Tim's Ancient Analog Synthesizer Page  

This is my Monophonic Synthesizer. It was designed and built in the late 1970s.
It is shown here with all the patch cords removed so the panels are more visible.
Some of the modules were never completed beyond the panel.
Click any image for a bigger version.

I apologise for the quality of some of the schematics. They were done before PCs
and schematic drawing software was available. Also, many of these designs are
obsolete now. There are many good synth schematics available on the web.

I've got a lot of other old schematics which I may add to this collection if there is any
interest. I read and recommend the SYNTH-DIY mailing list.  Due to spam, I
can't provide a mailto: link, but if you want to contact me, use tim (at) chromaticsound (dot) com.


Unfortunately, I seem to have lost the schematics for the VCO modules.
However, there are a number of good designs available on the web that I would
consider if I was starting today. See ASM-1 homepage for example.

VCF - 2 pole state variable

This is one of the better documented modules. Both the schematic and PCB diagram
are on this page. Also, I have scanned a research paper I did on the design, which contains
the schematic as well as a number of design equations and derivations. It is in Acrobat format:
Voltage Controller Filter Research Paper


This circuit uses the rather obsure technique of
parallelling the CA3080 inputs with a biased diode
bridge to compensate for the non-linear response
of the OTA. Thus the input levels could be increased,
and a better signal to noise ratio was achieved.
Much better VCA chips are available today.

ADSR Envelope Generator

Sample and Hold


Ring Modulator

The MC1595 is a true 4-quadrant multiplier.

LFO (8038 based)

I added an extra output stage to turn the symetrical
triangle output into a true rising or falling sawtooth.

Pseudo Random Noise Generator

This circuit is incorporated into the same module
as the LFO. It generates white and pink noise, as
well as filtered random low frequency control


This is a typical design using the now scarce