Tube Biasing and Specs

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Hey guys

 

Quick question: how do you know if a tube has an earlier distortion level than other?

For the same brand of tube and make (Ruby EL34BSTR say) - matched pairs.

 

Say I plug in a pair of tubes (call it pair A) and I show 65ma bias reading

Then I plug in another pair of tubes (call it pair B) and I show 80ma with no change to the bias pot.

 

In order to bring pair B down to 65ma (which is the right value for my amp) I have to adjust the pot accordingly

 

Which pair has the earlier distortion level?

Thanks