The 6550 tubes seem to be correct for your amp. Was the bias set properly when the tubes were installed? How often did you check the tube bias? The bias can drift as tubes age. If the bias is not set properly the tubes can be run much harder than they should.
power tube rating
I have a pair of VTL MB-450 amps, each with 8 6550 tubes. They were retubed in June of this year and now they need total replacing again. I was told that the tubes burned out this fast because they had a low IP value so I'm looking for someone to tell me what this value means, and what it actually measures. The tubes had a value of high 40's - low 50's and it's supposed to be high 60s. I need to know what this value is just so the next tubes I buy will actually last me longer.
Another question regarding tubes. The stock tubes are Svetlana, but does anyone recommend trying something else, maybe the Tung-Sol, SED or EH? Maybe KT-88s? I found the stock tubes to be "hard" sounding, so I'd like something warmer but with a full bottom-end.
Another question regarding tubes. The stock tubes are Svetlana, but does anyone recommend trying something else, maybe the Tung-Sol, SED or EH? Maybe KT-88s? I found the stock tubes to be "hard" sounding, so I'd like something warmer but with a full bottom-end.