I had a professional amp tech put my vintage univox under the bench. I got this amp from a friend and played it only for a few hours before the transformer started smoking. The amp tech recapped the amp and replaced some failing diodes and now it's working again. He got me some EHX 6973s, too. The problem is the output. It seems pretty low for this amp (U255R). He told me the speakers are pretty old and if I replace them with 2 Eminence 12" 8ohm speakers I will probably get a lot more out of it. This is a pretty old amp and everything, but I wonder if maybe it is the EHX tubes? They seem to have bad reviews. What could be causing low output? I notice the output signal is reduced further when the tubes get hot and start to break up.