From: kls30@duts.ccc.amdahl.com (Kent L Shephard)
Newsgroups: rec.audio
Subject: Re: A Golden-Ear perspective on CD players.
Date: 15 Apr 92 20:49:34 GMT
Reply-To: kls30@DUTS.ccc.amdahl.com
Organization: Amdahl Corporation, Sunnyvale CA

In article <1992Apr15.100238.22258@bristol.ac.uk> P.Smee@bristol.ac.uk (Paul Smee) writes:
>In article <1992Apr7.222913.16264@cunixf.cc.columbia.edu> reha@cunixf.cc.columbia.edu (Reha Elci) writes:
>>The CD sampling rate is at 44Khz. Why hasn't anybody pointed out that this 
>>sampling rate is not really sufficient to reproduce accurate high frequency
>>signals? 
>
>No, jj, don't do it. :-)  It hasn't been pointed out, because in fact
>sampling rate just over 2x the freq you want to reproduce IS
>sufficient.  44Khz sampling is more than enough to get you up to
>20Khz.  Go to your nearest friendly electronic library (columbia must
>have one) and look up Nyquist.
>
>>The number of bits is also somewhat of a problem. 16 bits mean, at best,
>>1 part in 65536 parts resolution. -20 * Log (1/65536) = 96.33 dB of
>>dynamic range (is this how it is calculated??). This also seems somewhat
>>low if you are interested in accurate and detailed sound quantification.
>
>This is 96dB above the noise floor, and while it may not be perfect, it
>is a much wider dynamic range than you can get from any other home
>medium, in practice at least.

I posted this statement a while ago and had no response. Here goes again.

Analog does not have infinitely small resolution.  There is a threshold
at which no change in analog input will produce an output.  Call it a type
of quantization error if you will.

If your threshold is 1mV and you input a .5mV change you will see no
change on the output.  So you can look at the dynamic range of most analog
equipment and compare directly with CD if you know what the threshold is.

If you do not know what the maximum signal output is and the threshold is
comparing CD to analog makes no sense.

Look at this component:
64x oversampling A/D can handle a voltage swing from +/-3.68 volts with
16 bit accuracy.  This gives a threshold of 112uV at the LSB.  This A/D
is also accurate to +/- .5 LSB which gives +/- ~70uV.

Remember on-amps do have a threshold voltage.  So if your op-amp in
an analog device cannot handle a resolution that small and doesn't have
a slew rate to handle +/-3.68V at full bandwidth. Your limiting factor is
your op-amp and your device will not sound as good.

So before you start telling me analog is better show me the specs for
threshold on the tape or record player you are talking about.

The A/D I'm talking about is the one in a Panasonic SV-3700 pro-DAT
machine.  Crystal Semiconductor also makes an 18bit version.

Same voltage swing but with a threshold of 28uV at the LSB and is accurate
to +/- .5 LSB.

>
>>Given the specs above, it is not too shocking to hear how some people
>>may prefer analog recordings, especially good ones, to CD reproductions.
>
>Analog and digital DO have different colorations, and I've got no 
>problems with the idea that some people like the analog presentation 
>better, while others prefer the digital.  However, the particular specs
>you've chosen to use are DEFINITELY not the reason.

Specs for analog preference are not the reason.  There was an article in
a music magazine a while ago where they took a "golden ear" studio
engineer and fed him signals through an analog eq and a completely digital
eq implemented with a DSP.

Turns out he was use to hearing the phase delay in the signal to tell how
much boost was given in a particular band.  When fed the digital signal
he liked the eq signal better because there was no "muddying" of the bass
at high boost levels.

>
>-- 
>Paul Smee, Computing Service, University of Bristol, Bristol BS8 1UD, UK
> P.Smee@bristol.ac.uk - ..!uunet!uknet!bsmail!p.smee - Tel +44 272 303132


--
/*  -The opinions expressed are my own, not my employers.    */
/*      For I can only express my own opinions.              */
/*                                                           */
/*   Kent L. Shephard  : email - kls30@DUTS.ccc.amdahl.com   */
Newsgroups: rec.audio