I convinced Keith Hilton to build me a customized HILTON pedal that works as a expression pedal for the KPA. Maybe there are other players here who would like to join in and maybe get the price down a bit?
I am playing his volume pedal for many years now and IMHO it is the smoothest, most lightweight, most precise and yet most dependable volumepedal I ever had. But sadly these pedals don't work as expression pedals with the KPA. (Not even with a Y-cable, because they have buffered input and outputs.) So now I have already spent a lot of money in expression pedals. I tried cheapo plastic pedals and later I tried the praised Boss FV-500-H, and also the Morley PVO Plus now even the Korg XVP-10. And, guess what, they are more or less all the same: nice and sturdy outer shell but none of the different mechanisms to transfer the pedal movement into an impedance is really smooth and convincing and the sluggishness of the pedal joints makes all of them just ok for use as a WahWah but totally inacceptable as a master volume control.
At the moment I am trying to contact the KEMPER support to get some info about what voltages and polarities are needed and then I hope that Keith Hilton can build us a wonderful optical expression pedal.