MOTM

Some time ago there was discussion of a tracking generator type circuit
on the MOTM list.  Jim Patchell designed such a board based on a circuit
submitted to the Synth DIY list by Martin Czech.  Here's a link to Jim's
site showing the technical details:
http://www.oldcrows.net/~patchell/shaper/shaper.html.  

I plan on building two of these for my MOTM system.  The design uses
inexpensive parts available from Mouser.

This board supports four positive and four negative breakpoints with
breakpoint and gain controls.  Adding the center range and gain
controls, this would be 18 knobs of controls, or a 5U MOTM panel.  This
is more than I want, so I plan on a panel that supports 2 positive and 2
negative breakpoints in a 3U form factor.  Here's what I had in mind:

__Knobs__
Breakpoint 1 +
Breakpoint 1 + gain
Breakpoint 2 +
Breakpoint 2 + gain
Center range
Center gain
Breakpoint 1 -
Breakpoint 1 - gain
Breakpoint 2 -
Breakpoint 2 - gain

__Switch__
Limit On/Off (limits output range as this circuit can create large DC
shifts)

__Jacks__
Breakpoint modulation 1 + input
Breakpoint modulation 2 + input
Breakpoint modulation 1 - input
Breakpoint modulation 2 - input
Input
Output

There's no bandwidth limitation on this circuit, so it can be used for
control voltages or audio.  The breakpoint modulation inputs allow
modulation of the breakpoint locations, a nifty feature that Jim added
at my suggestion.  

I'd like to find out who else would be interested in these.  Jim says
he'll be making another batch of boards soon.

John Loffink
jloffink@...