I am not all that familiar with subs that have, as paradigm calls them, ultra class D amplifiers so this maybe completely normal. With this design there are no heat sinks for cooling so I imagine they don't run as hot as other designs, but what I have noticed was that the back panel always stays warm when not in use. The amp turns on and off automatically, I can tell with the LED light. The light can be off for days but the back panel will still be warm. Also when the amp is on I can be watching a movie with not a lot of LFE effects at a medium volume and the back panel of the amp gets "very warm". Is my PW2200 defective or is this normal for a ultra class D design.