MOTM

You might want to consider making use of the "falling-edge detector." I
don't think you want to full-wave rectify the pulses you get; rather use two
half-wave rectifiers, one to "peel off" the positive triggers and one the
negative. Then you can have a separate jack with the falling edge triggers.
You can combine the positive and negative triggers to a third jack for the
'absolute value' triggers as well. I can imagine some neat effects possible
by having a choice of up/down/both triggers.

I'm no EE either, so I can't answer your technical questions. I've dabbled
(on paper) with things like this myself, based on examples in Forest Mims
books, but haven't actually tinkered anything together.

This may be the wrong approach, but... if *I* were going to make such a
differentiator, I would probably start with a simple lag-integrator circuit
(cheaper synths have a one-op-amp integrator, low parts count) and use the
same parts rearranged into a differentiator configuration. I *think* you get
essentially the same kind of specs, just a reversed filter response. That at
least puts you in the ball park of the range you want to filter, since
you're creating a kind of "anti-lag" circuit.

I'm sure a real engineer would do some serious eye-rolling over the above,
but when you're tinkering... you do strange things.


 -----Original Message-----
From: 	mark@... [mailto:mark@...] 
Sent:	Monday, 12 March, 2001 11:07 AM
To:	motm@yahoogroups.com
Subject:	[motm] looking for help with edge detector circuit

.....

Even if I can get the differentiator to work, I would end up with both
negative and positive voltages.  So after this differentiatior, I would
need an "absolute value circuit" or "active full wave rectifier", I found
two on page 222.......