www.Usenet.com
www.Usenet.com
| <-- __Chronological__ --> | <-- __Thread__ --> |
Archive-name: AudioFAQ/part3
Last-modified: 2000/12/14
Version: 2.15
10.0 CD Players, CDs, Turntables, and LPs
10.1 What should I listen for when evaluating a turntable or CD player?
For tape decks and turntables, beware first of speed variations
(wow and flutter). A good check for this is Richard Strauss'
"Also Sprach Zarathustra" (aka: The Theme From 2001), which has
a long, low, sustained organ note that comes in well before the
main theme starts, and is held through the first movement.
Concentrate on that. Make sure it doesn't wobble or warble.
There's also a good bit at the beginning of Pink Floyd's
"The Wall", but it doesn't go on as long, so you've got less
time to think about it. Tape decks are prone to losing
high-frequency notes, so pick something you like which has lots
of treble, and make sure it is clear.
The sound of a turntable is largely bound up in the kind of
cartridge mounted on it. Make sure to listen to a table with
a cartridge similar to what you're buying, and not one in a
different price bracket. If possible, audition the turntable
with the same arm and cartridge, so that you will experience
potential cartridge/arm interactions, too. Most cartridges
work better with one arm than another. Treat the
tonearm/cartridge pair as a system, rather than independent
parts.
For CD players, try some piano music. See if the high notes
sound tinny. Also, try something which has some soft parts,
not the same as turning the volume down. Distortion for CD
players (as for other devices) is measured at a high output,
but in fact in CD players (unlike others) it's likely to be
worse in soft passages of music. Most classical recordings
contain a suitable soft passage. Most rock music won't.
Distortion in CD players, if you want to call it that, is
a function of the granulation noise, or time-delay pre-echo that
can come out of the filtering. To listen for this, use material
that is rich in high-order harmonics, such as brass music.
Unfortunately, you can't reliably predict how a CD player
will sound by looking at specifications, features, or the
technology it uses. If you want to know how a player will
sound, you MUST listen to it.
10.2 Are some discs better than others?
Some recordings are better than others. Some artists are better
than others. Some recording engineers are better than others.
Some microphones are better than others. Some music is better
than others.
Ignoring that, there is some difference between discs. Some
of the very earliest discs were badly made and deteriorated
with time. The technical problems that caused those problems
have been solved.
Some "gold" discs are available which are advertised to have
better life and quality than common "aluminum" discs. These
sell for an extra US $15 or more per disc over the cost of the
same music on a common disc. Studies have shown that there is
an advantage to glass-encased, gold platters for archiving
computer data that is not error tolerant and will need to be
stored for many tens of years. I have yet to see a similar
comparison which justified any extra effort for storing audio
recordings for 50 years. Part of the reason for this is that
audio recordings contain error correction codes, allowing a
CD player to perfectly reconstruct minor flaws. Another reason
is that CD players can effectively reconstruct badly damaged
audio data, even if some data is completely missing.
Some discs seem to have pinholes in the aluminum, which are
visible when the disc is held up to a strong light. However,
these discs play fine and last very well, so the effect of these
pinholes is probably nil. Some have performed studies counting
errors on various discs with various players. They found that,
in general, the error count was consistent from one player to
another. Also, in general, most discs have a low, consistent
error rate which is perfectly correctable using the redundant
data stored on the disc. This study did find that one group of
discs had a higher error rate than all of the rest. This group
was the promotional discs, also called "music samplers" given
away by music companies to introduce you to their family of
artists and performers. Despite these higher error counts,
these discs still played fine.
If there is no abusive handling involved, I have rarely heard of
a disc that degraded with time. Of the few that have existed,
they tended to be from one of the bad batches mentioned earlier.
There is no doubt that some discs are mastered better than
others. Some are badly mixed. Some are so badly recorded that
there is noticeable clipping. Some are made from damaged master
recordings. CD technology is no guarantee of good music or of a
good recording.
10.3 Are CDs better than LPs?
Some excellent recordings are mastered digitally, and sound
great on LPs. This suggests that there is nothing inherently
bad about digital.
Some find that LPs sound better than CDs. Advocates of LPs
claim that the digital to analog (D/A) converter in home CD
players isn't up to the quality of the information on the disc.
They also claim that the analog electronics in a home CD player
can be poor.
Some believe that CDs do not sound like LPs because the CD does
not have the frequency response errors, the distortion, or the
stereo separation problems of LPs.
In general, though, there are good and bad CD players, just as
there are good and bad turntables, cartridges, and tone arms.
Any ultimate comparison would require ultimate equipment, which
is unaffordable. In moderately priced systems, there will be
some signal damage from the turntable system and some signal
damage from the CD player.
LP lovers often learn the nuances of cartridge selection, record
care, and even turntable and tonearm adjustment. They have
found that the turntable will sound different if the arm height
is adjusted, if the cartridge angles are changed, and if the
tonearm wire is moved. CDs do not offer as many avenues for the
home experimenter.
However, Audio Amateur Magazine has published modification
projects for CD players; particularly for Magnavox 560 and
similar European players. Audio Magazine has also published
such articles.
10.4 What turntable should I buy?
Despite improvements in motor technology, most great turntables
use belt drive. Rubber roller (idler) drive sounds the worst.
Select a turntable with a very heavy platter for the least wow
and flutter. Give the platter a rap with your knuckle. It
should not "ring" like a cymbal. It should feel and sound dead.
Also look for a turntable that has good isolation from base
to stylus. With the amp on and the turntable selected, but
with the turntable motor off, put an old record on the
turntable, lower the stylus onto the record, and then tap
the edge of the base. Not too hard, you don't want to send
the arm flying. At worst, you will hear a quick 'thump'
followed by silence through the speakers; if you're lucky,
you'll hear nothing at all. If the sound continues beyond a
quick 'thump', the mechanical isolation is not great, and you
should look at some other make. When you perform this test,
be sure to unplug the turntable power cord.
If the turntable has a tonearm, try to evaluate the arm,
too. A good arm should be adjustable in height. A good arm
should allow cartridge adjustments. A good arm will be very
rigid and have no bearing play. A good arm should accommodate
a wide range of cartridges. Despite this, some arms work
better with high compliance cartridges, while others are
at their best with low compliance. Ask.
Turntables by Denon, Dual, Linn, Michell, Oracle, Pro-Ject,
Rega, Sota, Thorens, and VPI are recommended. If you want a
turntable on a budget, consider the NAD 5120 at approx. $160.
10.5 What phono cartridge should I buy for my older turntable?
The $30 Grado ZTE+1 is a great value for any home user but a
purist. For the purist, there are still many choices, both
moving coil and moving magnet. Each sounds slightly different,
and has its individual strengths. Moving Magnet (MM)
cartridges tend to have higher output than Moving Coil (MC)
cartridges, with exception. Low Output Moving Coil cartridges
require unusual preamplification. Check with a dealer before
buying one. Some candidates:
Sumiko Blue Point $125
Denon DL-160 $125
Shure VST-V $150 (MM, Std Mount)
Audio Technica AT-95E (MM, Std Mount)
Denon DL-100 $85 (MC High Output, Std Mount)
Ortofon MC-10 Super MkI $110 (MC Low Output, Std Mount)
10.6 Will phono cartridges still be around ten years from now?
Most likely, there will still be cartridges available, but not
in the variety available ten years ago. They will become
"Special Order" in some stores and unheard of in others.
"Pro" or "DJ" cartridges will stay available in good supply,
"Audiophile" cartridges will stay available and very expensive,
"Mid-line" cartridges will become very scarce, and a few
"Budget" cartridges will remain available in copious supply.
At the same time, some makers will drop their cartridge lines
completely.
10.7 Will LPs still be around ten years from now?
There is a strong movement of collectors and purists who will
keep their collections and buy good used discs. Count on these
people to keep the used disc market hot for 25 years longer.
As for new music, less is being pressed today than 20 years
ago. Many popular artists are being released on LP in parts
of Europe, but availability is dependent on country. One
person said that many new LPs are available in Spain.
LP sales have increased recently in Japan and in the UK. Polydor
is now re-releasing older recordings on vinyl, and will continue
to press them as long as it is profitable. Likewise, there are
several re-releasing projects in Japan. Some are for Jazz
collectors and others are for pure analog as well as classical
music lovers. They are selling the LPs by subscription, with
shipments every 2 or 3 months. Each release includes about 20
titles. Japan has released over 100 LPs this way last year.
10.8 What about CD green pens?
In a nutshell, save your money.
A CD player "reads" information on the disc with a laser light
beam. Some believe that if you put a green stripe on the very
perimeter of the disc, then the light beam will not reflect
around inside the disc and will more clearly pick up the data.
Scientific studies of the data coming off of the disc have
failed to show any difference between a virgin disc and a green
painted disc. I have not heard of double blind listening
comparisons that have proved that there are people who can hear
the difference, although many have performed uncontrolled tests
with positive results.
10.9 What about CD stabilizer rings?
In a nutshell, save your money.
The data coming off of the disc is a serial string of ones and
zeros. If this bit stream has jitter, then it may reach the D/A
converter out of sync. If this happens, then the actual analog
signal recreated will have jitter, and won't be perfectly true.
The vendors of stabilizer rings say that using these rings will
reduce jitter and make a more perfect signal. Vendors also
claim that the rings can increase the mass of a disc, making it
spin more smoothly, and reducing transient load on the power
supply from the motor.
Some players will not play discs that have stabilizer rings on
them. The clamp can't handle the thickness. Other players play
ringed discs, but do not play them well, because the disc motor
was not built for the added load.
With those exceptions, scientific studies of the data coming off
of the disc have failed to show any improvement going from a
virgin to a ringed disc. I have not heard of double blind
comparisons that prove that people hear the difference, either.
10.10 What about CD spray treatments (ArmorAll et al)?
In a nutshell, save your money.
Current wisdom is to avoid any disc coating or spray. Some will
definitely damage the disc.
There are many theories on what ArmorAll can do to a disc. One
is that it reduces static which will attract the delicate head
of the laser detector to the disc. Another theory is that the
cleaner will fill voids in the disc with silicone, thereby
making it easier to read by reducing diffraction effects.
Scientific studies of the data coming off of the disc have
failed to show any difference between a virgin disc and a
treated disc. I have not heard of double blind listening
comparisons that have proved that there are people who can hear
the difference.
One of the strongest proponents of ArmorAll issued a "recall" on
his advice. He now warns that ArmorAll can damage the disc. He
also advises that you can clean ArmorAll off treated discs with
Dawn dish detergent.
10.11 Are 1-bit CD players better than multi-bit players?
In a nutshell, they are virtually the same.
There are some excellent sounding 1-bit players and some
excellent sounding multi-bit players. Some feel that the 1-bit
technology has more future because it can be improved with the
rapidly improving digital technology, while the multi-bit
players improve with slowly improving analog technology.
Multi-bit also has its advocates.
All of the various D/A converters try to do the same thing, and
try to achieve the exact same ideal performance. How well they
succeed is more a function of their skill and the quality of the
parts that they buy than the technique that they use. In other
words, the architecture of a D/A converter is less important
than the quality of its implementation.
10.12 Are three lasers better than one in CD players?
Some players have one beam, some three. All use one laser diode
to generate the beam. Three-beam is just a different method for
doing track alignment. Neither is better than the other.
There are good 1-beam players and good 3-beam players.
Manufacturers want advertising claims and "More Beams Is Better"
sounded good to some marketing people. Trust your ears.
10.13 Is the BMG 11-for-1 deal good?
Yes. You have to put up with their frequent mailings. You can
elect the "POSITIVE OPTION" and not have to answer each mailing
to avoid an order. You should expect to pay approximately $2.00
per disc for shipping and handling in the US and more elsewhere,
but even at that price and assuming that you will buy one of
their discs for $16.00, you still do well. Assuming, of course,
that you want at least 11 of the discs that they are offering
for sale. Some states requires sales tax on BMG sales, and some
states tax "free" discs, but the tax still is small compared to
the discount from retail.
The BMG collection contains over 2500 discs. This includes
classical, pop, jazz, and other. All BMG discs come from the
larger labels. Some rumored that BMG discs are inferior to the
discs sold in normal retail chains. This has not been
substantiated. In fact, BMG distributes their discs through
retail chains, as well as through the mail, so you may get a BMG
disc either way.
BMG has a web site. There is also a great CD Club FAQ on the
web. Try these sites:
http://www.bmgmusicservice.com
ftp://ftp.netcom.com/pub/ra/ramseyms/cd/CD_Club.FAQ
10.14 What should I do if there is a problem dealing with BMG?
The number to reach BMG is 317-692-9200. Their people have been
very cooperative with me and others. It is always good policy
to confirm any phone call with a letter, restating the problem
and the resolution you were promised over the phone. It is good
practice to write down the name of the person you speak with.
You can also contact BMG by FAX at 317-542-6090.
If BMG sends you something that you didn't order, DON'T OPEN THE
PACKAGE. Write REFUSED on the package and put it back in the
mailbox. They will accept the return and credit your account
for any charges.
BMG has hired a marketing firm to send out information on the
classical club. Call 800-264-9555, but don't expect customer
service from this number.
10.15 How do I get out of the BMG racket?
If you have taken any discs from BMG, you must either return
what you have ordered or fulfill the terms of your original
agreement. This often means buying one disc at full price and
paying for the shipping on all discs you ordered and received.
Once you have done this, you can quit the club at any time.
Take your next order form and mark it with a bold marker in
large letters "CANCEL MEMBERSHIP" and mail it to: BMG COMPACT
DISC CLUB, PO BOX 91413, INDIANAPOLIS, IN 46291 USA. It may
take a month to fully take effect, but they will honor your
request. While waiting for the cancel order to take effect, be
sure to return all future order forms marked the same way.
Otherwise, you may wind up with unwanted discs.
10.16 How do I get the most out of BMG?
Only buy one disc at full price, fulfilling your obligation.
Request the "POSITIVE OPTION" so that you save on postage. Only
buy from special fliers. Every month, except November and
December, they send out a "Two for half price then one free"
flier. They have almost all of the stuff in the regular fliers.
They even offer "Buy one get two free" sometimes. Wait for
those special deals. You can even order discs from an October
catalog using the order form that came in the February catalog.
You can get even more out of BMG by signing up, getting 8 discs
for the price of one, quitting, signing up again, etc. People
have done this successfully. BMG reserves the right to deny
membership to anyone, so you run a very slight risk of being
denied membership the 20th time. However, I have never heard
of anyone ever being denied membership for any reason.
The file CDClubFAQ.txt explains more than you ever wanted to
know about the BMG and Columbia music clubs. It is available
by FTP from: ftp.netcom.com in /pub/ra/ramseyms/cd
or by gopher at: biogopher.wustl.edu An HTML version
can be found at: http://www.blooberry.com/cdfaq/
Online BMG and CH Popular Catalogs are available at:
gopher://biographer.wustl.edu or
http://biogopher.wustl.edu:70/1/audio/bmg
Online BMG Classical Catalog is available by FTP from:
ftp.gmd.de in /music/cd-catalogs
Get file bmg-classical-collection_2ed.gz
10.17 What are the differences between multibit and Bitstream/MASH
Analogue to Digital converters (16-bit vs 1-bit CD players)?
Audio data is stored on CD as 16-bit words. It is the job of
the digital to analogue converter (DAC) to convert these numbers
to a varying voltage. Many DAC chips do this by storing electric
charge in capacitors (like water in buckets) and selectively
emptying these buckets to the analogue ouput, thereby adding
their contents. Others sum the outputs of current or voltage
sources, but the operating principles are otherwise similar.
A multi-bit converter has sixteen buckets corresponding to the
sixteen bits of the input word, and sized 1, 2, 4, 8 ... 32768
charge units. Each word (ie sample) decoded from the disc is
passed directly to the DAC, and those buckets corresponding to
1's in the input word are emptied to the output.
To perform well the bucket sizes have to be accurate to within
+/- half a charge unit; for the larger buckets this represents
a tolerance tighter than 0.01%, which is difficult. Furthermore
the image spectrum from 24kHz to 64kHz must be filtered out,
requiring a complicated, expensive filter.
Alternatively, by using some digital signal processing, the
stream of 16-bit words at 44.1kHz can be transformed to a
stream of shorter words at a higher rate. The two data streams
represent the same signal in the audio band, but the new data
stream has a lot of extra noise in it resulting from the
word length reduction. This extra noise is made to appear
mostly above 20kHz through the use of noise-shaping, and the
oversampling ensures that the first image spectrum occurs at a
much higher frequency than in the multi-bit case.
This new data stream is now converted to an analogue voltage
by a DAC of short word length; subsequently, most of the noise
above 20kHz can be filtered out by a simple analogue filter
without affecting the audio signal.
Typical configurations use 1-bit words at 11.3MHz (256 times
over-sampled), and 4-bit words at 2.8MHz (64 times oversampled).
The former requires one bucket of arbitrary size (very simple);
it is the basis of the Philips Bitstream range of converters.
The latter requires four buckets of sizes 1, 2, 4 and 8 charge
units, but the tolerance on these is relaxed to about 5%.
MASH and other PWM systems are similar to Bitstream, but they
vary the pulse width at the ouput of the digital signal
processor. This can be likened to using a single bucket but with
the provision to part fill it. For example, MASH allows the bucket
to be filled to eleven different depths (this is where they get
3.5 bits from, as 2^(3.5) is approximately eleven).
Lastly it is important to note that these are all simply
different ways of performing the same function. It is easy to
make a lousy CD player based around any of these technologies;
it is rather more difficult to make an excellent one, regardless
of the DAC technology employed. Each of the conversion methods
has its advantages and disadvantages, and as ever it is the job
of the engineer to balance a multitude of parameters to design a
product that represents value for money to the consumer.
All sampling techniques (so also D/A techniques) require an
analog reconstruction filter following the converter. This
filter inherently adds phase shift, frequency response ripple
and high frequency roll-off, depending on the characteristic of
the reconstruction filter (which depends on the position of its
poles and zeros).
An oversampling data converter generates a higher output
sampling rate than a simpler converter, so you can use a more
simple reconstruction filter, which is cheaper and more stable
in time and temperature and produces less noise. Also, modern
oversampling systems include digital filters which compensate
the response of the analog filter in the passband, so you can
achieve systems with an overall performance of 20 Hz...18 kHz
+/-0.05 dB. Also deemphasis is mostly done in the digital
domain.
So the "sound" of a CD player is more than just the number of
bits. It's the quality of the converter, the filter requirements
imposed by that converter, the quality of the filter, and of
course, the quality of the following analog components. Power
supply quality and clock jitter also influence the sound.
10.18 What is the best under-$200 CD player?
In this price range, most manufacturers give you more features
than construction quality or sound quality. If you want a
particular feature, then use that to guide your purchase. If
you are after the best possible sound quality, let your ear
be your guide. Sound quality still varies among models. Don't
trust reviews or advice alone.
10.20 What is the best under-$500 CD player?
Some recommend Rotel. Others recommend Marantz, NAD, or Yamaha.
The industry has made major gains in terms of sound consistancy
in the past years. However, models change every year and there
are models with design flaws. Let your ear be your guide. Also,
don't forget to check quality of construction. In this price
range, you should get more than a flimsy box and more durable
mechanisms than in the <$200 price range.
10.21 (removed)
10.22 (removed)
10.23 How can I clean a dirty CD?
Use a drop of dish detergent and lots of clean water. Do not
rub. Never rub or wipe in a circle. If you must stroke the disc
do it with a soft cotton cloth in a straight line from the
center outwards (radially). Rinse the disc in running clear
water, shake off most remaining drops, and lightly pat dry
with a soft, clean cloth.
10.24 Can you repair a damaged CD?
If the disc is lightly scratched on the bottom, then you can
polish out the scratch and probably repair the disc perfectly.
If there are lots of scratches or deep scratches, or there is
damage on the top, you may be facing a lost cause. The music
information is immediately under the label. If you scratched
the reflective layer, the disc is normally unrecoverable.
Before trying any repair, try washing the disc with clear water
and a bit of liquid dish detergent. Do not scrub or rub hard.
Rinse the disc with clear water and shake off as much water as
you can. Finally, wipe the last few drops off with a soft,
clean cloth, in a radial direction.
SMALL scratches can be removed with a scrufty T-shirt and
toothpaste, such as Tom's Toothpaste.
You may wish to try a thin coating of Johnson's Klear floor wax
on the bottom of the CD. Often it will cover the scratches
enough to allow playing. The refractive index is pretty close
to polycarbonate, so filled scratches will be nearly invisible.
You can buy professional plastic polishing compounds at many
hobby shops. The ones used for polishing acrylics, plexiglas,
etc. work. Ordinary lapidary jeweler's polishes also work.
You'll need a rough polish to remove the scratches, then tin
oxide to polish to a mirror finish. Telescope lens kits also
work. Novus plastic polish and cleaner has been recommended.
T-Cut, a car paintwork polish, works well for big scratches.
Reviewers at Audio Magazine recommend the "Memorex CD Repair
And Maintenance Kit" as the best tool for badly damaged CDs.
Another recommended polish is Meguier's Plastic Polish #17.
Sometimes, a gentle polishing will make a disc playable
even though the scratch is not fully removed. This may be
even better than complete scratch removal because it leaves
more protective plastic behind.
10.25 Can I add digital output to a non-digital-out CD player?
Some Magnavox CD players using the Philips chip set can be
modified. Look for a SAA7220 IC. If it has one, then it can be
modified. If you have experience modifying electronic
equipment, follow this procedure:
Take pin 14 of the SAA7220 IC and remove whatever terminating
resistor is on it. Connect it through a 560 ohm resistor to the
input of a wide band pulse transformer. Tie the other end of
the primary of the transformer to ground. Pulse Engineering
PE65612, Schott Corp 6712540, and Scientific Conversions
SC916-01 all will work. Bypass the primary through a 620 ohm
resistor. Connect the output of the transformer to an RCA jack.
Do not ground either side of the RCA jack. This output is now
S/PDIF compatible. (Thanks for the tip to Positive Feedback)
10.26 What can I get in the way of a CD test disc?
Each test disc offers something different. Some discs contain
useless filler which advertises a product or shows a unique
capability, but really doesn't help you test or improve your
system.
Many use the Hi-Fi News & Record Review test discs. So far,
these have received only positive comments.
Chesky produces 2 test discs. The first, "Chesky Jazz Sampler
Volume I" contains some excellent imaging test signals (called
LEDR), some well-recorded acoustic jazz, and other test signals.
The second, "Chesky Jazz Sampler Volume II" has similar music &
different tests.
Stereophile produces three test discs.
Denon also produces two test discs. The first, "Digital Audio
Check" is more useful for home use. The second, "Audio
Technical" is more for repair shops and test-disc addicts.
If you are looking for test CDs, one source of supply that
stocks lots of different test CDs is:
DB Systems
Main Street
Box 460
Rindge Center NH 03461 USA
603-899-5121
10.27 How do the letters ADD on my CD relate to sound quality?
The simple answer to this question is that there is no relation
between the three letter code and sound quality. Those three
letters refer to the recording and mastering tools used in
making the CD.
The first letter refers to the recording process. For example,
a disc labeled ADD was ANALOG recorded, where a disc labeled
DDD was DIGITALLY recorded. Analog recording means that some
form of conventional analog tape recorder was used, whether it
be a two-track home-quality recorder or a very expensive
wide-tape, high-speed, multi-track recorder. Digital recording
could be as simple as a two-track DAT recorder, or can be a
much fancier multi-track digital recorder.
The second letter refers to the recorder used in the mixing and
editing process. Mixing and editing is the process of combining
a multi-track master recording, setting levels, editing out
defects, adjusting equalization, and creating a two-track final
tape. There are good machines available for this which are
analog and good machines which are digital.
The third letter refers to the final master, which for a CD
is always digital. I have seen discs that are labelled
as AAD, ADD, DAD, and DDD.
Future releases may not have this three letter code on them
because they don't tell you anything that is significant. Also,
some codes have been used incorrectly on some discs, which
makes the information that much more meaningless.
10.28 How can I clean LPs?
There are expensive machines for this purpose which work very
well. One popular model goes by the name Nitty Gritty. These
machines spray cleaner onto the record, work it into the
grooves, and then vacuum the cleaner and dirt out. If you are
serious about records and have lots of them, it may be a good
investment for you.
If you have a more reasonable collection, you might be happy
with a good hand washing every now and then. To give your
records a good hand washing, start by preparing this wash:
1 gallon distilled water
1 gram Alconox (a laboratory detergent)
Also, get a natural bristle brush and trim it to the correct
stiffness/bristle length so that the bristles can get into the
grooves but aren't stiff enough to scratch the record.
Some record-cleaning recipies recommend alcohol. However,
alcohol will leach plasticizer from vinyl, and eventually
degrade LPs. Alcohol will also disolve the shellac of 78s,
so should never touch a 78.
Lay the LP flat and pour a thin coat of the above fluid on it.
Brush the wash into the grooves with the bristle brush. Brush
in the direction of the grooves, going through all grooves.
Flush the wash and dirt off with cool, running tap water.
Rinse the record with distilled water and pat it dry
with a soft, clean cotton cloth.
Also consider using a carbon fiber brush every time you play
the LP. It picks up some surface dirt and removes static.
10.29 How do you set the stylus pressure correctly?
Stylus tracking force is typically adjusted at the back of the
tonearm with a knob that is calibrated in grams at the stylus
tip. With the control set to zero, the stylus should sort-of
float above the record surface. The control is then increased
to the number recommended by the cartridge manufacturer.
Do not, under any circumstances, use a lower than recommended
force, as the cartridge may lose the ability to maintain
contact with the groove wall on passages of large amplitude.
This WILL result in RECORD DAMAGE.
If you want the best possible tracking and sound quality, you
will want to fine-tune the tracking force. Use a test record
and listen very carefully, or get the help of a good dealer
with a battery of instruments.
10.30 How do you set the anti-skating on a tonearm?
If you have a recommendation or suggestion from the
tonearm manufacturer, follow their advice first.
They will give you the best starting point.
Some tonearms come with calibrated anti-skate. The manufacturer
of these tonearms has tried to calibrate the anti-skate control
so that if you match the setting of the anti-skate to the
setting of the stylus pressure, you will have nearly perfect
anti-skate. Read the manufacturer's recommendations to see if
this applies to your tonearm.
You can see gross errors in anti-skate by looking at
the stylus. If you shine a light on the front of the
tonearm while playing a record, you will be able
to see whether the stylus is centered in the stylus
holder. If the stylus is biased to one side or another
while playing a record, then the anti-skate is way off.
More subtle adjustments can be made by listening for
mistracking. If you can, obtain a record with equal
left right modulation at high frequency with ascending
modulation magnitude (volume), such as the Shure
ERA-III, IV, or V test record. They have five bands of
"greensleeves" played on flute, and you fiddle until the
audible breakup is equal in both channels, and adjust
tracking weight until it occurs in the highest band.
This is, like other cartridge and tonearm adjustments,
easier for the experienced hand than the beginner.
Some high-end dealers have electronic instruments which
allow them to accurately adjust anti-skate and other
cartridge and tonearm parameters. If you can get this
service, consider yourself fortunate.
10.31 How else do you adjust a tonearm/cartridge/stylus?
There are a few other critical adjustments. Again, a good
high-end dealer may be your best resource. Your ear may
also be your best test instrument.
You need a level turntable. Use a quality carpenter's
level. Some people like the Shure stylus force gage for
setting stylus pressure accurately. Other tools which are
well recommended are the Geo-disk, a good protractor, and
above all, the Cart-Align, which uses a very precise
etched plastic mirror for cantilever alignment.
You'll also want to set the tracking angle. It CAN be
done by eyeball, but is best done with test instrumentation
and a record. There is also the cartridge angle, tonearm
height, etc. Read the instructions which came with your
tonearm for the best specific advice for that tonearm.
Tonearm cable is more critical than any cable anywhere else
in the signal chain. Cable capacitance directly sets the high
frequency characteristics of the cartridge. In addition, the
correct grounding of the shield is essential to minimize hum.
It may be necessary to change preamp input capacitors so that
the cable/preamp combination loads the cartridge with the
right overall capacitance. Replacing tonearm cable will have
a similar effect, but may be harder to change tonearm cable
than to change preamp input capacitors. Consult the
cartridge, tonearm, and preamp manuals for specific advice.
Also refer to 16.6 for more information on tonearm cable.
An excellent article on setting up a turntable is:
Stereophile, July 1990, Pages 62-85.
10.32 Do CDs deteriorate with time? What is their life span?
A CD consists of a polycarbonate top layer, an aluminum (or
gold) metal reflective layer, a polycarbonate bottom layer,
and some miscellaneous printing ink. Of these materials,
polycarbonate seems to be extremely stable with time provided
that it is well cared for. Do not use any liquids on a CD
that contain silicones or solvents. Do not leave CDs in
sunlight or other bright light. Do not stick labels on CDs.
Do not write on CDs. Do not expose CDs to temperatures higher
than normal room temperatures. Don't leave a CD under water.
Even the top side of a CD is critical and subject to damage.
Some pressings from the early 1980s used ink which damaged the
polycarbonate top layer and eventually got into the aluminum.
These inks are not in use today. Some earlier discs were made
with imperfect sealing around the perimeter of the disc. This
was evident because the aluminum in the disc extended all of
the way to the disc edge. These discs were known to fail due
to moisture getting to the aluminum and causing it to oxidize.
Modern CD factories have solved this problem as well.
With those cautions, modern CDs will last for more than 30
years without deterioration. Most of the CDs which were
made in 1983 are still around today and still sound good.
10.33 How much music can you possibly cram into a CD?
The longest seen so far (reported by Stuart Kahler) is a
MiC bootleg of Depeche Mode "Evolution", at 81:09. Next are 'No
Quarter' by Jimmy Page and Robert Plant at 79:38, the collected
singles CD release by The Sisters Of Mercy at 79:30, an MCA
reissue of Steely Dan: Greatest Hits at 79:17 and a Musical
Heritage recording of Bach: Goldberg Variations at 79:02.
Modern CDs are pressed using tighter track spacing than the
first CDs, because modern equipment is capable of holding
tighter tolerance than the original machines.
10.34 What are input and output levels and impedances for signal
sources, preamps, amps, etc?
We have been unable to find any formal standard on this topic.
However, there is an EIA Bulletin: EIA Consumer Products
Engineering Bulletin No 6-A (CPEB6-A) 1974, titled "Preferred
Voltage and Impedance Values for the Interconnection of Audio
Products". The key word in the title is 'Preferred'.
EIA CPEB6-A recommends 3mV at 47k ohms for magnetic phono
cartridges, 250mV at less than 10k ohms for tape and preamp
outputs, and 100k ohm minimum for tape, tuner, and amp aux
inputs. The bulletin also has information on microphones,
and headphones. You can order a copy through a technical
library or directly from the EIA.
10.35 Why are turntable speeds 78 RPM, 45 RPM, etc?
The speeds were chosen because that is the speed that resulted
when you used standard parts. Electric motors rotate at 1800
rpm, most shafts are 1/4". Those combinations with the proper
gears and idlers came out to 78 rpm. In reality it's 78.26
rpm. Tape recorder speeds evolved the same way.
The 78.26 was standardized after electric recording/playback
occured. Prior to that, speeds were "in the neighborhood of"
78 rpm. Some lower and some higher. 80 rpm was used in many
recordings. (Courtesy of Bill Vermillion)
10.36 Why is CD digital data written in 44.1 kHz samples?
The rate of 44.1 kHz was picked to be compatible with existing
50 Hz and 60 Hz video-based digital audio storage, where an
integral number of frame buffers could fit in a single
horizontal scan. Quote from Watkinson and Rumsey, "Digital
Interface Handbook" 2.7.6 Choice of Sampling Rate:
"In 60 Hz [525 line, 60 Hz vertical refresh) video there are 35
blanked lines, leaving 490 lines per frame, or 245 lines per
field for samples. If three samples were stored per line, the
sampling rate becomes 60*245*3=44.1 kHz. In 50 Hz video [625
line, 50 Hz vertical refresh), there are 37 lines of blanking,
leaving 588 active lines per frame, or 294 per field, so the
sampling rate becomes 50*294*3=44.1 kHz. The sampling rate of
44.1 kHz came to be that of the Compact Disk. Even though CD
has no video circuitry, the equipment used to make CD masters
is video based and determined the sampling rate."
The length of 74 minutes is determined by the physical nature
of the reading system. It's based on the encoding method, the
wavelength of the laser used (different wavelengths are
incompatible with current CDs) and the necessary support
information. During the development of the CD, von Karajan was
alledgedly asked how long a CD must be, to which he responded
it must be long enough to hold HIS performance of Beethoven's
9th symphony, but the parameters had pretty much already been
nailed down at that point.
10.37 What's the latest on DVD and DAD?
Check out the articles in The Absolute Sound on the subject,
from issue 112, which is also on the web:
http://www.theabsolutesound.com/dadforum-1.htm
http://www.theabsolutesound.com/dadforum-2.htm
http://www.theabsolutesound.com/dvdhope.htm
10.38 What's the latest on the MiniDisc(tm)?
Check out the MiniDisc(tm) organization web site for a minidisc
FAQ and other MiniDisc(tm) information.
http://www.minidisc.org
10.39 How can I record an LP or tape onto a CD?
That's a complex question, but basically, get a sound card for
your computer, get some cheap software for your computer, and
follow some of the advice at:
http://homepages.nildram.co.uk/~abcomp/lp-cdr.htm
COPYRIGHT NOTICE
The information contained here is collectively copyrighted by the
authors. The right to reproduce this is hereby given, provided it is
copied intact, with the text of sections 1 through 8, inclusive.
However, the authors explicitly prohibit selling this document, any
of its parts, or any document which contains parts of this document.
--
Bob Neidorff; Texas Instruments | Internet: [EMAIL PROTECTED]
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.
| <-- __Chronological__ --> | <-- __Thread__ --> |
