Make logarithmic scale of potmeters more natural (audio taper pot)

[Daniel Schürmann]

From the discussion in Bug #1296088 i came to the conclusion that our logarithmic scale is not like expected.

http://mathscinotes.wordpress.com/2011/12/22/potentiometer-math/

> This specification means that the potentiometer has
> * 0% of it full scale resistance value with the wiper at 0% of its full scale position
> * 20% of it full scale resistance value with the wiper at 50% of its full scale position
> * 100% of the total resistance value at 100% of its full scale position.

MIxxx volume control has currently 41 % with the wiper at 50%

http://www.ebay.com/itm/4pole-24-Step-Attenuator-Volume-Control-Pot-Log-A-10K-10KA-Stereo-Potentiometer-/400675811718

> Log scale 0-75dB attenuation.

0 dB = 1
-75 dB = 0.00017782794100389227
-37,5 = 0.01333521432163324 -> 50 %

[Daniel Schürmann (daschuer)]

http://www.diyaudio.com/forums/digital-line-level/198797-math-behind-logarithmic-volume-control.html#post2750538

Has 11 % at 50 % scale

[Daniel Schürmann (daschuer)]

Ops, I misread the Goldpoint Attenuator table.
It has 7,5 % at 50% scale. = -22dB
Range 0 -55db

[jus (jus)]

Fixed in https://github.com/mixxxdj/mixxx/pull/254

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/7439