12au7 tube?

There are so many variations in NOS Mullard tubes (different factories, different styles, a whole range of dates of production), that it's impossible to generalize about them.  I wasn't impressed with the pair that I got, but that doesn't mean that some other pair might sound fabulous.

That's one positive vote for the Apos Ray.  I'm feeling tempted.

You Can't beat Andy @ Vintage tube services.

marco,

The 3 types you mention above are all Philips Europe companies. Made in Holland, Belgium and France respectively. Each has a unique acid etched code which begins the second set of each code. For Philips/Amperex is was a delta or triangle on its side, Mazda a L and LA Radiotechnique a plus sign directly over a slash or minus sign. All have many internal similarities and all have the 4 seams coming out from the nipple on the tube tops. There is much online about these codes and is the only true way to identify a Philips Europe tube and I have never known these codes to be faked. Many of the Holland made tubes will be branded Philips as well as Amperex.

I think, RCA black plates from 50s give excellent balance, at least in my amp. 

Hello Marco1, I haven’t listened to my 12au7’s in a long time and I really didn’t get very interested in where they were made and for what purpose. But off the top of my head, some things I do remember, for instance the very popular and extremely good Amperex 7316 (12au7) was a later production tube made for computer purposes. I believe Mazda was made in France.  Somewhere around 30 yrs ago, I Own a Conrad Johnson preamp for 10yrs that used (2) 12au7’s in its linestage and that was when I rolled and collected many brands and pairs of the 12au7’s. I still have some components in my collection that use the 12au7 but since moved onto other preamps that use other type tubes. All of the well respected vintage brands are worth giving a listen like Mullard, Telefunken, Valvo, Mazda, RCA black plates, Philips, Amperex, and so on.  I have a big inventory of other vintage tubes as well EL34’s, 6SN7’s, 12AX7’s, 5751’s as well many other tubes. In my home, I have many tube amplifiers in my listening area. I prefer tube components and in the past did a lot of tube rolling to get the best sound. Nowadays,  I still use all vintage tubes because I personally feel they sound better. Im not a fan of many current production tubes.  The only areas where I am not using vintage production is the power tubes on 3 power amplifiers because the 3 amplifiers take so many EL34’s and I don’t want to burn up my good Mullards or Amperex, Teslas etc. My VTL mono amps use 16- EL34’s, Conrad Johnson Premier 1b, 12- EL34’s, Conrad Johnson Premier Four 8- EL34’s. I use my premium EL34’s in my smaller tube amps that only require 4 power tubes.  The most important point I would like to stress, no one tube can be recommended to someone to be the perfect tube for someone unless it is heard in one’s system. I’ve forgotten so much about all the tubes I have in storage. But one thing I remember, you need to put the tube in the circuit and give it a listen to hear if its what you’re looking for.  I recently picked up a Conrad Johnson Premier 3 and once again, pulled out my stash of tubes and started popping them in and out till I got the sound I was looking for in the linestage along with the phonostage.