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FAQ: rec.audio.* Sources 7/07 (part 3 of 13)

( Part1 - Part2 - Part3 - Part4 - Part5 - Part6 - Part7 - Part8 - Part9 - Part10 - Part11 - Part12 - Part13 )
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Archive-name: AudioFAQ/part3
Last-modified: 2007/07/12
Version: 2.17

See reader questions & answers on this topic! - Help others by sharing your knowledge
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 $40 Grado Prestige Black is a great value for any home user.
	However, some users comment that it can pick up hum from some
	turntables.  For the purist, there are many other 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. 

10.6 Will phono cartridges still be around ten years from now?
	Ten years ago, I wrote that cartridges will become scarce.  I was
	wrong.  Today, many manufacturers to make many common, good, and
	audiophile cartridges, including well respected makers like Grado, 
	Ortofon, Rega, Shure, and Sumiko. 

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.

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