[sdiy] Buchla 259 wave folder/Rail to Rail OPamps/CMOS inverts as opamps

[Romeo Fahl]

Looks like you just opened the door to CMOS based wave multiplication.

On Fri, Oct 2, 2009 at 11:41 AM, mark verbos <mverbos at earthlink.net> wrote:
> A while back Aaron asked if the OP496 was a decent replacement for a
> CA3160/CA3130 as used in the Buchla 259 wavefolder circuit. The circuit has
> 5 CMOS opamp stages in parallel set with different gains so that they all
> distort at various volumes, and then stay at the power rail making the
> overall output zig zag and fold over itself 10 times.
>
> Aaron was looking for a dual or quad opamp that would distort hard on the
> rail, like the ones in the original design, to get the same result. The
> OP496 costs about $6, so I don't see it as a viable replacement. I began
> wondered if a CD4069 could work for that. I mean, it has a MOSFET output
> right? it's used in lots of distortion boxes...
>
> Well, today I was doing a repair on one of my Buchla 259s and decided to try
> it out. I soldered some wires to the legs of a CD4069 and patched them into
> the module's sockets. It works, and it isn't noticeably  noisier. It does
> not sound the same as the original though, or look the same on the scope. It
> requires a bit more gain going in to hit all the folds. The thing is, this
> would be worth exploring more, since it's one chip instead of 5 and it
> eliminates 5 caps and 5 resistors. In a quick & dirty situation, this may be
> the ticket.
>
> Now I wish I had recorded a comparison....
>
> Mark
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>