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.