[sdiy] New and Improved Buchla waveshaper analysis

[mark verbos]

Aaron Lanterman wrote:
> 
> Here's my new rendition of the nonlinearity from the timbre circuity of 
> the Buchla 259 Programmable Complex Waveform Generator:
> 
> http://users.ece.gatech.edu/~lanterma/buchla_nonlinearity.png

that's more like it! Now there are as many points as I expected.

> 
> The original one I posted had a flat, zeroing part in the middle. That 
> was due to me accidentally losing a resistor multiplier when I did the 
> algebra on the analysis, which gave the nonlinear parts a gain of 
> thousands of times greater than they should have been, hence swamping 
> the direct part. Once I fixed that, I now get a nice "toothy" transfer 
> function.
> 
> Someone posted a link to oscilloscope plots of the Serge wavefolder; I 
> can't seem to find that link again, but this looks similiar to what I 
> recall seeing, except I remember the Serge gave a more rounded transfer 
> function.
> 
http://www.musicsynthesizer.com/Circuitry/nlt.htm

> Granted, I did my analysis based on assuming "ideal voltage starved op 
> amps" - the real Buchla circuit might give a more rounded transfer 
> function.
> 
> Here's my two new soundfiles:
> 
> http://users.ece.gatech.edu/~lanterma/buchla_timbresweep.wav
> http://users.ece.gatech.edu/~lanterma/buchla_symmetrysweep.wav

yes! That sounds like I remember.


> I'd like to do the same analysis of the Music Easel shaper - but I can't 
> find the power supplies to the op amps!

there is none. That RC4136 is run from +/-15 volts. It works too, I 've 
built it. It sounds very similar.

Mark