Well i had previous stated this in a post earlier...but i cant find it so ill restat it again since i have new info... i get a wispy sound from my amp...(kinda like when u just turn on a gas fireplace or light a gas stove) that comes through. Also now the sound has dropped in and out as i play. The amp also sounds muddier then when i first got it... It been about 2 years i ve owned this amp but i never really push it that hard so could it be the tubes or the amp? Ive had too return this amp like 3 times so im weiry but i beleive its probably a tube problem. How do i know for sure? How do i isolate the tube thats the problem? How do i change it etc... so i can get rid of that noise. I dont wanna bring it to a tech to replace the tube cuz im a broke student. Also apparently my amp is auto biasing...because it converts currents.

Thanks.