Seeking some troubleshooting help... Listening yesterday and hear a loud lower end thump come out of the right channel. Sounded like a louder version of if I were switching inputs. Lasted less than a second, then was fine for another 2 hours and did it again. No distortion, scratchiness, or anything else; the sound was perfectly fine leading up to and following the thump. From my initial research, it sounds like it could be a DC offset problem due to a failing tube? These are a pair of VVA refurbished MC30s so I dont think that there would be any cap issues. Other opinions welcomed, but looking to prevent it from happening again! Thanks in advance.