[sdiy] Modified potentiometer response curves?

[Mattias Rickardsson]

Hi all tweakers,

the response curve of a linear pot can be altered in clever ways.
For instance, shunting it to ground gives a "fake log"-ish curve:

	http://sound.westhost.com/project01.htm

and a "double-pot-ish" balance/pan pot is often constructed like this:

	http://www.headwize.com/images3/balvol.gif

I'm wondering... are there other clever ways of bending a pot 
response to new useful curve shapes by means of resistors and perhaps 
some OP-amp etc?

I'm dabbling a bit with a construction for a "bipolar log pot", 
almost like an x^3 curve, but it feels like wheels like these have 
probably been invented before. :-)


/mr


PS.
To conclude, I can mention this article where the "fake log" 
construction is strongly criticized compared to a "real log" pot, see 
the picture at the bottom here:

	http://tangentsoft.net/audio/atten.html

Blue curve is linear, red is [ideal] log.
I can agree with them for a big volume knob on a hi-fi amp playing 
various unknown audio sources with very different volume 
levels  -  but for use in synth contexts I actually consider a "fake 
log" response like the green curve to be far superior both lin and 
log pots. The majority of the pot turn becomes nearly log, but over a 
smaller output range - which suits the often quite well-known signal 
levels well - and the curves gets steeper in the maximum end, which 
makes it easier to incorporate an optional overdrive at the input pot 
of, say, a filter.