I had a little bit more time today to try and troubleshoot this static issue. I’m 99% sure it isn’t speaker related, since I got the same static sound when I played the amp through an external 1×12 cabinet. To check the grounding of the output jacks, I connected an alligator clip between the soldered ground connection on one of the output jacks and the ground terminal strip attached to the power transformer – this had no effect on the static sound.
It also doesn’t seem to be a bad power tube, since I got the exact same noise when I switched the power tube to the EL34 that came with the kit.
Today when the static was happening, wiggling the power tube and poking at the power tube socket pins did NOT have any effect on the static. However, poking at the solder connections on the eyelet board did – at first – seem to have an effect, although I could never isolate a particular connection. It seemed like poking at any solder connection on the board would cause the problem to stop. After a few minutes of this, however, the eyelet board poking stopped having any effect on the static.
I made a recording of the static, but I still haven’t had any luck getting attachments to work. I don’t know if hearing the sound would be of any help, but I could email an MP3 file of the offending noise to anyone who has a minute to listen to it – or if there is someone else who could attach the file to a post here on the board, I could email it to that person.
Again, thanks to everyone here for your time and assistance!