FAQs
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.
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.
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.
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 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.
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, Dual, Linn, Mitchell, Oracle, Pro-Ject, Rega, Sota, Thorens, and VPI are also recommended, but can cost more. If you want a turntable on a budget, consider the NAD 5120 at approx. $160.
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)
"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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Get archive "clubfaq" from "/pub/cd" on "jammin.nosc.mil" for more information on the BMG and Columbia clubs. Also in the same directory is an up-to-date listing of the BMG popular collection.
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.
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.
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. 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.
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)
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.
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
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.
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)
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.
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.
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.
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.
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.
