analog computers

[Grant Richter]

I don't think it is off topic.

Basically every synth module is a specialized analogue computer.
The state variable filter is the classic demonstration of a mass suspended
on a spring with a damper.

It's not so much a question of who "invented" the synthesizer,
since these types of circuits were being patched up on
analogue computers since the 1930s. I think that's why neither
Bob or Don will claim to be the "inventor".

Most synth modules use many more op-amps than are
available on a typical analogue computer. The types of
circuits that are available are limited to integrators,
summers and multipliers. The types of circuit used in analog
synth modules are those, plus comparators, switched inverters,
exponential converters, lots more multipliers, sample and holds,
voltage controlled switches.

Some of the big analogue computers have functions
for repeated computation, like sample and holds and
voltage controlled switches. But you would need a really
big analogue computer to patch up most synth modules.
And then it would only be one module.

The Lab Electronics Analogue Computer Trainer is eminently
"hackable" though. I bought one to study different filter designs.
I used a multi-section switch to change the integrator time
constants in decades and put 3080 OTAs before each integrator
stage with an exponential converter. The result is a "patchable"
filter with numerous coefficient pots and summers. Quite useful
for studying the Matrix 12 filter and other summed coefficient filters.

Dan Slater also wrote a very intriguing article in Computer Music Journal
on Chaotic systems. One implementation uses an analogue computer.

----------
> From: Christian Oncken <oncken at umr.edu>
> To: Grant Richter <grichter at execpc.com>; synth-diy at mailhost.bpa.nl; Paul
Perry <pfperry at melbpc.org.au>
> Subject: Re:  analog computers
> Date: Sunday, August 08, 1999 2:32 AM
> 
> Wow... can this thing make noise?  This looks very interesting.  Could
> someone please clue me in to the usefulness of analog computers in
music?
> Specifially the one described at the site below... what can it do?
> 
> please reply off list if this is OT.
> 
> Christian Oncken.
> 
> 
> 
> >You can still buy them new also. About US$250.
> >Normally pin plugs, but they will put banana plugs on if you ask.
> >Lab Electronics is run by a husband and wife engineering team.
> >The front panel is the printed circuit board with the
> >circuitry on the back.
> >
> >http://205.186.236.174/labelectronics/analogcomptrn.htm
> >
>