It doesnt look like an impedance problem, since you arent bridging the amp and the speakers are 4 OHM each. Do you have the gains set very high on the amp? Maybe you are working it harder than it really need to? What about the location of the amp, are you putting the heatsink to work? Is there air flow around the amp? Most importantly, is the sun hitting the amp? One last question, when you are playing music for that hour...how loud are you playing it?

Other than location, I am kinda lost about this also :thinking: