The ADSR Envelope Generator’s primary role in the modular synthesiser is to take a Gate input and generate dynamic control voltages which change over time. The Gate is usually provided by a sequencer or keyboard, when a key is pressed the gate goes high, which the key is released the gate goes low. The code within the module translates this gate signal to the various stages of the control envelope: Attack, Decay, Sustain and Release. This control voltage out can then be patched into a VCA to control volume, VCF to control frequency cutoff or VCO to control other modulation parameters such as FM or PWM.
Linear vs Exponential
The human ear hears both volume and pitch exponentially, so having exponential control over these elements is crucial. It’s usual to drive a VCA with an ADSR, however only one of these should be exponential.
Linear ADSR vs Linear VCA: No exponential control.
Expo ADSR vs Linear VCA: Good exponential control.
Linear ADSR vs Expo VCA: Good exponential control.
Expo ADSR vs Expo VCA: Too much exponential control.
The Equinox VCA and VCF are exponential, the VCO has both exponential and linear control.
+12V: 20mA, -12V: 20mA