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From: jer@peora.UUCP (J. Eric Roskos)
Newsgroups: net.music.synth
Subject: Re: Digital delays
Message-ID: <2061@peora.UUCP>
Date: Mon, 31-Mar-86 09:40:30 EST
Article-I.D.: peora.2061
Posted: Mon Mar 31 09:40:30 1986
Date-Received: Wed, 2-Apr-86 02:07:40 EST
References: <1176@unc.unc.UUCP>
Organization: Concurrent Computer Corporation, Orlando, Fl
Lines: 35
Keywords: nostalgia

> Aha!  This tells me what we have been talking about.  I remember the
> SAD-1024 being a *S*tereo *A*nalog *D*elay, a bucket-brigade delay in
> which charge sloshes along in 2 lines of 512 buckets each.  I think that
> the device was originally designed to be used with analog inputs and
> outputs, but I guess you could shift bits through it instead.  If this
> device is used as a digital shift register, is the noise introduced by the
> charge-transfer between buckets small enough so that bits reliably pass
> through?

Actually, the 2 applications I used an SAD-1024 in [which were both
designed by other people] used it as a digital device; I hadn't realized
it could be used as an analog device until it was mentioned in here!
Although actually it was a sort of "digital circuits used by analog
engineers" hybrid approach (see below).

> This is about $.01/Kbit, or about a thousand times cheaper than the
> SAD-1024.  Although the SAD-1024 might be easier to control, the
> difference in price could buy a lot of control hardware for the RAM!

I agree with that, though.  However, the problem really is that I was
thinking in analog synthesizer mode [the above synthesizers used a "top
octave generator" and then used plain TTL gates to divide down and narrow
the pulses before putting them into a small mixing and filter circuit that
included the SAD-1024; i.e., much like your typical electronic organ
circuit -- it had something like 900 diodes alone, and took about 40 hours
to assemble... however, it gave better sound than any pure digital
synthesizer I've seen, eventhough it could only make 3 distinct voices]
whereas you were thinking in digital mode, which is more reasonable
nowadays.  I have a hard time getting used to these machines that can do 8
times more than the old-fashioned ones on a 4x5 circuit board... :-) (The
above synthesizer -- I forget the model number, it was PAIA's old string
synthesizer -- required two boards that were each about 4 inches by 2.5
feet, not including the one that had the SAD-1024 on it).
-- 
E. Roskos