My old synths

Last update : august 30th 2005
 
My first DIY modular : the US1

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The US1 is my first 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)
schematic
1 x linear VCLFO Square, triangle and sine signals, V/Hertz.
Based on an application note of the ICL8038 waveform generator
schematic
1 x VC ramp generator Ramp generator, V/Hertz.
Based on PE modular synthesizer (1975)
schematic
1 x VCF HP-BP-LP The now famous Steiner-Parker VCF, designed by Nyle Steiner (Electronic Design, December, 1974)
schematic
I invite the DIYers to visit my page dedicated to this very filter, there they will find an improved version.
1 x HP filter A classical source controlled filter, 12db/octave high-pass filter
schematic
1 x VCA A differential pair of transistors with a voltage controlled current source.
schematic, lost origin
1 x balanced modulator A very classical design based on the µA796 (ancestor of the LM1496).
schematic
2 x AD shape generators Attack & decay (10ms to 10s).
schematic
1 x noise generator White and pink noise.
schematic,  lost origin
4 x voltage processors 1 x voltage adder
1 x voltage subtractor
2 x voltage amplifiers
schematics
Yamaha CS10 monosynth
The CS10 is a quite rare monosynth that was commercialized by Yamaha in 1978. I purchased it back in august 1978 for FF 3,100  (roughly US$ 620 of 1978). It has a V/Hz VCO with saw and square signals, PWM, a state variable multimode VCF, 2 ADSR envelope generators, a VCA, a LFO and a noise generator. It also provides an audio input with a schmitt trigger for processing external signals through the VCF.
The schematics and the service manual can be found at E-Music DIY archive
Mods : addition of an octave divider and of a V/Hz to V/octave converter, fancy knobs (aluminium cap) than the original ones (black plastic). Someday I might add chestnut cheeks to my CS10 just as did Erik G for his CS15.

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the new board

the new board installed
tt
the modified panel
Schematics of the mods
The PCB matrix
Component layout
CRUMAR Multiman-S polyphonic keyboard
The Multiman-S is a polyphonic keyboard featuring the following presets : string ensemble (cello,violin), brass section (nice sound), piano (a very bad mimic), a clavichord and an electric bass guitar. I purchased it back in july 1980 for FF 5,015  (roughly US$ 1,000 of 1980).
The Brass section is based on the famous voltage controlled Moog ladder 4 poles low-pass filter (I gathered that R. A. Moog collaborated with CRUMAR long ago...) with full control of the cut-off, the resonance and the envelope (AD). 
Here are the schematics of the Multiman S with the famous Moog ladder filter.
It also came with some optional devices such as a swell pedal, a frequency control pedal for the Moog filter and a low octave pedal board.
I think someday I will add to it a vocal filter bank in order to achieve an electronic "choir" effect! 

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