What is the best 12ax7 NOS tube ?????????

Both is true Eric, they often sound more refinded and they last much longer. (Especially the KT 88)

Do power tubes have much of a sonic signature? I'm curious as to what the sonic benefits are of rare and expensive NOS power tubes (EL34's in particular) costing sometimes hundreds of dollars each compared to new ones that run about 25.00 a pair on average. What are the benefits of NOS power tubes? Are NOS power tubes that much more refined sonically, do they have a longer life etc etc?

It really depends on the peice your placing them into. I have tried Telefunken and Bugle boy and didn't care for them any better than my Stock tubes.There is no such thing as the best,its all a matter of taste. I would suggest try some good used tube to see if the sound your getting is what your looking for. If you buy NOS and don't like them your out the money and they are not NOS any more to sell. Good luck

May be worthwhile to try a mix of Teles and Mullards.
Too many of a certain type will create an unbalanced preponderance.Have a look at the hktubeaudio forum to see which are considered RR grade.HK tube rollers know their stuff,and have good ears.
Raanan

Having had the largest stock in the USA, I can say there is no answer, only hints.

Tubes are like speakers. They will react different in different systems. If someone makes a recommendation to you, it should be at least based on the tube having the same "job" in their gear as yours, or better yet in the same EXACT gear. Tubes can be used in a number of ways. Driver, buffer, phase splitter, or gain.

It's a kick in a fanny to play, and the performance gains can be HUGE for little money. Telefunken will be tossed around a bit, but that is because they are the rarest and most expensive. Very well made.

I'm a Mullard (England) guy myself...and always seek them out. Typically they have a juicy midband. Amperex (usually Holland made, but sometimes they are actually Mullard made as they are both Philips Holland owned companies) are similar but more pop.

Want a golden glow? Brimar. Or Tungsram.

Biggest goof? The 7025. They are the worst testing...usually because the ones we see float about now are later GE and Philips ECG...both are not too cool.

Also...you may see people refer to using a 5751. This is a risky proposition. That is NOT a 12AX7. In some circuits they may work fine. Some sound lousy. Some not work at all.

Of coarse it is a matter of taste and the circuit, but some tubes to look for would be #1, the smooth plate telefunkens. While poeple often debate on whether they are the best, or what is better, they are always very good. Everybody seems to like them, and they always seem to work good in almost all applications. N.O.S. rca's, if you could find them will give you different than the tele, you could try 5751's, which is a lowwer amplification that the 12ax7 that is a direct replacement, that some poeole highly recomend. (g.e.'s are inexpensive). I was surprised with the newr sovtek 12ax7lps, I found it as smooth as a tele but warmer AND punchier, (that was only in one try, though).
It might be for you a good idea if you could find a source for decent used, so you could afford to buy some different one's and see which way you want to go. Especailly if you have more tube gear that would benifit from tube rolling.

It is indeed a matter of taste, having similar gear to Rcprince, I tend to agree with what he says about the Teles. Mazda France is a nice tube as well, close to the sound of the Teles, warm as well as lively and not so well known, hence cheaper.As far as the Tele fakes are concerend, I'd buy from a reputable seller to be on the safe side.

Without question, it is the Amperex "Bugle Boy"

It really depends on the circuit and your taste. My preference is Telefunkens, which are a smooth-sounding tube and seem made for my Jadis equipment; old Mullards are also quite good, although in my Jadis (and my Audio Logic DAC) they sounded a shade too bright, though a little punchier and livelier than the Teles. I'm sure others have their favorites, but it would be helpful to you if they used those tubes in the Rogue and could report on the resulting sound. Otherwise, do some tube-rolling of your own to see which tubes you like the best.

NOS Telefunkens are nice.I have three in the front end of my Audiomat integrated. Great sound and they last forever. However buyer beware as there are a lot of fakes floating around out in tubeland. You may want to check out www.audiotubes.com as Brent's got a lot of NOS stuff, lots of tube info and he is an excellent seller. Cheers