Best 12AU7 Type Tubes for a Preamp

Thank you everyone. The unit is (not actually but sort of) a preamp.  I have owned a lot of tubed preamps in the past and didn't think I would again but when I purchased Hattor's The Big Preamp to run in passive mode so I could have remote volume control and a display, I took a chance and also purchased their Hattor Tube Active Stage, which uses two 12AU7 tubes.  IMO, the unit sounds way better than it should for what it costs, and good enough that I am seriously considering keeping it in my main system.  The gain from my unit is +6dB.  FWIW, the Big Preamp can be run in passive mode, passive with the Tube Active Stage, or through its own internal NewClassD opamp output stage at a selectable  +3/6/9 dB gain.  The opamp output stage also sounds quite good.

Back to tubes, I like the idea of not having to rely on NOS tubes but wasn't sure if the Psvane or Genelex Gold Lion were even in the same league as the NOS offerings.  Back when I was using tubes in preamps years ago, it seemed everyone was after NOS 6922 tubes and the 12Au7/AX7 varieties were relatively inexpensive.  Times have changed.  Things sound good now, so I may just try the Psvane tubes and call it good, but I will also look hard at some of the reputable NOS tube sellers and see what I can come up with.

Mitch2:

Here's a recent 12au7 thread of interest.

DeKay

Back sometime in the mid ’90s, one of the best audio investments I ever made was retubing my 12au7 Cary preamp & my 6922 ARC amps via Andy at Vintage Tubes. He sold me a half dozen NOS Mullard 12au7s for the preamp, and the years that I ran that combination made for some of the best sound I have ever had.

That was a long time ago, however, with different amps, and my ears were a lot better, and I believe the room was more friendly than the one I am in now. About four years ago I bought some French 12AU7s (I think Cifte was the brand?) from Uncle Kevin at Upscale, and I did appreciate their sound, but things have never been as good as the way I felt about the equipment with Andy’s tubes. But I do need to defer to the disclaimer about amp & room & ear changes over the past 25 years.

I've never been impressed with the RCA clear tops...or Mullards for that matter. The best I've heard are the German tubes, be it Telefunken or Valvo or whatever brand got stamped on the glass. The labels are meaningless for most NOS tubes and the codes should be used to evaluate where they were actually produced. The tubes that came out of Holland are very nice sounding, if a bit "sweeter" than the German stuff. Phillips had tube plants all over the place and they often weren't all that particular about what brand came from which plant. Tung-Sol produced some really nice sounding, smoked glass 12AU7 tubes that rival the European stuff, but are very hard to find and easily worth the extra scratch. 

In short, the German stuff is the best and worth the money no matter what brand is on the glass. The Holland made tubes (usually Amperex, but code specific) are very nice and sweet with good detail and worth a premium, followed by European tubes in general that were manufactured by Phillips. Mullard is distinctively warm sounding and often flashes when first powered up. American NOS are hit and miss across the board, with the exception of the Tung-Sol tubes that were terrific. Of the American brands, seeking out the military and commercial radio designed variants are the way to go. 

Thanks all - you have offered some really good thoughts and suggestions for me to consider, and thanks @dekay, the linked thread did have interesting and useful information.  

I live about an hour from Andy Bouwman • VINTAGE TUBE SERVICES, and I can get up there almost any time I want for my work so there would be no need to ship tubes.  I purchased from him long ago so I know how meticulous he is, which means higher prices, longer lead times, but almost surely a more successful result than dealing with mass market type sellers.  Since I only need two tubes, I plan to call him on Tuesday when he is next open and then purchase whatever he recommends.  As a bonus, there is some really good mountain biking very close to his shop!

As a last thought, this thread has reminded me of what a helpful, friendly community we have here - thanks again.