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From: karn@petrus.UUCP
Newsgroups: net.audio
Subject: SR article on CD filtering
Message-ID: <386@petrus.UUCP>
Date: Sun, 30-Jun-85 00:41:40 EDT
Article-I.D.: petrus.386
Posted: Sun Jun 30 00:41:40 1985
Date-Received: Mon, 1-Jul-85 06:43:44 EDT
Distribution: net
Organization: Bell Communications Research, Inc
Lines: 22

The July issue of Stereo Review has a very good (for an audio magazine)
article comparing digital and analog filtering techniques. It provides
an overview of the two methods and how digital filtering eases the task
of constructing the (inevitable) final analog filter.

The conclusion? The author prefers digital filters -- not due to any
audible differences in phase response, but because digital filters ought
to be more reliable and may also provide a flatter amplitude response.
The following excerpt is also of interest. Can anybody provide a more
complete citation to the JAES article?

"The upshot of all this is that it has yet to be conclusively demonstrated
that any of the differences in high-frequency phase response between analog
and digital output filters are audible, audiophile opinions notwithstanding.
Carefully conducted tests reported in the Journal of the Audio Engineering
Society show that listeners cannot detect the operation of *either*
type of filter when impulses are being reproduced, even when several of
the filters are connected in series! Earlier experiments showed that
listeners could not detect the presence of steep-cutoff analog filters when
the cutoff frequency is as high as 20,000 Hz, as in CD players."

Phil