I can't seem to find decent tubes for my twin reverb. On a whim I bought a blonde finished twin reverb and I have had it repaired three times in the first six months of purchase. The problems were two tubes 6l6's twice and 12AX7 once. Whereas, the Mustang GT 200 that I play in the studio is never switched off and seems to get better with each software update. The latest software update is the best yet. I wonder whether the quality of tubes that are being manufactured nowadays are going to sound the death knell for tube amps, especially with the strides being made in SS manufacture.