[sdiy] Weird filter in OB-Mx noise circuit

[mark verbos]

You could tap out the red and white in that circuit if you wanted them. 
White (+3dB noise in Buchla speak) shows up at U25 pin 7 and red (-3dB 
noise) is at U21 pin 1.

he's mixing the red and white noise together to get pink. I'm not sure 
why he runs the red through a cap though. Maybe he just played with the 
circuit until he liked the sound and then re-used it in all his modules. 
It does change slightly from module to module. He simplified the final 
stage for the OBMX.

Mark



Aaron Lanterman wrote:

> 
> On Tue, 18 Apr 2006, mark verbos wrote:
> 
>> what you see there is Buchla's way of filtering down white noise into 
>> pink noise. It is similar to what he did in the 265  and 266 Source Of 
>> Uncertainties' noise sections.
> 
> 
> Oh, I know _why_ it's there - I just find it interesting that I've never 
> seen that particular combination of caps, resistors, and op amps 
> before... how did he come up with it, I wonder?
> 
> - Aaron
> 
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