Exponential potentiometer

Why do you want an exponential volume pot? Human hearing operates in a logarithmic manner ... exponential is the oposite to logarithmic and so would result in an even worse volume control than a standard linear pot...

Rod's project creates an approximation of a true logarithmic pot (almost all 'log' pots sold these days are linear log not truly logarithmic) over a relatively small range (about 20dB)
 

argo

Member
2001-02-12 3:35 pm
Estonia
AudioFreak said:
Why do you want an exponential volume pot? Human hearing operates in a logarithmic manner ... exponential is the oposite to logarithmic and so would result in an even worse volume control than a standard linear pot...



.. You are right but I don’t need that pot for volume control but for phase control. I just mentioned Rod's project because he uses simple risistor to turn linear curve into to logarithmic. So I thought one can do vice versa to produce exponential curve.

Argo
 

Havoc

Member
2002-02-06 9:16 pm
There are no "audible" differences between lin and log, but it is much more comfortable to use a log. It feels more right.

With a lin you would use only a small part of the turn range and it would be sort of compressed at one end. You turn it, and to make it twice as loud, you only have to turn it now half so far further. Twice as loud, again half so far (1/4 of the initial turn).

The log gives a more spread out use. Like if you turn it twice as far, it sounds twice as loud.
 
Quite right Havoc. But log tapers can suffer from large deviations between left and right channel. Especially at low volume settings. Log tapers are usually –20 dB halfway. A linear pot with a resistor parallel from taper to ground can mimic a log taper for volume control quite satisfactory. As a general rule this resistor need to be approx. 1/16 of the resistance value of the pot. This gave me satisfactory results and the same “feeling” of a regular log pot and synchronisation between left and right is far more accurate. However the driving stage must be capable of driving the total lower resistance without problems. “Full open” is sees approx. 1/20 of the normal resistance of the pot.