[sdiy] Digital pots for polyphonic portamento..

[Colin f]

> I'm building my MIDI2CV mono/poly module and have one question..
> I'm gonna have 6 voices CV's outs on my polyphonic mode
> and want to use a portamento pot that would control all 6 voices
> at the same time. I was guessing to use 3 dual 1meg digital 
> pots (6 pots overall)
> (Analog Device AD5242) and 6 caps to make the porta voltage glidings..
> Those are 256 taps which makes 1meg/256 = 3906ohms per steps 
> (+ 60 ohm for wiper).
> These would be place right between my MAX551 DAC's 0-5v outs 
> and my precision opamp 
> voltage followers. I don't want to create CV's 1v/oct 
> unprecision using them so..

If you're using a 12-bit convertor, do the portamento in software.
With any half decent modern microcontroller, you'll easily be able to
produce 6 simulated RC curves that you wont be able to tell apart from the
real RC circuits.
And software can easily provide alternate portamento modes, such as linear,
fixed time linear, glissando, etc.

Cheers,
Colin f