[sdiy] digitally controlled potentiometers

[John Mahoney]

At 01:39 PM 5/6/2007, 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.
>
>Paul S.

Although that sounds reasonable, I don't think that repeatability is 
the issue. I'm pretty sure that I've made adjustments that are finer 
that +/-3 degrees! Especially (for example) when there is a VCF 
that's self-oscillating or just on the edge of self-osc.

Where one digital pot doesn't provide fine enough control, you could 
use both coarse and fine controls.
--
john


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