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AM8140 Module - Roland 100M Dual ADSR
Overview This
module is a clone of the ADSR envelope generator in the Roland 100M analog modular synthesizer. Roland started out with Unijunction based ADSR's in their early synths such as the SH3 and 700M, but switched to a more traditional PNP/NPN
transistor version in the SH-7 and 100M around 1978. The specification for the 100M version states quite slow minimum Decay and Release times of 4ms, so I was a little reluctant to clone the design in case it was too slow, and I would
have a sleepy ADSR on my hands.
AM8140 Circuit The circuit is the same as the original with the same Japanese transistors but the following upgrades:
- TL07X Op Amps
- 1M log pots instead of 2M log - simply due to availability
- Selectable envelope stage times like the 700M (Fast/Slow)
- Front panel push button and LED
The circuit is really easy to put together and it works well. The envelope times are in fact very very fast and I had to increase the size of the storage
capacitor (to 15uF) to get to a nice 1ms to 10s range. The output control voltages are 0V to 10V and -10V to 0V.
The module has the following front panel controls for each ADSR:
Attack Decay Sustain Release Manual Gate Gate On LED
There are six 3.5mm jack sockets mounted on the left hand side of the panel, these are:
Ext Gate (x2) Output (x2) Inverted Output (x2)
Front Panel The front panel is a 3" wide FracRac with Alpha rotary potentiometers, with 15mm diameter plastic mixer knobs.
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