best tube source as far as burn in?

[iknowjohnny]

I'm not talking a few Ma. Most of the tubes i buy seem to drift 10 Ma or more. I have one pair that was almost 20 Ma apart afdter being closely matched at first. i'm sick of that happening ! I know what mismatching can do to the good, but when one is running at 70% or more and the other is still running way too cold thats not the kind of mismatch i think is good.

[Structo]

Then install a bias pot for each tube.

I have dual bias pots on my D'lite.

I know that only biases them the same at idle and doesn't take the transconductance into account but I have watched the bias with a signal going through it and both tubes seem to track evenly.

But my tubes may not be that far apart to begin with but I was told by someone that kknows more than me that have separate bias control was the way to go.