Gate out trigger circuit after initial trigger?

[StephenGiles]

I want to energise a trigger circuit which drives an envelope follower, and then stop it being triggered for a preset amount of time. How is this done? is it possible with a network of 4001 /4016??
Stephen

[Transmogrifox]

Go take a look on the web for a 1-shot multivibrator design.  You can set the time constant out to a couple seconds on an op amp monostable circuit.

[gez]

A 'retriggerable monostable' might be more useful.  If you drive it from a comparator with a variable 'threshold' control you can set it up to operate in a similar manner to an envelope follower.  Once the signal goes below the threshold set by the comparator then the monostable is finally allowed to finish its cycle.  If you play a note (of sufficient amplitude) in the interim the whole shebang starts up again (more musical than waiting for the cycle to end).  Works well, is simpler than envelope control (though different) but is prone to some of the same problems (hi frequencies need a boost if you’re using it with a guitar, otherwise you won’t necessarily trigger the damn thing).

Furthermore, the output of the monostable can be used as a control voltage.  Feed it to an active integrator set up to clip and you get a trapezoid output.  You can control the time of ramp-up/down to get slow attacks/decays.  Alternatively, use the output of the monostable to control switching.

The 4098 chip is ideal (one cap and one resistor in series with a pot), plus you get two in one package.

[StephenGiles]

Thanks for the suggestions. I've just been trawling through countless patents covering Pitch Extraction, some of which I saved and will give the numbers over the weekend - from a hit coming out of a 1 shot multivibrator search!
Stephen