Tube Basics 101: What is a rectifier tube for?

Elizabeth-

Actually, the preamp Phono board uses only (1) 12AU7 and (1) 12AX7. I see how you thought it was (2) 12AX7s from the quote I inserted, but if you re-read it again you will see. Also, I double checked on the Modwright website that I linkd in my post above to be sure.

So given that, I'm still not sure if either/or (12AU7 and 12AX7)are cathode followers, as you say. Do you still think so? Does this change any recommendations for tubes to change?

Thanks everyone for all the info. I'll check out that article and probably have some more questions.

In response to the preamp question, I have had great success in swapping out the 12au7, for NOS RCA cleartop 12au7's.

Hi, I would suggest that you call Andy at "Vintage Tube Services" and tell him what model pre you have and he will help you with selection and sell you tubes that are quite and won't break the bank.
Good luck, Tish

Elizabeth (or anyone)-

Is it safe to assume then that a 12au7 tube is always a cathode follower?

And if I can reiterate or summarize a bit:

Sounds like the 12au7 and 6sn7 driver tubes are most important to the sound and should be swapped out first if trying to upgrade the sound in some way. The 12au7, being a cathode follower tube - some say it is important as well, some say not as much affect to the sound. Same goes for the rectifier 5AR4 tube - some insist you should swap them out for better sound, some say it's not so important. But in any case the cathode follower and rectifier would not be the top choices for tube rolling until trying the others first.

Do I have this about right?