[sdiy] Buchla 258

[mark verbos]

Aaron,

be careful. In the modded verison on my site, I replaced the discrete 
OTA with a 3080, Don didn't do that. The discrete comparator allows him 
to derive a sawtooth in the waveshaper. There is a discrete comparator 
circuit very much like this one in "The Art Of ELectronics." He switched 
to 311's in his later oscillators.

Mark




Aaron Lanterman wrote:
> 
> As an addendum to my last e-mail asking for triangle VCOs - my comments 
> about Buchla before (the discrete OTA) was in regards to a 259 I think 
> (or maybe it was the Easel 208, I don't remember now).
> 
> Anyway, the 258 is different - looking at Mark Verbos' version, I see 
> the 3080, and the LF356 forming the integrator - and then there's three 
> transistors forming - what is that? I'm guessing it's some sort of 
> discrete comparitor, but I'm not sure why Buchla would want to use that 
> if he had 311s available...
> 
> I need up look up discrete BJT comparitors to figure out what's going 
> on, I think...
> 
> - Aaron
> 
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