Tube Basics 101: What is a rectifier tube for?

Kick a man while he's down.

Nnck,

Here is a link you may find informative....
A taste of tubes

Jea48,

Thank you for the reference. I never saw that wonderful article. Clever and informative. Thanks!

They use one 12au7 because it is a not too important cathod follower. The two 12ax7s are the audio tubes.
So get good 6EH7EH (Electro harmonix brand) or Tung Sol 6SN7GTB and get the matched so they are matched one left/ one right then the other two sides matched. (Sylvania are the NOS 6SN7WGTA to buy but cost is three times the others I mentioned.)
So say a 72/68 and another tube that is 67/72 for and example. If they are better matched so both sides are the same, they will cost more.
Same goes for the 12ax7s. (RCA)
When you can swap the sides and double the life that is cool.
I would swap the sides on a regular basis, like every three months/or six months if it is not to hard to do.

I disagree.

CF is very important in the circuit of the topology you described! Try bypassing the CF (without replacing it with a transformer)in your preamp's output circuit and you will see how important it is on how the preamp will sound and how it will perform driving the load.

Just my opinion....