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From: rfg@hound.UUCP (R.GRANTGES)
Newsgroups: net.audio
Subject: Re: A-B Tests - Whither digital audio, really...
Message-ID: <1156@hound.UUCP>
Date: Tue, 14-May-85 13:23:03 EDT
Article-I.D.: hound.1156
Posted: Tue May 14 13:23:03 1985
Date-Received: Wed, 15-May-85 01:18:59 EDT
References: <charm.659>, <361@boulder.UUCP> <1525@druxu.UUCP>
Organization: AT&T Bell Labs, Holmdel NJ
Lines: 19

[]
Just so as to maintain a balanced view from the corporation, now
that one area has spoken like a buggy-whip manufacturer's view of
the automobile in 1895, why should we go analog anyplace?
AT&T-Bell Labs has released photographs of a direct digital
speaker.D/A in the air, so to speak. I think it only handled 4 or 5
bits, but you have to start somewhere.
Meanwhile, there are a number of promising ways to drive a speaker
with essentially a digital amplifier, going D/A in the loudspeaker.
One way I got a patent on about 25 or 30 yrs ago is to use delta
modulation (or something like it) with the loudspeaker serving as part
of the decoding network for a very heavy pulse amplifier. One can
convert from PCM to Delta in logic circuitry, of course.
Probably it would not be much more expensive to build a direct PCM
to PAM converter with the loudspeaker as the load. You need fast high
current switches.
-- 

"It's the thought, if any, that counts!"  Dick Grantges  hound!rfg