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

[mark verbos]

I don't think that's the point....



On Oct 2, 2009, at 3:27 PM, Dave Leith wrote:

> Goldmine still has the original parts as low as .85 each
> http://www.goldmine-elec.com/
>
> worked for me
>
> On 10/2/09, 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
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