Dieter-
Ken Stone's Matrix mixer does the inversion thing without the multi-
taped center terminal pots. His design is shown here:
http://www.cgs.synth.net/modules/cgs33_matrix_mixer.html

He has a switch to turn it from normal (off-on) to Bi-polar (full
inverted-off-full non inverted) which is very nice. You may be able to
avoid the expensive pots my using some of his ideas (in your own
circuit of course). Maybe a taper can be found that would leave a wide
"off" zone and then no detent would be needed either (especially if
the mode can be switched from bi-polar to normal - the detent would be
odd in the normal mode)

I was wrong about the Buchla 205 - Looking at the schematics it
appears to not do the inverting bit. That is a very nice function but
if the cost/availability
of the pots is a problem, the "normal" version is still quite usefull.
-james

On Dec 4, 2008, at 11:13 AM, yahoo@... wrote:

> > I would like to see a 5x5 matrix mixer built around the Buchla 205
> > design. Each crosspoint would go from off, to full on, to full
> > inverted. Designed to pass audio or CVs. I know this module would
> not
> > be cheap because of the 25 pots, but it would be a very powerful
> > module for performance and patch building. I have the schematic and
> > parts kicking around but would love to see a true Doepfer unit and
> not
> > some DIY panel loudly sticking out of my rig like a sore thumb.
> >
> > -James
>
> Exactly this module will be released next year. Our only problem is
> that we
> could not find the potentiometers we want to use with center detent
> and
> center terminal (not the version used e.g. in the A-188-2 or A-138d
> but the
> horizontal version with the axis at right angle to the pcb). This is
> why
> it's not yet shown in the future modules list so far. Without center
> detent
> and center terminal it's hard to find the zero position and I think
> that's
> essential for a mixer with polarizer function. The simple version
> (only
> attenuators, no polarizers) could be released very soon as this is
> already
> available as a working prototype. But we want to try to find a
> manufacturer
> who is able to produce the desired potentiometer with center detent
> and
> center terminal. And the price will be not too much as all parts are
> located
> on one pcb only (that's why we need the horizontal version of the
> potentiometers). I think it will be in the Euro 100...150 range.
>
> Best wishes
> Dieter Doepfer
>
>
>



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