My main goal would be if I hear sonic degradation to determine the bad tube or tubes.
If you think you hear sonic degradation first swap power tubes side to side. It can’t be that all four degraded identically the same so it should sound different and you should know which pair and now just need to narrow it down to which one. Repeat the swap only this time one tube. Now you know which one it is. Unless there is no difference. In that case you know it was all in your mind. There never was a problem to begin with.
Unless its one of the input tubes. In that case swap those. Now this was a very low probability to begin with but at least now you know its not that. Finally you are down to the rectifier tube, which almost certainly its not.
Now the great thing at this point is when you realize you could buy a full set of tubes, all of them, and nice ones too, for much less than the cost of a pretty crappy tube tester. Which is why in 30 years I have never bought a tube tester.
Notice I’m not the only one. I’m with tablejockey on this. Honestly I think if you read what you wrote you will realize you are too.
my first choice in sound but had not wanted to deal with the extra upkeep
So all you do, realize the "extra upkeep" is imaginary. An old Jedi mind trick. These are not the upkeeps you’re looking for.
