I have this SVT2pro I bought used two years ago, I think it's a 2000 model. The issue is that it started making a weird noise when turned on. It sounds right for a while, and then the volume starts to oscillate, it goes down & up for 4 o 5 seconds, sometimes 10, and then it stops and sounds right again, but after a few seconds the volume starts to oscillate again. Sometimes you can't even hear the bass. After a few minutes the whole thing stops and the amp sounds good. It's like it only happends while the tubes are warming up, but it always occurs when I turn the amp on, even if I let the amp getting warm in stand-by for half an our. So, I thought it could be the tubes, though the guy that sold it to me said he had just taken it to get the tubes replaced, so I took it to a tech, and change all the tubes that haven't been changed for 4 or 5 years! So I get home, I turn it on, and... same problem! Now when I turn it on, and same thing, volume oscillates for a few seconds till the amp is warm (after 20 mins or so). It is true that after replacing the tubes, the amp sounds awesome (once that is warm), but I'm concerned that it could deliver a bigger problem, and also I can't trust in it's reliability: I can't take it to a gig!!! I don't know if it's going to stop sounding in the middle of a song or something worst! So, after all this reading, does this happened to anyone else? Ever? Or someone knows why could this be happening?