This is replica of the VCO in the Roland SH-5 monophonic synthesizer introduced in 1976. This was Roland first serious attempt at a more stable oscillator using a heated expo generator and fast CA3130 Op Amps, with a separate Op Amp power supply. It was used in the SH-5 as well as the System 100 and has a 5 octave range and 4 waveforms, as well as a sync facility.
Euro Rack Module: 14HP wide
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The AMSynths circuit is close to the original except for a new Tempco based matched transistor pair rather than the obsolete heated uA726 chip, as the exponential generator. This improves warm up time and precision. Original components have been used, along with a few careful upgrades:
- 1% integraor Polystyrene Capacitor
- LS312 Matched Transistor Pair
- Precision 5V and 10V references
- 8V regulated supply to CA3130 chips
The panel design keeps close to the original with a Pitch potentiometer, Range selection from 2' to 32', a choice of four waveforms (triangle, sawtooth, square, pulse), frequency modulation depth and pulse width. The VCO derives its frequency from the Doepfer keyboard bus, which can be switched off for a static VCO. We suggest using the VCO in pairs like the Roland SH-5 with the sync facility patched in.