## How to derive a gate from audio input?

Scope and XITE Development

Original topic on PlanetZ: https://forums.scopeusers.com/viewtopic.php?t=4874

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Posted: Sat Mar 30, 2002 9:22 am
by castol
hello all,
this may not be the right forum to post this, but you scopers seem to have an idea of how to do this sort of stuff which can be applied in the modular.
i am building an effects patch in the modular with two multi lfo a's i would like to be able to trigger on audio input. so as to be able to use the nice complement of , initial phase, restart, delaying and fading, on this module.
the envelope follower seems like a likely canidate for doing this.
i've done some testing on a simple patch with with just an oscillator, constant freq, attenuator, adsr env and vca. adding an envelope follower to try and trigger the adsr envelope on audio input.
hooking up the env follower straight to the env gate in, no matter what, the gate is allways triggered as on.
offsetting (via a 2 channel mixer) the envelope follower with a constant bi-polar val module i can get it to sort of trigger on and off based on audio input, but it is very scratchy (from being triggered at an audio rate?), and fiddly to get to work.
i guess what i need to do is hold this level after reaching a cetain threshold.
there is a "hold" button on the envelope follower, it is only a manual control though.
it seems to do what i am thinking, but would there be a way to do this based on an audio input threshold. whereby it would hold this level or value, and then after x amount of time release it to some value which would be interpreted by a gate input as off (i'm not sure what is on -vs- off or if even there are two value to a gate signal).
a sample & hold sounds like it may fit into the equation, no?
i'm not sure where to progress from here.
any advice would be appreciated.
what i'm probobly going to do for now is just use midi to provide the gate i want (the patch is intended to effect another modular patch). but i'd still be interested to know how to do it on audio input. as it would be that much more dynamic in effecting audio which isn't midi based.
thanks.