AM8008 SH05 VCO

Clone of Roland SH-5 VCO

This is replica of the VCO in the Roland SH-5 monophonic synthesizer introduced in 1976. This was Roland first serious attempt at a 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, SH-1 and System 100 and has a 5 octave range and 4 waveform as well as a sync facility. Roland took a lot more care with this VCO, including precision reference voltage rails.

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% Polystyrene Capacitor
LS312 Matched Transistor Pair
Precision 10V reference

The CA3130 chips can only work up to a maximum combined supply voltage of 16V, so there is a separate asymmetric power supply for these two chips (-5V and +10V). The CA3130 was one of the first fast FET Op Amps introduce in 1974 which makes it suitable as the core of the VCO. It has a P-Channel MOS input and a CMOS output stage, and is used as the integrator and comparator. .

https://amsynths.co.uk/home/products/oscillators/am8008-sh05-vco/