AM8112

SN-101 VCA & ADSR

This module is an accurate replica of the ADSR and VCA in the Roland SH-101 analog mono synth which was released in 1982.

The VCA is based on the BA662 OTA chip (AS662 clone) with two audio inputs without any attenuation (INA, INB), and an audio output (VCA OUT) with a rotary volume control.

There are no external CV inputs, as the VCA is controlled by the on-board ADSR. A small slide switch selects how the VCA is controlled; HOLD sets the VCA to a constant maximum level, ENV selects the on-board ADSR, and GATE selects the external gate signal.

The original ADSR circuit is based on a dual Op Amp with transistor switches and is a different topology to the contemporary Roland 100M. It has the following specifications:
Attack: 1.5ms to 8s
Decay: 2ms to 10s
Sustain: 0 to 100%
Release: 2ms to 10s
The AMSynths circuit replicates the original ADSR with the attack maximum increased from 4 to 8 seconds. The ADSR is triggered by the GATE external input or by both GATE and TRIGGER if the trigger input is connected. There is a manual momentary push button which also triggers the ADSR, and a red LED indicates a gate signal is present.

The ADSR output is available on the ENV OUT jack socket, so that the envelope CV signal can be patched into a filter, such as the AMSynths AM8101.

There are six 3.5 mm jack sockets on the front panel:
INA, INB - VCA audio inputs
GATE - tradiational +5V gate signal for VCA and ADSR
TRIG - +5V short trigger signal
ENV OUT - Output of the ADSR
VCA OUT - Ouput of the VCA
The module comes with a set of M3 mounting screws and washers, and a standard Doepfer power cable. Theere are soft red LED's in the sliders, set at a low level of illumination.

https://www.amsynthstore.co.uk/product/am8112-sn-101-vca--adsr