Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!zaphod.mps.ohio-state.edu!uwm.edu!csd4.csd.uwm.edu!info-high-audio-request
From: exspes@gdr.bath.ac.uk (P E Smee)
Newsgroups: rec.audio.high-end
Subject: Re: Improving
Message-ID: <10442@uwm.edu>
Date: 22 Mar 91 14:52:45 GMT
Sender: news@uwm.edu
Lines: 60
Approved: tjk@csd4.csd.uwm.edu
Originator: tjk@csd4.csd.uwm.edu

In article <10340@uwm.edu> rgaetz@hydra.unm.edu (Robert Gaetz) writes:
>    Well, I suppose it's easier to simply write off all these
>    reports of improved performance than to actually look into the
>problem, but luckily one company did look into it. ...
>surprising. In short, they felt it was _the_best_ cd player they've
>ever heard. It seems JVC had their engineers look into these effects
>based on the assumption that there was somthing making a difference.
>... they built a circuit that took a quick
>peek at the incomming digital signal to determine whether it was
>a high or low then generated a completely new signal which went to
>the DAC.
>  
>In addition to the reasons I mentioned before, the
>issue of 20th generation copies of digital material sounding
>different seems to be a clear sign that noise is a contributing
>factor to sound quality. If you listen to a 20th generation copy
>of an analog signal, you'd probly find that, among other things,
>it is a lot noiser than the original, so surely the data on a 20th
>generation digital signal will contain much more noise than the
>original.

No, this last assertion is untrue.  (I've quoted your first part, which
is a real effect, because I'm going to use it against you.)

Much like the regeneration in your JVC, when you perform a digital copy
of a digital tape, the equipment reads the signal from the original
tape, 'peeks at it' to determine whether it should be a one or a zero
(high or low), and then generates a completely new signal to put onto
the copy.  Analog copies, on the other hand, have to take what they're
given (including any tape noise and degradation imposed by the
circuitry it's already been through) and put that signal out to the
copy tape which will, of course, add its own tape noise on top.

If there is some effect which makes digital copies sound different than
the originals (an effect which I've been unable to spot myself) then
whatever it is, it's not the type of noise you seem to have in mind.

Now, there IS also one weakness with your JVC story, as well.  That is
that ALL cd players perform the same task.  They peek at the incoming
data, which will come from the tape heads (on a DAT) or from the laser
scanner (in a CD) in an incredibly sloppy form, which bears about as
much resemblance to a digital square wave as a packet of peanuts does
to the State Home for the Criminally Insane (apologies to Douglas
Adams).  They decide whether it's supposed to be a high or a low, and
generate a clean digital signal to send to the DAC.

It's entirely possible that JVC have found a more noise-immune way of
doing this.  Meridian (to pick another example) have managed to
convince themselves that noise generated by the DAC and later analog
stages can feed back into the digital part of the circuitry to cause
problems, and have designed a (very nice) CD player by concentrating on
minimizing that.

Or, in summary, there are effects which need looked at, but I think
you're only half-way to understanding them at the moment.  Keep
plugging away at it.

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