Wed Dec 22 22:00:23 EST 2010

Pot tapering - does it actually work?

Context: the problem is that it's hard to obtain dual-gang reverse log
pots for frequency control, but the linear parts are easier to get.

In ``The secret life of pots'' [1] it is explained how to create
different voltage divider or resistance curves based on placing
resistors in parallel with wiper and end.

How wel does this work?  And more importantly, what do the pots I can
(would) actually buy look like?

It all depends on the application, right?  Making a 20Hz to 20kHz RC
oscillator requires the middle position to have the geometric mean of
sqrt(1000) = +- 30.  This seems pretty steep to do with the parallel
resistor trick.

I wonder how good the tapers are for the log pots I got from Futurlec.
They give a 1/2 resistance of 13% or about 1/8, and they do seem to
have a dual-linear range with a knee at 12k for the 50k pot.

[1] http://www.geofex.com/article_folders/potsecrets/potscret.htm