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- Summary: Answers to common questions about audio equipment, selecting,
- buying, set-up, tuning, use, repair, developments, and philosophy.
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- Archive-name: AudioFAQ/part3
- Last-modified: 2000/12/14
- Version: 2.15
-
- 10.0 CD Players, CDs, Turntables, and LPs
-
- 10.1 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.
-
- 10.2 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 that, 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, allowing a
- CD player to perfectly reconstruct minor flaws. Another reason
- is that CD players can effectively reconstruct badly damaged
- audio data, even if some data is 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.
-
- 10.3 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.
-
- 10.4 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 will hear a quick 'thump'
- followed by silence through the speakers; 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
- should look at some other make. When you perform this test,
- be sure 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 will be very
- rigid and have no bearing play. 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.
-
- Turntables by Denon, Dual, Linn, Michell, Oracle, Pro-Ject,
- Rega, Sota, Thorens, and VPI are recommended. If you want a
- turntable on a budget, consider the NAD 5120 at approx. $160.
-
- 10.5 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. Moving Magnet (MM)
- cartridges tend to have higher output than Moving Coil (MC)
- cartridges, with exception. Low Output Moving Coil cartridges
- require unusual preamplification. Check with a dealer before
- buying one. Some candidates:
- Sumiko Blue Point $125
- Denon DL-160 $125
- Shure VST-V $150 (MM, Std Mount)
- Audio Technica AT-95E (MM, Std Mount)
- Denon DL-100 $85 (MC High Output, Std Mount)
- Ortofon MC-10 Super MkI $110 (MC Low Output, Std Mount)
-
- 10.6 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.
-
- 10.7 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.
-
- 10.8 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.
-
- 10.9 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.
-
- 10.10 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.
-
- 10.11 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.
-
- 10.12 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.
-
- 10.13 Is the BMG 11-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 11 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 2500 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.
-
- BMG has a web site. There is also a great CD Club FAQ on the
- web. Try these sites:
- http://www.bmgmusicservice.com
- ftp://ftp.netcom.com/pub/ra/ramseyms/cd/CD_Club.FAQ
-
- 10.14 What should I do if there is a problem dealing with BMG?
- The number to reach BMG is 317-692-9200. 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.
- You can also contact BMG by FAX at 317-542-6090.
-
- 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.
-
- BMG has hired a marketing firm to send out information on the
- classical club. Call 800-264-9555, but don't expect customer
- service from this number.
-
- 10.15 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.
-
- 10.16 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.
-
- You can get even more out of BMG by signing up, getting 8 discs
- for the price of one, quitting, signing up again, etc. People
- have done this successfully. BMG reserves the right to deny
- membership to anyone, so you run a very slight risk of being
- denied membership the 20th time. However, I have never heard
- of anyone ever being denied membership for any reason.
-
- The file CDClubFAQ.txt explains more than you ever wanted to
- know about the BMG and Columbia music clubs. It is available
- by FTP from: ftp.netcom.com in /pub/ra/ramseyms/cd
- or by gopher at: biogopher.wustl.edu An HTML version
- can be found at: http://www.blooberry.com/cdfaq/
- Online BMG and CH Popular Catalogs are available at:
- gopher://biographer.wustl.edu or
- http://biogopher.wustl.edu:70/1/audio/bmg
- Online BMG Classical Catalog is available by FTP from:
- ftp.gmd.de in /music/cd-catalogs
- Get file bmg-classical-collection_2ed.gz
-
- 10.17 What are the differences between multibit and Bitstream/MASH
- Analogue to Digital converters (16-bit vs 1-bit CD players)?
-
- Audio data is stored on CD as 16-bit words. It is the job of
- the digital to analogue converter (DAC) to convert these numbers
- to a varying voltage. Many DAC chips do this by storing electric
- charge in capacitors (like water in buckets) and selectively
- emptying these buckets to the analogue ouput, thereby adding
- their contents. Others sum the outputs of current or voltage
- sources, but the operating principles are otherwise similar.
-
- A multi-bit converter has sixteen buckets corresponding to the
- sixteen bits of the input word, and sized 1, 2, 4, 8 ... 32768
- charge units. Each word (ie sample) decoded from the disc is
- passed directly to the DAC, and those buckets corresponding to
- 1's in the input word are emptied to the output.
-
- To perform well the bucket sizes have to be accurate to within
- +/- half a charge unit; for the larger buckets this represents
- a tolerance tighter than 0.01%, which is difficult. Furthermore
- the image spectrum from 24kHz to 64kHz must be filtered out,
- requiring a complicated, expensive filter.
-
- Alternatively, by using some digital signal processing, the
- stream of 16-bit words at 44.1kHz can be transformed to a
- stream of shorter words at a higher rate. The two data streams
- represent the same signal in the audio band, but the new data
- stream has a lot of extra noise in it resulting from the
- word length reduction. This extra noise is made to appear
- mostly above 20kHz through the use of noise-shaping, and the
- oversampling ensures that the first image spectrum occurs at a
- much higher frequency than in the multi-bit case.
-
- This new data stream is now converted to an analogue voltage
- by a DAC of short word length; subsequently, most of the noise
- above 20kHz can be filtered out by a simple analogue filter
- without affecting the audio signal.
-
- Typical configurations use 1-bit words at 11.3MHz (256 times
- over-sampled), and 4-bit words at 2.8MHz (64 times oversampled).
- The former requires one bucket of arbitrary size (very simple);
- it is the basis of the Philips Bitstream range of converters.
- The latter requires four buckets of sizes 1, 2, 4 and 8 charge
- units, but the tolerance on these is relaxed to about 5%.
-
- MASH and other PWM systems are similar to Bitstream, but they
- vary the pulse width at the ouput of the digital signal
- processor. This can be likened to using a single bucket but with
- the provision to part fill it. For example, MASH allows the bucket
- to be filled to eleven different depths (this is where they get
- 3.5 bits from, as 2^(3.5) is approximately eleven).
-
- Lastly it is important to note that these are all simply
- different ways of performing the same function. It is easy to
- make a lousy CD player based around any of these technologies;
- it is rather more difficult to make an excellent one, regardless
- of the DAC technology employed. Each of the conversion methods
- has its advantages and disadvantages, and as ever it is the job
- of the engineer to balance a multitude of parameters to design a
- product that represents value for money to the consumer.
-
- All sampling techniques (so also D/A techniques) require an
- analog reconstruction filter following the converter. This
- filter inherently adds phase shift, frequency response ripple
- and high frequency roll-off, depending on the characteristic of
- the reconstruction filter (which depends on the position of its
- poles and zeros).
-
- An oversampling data converter generates a higher output
- sampling rate than a simpler converter, so you can use a more
- simple reconstruction filter, which is cheaper and more stable
- in time and temperature and produces less noise. Also, modern
- oversampling systems include digital filters which compensate
- the response of the analog filter in the passband, so you can
- achieve systems with an overall performance of 20 Hz...18 kHz
- +/-0.05 dB. Also deemphasis is mostly done in the digital
- domain.
-
- So the "sound" of a CD player is more than just the number of
- bits. It's the quality of the converter, the filter requirements
- imposed by that converter, the quality of the filter, and of
- course, the quality of the following analog components. Power
- supply quality and clock jitter also influence the sound.
-
- 10.18 What is the best under-$200 CD player?
- In this price range, most manufacturers give you more features
- than construction quality or sound quality. If you want a
- particular feature, then use that to guide your purchase. If
- you are after the best possible sound quality, let your ear
- be your guide. Sound quality still varies among models. Don't
- trust reviews or advice alone.
-
- 10.20 What is the best under-$500 CD player?
- Some recommend Rotel. Others recommend Marantz, NAD, or Yamaha.
- The industry has made major gains in terms of sound consistancy
- in the past years. However, models change every year and there
- are models with design flaws. Let your ear be your guide. Also,
- don't forget to check quality of construction. In this price
- range, you should get more than a flimsy box and more durable
- mechanisms than in the <$200 price range.
-
- 10.21 (removed)
-
- 10.22 (removed)
-
- 10.23 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. If you must stroke the disc
- do it with a soft cotton cloth in a straight line from the
- center outwards (radially). Rinse the disc in running clear
- water, shake off most remaining drops, and lightly pat dry
- with a soft, clean cloth.
-
- 10.24 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.
-
- 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. Novus plastic polish and cleaner has been recommended.
- T-Cut, a car paintwork polish, works well for big scratches.
- Reviewers at Audio Magazine recommend the "Memorex CD Repair
- And Maintenance Kit" as the best tool for badly damaged CDs.
- Another recommended polish is Meguier's Plastic Polish #17.
-
- Sometimes, a gentle polishing will make a disc playable
- even though the scratch is not fully removed. This may be
- even better than complete scratch removal because it leaves
- more protective plastic behind.
-
- 10.25 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)
-
- 10.26 What can I get in the way of a CD test disc?
- Each test disc offers something different. Some discs contain
- useless filler which advertises a product or shows a unique
- capability, but really doesn't help you test or improve your
- system.
-
- 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 three test discs.
-
- 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.
-
- If you are looking for test CDs, one source of supply that
- stocks lots of different test CDs is:
- DB Systems
- Main Street
- Box 460
- Rindge Center NH 03461 USA
- 603-899-5121
-
- 10.27 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 recorder used in the mixing and
- editing process. Mixing and editing is the process of combining
- a multi-track master recording, setting levels, editing out
- defects, adjusting equalization, and creating a two-track final
- tape. There are good machines available for this which are
- analog and good machines which are digital.
-
- The third letter refers to the final master, which for a CD
- is always digital. 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.
-
- 10.28 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
- 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.
- Some record-cleaning recipies recommend alcohol. However,
- alcohol will leach plasticizer from vinyl, and eventually
- degrade LPs. Alcohol will also disolve the shellac of 78s,
- so should never touch a 78.
-
- 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.
-
- Also consider using a carbon fiber brush every time you play
- the LP. It picks up some surface dirt and removes static.
-
- 10.29 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.
-
- 10.30 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.
-
- 10.31 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.
-
- 10.32 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.
-
- 10.33 How much music can you possibly cram into a CD?
- The longest seen so far (reported by Stuart Kahler) is a
- MiC bootleg of Depeche Mode "Evolution", at 81:09. Next are 'No
- Quarter' by Jimmy Page and Robert Plant at 79:38, the collected
- singles CD release by The Sisters Of Mercy at 79:30, an MCA
- reissue of Steely Dan: Greatest Hits at 79:17 and a Musical
- Heritage recording of Bach: Goldberg Variations at 79:02.
- Modern CDs are pressed using tighter track spacing than the
- first CDs, because modern equipment is capable of holding
- tighter tolerance than the original machines.
-
- 10.34 What are input and output levels and impedances for signal
- sources, preamps, amps, etc?
- We have been unable to find any formal standard on this topic.
- However, there is an EIA Bulletin: EIA Consumer Products
- Engineering Bulletin No 6-A (CPEB6-A) 1974, titled "Preferred
- Voltage and Impedance Values for the Interconnection of Audio
- Products". The key word in the title is 'Preferred'.
-
- EIA CPEB6-A recommends 3mV at 47k ohms for magnetic phono
- cartridges, 250mV at less than 10k ohms for tape and preamp
- outputs, and 100k ohm minimum for tape, tuner, and amp aux
- inputs. The bulletin also has information on microphones,
- and headphones. You can order a copy through a technical
- library or directly from the EIA.
-
- 10.35 Why are turntable speeds 78 RPM, 45 RPM, etc?
- The speeds were chosen because that is the speed that resulted
- when you used standard parts. Electric motors rotate at 1800
- rpm, most shafts are 1/4". Those combinations with the proper
- gears and idlers came out to 78 rpm. In reality it's 78.26
- rpm. Tape recorder speeds evolved the same way.
-
- The 78.26 was standardized after electric recording/playback
- occured. Prior to that, speeds were "in the neighborhood of"
- 78 rpm. Some lower and some higher. 80 rpm was used in many
- recordings. (Courtesy of Bill Vermillion)
-
- 10.36 Why is CD digital data written in 44.1 kHz samples?
- The rate of 44.1 kHz was picked to be compatible with existing
- 50 Hz and 60 Hz video-based digital audio storage, where an
- integral number of frame buffers could fit in a single
- horizontal scan. Quote from Watkinson and Rumsey, "Digital
- Interface Handbook" 2.7.6 Choice of Sampling Rate:
-
- "In 60 Hz [525 line, 60 Hz vertical refresh) video there are 35
- blanked lines, leaving 490 lines per frame, or 245 lines per
- field for samples. If three samples were stored per line, the
- sampling rate becomes 60*245*3=44.1 kHz. In 50 Hz video [625
- line, 50 Hz vertical refresh), there are 37 lines of blanking,
- leaving 588 active lines per frame, or 294 per field, so the
- sampling rate becomes 50*294*3=44.1 kHz. The sampling rate of
- 44.1 kHz came to be that of the Compact Disk. Even though CD
- has no video circuitry, the equipment used to make CD masters
- is video based and determined the sampling rate."
-
- The length of 74 minutes is determined by the physical nature
- of the reading system. It's based on the encoding method, the
- wavelength of the laser used (different wavelengths are
- incompatible with current CDs) and the necessary support
- information. During the development of the CD, von Karajan was
- alledgedly asked how long a CD must be, to which he responded
- it must be long enough to hold HIS performance of Beethoven's
- 9th symphony, but the parameters had pretty much already been
- nailed down at that point.
-
- 10.37 What's the latest on DVD and DAD?
- Check out the articles in The Absolute Sound on the subject,
- from issue 112, which is also on the web:
- http://www.theabsolutesound.com/dadforum-1.htm
- http://www.theabsolutesound.com/dadforum-2.htm
- http://www.theabsolutesound.com/dvdhope.htm
-
- 10.38 What's the latest on the MiniDisc(tm)?
- Check out the MiniDisc(tm) organization web site for a minidisc
- FAQ and other MiniDisc(tm) information.
- http://www.minidisc.org
-
- 10.39 How can I record an LP or tape onto a CD?
- That's a complex question, but basically, get a sound card for
- your computer, get some cheap software for your computer, and
- follow some of the advice at:
- http://homepages.nildram.co.uk/~abcomp/lp-cdr.htm
-
- 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.
-
- --
- Bob Neidorff; Texas Instruments | Internet: neidorff@ti.com
- 50 Phillippe Cote St | Voice : (US) 603-222-8541
- Manchester, NH 03101 USA
-
- Note: Texas Instruments has openings for Analog and Mixed
- Signal Design Engineers in Manchester, New Hampshire. If
- interested, please send resume in confidence to address above.
-