Triggering autowah/envelope follower with drums?

[sfr]

After playing with my new wah pedal, I'm interested in building an auto-wah/envelope follower type pedal where the effect is triggered by the snare or kick drum.  I played around with some stuff in my recording software and found it useful - could actually be cool using it to trigger a variety of effects depending on the situation.

Looking at some schematics, it seems easy enough to figure out where to feed the external input, but the part I'm wondering is what to use to get the drums into this input - a microphone?  Some sort of piezo thing?  Some sort of commercial drum trigger?  (Considering that I want to use traditional acoustic drums to trigger an effect, rather than replace a drum with an electronic one, perhaps that last one isn't ideal?)  Any ideas?

[Mark Hammer]

A piezo disc would be just fine.  Ordinarily, the recommendation would be to use a high-impedance buffer on the input, but in this case all you really care about is envelope, and the audio properties of an impedance-mismatched piezo sensor are of little concern unless bandwidth loss at the low end hampers triggering.  The typical gain of most envelope-follower/rectifier sections is usually high enough that a solid thwack on a drum skin with a decent 1" disc mechanically coupled to the shell ought to generate at least 100-250mv which compares quite favourably with a solid power chord.

The DrQ/Quack/Nurse-Quacky configuration is probably the easiest arrangement to co-opt for this, since the sensitivity of the rectifier is separate from the filter (as in the Mutron).  The Bassballs and DOD-FX25 structure would also work nicely.  My guess is you'll want to aim for a very quick attack time so the resistance after the rectifying diode (the one in series after the op-amp) should be minimal.  Also recommended would be a slightly larger cap to ground and a variable decay pot.  Shorter decays create a more percussive feel, which is what you're going for, I gather.

[StephenGiles]

And if you want to combine this with the old disco drum effect, the EH Spacedrum would do the trick