300B replacement

Think it would be better to replace both at the same time as then you would have the same amount of hours on both tubes, instead of just replacing one. If you only replace the one tube, and 1-2 months later, the other one goes bad, then you have to replace that one...the "older" of the two tubes is going to have more hours on it.

Let me try this again...

I think it would be better to replace both tubes instead of just the one as you really dont know how many hours are on the other one ( the good one ).

If you were to replace just one tube , and 1-2 months later, the other tube goes bad, then the " newer " one has more hours on it. That is why when buying tubes, its best to buy them in pairs/quads.

The major drawback of replacing both is the financial side of the equation. The Western Electric 300B is probably about $400 each. I would try replacing one and than listen to hear if there is any imbalance between the channels. If there is then, I would purchase another one. $800 to $1,000 is a lot to pluck down for 2 tubes. Of course, there are other reputable tube manufacturers that produce the 300B for a lot less money. Even if you buy 2 new matched tubes, they might also have different lives and each time you would be wasting at least one good tube, if you always replace them in pairs.

fwiw I have a pair of these and they sound terrific

http://www.sophiaelectric.com/pages/se/princess_300b.htm

Use a bias meter.