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

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.

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

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

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?

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