- There's a short in your speaker wiring somewhere
- or a blown speaker
- or you are recycling the speakers from an old all-in-one system and they're too low Ohms
Check your speakers first. If they are less than 8 Ohms, or there's no label on them which gives the Impedance (in Ohms) then I'll lay money that they aren't suitable for the amp. Stop using them and get some proper 8 Ohm speakers.
Wiring shorts might be only a single strand of copper wire. But it's enough that at higher volumes it conducts enough current between the speaker terminals to trip the amp's protection mode.
Fix the problem. Go through your wiring. Check using a torch. If all looks good then it's a blown speaker.
Remove the speaker wires from the amp. Switch the amp on and turn the volume up full. The amp should stay on. Turn the volume down and switch off.
Now connect ONE speaker only. Try the amp on and volume up again. If it trips out then that's the faulty speaker. Repeat by adding one more speaker each time. When the amp trips, the last speaker added is the culpret.