[sdiy] Back to that drum topic...

[Gene Stopp]

Hi DIY,

Been watching that drum thread recently... turns out I've been tossing
around the same kind of ideas lately. A while back I made a drum set for my
kids (which is a great excuse these days to make something for ME). It
consists of an Alesis DM-5 rackmount drum module and a bunch of old
margarine tubs with PC speakers in them as triggers. The tubs are screwed
into a piece of wood mounted on top of the DM-5 so the whole thing is
somewhat portable. It was meant as a test setup but it worked so good that
it's still that way.

Anyway I also have a Moog drum controller that sits next to it, going into
my big analog mess in the music room. It's currently wired into a modular
and naturally makes some pretty wild sounds. I want to free up the modular
stuff and make a little portable sound module dedicated to the drum -
something portable that makes noise and holds a power supply for the drum.

So here's what I've been thinking:

a) An ASM-1 stuffed with low-cost parts like non-matched pairs and no
tempco's (save those parts for keyboard use), with some kind of limited
front panel controls pre-patched for drum noises

or

b) Some kind of circuit dedicated to percussive synthesis

One idea:

Multiple fixed oscillators at non-harmonic intervals each with their own
decay envelope

Osc 1 ---> VCA ---> output mixer
Env 1 ------^

This circuit times six or eight? Each osc would have a tune control, each
env would have a decay control. Also one chain with a noise source instead
of an oscillator maybe...

I'm thinking the oscillators could be simple tri-square dual op-amp jobbies
with a tune pot. The VCA's could be 3080's etc. (you can mix their outputs
by shorting them together, I've been told). The Env's could be simple
decay-only contours all hit with the same trigger pulse.

Any thoughts? Would it be useful to apply the envelopes to the pitch of the
oscillators, also? Is there a cheap low-parts-count way to slightly alter
the frequency of the integrator-comparator type of oscillator without making
the integrator an OTA?






Best Regards,

- Gene