A common ratio2Db() and dB2Ratio() function would be nice. 

I Will do a ControlAudioTaperPot Class like that: 
ControlAudioTaperPot(minDB, maxDB, neutralParameter) to setup the scale. 
minDB will be the minimum of the dB scale. The actual minimum value as ratio (the CO value) will be 0 (-Infinity dB) because of a linear overlay. 

A associated VUMeter should have the same scale, to match the Slider position. 

The step up step down COs should be re factored to go parameter steps instead of value steps.