How do you test different tubes?

Elizabeth and others who feel the same are wrong -- placing opinion in front of any real experience. I started out like most without any knowledge or even a tube tester. But you can learn a lot without getting burned if you are willing to put in the time reading and asking lots of questions from people who know more than you. I can (now) do far better on eBay than paying premium prices to those (supposedly reputable) sellers, whose "NOS" tubes often turn out to be on their last legs!

There are some sonically amazing tubes to be had for little money if (like with all things!) you are a knowledgeable shopper. Saying that all the great NOS tubes are gone is just the lament of persons too lazy to put in the time and effort. It's absolutely not true and I can prove it! There are some excellent current manufacture tubes, but like excellent current manufacture gear, there are only a few types to choose from, and they are (mostly) very expensive. And they can fail without warning, just like any tubes. At least when you buy an ANOS tube (stands for ALMOST new old stock ;--) you know you are getting a tube which has been in service without failure. Sort of like buying used cables which have been thoroughly burned-in!
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Tube rolling is fun. I have a couple of components which use 6 volt small signal tubes (6DJ8, 6922, 7308). The tricky part is getting good tubes. Unless you have access to a reliable tube tester you are at the mercy of the tube seller. A weak tube will still work for awhile, but you would never know it's weak without a tester. If you are serious about tubes, a tester is a must. You can pick an old surplus miltary tester (TV7, TV10, etc.) for a few hundred bucks. Electronic surplus stores are an excellent place to shop (or ebay) for a tester as well as surplus tubes.

Bryans I found asking for input on a specific tube and piece of gear helps but buying and trying is probally the true test;you just need to set your $$$ level for cost and keep it within sight.
As Ducks2007 points out it is fun and a learning experience as well.

Tubes can make a very major difference in the sound of your equipment. The price of the NOS power tubes, at least KT88, that have a limited and finite life seem too expensive to justify adopting as a regular in the lineup. There are many very highly performing reissues and new production tubes that are much more cost effective. Although we all want to fall in love with the romantic idea of a NOS tube, tucked away in some drawer for 50 years, it doesn't mean that it will be any good.

Truemaineac - in lieu of NOS, sometimes you can find very good used pulls from old equipment. I found a source where I located several pairs of bugle boy 6DJ8s for next to nothing. I just lucked into them, but keep that kind of source in mind. Swap meets, junk places, etc. They were pulls from some junker oscilloscopes.