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Path: senator-bedfellow.mit.edu!faqserv From: neidorff@unixyztrode.com Newsgroups: rec.audio.tech,rec.audio.opinion,rec.audio.misc,rec.audio.marketplace,rec.answers,news.answers Subject: FAQ: rec.audio.* Sources 5/97 (part 3 of 13) Supersedes: <AudioFAQ/part3_872763743@rtfm.mit.edu> Followup-To: poster Date: 28 Sep 1997 09:06:09 GMT Organization: Unitrode Corp. Lines: 798 Approved: news-answers-request@mit.edu Expires: 11 Nov 1997 08:58:45 GMT Message-ID: <AudioFAQ/part3_875437125@rtfm.mit.edu> References: <AudioFAQ/part2_875437125@rtfm.mit.edu> Reply-To: neidorff@unixyztrode.com NNTP-Posting-Host: penguin-lust.mit.edu Summary: Answers to common questions about audio equipment, selecting, buying, set-up, tuning, use, repair, developments, and philosophy. X-Last-Updated: 1997/07/31 Originator: faqserv@penguin-lust.MIT.EDU Xref: senator-bedfellow.mit.edu rec.audio.tech:57575 rec.audio.opinion:130202 rec.audio.misc:39671 rec.audio.marketplace:129386 rec.answers:34313 news.answers:113248 Archive-name: AudioFAQ/part3 Last-modified: 1997/7/31 Version: 2.12 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 of these D/A techniques require an analog filter following the converter. This filter inherently adds some phase shift and high frequency roll-off, depending on the frequency and number of elements (poles, zeros, order, etc) in the filter. An oversampled data converter can generate a higher data rate than a simpler converter, so can get by with a higher frequency filter, and thereby less filter artifacts in the signal. Also, some filter designs are inherently poorer than others. As is often the case, the easier designs to implement (Chebyshev) are also worse phase shift than the more sensitive designs, which may use a Butterworth topology. 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, 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) 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. Note: My e-mail address in this FAQ is "Spam-Blocked". Remove "xyz" to use. -- Bob Neidorff; Unitrode Corporation | Internet: neidorff@unixyztrode.com 7 Continental Blvd. | Voice : (US) 603-429-8541 Merrimack, NH 03054-0399 USA | FAX : (US) 603-429-8564 Note: Unitrode Corporation has openings for Analog and Mixed Signal Design Engineers in Merrimack, New Hampshire. If interested, please send resume in confidence to address above.