How do you test different tubes?

Byans I'm afraid that's the price of admission and knowledge. Learn a little spend a little

And then also you are usually buying those tubes someone else 'did not like'
So the unwanted tubes just keep going round and round...
Good tubes wind up in 'collections'

IMO the problem is all the good tubes are ALREADY in someones stash, and have been for years.
My recommendation is buy new tubes, not NOS or used ones.

PS I do own a tube preamp, but i really have little interest in tubes for the reasons i mentioned.
Maybe i am wrong.. but I do not think so.

Elizabeth is right.

NOS tubes in any quantity are all gone, used, and burned out, and have been since the 80's.

Only the Russians and Chinese have made tubes in any quantity since then.

The Russian tube factories are controlled by the Russian mobs, and tube types come and go. The Chinese tube quality is very "spotty".

Try and find what is the best of new tubes, and buy a lifetime supply!