12au7 tube?

I’ve run 12AX7 and 12AT7 as signal tube in my integrated.  No experience with lower gain 12AU7, however I have found consistent sound signature across mfg with AX7 and AT7.  Mullard = warm, smooth with less detail, Telefunken = master of transparent balanced detail, Amperex BB = clear, clean sparkling treble extension. My favorite that combines all three are Raytheon black plates from 50’s = warm, strong bass and midrange with great treble and detail up and down frequency range. Doesn’t have full extension and sparkle of BB, but has warmth of Mullard, but not too warm, detail and transparency of Telefunken but not at expense of bass, and superb treble extension but doesn’t leave out beautiful midrange. Goldilocks of signal tube in my system.

I suggest thoroughly combing through Brent Jessee's descriptions of 12AU7 tubes or any other tubes for that matter. Depending on your tastes and preferences, you may or may not like the sound profile of the German brands. Telefunkens and the other German tubes are more stark and less warm than the Dutch, Belgan, French and British sound.

Re: current production Gold Lion and Tung Sol tubes, I find that the Gold Lions are tilted toward the upper mid range and highs and that the Tung Sol tubes are tilted the other way, more toward the mid bass and bass.

Unfortunately, current production tubes just can't match the abilities of NOS tubes and there are NOS tubes available that can be had for the same cost or even less than the better current production tubes.

I also suggest to sticking to the better tube suppliers such as Brent Jessee instead of buying on the "open market". My results on "open market" buys have been a mixed bag that were mostly disappointing.

And all things being equal, pick up a current production Gold Lion 12AU7, an excellent reference tube to judge all others, NOS and current production, based on my experience with the 12AX7.

Thanks everyone. I have a bunch of tubes incoming. Radiotechnique, Genalex Gold Lion, Brimar, Amperex.

i don't know how good they are, but, a local dealer helped to sell off a very valuable collection of tubes.  Included in the collection were something like eight original Genelex  B749 tubes (12AU7 variant).  These sold for north of $1,000 each.