need to know what pair of 12au7 sounds great in a preamp
i have tried rca clear top sound very good that's the sound iam looking for but more of it...japan brand 12au7 no magic...the siemans were ok...
Haven't tried them but I've heard good things about the Yugoslav El 12au7's and 12ax7's ~$10 a tube based on the Telefunken design.

I use Mullards. I think that is what you are looking for. They are like RCA, but more of it.

My favorite "12au7" were the industrial equivalent pair of 1952 "D" getter Hytron 5814s. The best part, I got them for $10 on Ebay. I no longer have a component that uses 12au7 / 5963 / 5814 but will not be parting with these ever.
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Really fantastic. A little more pricer than others, but something special. Purchased some for an EAR V20 from Kevin at Upscale Audio.
Telefunkins. They are the best 12AU7 and 12AX7s out there. Clean, linear, extended on both ends and still
posses that midrange majic.
Telefunkins. They are the best 12AU7 and 12AX7s out there. Clean, linear, extended on both ends and still have that beautiful midrange magic.
Ditto on Kevin Deal's 6189. I've heard a bunch of 12AU7's - incl. Mullard and Tele's mentioned here - and the RT is the best. It smokes the RCA clear top like a good cigarette.
I almost hate to get into this because I have found that the Telefunken tubes are NOT always the best of their type. Both the 12AX7 and 12AU7's have an unnatural thickness in the midrange. Only the ribbed plate 12AX7 (If you can find them) overcomes this problem. Yes, the ribbed plate 12AX's may be the best ever made, but, everyone loves the smooth plate Tele's and they are only the best if your system needs this flavor. As far as AU7's go, there is a Mullard tube which is better than anything else I have ever tried regardless of what circuit it is used in. I wish I could tell you which tube it is, but, honestly, I am just not sure. It is not the really old version which sounds great, but, a bit too rich and romantic, nor is it the later version which lacks magic altogether. This tube does however have the "old" style logo. Remember, there is more to a tube than it's manufacturers name. There were many incarnations of the Mullard 12AU7 through the years and they all sound different. I guess this also goes for most tube brands- I have some old Yugoslavian AX7's supposedly made on retired Telefunken machinary which sometime impress me as being even better than the ribbed plate Tele's themselves.
My 12AU7s and 12AX7s are all ribbed-plate Telefunkens from Andy at Vintage Tube Services. In my opionion, for the most linear sound top to bottom, they are the best. Jason
Yugoslav El 12ax7's,that's what i have in my paragon 12 preamp now,they are new, maybe they have to break-in??? based on the Telefunken design maybe,sound i dont think so.
I have about 40 Baldwin 12au7 tubes I recovered from an old organ. I wanted the 5u4s and could not stand to let the rest go to waste. They are made in the USA, have green type and test very strong. If any of you would like to give them a try e-mail your address and how many you want. And Please let me know your opinions.

How about Amperex Bugle Boy 7316?... about to try out a pair myself here in a few days. I'll report back..
I'll have to agree with Jason. Of course, I don't think Telefunken made a bad tube. They're definitely the cat's meow when it comes to the AU and AT.