Adjusting the Taper of Audio Pots Pt2

Posted: April 24, 2014 in Effects, Ideas To Be Developed
Tags: , , , , , , ,

Anti-Log Pot Chart

This is a graph for one of the pots I tested.  All of them had a similar change in the curve.  As Mr. Keen notes in the link in my original post, the smaller the fraction of the total resistance, the more it’s pulled in the anti-log direction.  This pot had an actual resistance of about 225K.  Other pots I tested were in hundreds of K ohms of size and the resistors were as low as 68 ohms.  Up to about a fraction of an order of ten, the upper response, from 7 to 10, became more linear in the anti-log direction.  Once you’ve exceeded an order of 10 less than the pot value, the taper doesn’t really change very much.  So, if you are like me and have a bunch of small value resistors, you can use them for this trick and get good results.

For my guitar effects builds, I would expect that a user would think 5 is the center.  With either of these examples, they would be wrong, since it’s logarithmic.   However, in my experience, most players seem to think moving counter-clockwise from 5 is cutting the frequency in an equalizer of any sort and from 5 to 10 is boosting it*.  They usually use the range from 5 to 10.

What it comes down to is: for any function that will be adjusted from usually spend the bulk of it’s time from 5 to 10, an anti-log curve is quite useful, because the slope is more gradual in that range.  For gain, distortion, or treble, a linear or logarithmic taper is probably better, but ant-log could still be used.  Volume could go either way, depending on what’s being built.  I’m impressed enough with this that I will probably use it for bass and volume controls on my pedals.


*Any passive EQ is shunting frequencies anytime the wiper is moved below 10 (and just having a pot in the circuit attenuates some high frequencies).  In reality only an active EQ can boost.  Designers just make the largest value big enough to allow users to get good results from the passive controls when they’re used in middle ranges.


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