I guess hot is a relative term. The thermometer I have set on top of the amp is reading 43C after running for several hours at low volume on an open (no top no sides) peg board (holes) shelf.
It feels hot to me!
Right, like Eric says hot is relative. If you want to compare the meaning of "hot" try the same test with Class A, AB, tube or any other amp. Its the reason why Class D amps are now finding their way into heat sensitive applications such as integrated digital streaming devices or music servers.
