How do you test different tubes?

I hear people recommending different brand of tubes for amps, preamps, etc. My question is how are people doing this? Are there dealers who loan tubes like other gear? I would hate to have to purchase different sets of tubes, try them, find the one I like best, and then trying to sell the set I don't like.
Byans I'm afraid that's the price of admission and knowledge. Learn a little spend a little
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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!

One thing that is nice about tubes is that they can be very easily tested for quality control. Because of that used tubes are a very viable option. The market in used tubes is virtually unlimited.

Also, in my experience the price of tubes is distorted by collectors/hoarders. Certain tubes and brands are commanding very high prices when there are readily available alternatives at much lower costs. For example, Mullard or Telefunken 12ax7s compared to U.S. made "organ" grade equivalents.

One last point, the differences between high quality, properly functioning tubes is subtle, yet like most things audiophile related users describe the differences as huge and earth shattering.
I disagree that tube rolling is pointless. Even if you believe there are no longer any good old tubes available, there are usually several new tubes to try. There are no lending programs however and as already stated the only way is to buy and try. You can sell what you don't like. Just because you didn't like the sonic of a particular tube it does not mean it is a bad tube, just not your taste. I happen to believe you can get some good old tubes but the price is getting extremely high.
While there aren't any tube lending libraries there are tube dealers whom people have learned to trust like Jim McShane, Kevin Deal, Brent Jesse and others. They can't tell you which tubes you would like in your equipment but they test the tubes, stand behind them and can give you general guidance about what might work for you. Here's one thread that's a few years old but should give you someplace to start.
Andy at Vintage Tube Services has the real deal. The idea that there are no good NOS tubes out there is patently untrue. As Elizabeth indicated, many private sellers are offing ones they did not like, but the best dealers are getting ones through means others do not have.

The last place I would buy a tube is eBay FWIW. At least not at full price as you will need to sort them.
I just spoke with Brent Jesse ( regarding NOS 6SN7 tubes. He has an impressive supply of very high quality NOS tubes of all types. He allows you to buy, try, and return for upgrade or refund (-20% restocking fee). Although I didn't end up buying from him this time (I found what I wanted locally), I plan on doing so in the future.
I concur that there are legitimate vendors as named above along with the Tubedepot & Tubemonger that you can get quality new in box NOS tubes, and at reasonable prices which normally to my ears sound a lot better than the new production.
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NOS tubes are definitely available. Here on Audiogon I regularly see people selling off NOS tubes from their collections that they realize they will never use.

There are crooks out there so you have to be careful. It's best to have a tube tester if you are going to buy NOS or used tubes and buy from someone who will allow returns.

If you don't want the hassle of learning about tubes and tube testers, the tube sellers noted above can get you top quality tubes for a price.

IMO, NOS tubes can make a difference in the sound of your system that is worth the price.
Viridian: Please let us know how your "giant" Sylvania works out. I'm really curious to know how you came by it and at what cost!
NOS last longer, and NOS sound much much better than currently manufactured tubes; they cost more for a reason. Read other threads on this subject and you'll discover why we buy NOS tubes as opposed to current manufactured tubes.

NOS stands for New Old Stock, and when I buy from a reputable tube dealer, I assume that is what it means. I've bought tubes from the same dealer for years, and considering the short life span of current tubes as opposed to the long life of NOS, I've gotten my money's worth.
Tube rolling is fun and there is an endless supply of NOS, good-used tubes from all over the world. I would use cables as an example of what tube rolling is all about.

Telefunken and Valvo tubes really are special. Whether or not they are worth the scratch is no different than asking whether or not kimber, Tara Labs, Cardas etc. are worth the money.

Having said all that, some of the new stuff sounds really good and the old Russian military tubes are plentiful, sound good and are dirt cheap.
Isn't it great how you can continually upgrade the same piece of quality tube gear simply by changing tubes. My guess, however, is by now I'm preaching to the choir!
Not aware of a commercial loan program.

However, in response to other posts in this thread, there are numerous well testing (per the sellers) OLD PRODUCTION TUBES available here in the A'Gon ads as well as Ebay and various other established vacuum tube dealers.

Recently purchased 7 "new" testing Amperex Holland 12au7's on Ebay (one was a dud, but the listing was for 8 untested "pulls") for less than $65 delivered.

This was my first tube purchase in 5-6-7 years and I was still able to find a bargain (as well as the specific tubes/production period, manufacturer and construction) that I wanted to try in my setup.

Bryans: Your best bet is receiving feedback from other owners of your gear (then sort through the input).

Lars hits it on the head as this is just the case with my budget gear running tubes that currently sell for much more than the electronics.
Isn't it great how you can continually upgrade the same piece of quality tube gear simply by changing tubes. My guess, however, is by now I'm preaching to the choir!
+1 Although some new (EAT) and NOS (WE 300b) can be as expensive or more than some equipment as DeKay mentioned.
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!
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.