Quick answer
Clipping or harsh output at moderate volume is almost always gain set too high versus headunit output. Start at minimum gain, set a sane headunit test level, then raise gain only until distortion is barely audible - then back off slightly and repeat per channel if needed.
Problem
- You are setting amplifier gains without clipping the speakers.
Symptoms
- Distortion only at high volume.
- Amp clip LEDs flash.
Cause
- Gain is set beyond clean headroom for your headunit’s output voltage at real listening levels.
- Charging system voltage sags at the amplifier under headlights, fans, or winch load.
Fix Step-by-step
- Start with amp gain at minimum.
- Set headunit volume to a sane test level with a clean test tone or known track.
- Raise gain until just before audible distortion - back off slightly.
- Repeat per channel if gains are independent.