Pro One

Analogue monosynth with two oscillators based on the CEM 3340 VCO chip. Oscillator A offers saw and pulse waveforms, Oscillator B offers saw, pulse, triangle, and has an additional noise source. The design allows for programming because of multiple modulation options: Filter output, VCO B and LFO can modulate VCO A or B (frequency modulation), pulsewidth, or VCF cutoff. The LFO offers saw, triangle and pulse waveforms. The filter is also based on a chip, the CEM 3320, providing a 4-pole lowpass with cutoff, resonance controls. ADSR Envelope and keyboard tracking are also modulation sources for the cutoff control. The VCA has a seperate ADSR envelope control. There’s an arpeggiator with up, up/down patterns and has a latch mode. The sequencer can hold two 40-note sequences offering pitch control for the oscillator pair. External control is possible with the CV and Gate controls.

The synth has a 3 octave 37 key keyboard, of which there are two variants; the more reliable J-Wire and the membrame versions. The J-Wire can be identified visually, becaue all the keys have 2 small plastic extrusions at the top end of each key (usually hidden behind the top cover). The keys from the membrame version have metal mounting clips protruding from the top end of each key.

The Pro-One is a popular synthesizer, and valued for it’s raw sound and flexibilty in creating sounds, but not for it’s crappy build quality. About 10 thousand Pro Ones were produced from 1981 to 1984.