[sdiy] VCRs and OTAs (Re: saw-to-tri / Voltage Controlled Waveshape)

Harry Bissell Jr harrybissell at prodigy.net
Mon Aug 4 16:32:42 CEST 2003

I'm thinking more of circuits where a pot does
two things... such as pass an increasing signal
to one terminal at the same time it passes a
signal to the other... like a pan pot, or
or the pot used for variable duty cycle in the
LFO we were discussing (early in this thread).

Agreed... we can do voltage control... but sometimes
that means that we feel a LOT of pain dealing with the
not-so-ideal active components (like the OTA)

OTA feedback in a filter is OK, because you probably
don't care about the small but variable offset voltage
(its not a big bug there) but in a VCO it could be
a showstopper...

H^) harry

--- john mahoney <jmahoney at gate.net> wrote:
> > There are ways to use OTA's to simulate variable
> resistances...
> Looky here, a DIY polysynth using an OTA for voltage
> ctrl'd Q on the VCF:
>     http://membres.lycos.fr/romcio/poly/adsr.html
> > but a simple pot is still hard to beat
> Sure, knobs is good! ;-) I always liked the TG-33
> for its little joystick,
> speaking of crossfades.
> But VC means never having to turn a pot, and manual
> control isn't for
> everything.
> --
> john

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