Tube Basics 101: What is a rectifier tube for?

Elizabeth-
Thanks again for the basic no-nonsense info.

It appears the my preamp has no main cathode follower. The only tubes in it are the ones I mentioned: (2) 6SN7 drivers for the main, (1) 12AX7 and (1) 12AU7 for the phono and the (1) 5AR4/GZ34 rectifier.

I suspect the preamp I am talking about (once again, the Modwright LS100) is more of a 'hybrid'design than a true tube preamp, but I dont know the distinctions exactly. In any case, there doesnt appear to be a cathode follower - dont know if that seems strange to any of you?

Also, I wonder what all of your opinions are about something I was reading in another thread here on Audiogon. There was a link to another article (Joe's Tube Lore - http://www.audioasylum.com/scripts/d.pl?audio/faq/joes-tubes.html) where the author basically said that there are no 12ax7 tubes that are all that good. The author suggested that anyone interested in getting better sound should replace the 12ax7 tubes with 5751 tubes, which are, for the most part, interchangeable with the 12ax7.

Is this something that is a given or fairly common knowledge? Would you agree with this assessment? And also, if you do replace 12ax7 tubes with 5751 tubes, can you still use the 12au7 cathode follower, or do you need to replace those with something different as well?

Thanks again everyone!

Hello Mr N- While it is certainly true that everyones' aural accuity, and system resolutions vary; tubes in circuit make a dramatic difference, and one must be nearly deaf to miss their impact. Since you mentioned the 6SN7 family, I'll start there, as the driver will have an effect on ALL your inputs. This tube: (http://cgi.ebay.com/2-MATCHED-Sylvania-BAD-BOY-VT-231-6SN7-GT-6SN7GT-Tubes-/300532799867?pt=Vintage_Electronics_R2&hash=item45f926997b) is an excellent performer, that won't break the bank(like my faves; the TungSol round plates, and Sylvania 6SN7W, tall bottles). They are easy to find(right now anyway). Whatever you buy; be certain the triodes are balanced, and the pair also(if more than one is used in that stage). When you replace the phono tubes; once more, balance is important, but also- get CERTIFIED LOW NOISE tubes, as the gain there is much higher, and any noise will be amplified(http://www.upscaleaudio.com/testing-signal-tubes). After you've gotten accustomed to the new flavor of your system; find a NOS Mullard(Blackburn Plant) GZ34(http://www.tubeworld.com/5ar4.htm), and enjoy! OH, BTW: The Mullard rectifier will probably outlast you, and your preamp. Here is a site that will give you an idea of what presentation to expect from some of the difference NOS tubes in the 6SN7 family. I've tried all the top contenders listed, and can vouch for the veracity of the opinions given(http://www.avclub.gr/forum/archive/index.php/t-4376.html).

While it is certainly true that everyones' aural accuity, and system resolutions vary; tubes in circuit make a dramatic difference, and one must be nearly deaf to miss their impact.

Well, again, I am pretty new to tubes, so I cant say that that couldn't be the case.

When you replace the phono tubes; once more, balance is important, but also- get CERTIFIED LOW NOISE tubes, as the gain there is much higher, and any noise will be amplified

But my preamp has only one driver tube in the phono - a single 12ax7, so I dont know how to take what you are saying. Match it to what? Should it be matched to the 12au7 follower?

And thanks for the specific recommendations. Will definitely consider some of these. Hoping for more recommendations as well.

On a side note, others have told me the new stock Shuguang Black Treasure 6SN7/CV181-Z are good tubes to use. This is not to bring up the NOS vs current stock debate. But I wouldnt mind having one or 2 recommendations from both (NOS and current options) for each of the tubes in my circuit.

I based my comment on what you said about having a 12AX7 and 12AU7 in the phono circuit. Both are, "dual triode" tubes, and(as you have one each for both channels), if the two triodes(WITHIN EACH TUBE) are not balanced, neither will the sound be, from that stage of your system. Of course: that will bother some, more than others. Did you look at the Upscale Audio page, on grading tubes? The better the grade, the closer the triode balance(from most sellers). Personally- I've never heard a Chinese tube that I wanted to listen to again. But- who am I to say what's right in someone else's listening room? Happy listening!