Present. I was occupied this weekend with other things, but I did manage to read your reply, and thanks for the advice.
Saturday night, the hum started happening on one side mostly, then the other, and then at the same time again. This time the hum and distortion stayed, though it is often intermittent. I tried switching the interconnects as suggested, with no luck, so I started pulling and switching out tubes. I noticed that when I switched the 12AT7's from one side to another, the hum only occurred on one side, when it was originally going on both sides. I found some other 12AT7's that I didn't know I had and put them in. The hum disappeared! And, the amps started sound much more alive and "sparkly" than before. The tubes that I had been using were the originals that came with the kit, so they must have been going dull slowly for some time now, so slow that I didn't notice. I was pleased that I had found the solution to the problem, until...
Sunday night, one side started to hum again, then the other. A few seconds later a strange thing happened. From outside on the street I hear a Bzzzzt! Pop! Pop! And my lights dim and then flicker on and off and the hum increases. Then, Pop! Pop! BAM!! And all the electric wall sockets go out, but not the overhead lights (which I hardly ever use, instead using floor standing lamps so I didn't notice right away). It turns out that a power line of some kind had fallen loose and shorted out everyone's wall sockets on the block (I also found out that all the street lights and overhead ceiling lights in all the buildings are powered by another power plant and is on the same circuit as the hospital on the hill - weird).
Now, I'm starting to think there may have been something wrong with the power in my neighborhood after all that was causing this. There have been some other appliances that have been mysteriously faulty, only to work again later. It turns out that my landlord, who lives below me, has also had the exact same appliances malfunction in the same way only to work later. I also remembered that he had a microwave oven that would turn on, but not heat anything up, then work fine later. Microwave oven - tube related? Hmmm.
I remembered to switch off all the amps after the power went off, and the power company didn't get it fixed until after 2am, so I haven't had a chance to try them again. I don't know, but it seems like such a strange coincidence that I would have seemingly solved the problem with new tubes, only to have the problem come again, and worse than ever, just as a power line drops outside and then everything goes out. It could be just a coincidence, and power was last thing you said would cause the problems, but then...I don't know what to think now. I guess I will just have to see how the amps function now that that power line has been replaced or repaired.
