[sdiy] RE: Modified potentiometer response curves?

[Mattias Rickardsson]

At 14:24 2008-05-08, Paul Perry wrote:
>-----Original Message from Mattias R-----
> >I'd say that voltage transformation is a very different thing from pot
> >curve modification, where the input voltage should pass with only a
> >change in amplitude and where it is the _pot_ value that is actually
> >subject to a transformation.

I perhaps should have clarified from the start that it's mainly input 
sensitivity pots (for audio input levels and modulation amounts) that 
I'm considering here, not just CV offset pots (for cutoff frequency, 
oscillator tuning etc) where the output voltage can be tilted with 
diodes and other unlinear stuff. Sorry. :)

>Yes indeed.
>But - depending on your application - the problem might be best solved via a
>VCA approach, seeing as this is indeed S-DIY.
>
>In any case, an interesting way to get fairly extreme results is to have two
>op amps, controlled by ganged pots that are modified in slightly different
>ways, and then take the difference between the two outputs.

Yes, adding or subtracting two versions feels like the right way of 
getting some exotic curves. Would be nice to minimize the OP count, 
though... maybe even just use the input summing OP-amp that's already 
available with both its (-) and (+) inputs?  :-)


/mr