Pay attention to pair of tubes in Class AB

[kldguitar]

In class AB, It is very important to pair the power tube . Different manufactures have their know-how in matching power tube. Because only after many hours burn, the tubes are stable and can be matched in right. But fewer tube manufacturers like wait so longer time. So when amp manufacturers received the power tube, they need burn them and pair them careful. But it is difficult to DIY people who buy fewer tubes in retailer.
It still good to pay attention the pair of power tube.

[Chuck H]

This is a good and useful piece of information. Thank you.

Most of the time the tubes bought by small builders and players are already pre selected, and possibly "burned in", to be properly matched. Though there is an extra cost paid for tubes bought this way.

The truth is that the tubes would have to be grossley dissimilar for there to be an actual problem with operation AND there is some speculation about whether or not matched tubes actually SOUND better than when there is some mismatch (in guitar amps, not hi fi).

Nice to see you participating without trying to sell something. Lot's of help and info here for members that participate and don't just log in to try and sell us something or only get help for themselves. Participation and discussion is what we do here.

[kldguitar]

In fact, unmatched power tube easy damaged ,or short their life. It is not enough to match by tube manufacturer, when people have them, they still need select them careful.

[Gtr_tech]

Depends on how "unmatched" they are. Even grossly unmatched output tubes can be used....so long as the person installing them knows enough to set bias according to the one that draws the most current. Not optimal, but it can/will operate.

A standard (non bifilar wound) output transformer will unmatch a perfectly matched pair anyway. Nothing to obsess over....

[Enzo]

And the tubes and transformers will have a hard time telling the difference between mismatched tubes and assymetrical signals.