To use the Expression Pedal functionality of an Eventide Stompbox you should connect the output of your expression pedal to the Expression Pedal jack on the Stompbox, and not connect your guitar or anything else to the expression pedal when used in this manner. If your expression pedal has a fine tuning knob try turning it all the way up or all the way down to make sure that you're getting the full range of the expression pedal.
