MUSICAL_ENVELOPE_GENERATOR_AND_MODULATOR

Published:2009/7/9 1:38:00 Author:May | From:SeekIC

A gate voltage is applied to initiate the proceedings. When the gate voltage is in the ON state, Q1 is turned on, and capacitor C is charged up via the attack pot in series with the 1-kΩ resistor. By varying this pot, the attack time'constant can be manipulated. A fast attack gives a percussive sound, a slow attack gives the effect of backward sounds. When the gate voltage returns to its OFF state, Q2 is turned on and the capacitor is then discharged via the decay pot and the other 1-kΩ resistor to ground. Thus, the decay time constant of the envelope is also variable. This envelope is buffered by IC1, a high-impedance voltage follower and is applied to Q3, which is being used as a transistor chopper. A musical tone in the form of a square wave is connected to the base of Q3. This turns the transistor on or off, Thus, the envelope is chopped up at regular intervals, which are determined by the pitch of the square wave. The resultant waveform has the amplitude of the envelope and the harmonic structure of the square wave. IC2 is used as a virtual earth amplifier to buffer the signal and Dl ensures that the envelope dies away at the end of a note.



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