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Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxn!charm!prk
From: prk@charm.UUCP (Paul Kolodner)
Newsgroups: net.audio
Subject: cd oversampling
Message-ID: <707@charm.UUCP>
Date: Sat, 27-Jul-85 10:44:55 EDT
Article-I.D.: charm.707
Posted: Sat Jul 27 10:44:55 1985
Date-Received: Mon, 29-Jul-85 06:11:39 EDT
Organization: Physics Research @ AT&T Bell Labs Murray Hill NJ
Lines: 15

Douglas Hamilton made two boo-boos in his response to media interest in 
cd players:
1.  I think the original posting was in jest.  I think the original
poster knew that that is NOT how they do it!
2. About oversampling:  The"staircase" waveform that results from
straight reconstruction fron discrete samples exhibits white noise 
all over the frequency spectrum, not just at the high end as he
suggests.  This noise is inaudible with 14-bit sampling, so it's
not the issue when it comes to oversampling.  Oversampling does
not shift this noise to higher frequencies, as he suggests.  It merely
allows for less phase distortion.  A second thought:  why they call
the output filters "anti-alias filters" I'll never know.  The aliases
are either prevented by filtering before digitization, or else they can't
be removed at all.  Oversampling introduces new aliases, but they are
above the original Nyquist frequency and are removed by output filters.