ADSR & VCA (Note the 'rat tail' with 0.1" 3 way socket for the normalised gate signal) 

ADSR/VCA Front Panel

ADSR & VCA Front panel 

You can find the UK parts listing in PDF form here. 

The standard issue of the ADSR & VCA module has the envelope generator output connected directly to the VCA CV input, but on my second unit, I have brought the VCA control voltage input to the front panel to allow external control of the VCA. To keep the same form factor, though I have sacrificed the OUT- socket. 

The modified Schaeffer front panel file is here. 

New update: 

I have added an LED indicator circuit which gives a visual indication of the envelope level. The LED is fitted just to the right of the 'RELEASE' legend on the front panel. 

This is based on a standard V/I convertor circuit, but with some modifications suggested by Tony Allgood. Diode D1 is added in anti parallel with the LED, otherwise the output of IC1B will be slammed into the +ve rail at every -ve excursion of the input.  The 100R series resistor, R2, keeps the power-on surges to a minimum. R3 reduces the small signal DC gain to 10 (with R1) so helps noise injection into any audio signals driving the circuit. C1 reduces the AC gain at HF to really silence any nasties. 

Here's the indicator circuit on a small piece of Veroboard 

I have also used a quad version of this circuit (with TL084s) and bicolour LEDs as indicators in my Control 3 module. (Note that with bicolour LEDs, Diode D1 is not necessary. 

ADSR/VCA Project Page 


Page last updated: 4th November 2004