[sdiy] moog module designs

[Tim Daugard]

Sorry all,

I've updated the PDF file.

 http://home.sprintmail.com/~daugard/DCP_21.pdf

The first change was answer a question from Harry about the rails. In my
case the +12 V and ground. After discussing the circuit, and thinking
about it when I should have been paying attention to my wife at lunch,
I've come up with a way to make it voltage controlled. I also think I
can pull the pin from the supply connector (top rail) and feed it from a
control signal buffer. I can feed the buffer from an LFO or envelope
generator and have instant voltage control. One more thing to add to the
list of things to try.

I posted this PDF as part of a discussion that started with Kevin about
moog modules. This just happened to be a page I was proof reading last
night (and a relatively simple module.) Ian Fritz pointed out that the
description mentioned an R7 that is not in the schematic. He is right. I
had made an ink change in my book, and missed it when I put the changes
in this morning.

I also realized that I had miss placed a decimal point (actually was
short one zero) when I put the numbers in my spread sheet. The response
curve has been updated, but still ignores the effect of the clipper on
the response.

http://home.sprintmail.com/~daugard/sch_symb.htm

Is the link to my schematic symbols that I put up a while ago. On that
drawing is the schematic for an LFO. It shows two different outputs I
typically use. It has an opamp buffer output and a current limited
transistor output. Either one can be connected to which ever pin you
want to use as an input to this circuit.

. . . and finally to link it all back to the earlier discussions, any
moog module I reproduce (emulate? copy? steal the design from?) will be
adjusted so it can feed a module configured like this input. And to tie
it to the CMOS discussion, the 4066s I have and use, drift the end of a
capacitor tied to an input to the negative supply rail when it is shut
off. This means that if a signal is AC coupled to a 4066 input pin and
the switch associated with that pin is shut off, the AC signal will be
periodically below the negative supply rail. If the input pin is more
negative from the supply rail, a signal current flows through that pin
(to the negative supply? I'm not sure of the physics of this problem
yet - just verified the effect through experiment) and causes signal
bleed through / distortion on the switch that is turned on. That is why
the output of the clipper is referenced to the half supply point. It
feeds enough current to a shut off 4066 to prevent bleed through.

Tim - who has to get off the computer before his wife comes back from
the errand she is running - Daugard

 AG4GZ 30.4078N 86.6227W Alt: 3.7 M
 http://home.sprintmail.com/~daugard/synth.htm