yeah, i need to check it out when playing with it like you did. i'm not saying i don't believe you - i do. i'm just saying that I thought volume pedals use a log curve to match human hearing, meaning it is adding more signal from 0-50% than from 51-100%. I think you're saying that they normally do the opposite.
A logarithmic curve I would believe behaves as I describe. as X moves from 1 to 20, there is a greater difference in Y than from when X moves from 20-40. That's why I posted the wikipedia link to a logarithm. IE - a logarithmic curve is the inverse of an exponential curve.
Making things more complicated is that a decibel is a logarithmic unit of measure http://en.wikipedia.org/wiki/Decibel
IMO,it doesn't match up linearly to how I'd quantify volume: http://www.gcaudio.com/resources/howtos/loudness.html
Butit works better than the input data used to calculate db's, which would get exponentially larger in relation to perception of volume. So our perception is logarithmic but likely not using the same base as how db's are measured.
There's a huge aspect of this we're not talking about. What are the % values of the expression pedal actually being fed into? how is volume actually being calculated on the Pod? For instance, how does the Volume knob on the amp relate to output db? To me, it sounds like the volume is exponentially getting louder as you turn up the knob. It seems like a linear db movement - if 1% = 1 db and 100% = 100 db then 50% = 50 db.
So if the pedal's movement is exponential to produce a linear db value, which actually relates to an exponential increase in volume, that's a double whammy - you are multiplying exponents. If it was simply linear, the result would still be exponential, only less so. If the pedal used a logarithmic curve, then you'd have a more linear increase in volume IMO.
That's why I think audio tapers are logarithmic - they feed into amplifiers that are exponentially increasing the signal. So a logarithm into an exponent gets you a linear increase, more-or-less.
And FWIW, I thought the expression pedal was controlled by an optical sensor, not an audio taper/potentiometer.