Replace power tubes in pairs? Preamp tubes?

[ctc]

I know that the power tubes need to be matched in pairs, so should I look at my tubes and order one of each color, or if one tubes goes bad should both in the pair be replaced at the same time?

I know that the preamp tubes are not paired, so is it ok to only replace them one at a time as they go bad?

 

[HaggertysMusic]

Its always been recommended to me to replace power tube in matched pairs. If your amp has four power tubes the two inner tubes are matched and the two outer tubes are matched.

Preamp tubes are not matched and therefore can be replaced one at a time without any ill effects.