Operation Manual

6.2 ADSR 69
6.2 ADSR
The ADSR is an envelope generator. It uses a gate signal for input and
generates an output envelope signal. An envelope is a time varying signal
having a value between 0 and 1 Volt. It is divided into four, the Attack, Decay,
Sustain and Release which can be adjusted as shown in Figure 2. The attack
is triggered by an input signal exceeding a threshold value of 0.1 Volt. During
this phase, the output signal goes from 0 to 1 Volt during the time set by the
Attack knob. When the output reaches 1 Volt, the decay phase begins, and the
output signal decreases from 1 Volt to the sustain level during the time set by
the Decay knob. The sustain level, set by the Sustain knob, is then held until
the input signal drops to less than 0.1 Volt. The output signal then decreases
to 0 Volt during the time set by the Release knob. The red LED beside each knob indicates the
current phase of the output envelope. Finally, the lin/exp switch is used to determine the shape
of the different segments of the envelope which can be either linear of exponential. Note that in
Figure 27 the segments are exponential.
attack decay release
sustain
key pressed key released
1Volt
1Volt
Figure 27: ADSR response curve
The default value of the following parameters is set during construction
• Attack: duration, in seconds, of the Attack phase.
• Decay: duration, in seconds, of the Decay phase.
• Sustain: level, in Volts, of the sustain phase.
• Release: duration, in seconds, of the release phase.