[sdiy] Ridiculously PC (Phase Correct)

[Grant Richter]

Well, having stared at the 208 and 259 a good bit...

The 259 waveshaper produces the same result as the middle section of a Serge
wave multiplier.

See

http://www.musicsynthesizer.com/Circuitry/nlt.htm

for the transfer function.

The balanced modulator has a really funky circuit with two Vactrols in the
feedback loop of an op-amp. This is just the usual trick of putting a
non-linear element inside a feedback loop to compensate it. I believe the
trick also considerably extends the high frequency response by forcing
exaggerated slew rates at higher frequencies.

I have a number of oscilloscope shots of an active 208 oscillator in various
places. Have not had a chance to post them as planned.


> From: Don Tillman <don at till.com>
> Organization: Don's house, Palo Alto, California
> Reply-To: owner-synth-diy at dropmix.xs4all.nl
> Date: Wed, 7 Nov 2001 23:09:06 -0800 (PST)
> To: cfmd at swipnet.se
> Cc: synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] Ridiculously PC (Phase Correct)
> 
> Date: Thu, 08 Nov 2001 01:11:24 +0100 (CET)
> From: Magnus Danielson <cfmd at swipnet.se>
> 
> We then discussed the building of a phase correct oscillator based on
> a triangle core. As I was looking into just one such oscillator this
> evening (actually just the schematics, but who cares) I saw that it
> indeed is phase correct. So, there is commercially made phase correct
> VCOs, and the winner is: Buchla 259!
> 
> Anyone interested in the details can pick the schematics of my site.
> 
> Ummm... this is going to require some time to digest.
> 
> (That's my understated way of saying "Good Lord, this thing is
> insane!") 
> 
> -- Don
> 
> -- 
> Don Tillman
> Palo Alto, California, USA
> don at till.com
> http://www.till.com
> 
> 
>