Setting up
Setting up requires only two settings to be made:-
- P407 is set to determine the maximum volatge attained in the ATTACK curve,
- P401 is set to define the maximum SUSTAIN level that can be set by the panel control P402
The voltage at U402 pin 5 should be set to the desired minimum trigger level for the module. We recommend a setting around 1.5V as this compliant with the MOTM specification.
For general compliancy control signals should be from 0V to +5V. To comply with this the voltage at SP should be set to 5V by adjusting P401. The reader should note that, in this case, when P402 (SUSTAIN LEVEL) is set to maximum, there will be no DECAY curve and the envelope will follow an ASR curve. Readers may wish, therefore, to set the SUSTAIN LEVEL to a slightly lower level thus ensuring that the DECAY portion of the curve has positive action.
With P401 set we can now set P407 (ATTACK PEAK) which determines the maximum voltage that the ATTACK curve will reach before switching to the DECAY portion of the curve.
Set both P402 (SUSTAIN LEVEL) and P407 (Attack peak) to maximum and P403 (DECAY) to minimum. The following steps will then need to be repeated until the signal at ENVELOPE OUT rises to the desired ATTACK PEAK level and then immediately starts to decay :-
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generate a GATE signal, the ENVELOPE OUT signal should now, slowly, rise,
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when the signal goes above the desired Attack peak level adjust P407 until the ENVELOPE OUT signal starts to decay,
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remove the Gate signal and allow Envelope Out to drop to almost 0V,
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repeats steps 1 to 3 until signal at Envelope Out rises to the desired Attack Peak level and then immediately starts to decay.
The aim of these steps is set a level at the output of P407 which will cause the flip-flop, built around U404, to go from a Logic `0' state to a Logic `1' state at the same time that the envelope curve reaches the desired Attack Peak level.
This completes the setting up for the ADSR module.