My XLS is 8 ft from my chair, and I only know the fan is running b/c I can (sometimes) see it start to spin up through the front panel grill!
It's also sitting on top of almost all my other amps & processors....so it does get warmish...still can't hear it, but I assume it's a variable speed fan controlled by a temp sensor circuit, so could have a 'hurricane' mode if really needed.
I wouldn't put one of those on top of a high powered receiver, more out of concern for the receiver than the amp, though.
It's also sitting on top of almost all my other amps & processors....so it does get warmish...still can't hear it, but I assume it's a variable speed fan controlled by a temp sensor circuit, so could have a 'hurricane' mode if really needed.
I wouldn't put one of those on top of a high powered receiver, more out of concern for the receiver than the amp, though.