve with time.

 The Consumer Reports frequency-of-repair data base
 is larger than any similar data base published and
 can be trusted as well as any statistic.

18.0 Retail

18.1 Should I use an up-scale retail store?
 This is probably the best place to listen to gear in a
 controlled environment, next to your home.  This is the best
 place to find expensive, high quality gear.  This is the place
 which is most likely to have a good policy on home trials and
 a liberal return/upgrade policy.  This is also likely to be
 the most expensive place to shop.  One exception to this is
 that these stores have the ability to sell demos, returns,
 and discontinued gear at very advantageous prices.

 Some up-scale dealers will negotiate price on large
 systems or expensive purchases.  It never hurts to ask.

 There are definitely better and worse local hi-fi stores.  If
 you find a really good one, it is probably worth the extra money
 to buy from them, rather than from discounters.  A really good
 store will not push you to buy what they want to sell.  A really
 good store will allow you to take your time with your decision.
 A really good store will not distort the truth in describing
 equipment.  A really good store will help you get the most out
 of your purchase by showing you how to set it up.  They will
 tell you what placement works best for the speakers.  (Don't
 believe them if they tell you to put them anywhere.)  A really
 good store also selects their lines carefully.  They don't want
 dissatisfied customers or warranty returns any more than you do.
 A really good store will also have technical equipment and/or
 skilled technical people that can perform tricky adjustments
 correctly, such as cartridge and tonearm alignment.

 Due to the nature of the customer, a hi-fi store in a shopping
 mall is likely to use high-pressure sales techniques.  They know
 that the majority of their customers are distracted easily by
 299 other stores.  Most of their sales go to customers that
 come in for 3 minutes, select something, and leave.  There
 are exceptions to this, of course, but if there was a good
 generalization, it would be to look elsewhere.  There are stores
 in large buildings, small buildings, private homes, shopping
 plazas, and every other conceivable venue.  Search from among
 these to find one that meets your needs and fits your style.

18.2 Should I use a discount store?
 If you need to listen carefully before making up your mind,
 discount stores can be very frustrating.  If you know exactly
 what you want, then this can be a great place to save money.
 Don't expect knowledgeable sales help or after-sale support.  Be
 sure to ask about the warranty  (see 19.1 below on warranties).

18.3 Is it right to negotiate price?
 Most people feel that it is fair to negotiate.  Some feel that
 it is fair to lie in negotiating, as the sales people frequently
 lie to you also.  Others think that lying to get a lower price
 is an immoral practice.  It may even be illegal, an act of
 fraud.

 Some people feel that if you negotiate over price, you encourage
 stores to mark prices artificially high, so that the stores have
 room to negotiate.  Others feel that in negotiating, you are
 asking the store to accept a lower profit, or asking the sales
 person to take a lower commission and are directly hurting them.

18.4 How can I negotiate price effectively?
 A great source of information on this topic is available from
 books on buying a new or used car.  However, some very helpful
 general tips include:
  Know the competition and the dealer.
  Know the gear.
  Know the prices available elsewhere.
  Believe in your research, not their words.
  Stand your ground.
  Be nice to the people but hard on the deal.
  Be prepared to walk away if they won't agree.
  Expect their lines and prepare responses in advance.
   For example, expect the dealer to claim that the
   Nakamichi deck is the best cassette deck on the
   market.  Be ready with a reply such as at that
   price, you can buy a DAT machine which has
   better frequency response, lower signal to noise
   ratio, etc.

18.5 It sounded great in the store.  Is it great?
 Never let anyone else pick stereo for you.  Especially not
 speakers.  They all sound different, and you don't need a golden
 ear to hear the differences.  Listen for yourself and ignore
 what the sales people say.

 If you are still unsure, ask the sales people to let you take
 the gear home for a home trial in exchange for a large deposit.
 Home auditioning takes 99% of the risk out of store auditions.

18.6 Do sales people try to trick the customer?
 Some do and some don't.  Some will treat unpleasant customers
 badly and treat friendly people well.  Most sales people aren't
 wealthy.  They sell stereo to make a living.  If they can sell
 you a more expensive piece of equipment or a piece of equipment
 with a higher profit, they will make more money.  Usually, this
 figures into everything they say.  Some sales people claim to be
 altruistic.

 Some sales people really are open and honest.  They may starve
 with this approach, or they may have a nice enough personality,
 a good enough product line, a good enough store behind them, or
 enough technical background to overcome this "limitation".

18.7 How can sales people trick the customer?
 Often, a customer will trick him or herself without help.  We
 are often swayed by appearance, sales literature, position of
 the equipment in the show room, and our own desire to buy what
 others will like.

 Some times, the sales person will actively try to push a
 particular piece of equipment by demonstrating it against
 another piece of equipment which is inferior or defective.

 Some sales people will demonstrate a set of speakers while
 simultaneously driving a subwoofer, even though they are not
 telling you this.  With the subwoofer, it probably will sound
 better.

 Some sales people will demonstrate one set of speakers louder
 than others.  Louder almost always sounds better.

 Most stereo buyers go into the store, spend a few minutes
 selecting what they want, lay down big bucks, and leave.  They
 don't need to be tricked.  They don't listen carefully.  They
 trust the sales person's choice as best in their price range.
 For non-technical reasons, these people are the most likely to
 be satisfied with their purchase.

18.8 What should I ask the sales person?
 What do you want to know?  Seriously, the best questions are
 those which the sales person can answer without distorting the
 truth.  Don't ask a sales person to compare their brand to a
 brand they don't sell.  Don't ask "how good is the ...".  Ask
 questions of fact.

 Here are some questions you may want to ask:
  If I don't like it can I return it for a full refund?
  Can I try this out at my home in exchange for a deposit?
  What does the warranty cover?  For how long?
  What do I need to know to set this up for best sound?
  Do I get a manufacturer's warranty with this?
  Where do I take this to get it repaired under warranty?
  Where do I take this to get it repaired out of warranty?

18.9 How do I impress the sales person?
 Why would you want to?  You have money and he doesn't.

18.10 How do I get the best service from a sales person?
 Be honest with the sales person.  Set some reasonable request
 and ask them to meet it.  For example, say that you will buy
 this if you can try it at home first and listen to it
 side-by-side with a piece from another store.  Alternately, say
 that you saw the same thing at store Z for $xx less, but you
 will buy it from the guy if he will match the price.

19.0 Miscellaneous

19.1 What do I need to know about warranties?
 Warranties have a few basic components.  The first is the term
 of the warranty.  The second is what is covered.  The third is
 who supports the warranty. The fourth is what restrictions.

 Term is fairly self evident.  What is covered is more detailed.
 In audio electronics, typically everything is covered with a
 "parts and labor" warranty.  Often mechanical components such as
 tape heads are covered by different terms, such as shorter terms
 on labor and longer terms on parts.  Likewise, speaker
 warranties vary widely, from unconditional with no term limit to
 a basic 30 days parts and labor.

 Some warranties come from the manufacturer.  Others come from
 the dealer.  Still other warranty support is available with
 certain premium charge cards.

 A common restriction on some warranties is that the equipment is
 not covered unless it is sold by an authorized dealer.  A few
 dealers have lied about being authorized dealers.  Equipment
 sold by an unauthorized dealer is almost always sold completely
 legally.  This unauthorized dealer may, in fact, be fully
 authorized to sell, but not authorized to sell manufacturer's
 warranties.  In buying gear this way, dealers can get it
 cheaper, and provide the service themselves.  This kind of gear,
 with a full warranty from the dealer is referred to as gray
 market equipment.  Manufacturers discourage buying from these
 gray market dealers, but the risks are fairly low.  If the
 dealer is local and well established, the risks are minimal.

 If you buy equipment mail-order, a dealer warranty may be a pain
 in the neck, especially if you have to ship the gear to the
 dealer more than once to get it fixed correctly.  Then again,
 some factory service requires shipping gear far away at your
 expense, too.

 Frequently, home audio equipment is sold with a warranty
 restriction that if the gear is used commercially or in any
 profit-making enterprise, then the warranty is void. This is to
 protect the manufacturer from having to frequently repair
 equipment meant for light service.  Professional audio equipment
 often comes with very liberal warranty terms, such as lifetime
 parts and labor.  Professional gear takes heavy use and severe
 wear from constant transportation.  It is expected to be able to
 take this abuse.

 All gear, electronic and mechanical, is known to have three
 principal failure modes: abuse, infant failure, and end-of-life
 failure.  In addition, a few of the failures occur at random.

 Infant failure occurs in the first fifty hours of use, and is
 the principal responsibility of warranties. Infant failure is
 frequently caused by defective parts or a design defect.

 Abuse failure is that caused by a person who pulls a cable too
 hard, bangs the equipment on the table, pushes the controls too
 firmly or too fast, or does anything else which the manufacturer
 did  not expect. These are the gray areas of warranties.  They
 do not represent a manufacturing defect in the manufacturer's
 eyes, but they do leave you with a broken device.  To get
 the best chance of coverage against this kind of failure, select
 a brand or a dealer with a very liberal warranty policy.

 End-of-life failures are rarely covered by warranty.  Tape heads
 have a finite, calculable life, as do rubber rollers, speakers,
 cables, batteries, bearings, and motors.  The life of some of
 these components can be extended by intelligent care.  For
 example, the life of common rechargeable batteries can be
 extended by good recharging practice.  Likewise, some cleaners
 can dry out rubber, and will lead to premature failure. Don't
 expect warranty support for any of these problems, and if you
 get it, feel lucky.

|19.2 What is blind testing?  Non-blind?  Double-blind?
| If you want to compare pieces of equipment, recordings, or
| people, you could run an experiment.  You could select an
| experimenter to initiate various trials, select some subjects
| to listen to the sounds, and then ask the subjects questions
| about what they hear.  However, if you want meaningful
| results, it is necessary to set up the experiment correctly,
| and ask the right questions.
|
| One of the major problems with any experiment is that the
| subjects may become aware of the experimenter's hypothesis
| and allow this awareness to influence their behavior.  One
| technique for preventing such bias is to keep the person
| who conducts the experiment unaware of the hypothesis of the
| research.  Unfortunately, experimenters invariably form SOME
| hypothesis of what's going on, and these hypotheses affect
| how they deal with subjects.
|
| A more reasonable solution involves allowing the experimenters
| to know the true hypothesis but somehow keeping them ignorant
| of the specific experimental condition of each subject.  This
| is known as a Partial Blind Experimenter technique.  An example
| of this is that the person running an experiment knows that the
| main experimenter wants to determine which connecting cables
| are best at signal carrying, but would not know which cables
| are being used at any given time during the experiment.
|
| It is also important for subjects not to become aware of
| the experimenter's specific hypothesis.  Subjects often
| become highly responsive to any cues, intended or unintended,
| in the research situation that suggest what they are supposed
| to do to appear normal or "to make the study come out right."
| This problem can be present in judgment experiments,
| particularly those in which each subject is exposed to more
| than one variation of the stimulus. Such a procedure, by its
| very nature, increases the probability that the subject will
| begin to guess which aspects of the experiment are being
| systematically varied by the experimenter.
|
| Many studies avoid this problem with what is called a Blind
| Subject technique.  Using this approach, subjects are not told
| specifically what the hypotheses are.  Additionally, subjects
| are not told what specific experimental conditions they are in.
| For example, a subject might be told that he/she is supposed to
| determine which stereo system sounds better, when in fact the
| experimenter wishes to examine which color or appearance of the
| same components looks better to subjects.
|
| When both a Partial Blind Experimenter technique and a Blind
| Subject technique are used at the same time, this is called a
| Double Blind experiment.  Double Blind experiments have higher
| probability of producing statistically valid results than
| Partial Blind Experimenter alone, Blind Subject alone, or other
| techniques.  Double Blind experiments are highly recommended.

19.3 Where can I get a service manual for brand XXX?
 The most reliable source of supply is the manufacturer's sales
 office in your country.

19.4 Where can I get good repairs on brand XXX?

19.5 How can I take 115V gear over to a 230V country or vice versa?
 Some equipment is available with an international power supply,
 which can be rewired by any serviceman to either power line
 voltage.  If you expect to be moving abroad, look for this kind
 of equipment.  Often, the same model is available both as US
 only and as International. Some equipment will be rewirable and
| won't say it.  Adcom amps are known to be rewirable.

 If you know that your gear is limited to one power line voltage,
 you can order a new power transformer for that receiver, CD
 player, amplifier, or tuner which will be wound differently.
 Contact the manufacturer's local service center.  This can be
 very expensive.  A new  transformer for a 40 watt receiver would
 wholesale for under $25 but cost $75 from a service center.

 Another alternative is to buy a power transformer that will
| convert 115V to 230V and vice versa.  This is only practical
| for smaller gear.  Larger power amps require prohibitively
| massive and expensive transformers.  Also, the addition of a
| transformer may hurt the sound quality.

 Here are some common transformer models and 1992 list prices.
 Power ratings are total line current multiplied by line voltage
 (2A at 115V is 230 watts).  Larger transformers cost more. Some
 of the costlier transformers are constructed with plugs and
 jacks for immediate use.  Those marked * have wire leads and
 need safe connections to be used.

 Before spending money, check into other things about audio in
 the new country.  Broadcast frequencies are slightly different
 in some countries than in others, so a receiver or tuner bought
 in one country may not be able to receive some or all of the
 stations in another country.  The US separates the AM broadcast
 band frequencies by 10kHz while the UK uses 9kHz.  Similarly,
 the US separates FM stations by 200kHz, where the UK has
 stations on a 50kHz spacing pattern.  It MAY be very simple to
 modify a receiver from US to UK spacings, but may not.  Last,
 but not least, some equipment will NOT work well on 50Hz power.

 Step Down (230V in, 115V Out)
  MagneTek/Triad N1X* 50 Watts $11.83
  Stancor  P-8620* 50 Watts $14.16
  MagneTek/Triad N3M 85 Watts $29.95
  Stancor  P-8630 85 Watts $43.65
  MagneTek/Triad N6U* 200 Watts $25.72
  Stancor  P-8632 200 Watts $51.80
  MagneTek/Triad N5M 250 Watts $42.60

 Step Up (115V In, 230V Out)
  Stancor  P-8637 85 Watts $43.10
  MagneTek/Triad N150MG 150 Watts $49.46
  MagneTek/Triad N250MG 250 Watts $54.69
  Stancor  P-8639 300 Watts $55.51

 The Stancor and MagneTek Triad lines are carried by
 large electronic distributors.

19.6 Are there really good deals in country XXX?

19.7 How do I find out how much an XXX is worth?
 There is a "Blue Book" for used audio equipment called
 "Orion Blue Book-Audio".  This guide lists both a
 wholesale and a retail value for most audio gear.
  Orion Research Corporation
  1315 Main Avenue Suite 230
  Durango CO  81301 USA
  303-247-8855
 Last I knew a guide costs $150. Each Nov, a new book is printed.
| After August, the old book is discounted. If you need a single
| quote from the Orion Blue Book, send a polite request to:
|  [e-mail]
| and you may get a quote back by e-mail.

19.8 Do people really hear those differences?
 Who knows?  They sure think that they do.

19.9 Why do people disagree on what is the best sound?
 There are at least three different measures of what is "Perfect
 Sound".  All three have advocates, and all three are right, in
 their own way.  In general, whether they admit it or not, most
 listeners fit into one of these three preference groups:

 1. It must sound like live music.  These people know what
  voices sound like in person, they know what instruments
  sound like without any amplification, and they have
  heard orchestras perform unaided by sound systems.  They
  want to accurately reproduce that sound.

 2. It must sound like the recording engineer wanted it to
  sound.  The recording engineer listened with extremely
  good equipment to the sound coming out of the
  microphones, and mixed them together for what he, at
  that time, felt was artistically correct.  It may not
  have been the same as live, but it was exactly what he
  wanted.  In the extreme, people like John Fogerty used
  to audition his final recording mix in his truck to see
  how it would sound through a common, lousy stereo.

 3. It must give me the most pleasure.  No matter how good
  or bad live sounds, no matter what the recording
  engineer intended, if buy some equipment will give me
  more listening pleasure then it must be the best.

 With these three perspectives, it is clear that no one system
 will satisfy everyone.  Add to that confusion the variable that
 everyone likes a different kind of sound, has heard live music
 under different conditions, and has a different idea of what the
 engineer intended.  There is an enormous range of possibilities.

 Another set of reasons is that people look for different things
 to be right.  Some want strong bass; others want male voices to
 sound like  male voices; others want violins to sound like
 violins. Systems rarely do everything equally well. Speakers (in
 particular) are compromises.  Look for the speaker where the
 designer had your priority first.  You are perfectly right to
 select speakers based on YOUR personal taste.

 Confounding the situation further, we all say the greatest
 things about the stuff we already bought.  To do otherwise would
 be to admit that we are either stupid or deaf.

 Still another reason is that most people haven't heard enough
 variations.  Until you hear a system that can truly reconstruct
 the three-dimensional accuracy of a stereo image accurately, you
 may never realize that it is possible.  Some excellent
 recordings contain enough information that with a good enough
 system, you can hear up-down, in-out, and left-right
 distinctions very clearly.  However, we will never experience
 this until we are fortunate enough to hear such a fine recording
 on a very good system.

 Finally, some of us really can't hear much difference.  We
 aren't deaf, but we don't have a well trained ear, don't know
 exactly what to listen for, and may even have slight hearing
 deficiencies, such as bad sensitivity to high frequencies which
 comes with older age, or hearing damage from listening to loud
 sounds (machinery, rock concerts, etc).

19.10 How do I contact the manufacturer of XXXXX?  How do I get repair
  service on XXXXX?  How do I get replacement parts?
 Some magazines publish lists of contact phone numbers for the
 manufacturers of equipment.  In the US, Consumer Reports has a
 small listing in each issue and a more comprehensive listing
 in their March issue.  Also, Audio Magazine has an exhaustive
 listing in their October "Equipment Directory".  In Europe, look
 in "What HiFi?".

 You can find many addresses by reading ads in hifi magazines.
 You can also find out by asking at your friendly local hifi
 shop, especially if you've built up a relationship with them.

 A good source for parts and service is often the manufacturer's
 repair center.  The best way to locate one near you is to look
 at the literature which came with your equipment when it was
 new.  Failing that, see the ideas mentioned above in 19.10.

 There is an old list of addresses and phone numbers called
 "Music Equipment Mail/Phone List". This is posted periodically
 to news.answers, and contains many addresses of equipment
 manufacturers.  This list is also periodically posted to some
 music newsgroups.  If you don't see it posted at your site,
 you can get a copy by sending a request to its maintainer,
 [e-mail] (Rich Kulawiec).

20.0 Network Protocol

20.1 What are the other newsgroups on audio and music?
 rec.audio.pro: This newsgroup is dedicated to professional
  audio.  It includes discussion on record production,
  studios, studio equipment, DJ equipment, recording
  concerts, sound reinforcement, mastering, mixing,
  special effects, and other topics which might apply to
  audio professionals.  If you are a home audio buff but
  like tape recording, you can find good advice here.
 rec.audio.high-end: This newsgroup caters to audiophiles and
  serious music lovers who are interested in discussing
  the subtle differences between expensive equipment, the
  nuances of selecting the best cables, the love and lore
  of LPs, and other details of audio that are inaudible to
  the untrained ear.
 rec.audio.car: This newsgroup supports discussion on different
  brands and models of car stereo, and also is an open
  forum for talk about car stereo installation, speaker
  selection, custom crossovers, and the special noise
  problems which occur in cars.

20.2 What network mailing lists are out there which aren't on usenet?
 There is an informal group of people interested in using DAT
 recorders to record "Grateful Dead" concerts. These people call
 themselves "Dat-Heads" and have a daily E-Mailing List.  To
 subscribe to this list, send a message to:
  [e-mail]
 asking to join the mailing list.

| There is also a general turntable chat mailing list.  To
| subscribe to this list, send a message to:
|  [e-mail]
| asking to join the mailing list.

20.3 Should I post a question about "XXXXXXXXXXXXX"?
 If it is related to professional audio, take it to
 "rec.audio.pro".  If it relates to very expensive audio
 equipment or a request for opinions on subtle sound
 differences, you might want to take it to the newsgroup
 "rec.audio.high-end".  If it's related to car audio, there's
 rec.audio.car.  Otherwise, if it isn't addressed in the FAQ
 and it isn't a question for one individual, do it!

20.4 How can I suggest a change to the FAQ?
 Send an E-Mail message to [e-mail] and explain your
 suggestion or correction in detail.

20.5 Where is the FAQ for rec.audio archived?
 This FAQ is available via ftp.  Assuming you have access to the
 internet, the scenario is approximately:
  ftp research.att.com
   # research's IP address is 192.20.225.2
  <login as anonymous; password is your email address>
  cd dist
  get audio.faq
 If you have problems or need further help with accessing the FAQ
 via internet, send e-mail to
  [e-mail]
 This FAQ is also archived at: rtfm.mit.edu in
  /pub/usenet/news.answers/AudioFAQ
 To get the entire FAQ, from the mit archive, you need to
 get all four of the following files:
  part1
  part2
  part3
  part4

20.6 What does FAQ stand for?
 FAQ stands for "Frequently Asked Questions".  It is assumed that
 a FAQ also contains FGA or "Frequently Given Answers".  The
 newsgroup rec.audio has very few FGAs due to the personalities
 involved and the nature of audio.  For that reason, this
 document is called a FAQ.

20.7 Why did I get a bitter reply when I posted a simple opinion?
 Some feel that rec.audio is populated by people with very strong
 opinions.  The whole audio industry is filled with opinionated
 people.

 However, for the most part, these people like voicing their
 opinions and reading others.  What may have sounded like a
 severe rebuttal may have instead been an outlet for the other
 person's frustrations or a challenge to you to "play the
 `rec.audio' game" and back up your words with some spirit.

 Be sure to stay light when reading rec.audio.  Otherwise, you
 are likely to take yourself and everyone else too seriously.
--
Bob Neidorff; Unitrode I. C. Corp.  |  Internet: [e-mail]
7 Continental Blvd.                 |  Voice   : (US) 603-424-2410
Merrimack, NH  03054-0399 USA       |  FAX     : (US) 603-424-3460