Anyone know what would cause an amp to cut out briefly?

Ever since I purchased my Sun Audio 300B amp, it's cut out briefly every listening session.... but only once. It feels like the left channel goes first slowly then both channels and then in a second it all comes back one. Once in awhile it'll do it twice in succession but never more than total one 10 second time period per listening session. It doesn't matter if I've let it warm up for hours or minutes. It almost always happens in the first 20 minutes of listening. Doesn't matter what listening level. It's not clipping or anything like that. It's definitely the amp because I've swapped it out numerous times and it's never happened when the amp wasn't in the system. I've also swapped out all the tubes. 

Completely bewildered by this.


It's definitely strange that it only happens once per listening session. Have you checked the power supply or tried plugging it into a different outlet? Sometimes, electrical issues can cause these types of problems. If that doesn't work, it might be worth reaching out to Sun Audio's customer support or bringing it in for a professional to take a look.

Or it's a manufacturing defect. It's a symptom of a joint that wasn't soldered. First place to check is where the B+ splits to the power tube plates.