muSonics Vanilla Oscillators - 5U Moog format module

Vanilla Oscillators is a dual oscillator using a core derived from Gene Stopp's ASM-1 and pulse shaping from our old 901 VCO.

There are two identical sections with a hard sync switch in between them. The left primary control input normals to the right primary control input so only one control signal needs to be patched to operate both of the oscillators. Sawtooth and rectangular waveforms are available on the front panel.

Coarse tuning has a bit more than a four octave range and the Fine tuning is approximately half of an octave. It is calibrated such that if Coarse is all the way down and Fine is in the middle with zero volts control input its pitch will be C0 at 16' which is about 32 cps.

Frequency Modulation is an attenuator for the FM input. This is an exponential input like the primary control input but is twice as sensitive to allow for wide modulations.

Pulse Width sets the base duty cycle of the rectangular output. There is also a PWM input which adds to this control.

On the rear of the module are an assortment of headers to connect to other modules in the system. In addition to a primary control bus input which is normaled to the left primary control input, there are inputs for the FM normals.

All four waveforms are presented here plus two not available on the front panel. The left VCO has a triangle and sine available inside the system and a control input for the sine level.

The circuitry inside this oscillator was outlined by Gene Stopp before he died. He wanted the new muSonics 901 to have the core of his ASM-1 synthesiser and the wave shaping of the old 901. This is not yet the new muSonics 901 so I thought it was more appropriate to use the sine shaper from Tom Oberheim's 1970s LFO because of the nature of The Vanilla Synthesizer.

I had to update these circuits quite a bit because components that used to be critical no longer exist. New components had to be selected and even though I limited my choices to the commodity market their performance and tone are incredible. I'm very proud of this oscillator.

Historical note: The ASM-1 core was based on Terry Mikulic's VCO from issue 62 of Electronotes. This is the most influential single paper for synthesiser design since Dennis Collin's AES paper outlining his State Variable Filter.