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All that being said, commercial pots deviate from this characteristic. For example, if you look at the datasheets on the ALPS website, you'll see that they have less than 0.3162 in the middle of the travel for their log pots. I'm not sure why they do that, perhaps it is just a rule of thumb that 1/10 power gives half the volume.


This is due to the process used to fabricate potentiometers. It would be quite difficult and expensive to fabricate a gradually thinning carbon layer, so the element is realized by depositing four (or more) different, essentially linear segments that approximate the desired response (piecewise linear interpolation/approximation).