Over loading?

+1 imhififan - I concur with everything he said. For me I changed my 15 amp breaker to 20 amps because it popped occasionally on power up only, never while playing loud. I had 9.6kW output into 4 ohms though...

I just double checked my panel and it's 12awg on the breaker I changed to 20amps. Same wire is used for the kitchen which has 20amp breakers. I don't know what the run length is but it's closer to the panel than the kitchen...