Sounds like it might have cut off due to thermal overload. Make aure it has space all around and at least 2" on top
10 responses Add your response
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.
2" is insufficient room for cooling above most amplifiers! For a space that restricted I would use a fan for cooling. You need a good 10" to a foot above the amp- otherwise even though the heat might not trip the protection, the amp will be running warmer and things like filter capacitors really don't like that- they will have a shorter life.
Adequate cooling is important for any power amplifier.