tube matching

[olds1959special]

When my amp tech fixed my AI pre-amp, he put in what appear to be Telefunken and RCA 6922's (two pairs) but put them in so that there is one RCA and one Telefunken per section. So the phono stage is v1 Telefunken v2 RCA and the line stage (what I use) is v3 RCA v4 Telefunken in their placement.

I seem to remember he said the tubes were "gain-matched"

Do the tubes in the L and R need to be brand matched too?

 

[solderdude]

It depends on how much feedback (and gain) is used in the pre.
The more overall (or local) feedback is used the less the importance of matched tubes is.
When there is little to no feedback matching gain ensures both channels will have closely the same gain.

For output stages tube matching (and bias adjusting) is a thing... until time has gone by and one or more has dropped in emission.

It is also a great way to ask more money for 'matched' tubes as well.