OK, lots to respond to!
YES! That's exactly the deal with the '59 RCA tone. GREAT Dire Straits/ blues/ Robin Trower stuff on the clean channels! Dude, if you want one, let me know and I'll sell ya one of my used ones (NOT NOS or in collector's condition, but they test pretty strong and work without any issues that I can hear) for less than 50-60. I really don't want to get into that on the forum here, but I picked up a set of 4 for a great price, and I really don't need them all, so I'll be happy to share the joy! (And no, I don't have enough to give up more than ONE, and I'm not in the business of sellin tubes! lol)
Doug's Tubes Cocktail -- The RFT ECC83 that I used in V2 is a NOS (almost-equivalent) to a JJ ECC83. So a JJ ECC83 in V2 is a great choice. Note that a Penta 12AX7 is THE SAME as a Shuguang 12AX7, except that Penta Labs screens them and selects the best of the ones that they receive. I personally don't care too much for the tone of the Chinese tubes, so I try to limit them to the cathode follower positions (based upon rumours that other tubes in those positions cause trouble in the Roadster and Road King pre-amps). This may not be an issue in the Mark V, which is a different pre-amp design. I also elected not to use the Sovtek for my phase inverter based upon less than stellar reviews of that tube.
Clean tones should not be affected quite as much as distorted ones. From my limited experience so far, the richness of cleans is changed just a little from tube to tube, and in some potentially significant ways depending on your tastes, but most of them provide pretty standard performance when not overdriven. I suspect (and someone can correct me if I'm wrong) that the clean channel tones are based more on the amp circuitry than the tubes. Ya really need to do some experimenting and see what your ears and spirit think. BUT each tube seems to provide a really different response when they start to distort. Changing the 12AX7s should not really impact the way that the rectifier (diode and various levels of tube rectification) responds. The general tone changes when switching among the rectifier choices seem similar with new preamp tubes. I doubt that you'll get any bad surprises in that aspect. So, you'll need to study the Mark V tube layout that's in the Mesa manual. Each tube has a different function in the various pre-amp channels and sub-channels. Each 12AX7 tube actually has two separate sides, so will have two distinct roles in the scheme of things. The most important tube is the first gain stage -- this is usually position V1, which sets the overall tone of the amp. The next most important tube when it comes to tone is probably the phase inverter/ driver (usually the last one in the cascade --- V7 I think for the Mark V). This one sends a balanced final signal to the power amp, and drives the 6l6's or EL34's. This one should be selected to have matched triodes for optimum performance. (Note that in the Doug's Tube Cocktail, the Sovtek was specifically selected for this function!) The second and third gain stages are also important -- they add color to the tone on top of the first stage. The least important (until they start to go bad, of course) are the reverb sender and receiver, and the effects loop sender and receiver. (Did I get all this right , guys?) (lol) This is the way that I understand things, at least, but I'm always learning more! (Just be gentle but firm when pulling them and pluggin them back in, make sure that the pins a properly aligned, and you should be just fine. Also be careful with the tube tips when you put the spring-loaded caps back on so that you don't accidentally break one off. But do make sure to turn the amp off, let it coll off a little, and unplug it!) The advice that others have posted is right on the money!
Later!
Craig
