My first DIY analogue modular

The US1
Last update : june 7th 2009


The US1 is my first Do It Yourself modular (US1 shamelessly stands for Usson Synthesizer #1 !). I built it around 1979-1980 when I was a biology student at the University of Grenoble, France. In those days, I was an unwealthy student and I could not afford expensive specialized chips. It is all made with 741 OPAs and discrete components. The only "sophisticated" ICs were a ICL8038 waveform generator and a µA796 balanced modulator.
Connections were made with 2.5mm jacks. This choice was really bad but not too hard on my wallet then...

List of modules


 2 x exponential VCOs Saw and square signals, 1V/octave.
Based on a circuit designed by T.W. Stride (Wireless World, october 1977)

1 x linear VCLFO Square, triangle and sine signals, V/Hertz.
Based on an application note of the ICL8038 waveform generator 

1 x VC ramp generator Ramp generator, V/Hertz.
Based on PE modular synthesizer (1975)

1 x VCF HP-BP-LP The now famous Steiner-Parker VCF, designed by Nyle Steiner (Electronic Design, December, 1974)

1 x HP filter A classical source controlled filter, 12db/octave high-pass filter

1 x VCA A differential pair of transistors with a voltage controlled current source. 

1 x balanced modulator A very classical design based on the µA796 (ancestor of the LM1496).

2 x AD shape generators Attack & decay (10ms to 10s).

1 x noise generator White and pink noise. 

4 x voltage processors 1 x voltage adder
1 x voltage subtractor
2 x voltage amplifiers