12ax7WA

Manufactured for the military.

Thanks I did some research and found the W stands for Military use and the A for first run B denotes 2nd run C for third run. Thanks for chiming in.

I received a pair of Sylvania 12AU7WA tubes in the little white boxes with the Federal Stock Number stamp a while ago. Holding those boxes in my hand transported me back to my early Air Force days in 1974.
Not sure if it was the memory or the sound but they are my favorite 12AU7 tubes.

Timrhu, have you tried the Mullard 12AU7 10 M tubes?, can you elaborate more on the Sylvania 12AU7WA tubes?, what did the y cost, what did you compaire them too?, what is the sound and presatation like?

Timrhu, have you tried the Mullard 12AU7 10 M tubes?, can you elaborate more on the Sylvania 12AU7WA tubes?, what did the y cost, what did you compaire them too?, what is the sound and presatation like?
Audiolabyrinth

Not sure about the 10 M designation but I did try pair of Mullards. They were delivered with the Unico and seemed to have a very smooth sound, kind of what I expected tubes to sound like.

The Sylvania tubes were much more lively with more top end bite and detail. They also excelled with bass presentation. As I said, the Sylvania 12AU7WA ended up as my favorite. I don't remember what I paid for them but it was in line with many other NOS 12AU7 tubes I was looking at. And again, this particular pair had not been used.

There were many other 12AU7s auditioned. RCA, GE, Philips and a others I don't recall. Most of these were obviously used but all worked. They were mostly purchased on ebay so the fact they all worked well was nice.

12AU7?mullard 10M are totally different than regular mullards. They are the best more open.

Jwm, I have had my eye on getting the 12AU7 Mullard 10 M tube for a long time, can you elaborate on the sound of these tubes?, all I know is that most tube users say this is the holy grail of the 12AU7 tube., very exspensive, a little rare,hard to find., have you owned some of these tubes?