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Path: utzoo!watmath!watdcsu!herbie
From: herbie@watdcsu.UUCP (Herb Chong, Computing Services)
Newsgroups: net.audio
Subject: CD's, delta-modulation, and all that
Message-ID: <517@watdcsu.UUCP>
Date: Tue, 16-Oct-84 22:21:46 EDT
Article-I.D.: watdcsu.517
Posted: Tue Oct 16 22:21:46 1984
Date-Received: Wed, 17-Oct-84 06:27:44 EDT
Organization: U of Waterloo, Ontario
Lines: 32

I apologize for the misunderstanding of delta-modulation.  I was
remembering an article in Audio a few years back describing it.
I do remember that dbx had a lot of problems initially trying to
solve the breathing problem with the device.  Does anyone know how
they did it?

A few random thoughts about dynamic range of CD's.  I said a while back that
120 dB was a target that some people around here were aiming at.  I also
said that someone was working on a compander to do that for a 16-bit
linear system like CD's.  Well, a single channel was constructed about
6 months back and tested.  Breathing was not very bad because of the
low 1.3 dB/dB compression ratio, but, as expected, noise was the major
problem.  This project was wire-wrapped just to see if it would actually
function and it did.  I don't have the catalog number of the VCA's used,
but they were about $100 each in small quantities and their specs were
in line with what was required.  I will dig up the technical report
and follow up later.  The people who worked on it still think that 120 dB
dynamic range is required for the system mostly to protect the recording
engineers from incorrect level settings.  Having done no live recording,
of my own, I can't say.  The leader of the project has, with both analog
and digital recorders, under relatively controlled and uncontrolled 
situations.  He sees it as a safety blanket for slightly too high
recording levels.

Herb...

I'm user-friendly -- I don't byte, I nibble....

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