12au7 tube?

I think, RCA black plates from 50s give excellent balance, at least in my amp. 

Yeah, it can just be different, not better or worse. That's what Brent from Audio Tubes told me when I asked him about possible comparison in my amp between RCA black plates and Mullards, don't remember the exact model. And I decided not to get the Mullards since I liked the sound I had and didn't want it to be any warmer than it was. But someone else might've wanted exactly that, it would've been excellent sound too.

But for 12AX7 in the preamp my Mullards go nowhere.

No, we are not, but still crazy enough.

Tube rolling seems to be the correct way to begin fine tuning the sound. Cables and power cords should come next, I would think.

Ray tubes ? Made in China or where ?

marco1, I see. I just don't want any Asian tubes in my amp, or current production Russian ones, for that matter. I am a NOS or good used Old Stock kind of guy. I just have to use earlier production Svetlana/SED EL34 "Winged" because Western vintage tubes are too expensive, when you can find a matched quad.

mulveling, it's interesting what you previously said about power tubes influencing sound more than signal tubes. I remember conversation with Kevin of VAC and he said exactly the opposite. I myself have no opinion, I didn't compare power tubes, but doing a little of tube rolling with 12AX7 in the preamp and 12AU7 in driver slot reveals big differences.

mulveling,

I see, now I understand what you were saying. So you were both right.

lowtubes, though I did not compare EL34 tubes yet, I too can't say that I hear anything special from SED tubes, not that I expected it. They seem to be alright, nothing more. That's why I of course want to find a reasonably priced matched quad of XF1 or XF2 Mullards, even used from a reputable source. Tesla, yes, I heard about them, saw them on ebay and nowhere else.

Do you ever somehow try to musically match 12AU7 driver and power output tubes in advance or it is just a matter of experimentation? I mean, if I am lucky at some point and get a set of EL34 Mullards should I also consider replacing 12AU7 RCA blackplates driver tubes with Mullards ?

Well, most audiophiles are hard to please and always strive for even better sound than they might already have.

I see, no real reason to think that one tube brand everywhere would have an advantage.

With cables, I think it might depend, though I don't have enough experience to be sure.

Yeah, he meant black plates, of course. I think, RCA actually invented both 12AX7 and 12AU7 tubes. 1948-1956 production years are thought to be the best.

For $180 you can get a NOS matched pair of Mullards or RCA black plates, and probably other brands too, I just didn't look.

These were prices from audiotubes.com, a very reliable source of tubes. In fact, RCAs are $100 for a matched pair.