velfax

Hi, does anybody know how to adjust the amount of volume given? I don't know how to explain my problem but it's like the volume knob of a fender amp. When you turn to 1 or 2 you almost have full volume. It feels like the first half inch of movement the expression pedal gives 70% volume right away. It doesn't feel natural and is hard to control with the foot. I couldn't find nothing about this on the manual, and I don't even know if it is possible to adjust that. Thanks in advance