Analogue Computers

[Grant Richter]

Dan Slaters article on chaotic synthesis sparked my interest in analog
computers again.
Nice to see Comdyna is still in business, their pricebook puts the GP-6 at
about $2K new.
An extremely well designed unit. Uses banana plugs.

http://www.comdyna.com/

A more affordably priced unit is available from LAB electronics.

http://www.surfindia.com/labelectronics/

The Model X-3 Analogue Computer Trainer is available for $213 plus $35 S/H.
It is a large blue PCB which forms the front panel for the unit.
That is enclosed in a black briefcase similar to a Synthi. The circuitry is
on the back of the PCB. Connections are made to pin plug binding posts.
It comes with roughly 25 brightly colored pin to pin connectors. A large
analog Center 0 meter with ranges switchable from +/-15V (300K) to +/-1.5V
(30K)
Three Summers, four Integrators and a Differentiator. Each op-amp stage has
two LED's with it, one lights when the op-amp is above 10V,
the other when it is below -10V. The unit contains a +/-15V 1 amp power
supply brought out to four sets of binding posts and 
six 1K 1W wirewound potentiometers brought out to binding posts. All
resistors are 1% metal film. Input resistors are 1 Meg and timing
capacitors are 1.0 uF mylar film.

I had to hotrod it of course. I added a big switch to switch all the timing
caps over 5 decades. To the differentiator I added a switch to reverse the
op-amp leads and make it a "hysteric comparator" for patching oscillators.
As I was staring at it I realized that if you replaced the input resistors
with OTA's you would have virtually every filter ever imaginable under your
fingertips. Including those ones Bernie Hutchins used to diagram in
Electronotes.
Sort of a big patchable super-module in a briefcase. Which is my next
project, but first I have to replace all those pin jacks with banana jacks.

I put up a little web page with some pictures:

http://www.execpc.com/~grichter/analogue.htm

Be absolutely groovy to each other,

Grant Richter
Wiard Synthesizer Company - "Oxygen Free Modules"
http://www.wiard.com/