Amp shut off and came back again.

Ok.
Thanks.
I was listening in class A mode with much bigger than normal level, and the amp got hot.
lt has just about 2” from the top. Probably I need a taller rack.
Thanks again.

Could be a power conditioner/protection device if you have that upstream. I've had that happen to me before when I was using such a device with an amplifier. 

Sorry, didn't see your 11:18 post

It sounds like the power dissipation protection. Playing at a high volume level, the speaker load at that instant may have presented to the amp a (say) 45 degree phase angle which doubles the power drawn from the amp -- but only a quarter the delivered power is used by the speaker (i.e. there is no spike in volume). That would account for the very high heat sink temperature and the amp only shutting down for a second. If it was a thermal cut out, it would have taken longer for the amp to resume since the heat sink temperature does not drop that quick to reset the thermal cutoff device.

Thanks again.
l feel relieved.
My amp (Plinius SA 102) seems to get hot easily when operating in class A and pushed hard. It might need more breathing room too.