Hey everyone, So I just recently bought a used SVT-3 Pro this summer and it has been working great up until now. The other day it started making a loud hum when it is first turned on and you hear the popping of turning on the racktuner thru the cab now and the sound of the bass is horribly muffled. After about ten minutes though, the sound goes away and it plays fine. Is this because the tubes are getting old and need more warm-up time or could it be some electrical issue? The guy I bought it from said the tubes were last changed in 2006 I believe.