The recommendations posted here have been good. Personally I believe that the DeHavilland Mercury is an excellent option. I don't feel that additional 6SN7s are needed in the signal path. Type 85 tube is a good alternative.
Very simple circuit design.
Soft start with tube rectifier
I believe that it will match beautifully with a 300b amplifier using 6SN7 driver/input stage,
Charles
Very simple circuit design.
Soft start with tube rectifier
I believe that it will match beautifully with a 300b amplifier using 6SN7 driver/input stage,
Charles