I just got done rechecking this. Enter calibration mode by holding both buttons down, disconnect power, reconnect power while holding buttons down, both LEDs flash, when they stop release buttons. At this point effect is bypassed so press bypass button to engage effect. Depth control is full counterclockwise, harmonic mix full counterclockwise, no sound. This is after adjusting low trim pot 20 turns clockwise, green light (low optocoupler LED) is visible, however it is not pulsing but on steady.