[sdiy] digitally controlled potentiometers

[Andre Majorel]

On 2007-05-06 12:39 -0500, Paul Schreiber wrote:
> Just something to think about:
> 
> The average person, turning a standard 300 degree rotation pot,
> can set that pot to ~50 *repeatable* positions. Or within +-3
> degrees. Digital pots having 128 discrete steps actually have
> *better resolution* than you yourself turning a pot and then
> having it "remembered" (like say a P5 or OB-8).
>
> No one will even notice 128 steps as a 'loss of accuracy',
> zipper or no zipper. Certainly 256 steps (8-bit binary weighted)
> is overkill.

On an MS-20, the fine tune pot for VCO2 has a range of a little
above +/-1 octave. At 100 Hz, you can reliably set VCO2 to within
about 0.2 Hz of VCO1. That's less than +/-0.003 octave.  With a
digital pot you'd need about 350 steps to have the same
resolution.

But it's a pain to do. As a user I would certainly prefer two
7-bit pots in coarse/fine arrangement to a single 9-bit (or 14-bit
!) pot.

-- 
André Majorel <URL:http://www.teaser.fr/~amajorel/>
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