I've liked the Tungsram Industrial grade 12au7 from Hungary (dated 1971) available from A'gon member Tubemonger. Very quiet and detailed.
What are the best drop in subs for a 12AU7??
I am considering a Minimax preamp, but understand that they sound best with rolled 12AU7s. I have some Mullards which I would try first but have heard that there are even better choices of slightly different tubes. What are they and are they difficult to find? Thanks any help is appreciated.