From the Oakley website:
This is a very popular dual purpose module. Not only does it feature the classic four stage envelope generator, but it also has a high quality VCA onboard.
This highly useful circuit implementation hardwires the ADSR generator to the control input of the VCA. The signal at the VCA’s other input, the IN socket, will then be multiplied by the ADSR waveform. You can use any signal into this input, audio or CV. If you use CV, then the ADSR output level will be governed by the level of the CV. If you use audio, then the ADSR waveform will control the volume of that audio signal.
A typical use would have the IN socket being driven by the velocity CV from a midi-CV convertor. Thus the harder you hit the keys, the greater the ADSR output level. If you use this to control a filter sweep, this can create brilliantly effective touch sensitivity to your patch.
The circuit is configured so that if nothing is plugged into the IN socket, the module will behave as a traditional ADSR module. The output will rise to +5V at the attack peak.
The ADSR is operated by a gate signal, but can be triggered by slow rising CVs too, due to the built in schmitt trigger function. No additional ‘trig’ input is required.
The ADSR/VCA module is built on one PCB called the VC-ADSR board. Although the 1U panel design does not imply a voltage controlled design, the internal electronics are all voltage controllable. This allows blisteringly fast minimum attack and decay times. And yet, the controls with their true exponential response allow you to adjust the times with ease.
Also on this module is an LED. This gives a visual indication of the output level of the internal ADSR waveform.
The following times are for the unit in standard mode. Multiply all quoted times by 5.5 to get the times produced when in ‘extended’ range.
- Minimum attack time: 0.75mS
- Maximum attack time: 12 seconds
- Minimum Decay/release time: 1.8mS to fall from 90% to 10% of initial value.
- Maximum decay/release time: 15 seconds to fall from 90% to 10% of initial value.
- Normalised output voltage: Attack peak at 5V from OUT+
- Gate input to activate ADSR: >3V
- Range switch added.
- Front-Panel-Express MOTM style panel