Select the Q-Wah algorithm and go into PARAMETERS. Set Mod Source to “Manual.” Then, map Manual Mod to your expression pedal by holding down the Quick knob to enter Parameters Mapping. Under Ctl Source, map it to your expression pedal or set it to LEARN and move your expression pedal. The H90 will automatically detect the expression pedal. Adjust the Q-Wah’s Intensity, Bottom, and Depth to taste.