Tube Basics 101: What is a rectifier tube for?

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?

A power supply's rectifier(and it's quality) is VERY important to the sound of any amplifying circuit(phono, mic, preamp, power amp, etc). Anyone that has taken the time to install, say a Mullard Blackburn GZ34/5AR4, in the place of most other tube rectifiers(of the same family), or Fast/Soft Recovery Epitaxial Diodes, in the place of standard SS rectifiers, will likely attest to the improvements of presentation(across the board). Generally speaking; the sound will open up, have greater dynamics and a smoother(less grainy) high end. What you are listening to, through your speakers IS(in actuality) your house current, as prepared by your power supply. Your speakers are connected to your power supply, through your output devices(tubed or SS), and the DC output of said power supply is modulated(YES- the correct term) by those devices(basically switches), as directed by the musical signal. Is that the WHOLE story? NO! Every gain stage is important. Phase splitters and driver tubes BOTH contribute tremendously to one's final sound. BUT- to ignore the importance of the power supply's rectifiers, is to rob yourself of MUCH musical pleasure. I didn't stay at a Holiday Inn, but I have been modding audio equipment, and pro gear, for over 30 years and have made many a discerning ear happy, in that time.

Rodman99999-
I appreciate that, in the end, every tube in the circuit will matter to the sound and performance. I was fully expecting that reponse.

I just wanted to get some sort of consensus as to which tubes would have more bearing on the sound/performance - driver, rectifier, cathode follower, others?. So if you were wanting to change tubes one at a time and hoping to enhance sound/performance, in which order would you change them?

Drivers - Rectifier - Cathode Follower?
or
Drivers - Cathode Follower - Rectifier?

Also, I have to assume that, like everything else, eventually the law of diminishing returns comes into play. Not everyone's ears or systems are designed to be able to discern the differences between every single cable or interconnect that you insert here and there. I fully expect that the same is going to be true of tubes.

I'm completly new to tubes. I just want to approach things from a logical standpoint and roll out the tubes one at a time starting with the ones most likely to alter the sound. At some point I might say, "Thats good enough" or maybe I wont even be able to discern any differences.

Thanks!