for $575.

the seller says the tubes are probably original. they are mesa tubes.

question: do tubes need to be replaced on any kind of regular basis, or just when they start to die? and if they should be replaced, how much am should i expect to spend?
average tube life is 1-2 years, playing an average of a couple hours a day. They can last longer, but the sound quality will begin to suffer after a point. They can last 10 minutes, or 10 years, that's just the nature of vacuum tubes. It's considered maintenance to change the tubes every couple years. Preamp tubes on average will last about twice as long as power tubes. Figure about $20 a piece for Mesa power tubes, about $7 a piece for mesa preamp tubes. You can use other tubes that may be cheaper, but the Mesa tubes are tested to be in the correct bias range for their amps, and they have a 6month warranty. Vaccum tubes can go at any time, just like a lightbulb, it's an old tech.

If it has the original tubes, you are going to want to change all of them when you get the amp. It's always a good idea to take a used amp to a tech for a once over anyway.
"The fool doth think he is wise, but the wiseman knows himself to be a fool." - W.S.
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