Modular Beast

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There is an old-skool 'Digisound 80' synthesizer at LAG:

Formant.jpg

Originally built at the 'Synthese Studio' in Maastricht in the early 80's it was used for a lot of experimental work on audio and visual performances.

It needs some love, but mostly functions. Although many of the labels are worn and many of the knobs and ports are undocumented.

You are welcome to come to the lag to play with this beast from the past!

As the machine is in a fragile state we are in the process of renovating it.

About

The Digisound modular synth was published in the 80's by Charles Blakey. Some of the modules where described in two British electronics magazines - Electronics Today International (ETI) and Electronics & Music Maker (E&MM). A digital reference for the Digisound 80 system can be found here.

One of the filter modules originates from the 70's electronics magazine 'Elector' (or 'Elektuur' in the Netherlands). A reproduction of the original Elector articles with designs and explanation can be found here.

The Modules

Power Supply

A rather straightforward +/- 15V power supply. We removed the cable-spaghetti in the back and made a powerbus, which has the following pinout:

+15V      0V     -15V     0V
 _______________________________
| O   O   O   O   O   O   O   O |
| O   O   O   O   O   O   O   O |
|_______________________________|
      0V    -15V      0V     +15V

So that's a 16-pin plug with +15V at the sides, -15V in the four middle poles, and ground inbetween. It's symmetric, so it's impossible to plug it the wrong way around.


VCF (project 80-7)

Labeled PROJECT 80-7 on the PCB, it has 'State Variable Filter SSM2040' handwritten on it.

IC's: LM13700N , SSM2040 (careful: unobtainium), TL072CP (2x), TL081CP

More documentation on the Project 80 VCSVF page.

VCF (project 80-6)

Labeled PROJECT 80-6 on the PCB, it has 'VC LPF' handwritten on it.

IC's: CEM3320 (careful: unobtainium), TL071CP , TL072CP

More documentation on the Project 80 VCF page.

Envelope Generator

There is a little additional circuit to improve triggering with a Schmitt Trigger

Links