Set to (High Pass) if powering door speakers to cut out low bass that causes distortion.

Set to (Low Pass) if powering a subwoofer to ensure it only plays deep bass notes.

Based on the official manual and product data , here are the key specs: Specification RMS Power (4 Ohm) RMS Power (2 Ohm) Bridge Mode (4 Ohm) Frequency Response 20Hz – 20kHz Signal-to-Noise Ratio Input Sensitivity 0.15V – 5V Low/High Pass Filter 30Hz – 500Hz User Experience & Community Feedback

Do not use the Gain knob as a volume control. Start at minimum, turn your head unit to ~75% volume, and slowly increase the gain until you hear slight distortion, then back it off slightly. Summary Verdict