[sdiy] saw-to-tri (was Re: Voltage Controlled Waveshape)

[harrybissell]

Hi John...

well of course they are.  Similar devices are used to tune circuits
such as phase shifters (where they are common)... but they do
not have the range and linearity that an actual 'pot' does.

There are ways to use OTA's to simulate variable resistances...
most useful if one end of the resistor 'happens' to be grounded...
but possible as two terminal networks as well.

The Vactrols are slow, and cannot go down to 'zero' (or even near)
ohms.

However, do not despair because the citizens of s-diy are probably
the world's foremost experts on how to control things electronically... :^P

but a simple pot is still hard to beat

H^) harry

john mahoney wrote:

> > The hard part is to replace this circuit with one that electronically
> emulates [potentiometers].
> >
> > (and Vactrols don't do it well...)
>
> You mean VCRs aren't Voltage-Controlled Resistors?! <G> Actually, Google has
> lots of results for Voltage Controlled Resistor, mostly about FETs.
>
> Looks like Vishay makes JFET-based VCRs:
>     http://www.vishay.com/docs/70293/70293.pdf
> I can't tell if those parts would work well in a synth. Somebody else know
> about these VCR devices? Are they used in synths at all? Thanks!
>
> --
> john