What are the symptoms of an overheating amp? I ask because tonight I was gaming with my door closed and the room got pretty damn hot, probably in 30's (c). I noticed a whistling through the headphones. So I unplugged the optical cable from my PC and it was still there. Turned off my DAC... still there. Then, turned off my tube amp. The noise went away instantly (as opposed to fading away as music does when you turn a tube amp off). I left it for 5 and opened my door and it seems back to normal now.
Could this whistling be a sign of an overheating amp? I use my PC -> Zero '09 DAC -> Little Dot MKIII (LD's are notorious for their heat I think).