[sdiy] TR-808 HH patch on modular

[Jeff Farr]

I've got some knowledge in this particular area :)
It's pretty late here, so I won't get into too much detail as I'll
surely make a mistake.

The 808 doesn't use white noise as the source for the hats, and as
such you will have a rather difficult time re-creating their character
with a modular system (CR-78 is a different story).  What it does use
is the same schmitt trigger oscillator that is used to create the
cowbell, the signal path travels to the envelope generator for the CB
and cymbal circuit in parallel and is filtered through a simple RC at
the cymbal (although, as mentioned there may be more frequencies fed
to the cymbal than to the CB).  The source is then passed onto the
hats, where the closed and open circuits use a different RC filter to
create a separate tonality for each.  IIRC the source for the CB, CY,
and HH's all come from a single point at the output of the schmitt and
it's nothing but RC processing that creates the difference in
tonality, but there may be some other processing going on here.  In
any case it is all very simple, almost crude, so don't try to get
fancy.

If I were to choose a modular system for recreating the sound it would
not be anything "moogy" and instead I'd be looking for some oddball
Buchla FM oscillators and simple low rez filters to do the job.  Using
ringmod on some cheap sounding OSC's to approximate the source tone
and then EQ's to do the processing is probably your best shot...
maybe.

The upside here is that the circuit to create the source signal
consists of a schmitt trigger and some RC's, nothing more.  You could
easily breadboard it in an hour :)   I've found the increasing the Q
in the signal chain can have some interesting results so processing it
through a modular would likely be rather entertaining :)

here is a schematic courtesy of Sebastian, indeed it looks like the CB
gets two squarewaves while the cymbals get 5

http://xlargex.xl.funpic.de/projects/808/schema/808_NOISE300dpi.jpg