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From: ijb@druxv.UUCP (Ira Blumberg)
Newsgroups: net.audio
Subject: CD player sound
Message-ID: <1294@druxv.UUCP>
Date: Wed, 1-Feb-84 12:33:52 EST
Article-I.D.: druxv.1294
Posted: Wed Feb  1 12:33:52 1984
Date-Received: Tue, 7-Feb-84 09:37:05 EST
Distribution: net.audio,dr.audio
Organization: AT&T Information Systems Laboratories, Denver
Lines: 21

There appear to be 2 different types of decoding and filtering systems
for CD players which could make a major difference in some of the more
subtle aspects of sound as discussed in this forum previously.  One
system is the standard 16 bit D to A conversion with sharp filteration
above 20khz.  This appears to cause major phase shift in the frequencies
above 1khz.  This is the system used by Sony and most of the other
Janpaese companies.  The other system involves 14 bit D to A converters
but samples the CD at 4 times the normal rate.  The oversampling
retrieves all the information and cancels out most of the frequencies
above 20khz.  For this system filteration is only necessary around the
60khz range and much less steep filter slopes are necessary.  This seems
to cause almost no phase distortion.  This system is used by Phillips
and some of the other European manufacturers.  From a technical stand
point the Phillips system sounds far superior, especially in light of
the fact that the Phillips design seems to have some of the best error
correction as well.  I have not been able to get side by side
comparisons of the Sony vs. the Phillips processes, but this seems like
the thing to do.  Has anyone out there tried this type of comparison? 
I'm sure the net is curious to hear any results.

--Ira (just an audio novice cause we have too many gurus already)