Conference cookie::notes$archive:cd_v1

NO amplifier can have a "dynamic range" as good as a CD could theoretically
be.  Most CDs have a design range of 90 DB or more.  This is a ratio of 1
billion to 1.  Thus, if the quietest possible sound that you wanted to hear
required .001 watts from your amplifier, the loudest possible sound would
require 1 million watts!

Luckily(??), the majority of the music recorded on CDs has only about 30 to
50 db of range.  One rock CD I have has an average range of only 10db!

How about a digital amplifier?  All it would need would be a fast multiplier.
You take in a digital number like 002030(8), and multiply it by an
amplification factor, then feed it to a D/A converter.  This would also
prevent the degradation of the signal from the CD player to the amp, since
that signal would be in digital form.

Then there are also digital speakers like Sony now sells.  They are square
instead of being that embarrassingly analog circular shape.

_______________
!d!i!g!i!t!a!l!  we change the way the world sounds.
---------------

If you find DAC that can give that kind of performance at high power, let
me know.  Most so called "power" DACs that I have seen consist of a simple
DAC followed by an analog power amplifier (which tends to be a lot more
crappy than the average audio amplifier), which puts us back into the
original situation that we're in now.

Re .2:
     What makes you think those square Sony APM speakers are "digital"?
They're driven by an analog signal like any other speaker.

The intent of the square piston is to eliminate distortion due to uneven
piston motion, but the results from what I've heard are disappointing.

				Steve

If a CD really has 90 dB of dynamic range, some of your more basic
equipment is inadequate.  Start with your ears; nobody over the 
age of 18 wants to hear too much more than 100 dB of sound pressure.
Then your house, with an ambient level of 30 to 60 dB, depending on
where you live, what appliances are running, and whether you have
teenagers.  My answer is that modest equipment or a good pair of
headphones will do, even though nowhere as good as the CD.

High end types need not reply, it's your money and you should be 
free to spend it where you feel you are getting value.  Golden ears
should have golden equipment, I guess!

paul

RE:.4

	I have those speakers that you are not to fond of and
find that they play extremely well for their size.
	I always thought speaker sound was a matter of taste -- was
it not ?

	The idea of the elements having a square geometry is
so that area is maximized.  The result is most air volume
pushed for the size of the speaker.

Mike

re .2
Can't you guys take a joke?

Oh, sorry.  Ha Ha.  (%^0)

RE: .1

I thought that the way the unit "decibel" was defined was that each 10
decibels represents a doubling in loudness.  The scale is logarithmic, but
with a base of 2 instead of 10.  Thus, a 90db dynamic range is a ratio of
2**9 = 512 to 1, not 1,000,000,000 to 1.

I would guess that the only problems some amplifiers might have with CD
players would be where the parameters on the amplifier are substantially
poorer than those of the CD.  For example, an amplifier with a signal:noise
ratio of 60db would be fine with LPs (where the s:n ratio is 50db or so),
but would be inadequate for the quieter passages on some CDs.  Ditto for
an amplifier with a poorer harmonic distortion, channel separation, or
frequency response than the CD player.

I have a NAD 3050 50-watt amplifier and it does just fine with my Sony CDP-302.

--PSW

Nope.  Decibels are log base 10 (hence "deci" and not "bi" or "duo").
10 db is supposed to represent a "doubling" in loudness, but decibels
don't really measure percieved loudness -- the unit for that is the sone.
3db represents a doubling in power, so to double loudness one needs over
8 times as much power.  Ears are amazing things

the formula for decibel is dB = 10 log p1/p2, thus a doubling of power
comes out as 3 dB.  10 dB is indeed 10 times as much power, 20 dB is 100
times as much, etc.  90 dB is still 1 billion to 1.

A 3 dB increase in sound level is minimally discernable to your ears, yet
it takes twice as much power to do it.

Doubling the power means actually something like 3.0103 dB ... whether you
can hear the difference between 3.0 and 3.0103 dB is another matter.  :-)

(sorry, but I'm pedantic!)

I have my doubts about the usefullness of the "90" Db dynamic range
an CD is supposed to offer. It sure sounds like a lot, and at the same
time, it is enough?

The 90 dB is based on a theoretical calculation (see also AUDIO notes)
being the ratio between the lowest and highest possible voltage from
a 16 bit system. But, at the lowest possible level, there is NO relation
to music whatsoever: it is just a 0 or 1. Thus it seams to me the the
range of music loudnesses available through a digital system is a function
of acceptable distorsion. and is definitly NOT 90 dB for a 16 bit system.

To verify this, I used a DENON test CD which has the same fragment of music
recorded at normal level, -20 dB, -40dB, -60dB. At normal listening level
for the "normal" recording level the -60 dB comes out as barely audible.
You know its there, you hear the leading theme but you have a hard time
recognizing the instument. Turning the volume up you can make the -20 dB
sound just like the normal recording. Turning the volume up even more
you can probably get the -40 dB recording sound as loud as the normal one,
but it sounds different, not so good, no "body". Turning the volume WAY UP
makes the -60 dB recording recognizable but reveals the enormous distorsion
that is inherent in the system. (if my calculations are correct, at that
point you are just using some 5 or 6 bits for amplitude info). Actually the
flyer with the record reads: "As no diher signal is added, quantization
noice becomes apparent at lower levels."

Hein van den Heuvel.

I'll put the previous reply as note into the AUDIO notes file.
I think that would be a better place for a discusion of the
general problem as it is not only related to CDs.

Hein.

Well, to get back to the original purpose of this note entry..... :^)

I have a the Carver "cube" (I think it is model M-400) amplifier, with 200
watts per channel......the cube is about 6 inches on an edge, and one of
the most impressive things about is is that it just barely gets warm to
the touch!

My speakers are Polk Audio model 10......this combined with a Sony CD player
seems to me to be an extremely good combination!!!!!


				Jeff

I also vote for the "cube"! Jeff and I bought ours at the same place and
time (Geez... must be 4 years ago now!) and both have had nothing but good
things to say since. We also have the same CD player, a Sony CDP-111.

I'm in the process of updating my current speakers (once the cat gets her
claws taken out!) from power-hungry Epicure 400s to some model of Polks yet
to be determined. I'm looking forward to the day I bring home the new speakers!
Depending on what I find out in the next few months I might even go for a
sub-woofer system instead of Polks.

Ray