Best 12AU7?

My favorite 12AU7 has been the French CIFTE from the early to mid 60's. 

They have gotten expensive and tough to find.

If you are using this in the buffer stage you recently posted about I would not drop a lot of coin into tube rolling.

Maybe try an RCA clear top as they are clean sounding and cheap as chips to see if it makes much of a difference.

I use expensive vintage tubes in my inexpensive kit gear, but in gain and driver stages.

DeKay

Agree Telefunken are the best I have heard for a detailed brighter sound.  Rca cleartops are an amazing value and sound extremely good on the brighter side as well. Can’t go wrong with either.

I really like the mil spec triple mica black plate RCA 5814A I just found. Detailed, smooth, not dull, and not too bright either.

Upscale Audio has very good NOS and new tubes. Check them out.