AM8010 VCA

Replica of the VCA in the Roland SH-5 mono synth introduced in 1976. A simple design based around the CA3080 OTA chip, but with the unusual addition of a Panning control and dual output

The AMSynths circuit is similar to the original and based around the CA3080 OTA chip. A modern AD8273 Class D Audio Line Driver has been added to improve the final output stage, providing both level and panning controls. The complex CV driving circuit of the original has been simplified as the CV levels in the rest of the AMSynths range of SH05 modules have been normalised to +7.5V.

The panel design keeps close to the original with 2x signal inputs that go straight into the VCA. There are two modulation inputs (MOD, ENV) for connecting external CV’s to control the level of the input signals, and a gain control labelled HOLD. Then finally there is a overall signal output level control (OUT LEVEL) as well as a center detent panning potentiometer and two outputs (LEFT and RIGHT).

There are six 3.5 mm jack sockets on the base of the front panel:

2x signal inputs (INA, INB)
2x modulation Inputs (MOD, ENV)
2x audio outputs (LEFT, RIGHT)
Module Output Level This module is designed to be the final stage in a Euro Rack setup with the stereo outputs connected to professional grade mixers and audio converters. The output level is therefore lower than the input level, with a typical single 5V peak input signal into the VCA creating an output at +4dB when the OUT LEVEL is set to 8.

Module Outcome & Availability The PCB’s were laid out in late 2017 and a prototype tested before Xmas. A couple of defects were corrected and the VCA works well, with a really nice Panning feature. The production PCB’s were ordered in the Summer of 2018 and completed modules and PCB sets are available in our web store.

https://amsynths.co.uk/home/products/amplifiers/am8010-sh5-vca/