[sdiy] Figureing out Buchla timbre waveshaper

[mark verbos]

Aaron,

The FETs are a VCA controlling the level of the sine going and it's 
symmetry to GND. The CA3160s are all set to have so much gain that they 
distort, each art a different level. The fact that they alternate into 
the output mixer makes the gain zig zag between + and -. The diodes on 
the output section are a limiter, A sine wave goes in and as the voltage 
going to the FET based VCA is increased the top and bottom of the wave 
folds over on top of itself several times. The symmetry makes the folds 
happen more to one side as it is increased. This is very similar to the 
Serge wave multiplier middle section in sound, but not at all in 
implementation.

Mark



Aaron Lanterman wrote:
> 
> I've made some progress in figuring out the schematics to the Busic 
> Easel, particularly how the oscillator works.
> 
> But... I'm totally stuck on figuring out the timbre generator, which is 
> some sort of waveshaper thingy:
> 
> http://www.simple-answer.com/buchla_timbre.jpg
> 
> A sinewave goes in and who knows what comes out...
> 
> There's a whole bank of op amps - TL082 it seems - doing I'm not sure 
> what. Then there's some diodes on the right part of the page...  and a 
> dual FET near the imput.... man, I have no idea how to start thinking 
> about this circuit.
> 
> Any hints?
> 
> - Aaron
> 
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