VC Decay

[richardc64]

I'm trying to control the decay of a percussive envelope with a foot pedal, so that a higher CV = shorter decay. But all I can get is long and short, without any "in between." I've tried different values of base resistor and ways of biasing the transistor. I tried changing to a pnp transistor and reversing the pedal so that a lower voltage causes a shorter decay, but that, too seems to only want to be fully on or fully off.

Any ideas? (No LDRs, please.)

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[blue hell]

Try to replace the 100 E resistor with a diode (arrow pointing right), that way the cap would be loaded quickly but can not (immediately) unload to the left (when the pulse goes low) and so it has to unload through your decay circuit.

The left form has a problem I think in the way the transistor is controlled, basically a transistor is a current controlled device while you try to use it as a voltage controlled device there ... at least I think the 100 k base resistor would still be to low ... you could omit it and put like 10 k or so between the emitter of the tranny and ground instead. The 4k7 collector resistor could go then as well I think.

The right form more or less has that construction, so I'd expect that to work better (unless I didn't lool good enough ).

[richardc64]