I have a DSL 100H, I've had it about 3 years now and love it. A little while back i started noticing the clean channel volume would go up and down sometimes would stay down for a bit and come back up. It starts doing this about 5 min after i start playing and lasts about 20 min or so, then seems to be good for the rest of the session. if i change channel to dirty and back to clean it sometimes brings the volume back but not always. All the research i did pointed to a bad tube so i ordered a full set of tubes, i installed and checked the bios and both sides where 87ma and does not need adjustment i believe. We'll it has the same issue as before and is frustrating the hell out of me. would really appriciate any input in diagnosing the problem .