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Thats for the insite. Yes, if you have an all tube amp having spares around is a good Idea. Not as important for the 12ax7's or preamps tubes but the output tubes really should be matched Pairs or Quads.

Joe

I disagree that matching is important for guitar amps. We're not talking about hi-fi here. If they're a little mismatched, you'll get just a little bit of second harmonic distortion, which actually sounds good. Perfectly matched pairs or quads cancel all even order harmonic distortion. If they're so badly mismatched that you get bad ripple frequency humming or one tube seriously overheating while the other's OK, one of the tubes is not within spec for the tube type; it's defective. (It happens with today's new tubes, and it also happened back when the "NOS" ones were new, which means it still happens with the NOS ones as well, but it's not too common.) Those harmful consequences that are often mentioned to reinforce the "necessity" of tube matching aren't the result of normal variations within a tube type.

Tube matching was originally more of a marketing idea than anything, and aimed at the hi-fi guys. It makes a lot more sense for them, since they regard any distortion as highly undesirable. But the only thing that's usually matched is idle current at some particular bias setting. The tubes still may not cut off at the same grid voltage, one may cut off more sharply than another, they may have significantly different transconductance and thus not be truly "matched." The standard matching procedures won't catch any of these differences. They rarely stay matched for idle current after they've been in service for a few hundred hours. And back to my first point, they'll only sound better when they get mismatched a bit.

The classic experiment in mismatching power tubes was reported in the Radiotron Designer's Handbook, 4th Ed. pp. 581-2. Two entirely different power triodes, a 2A3 and a 45, were used together in a push-pull amp. There is a 12% difference in their amplification factors, and more than a 2:1 ratio of their mutual conductance and plate resistance. But it only produced 5% second harmonic distortion, which most people would not find objectionable in sound reproduction and it certainly wouldn't be objectionable in a guitar amp.

I don't bother with matching power tubes, and I never will. It is a nice "profit center" for tube dealers. I'll save my money.

Everyone is entitled to their own opinion and what they want to use in their amp. Lets not make a bigger issue out of this. Folks can decide for themselves whether they want to use matched or un-matched tubes. Tubes used by high end audiophiles are not subjected to the same stresses as those in a guitar amplifier. When tone is important, like for myself even the preamp tubes are important enough to have within spec. Because I can hear and feel the difference. using just any tube won't have what I want or expect from my equipment.

The truth is the best place to buy tubes is from your amp technician who allows you access to one of his tube testers. Your amp will sound better, and you will save time and money. Telling folks to just buy any tube just because they appear cheaper is not right. Sorry. Since most folks don't know the procedure for blueprinting their amp let alone Biasing it,even what entails "burn-in" time and then be readjusted two days after you put new tubes in. I recommend they use matched tubes and have it professionally Bias.

Joe

I disagree vehemently on nearly every count, but you're certainly entitled to your opinion. Mine's backed up by solid data.