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Favorite Preamp Tubes in Your Mesa Boogie 400+?

whoatherechunk

whoatherechunk

Apr 4, 2008
4,085
11
#1
So I've been looking around here on TB and have seen that the 12AU7 swap is popular. The general consensus is cleaner headroom at higher volumes (?). Anyways, I'm just looking for some options so I can gather your opinions, dissect them, and shop around. Let me know the brands/model and why you enjoy them (tonal qualities,etc)! I don't care if you like Sovtek's, Ruby's, EHX's, Svetlana's, JJ's, etc....I'm most likely looking at a retube soon so I'm looking at options to get my baby up and running in tip-top shape. As always, I'm interested in hearing your opinions. Thanks guys!
 
#7
I'm not a tube guru *at all* so I'm subscribed & like the OP eager to hear if any readily available pre tubes make a nice difference.

(FWIW, I had Mesas & just put in some SLM "Hot Rod made in China" 12AX7s that were originally from an Ampeg preamp. Plus an old RCA 12AU7. The innards of the SLMs look absolutely identical to the Mesas, so I suspect they're the same thing. I think the 12AU7 mod made the biggest difference for me just now.)
 
#8
When I had mine I swapped all the preamp tubes for JJs and the driver for a 12AU7. Worked for me. I know at the time the driver 12AU7 swap was originally being discussed the 12AT7 idea was negated quite strongly - I am not a tube expert so cannot recall exactly why, suffice to say that consensus was that the if you are going to do it use a 12AU7 and nothing else.
 
#10
I think (and I might be wrong here) that it was found that Mesa had voiced the 400+ around the use of cheapie AX7's, thus the amp sounded better with them.

Now, I haven't messed with the tubes in my 400+, so I can't say if thats snake oil or not. Anyone able to give some input?
 
#11
According to PBG, what lorenk said nailed it. Supposedly the 400+ was voiced for cheaper "Made in China" tubes due to the lack of availability of quality NOS tubes in the open market. It's all in the PBG 12au7 swap thread.

Oh and sorry chunk, I'll get on those tubes today and letcha know what I got under the hood.
 
#13
Hey chunk,
Mine is loaded w/a quartet of GT 12AX7's and 12 Mesa 6L6GC's in the power section.

I just swapped out the driver tube w/a Ruby 12AT7. I'll letcha know what I think of it once I fire it up and jam on it for a li'l bit.


** OK, I tried the swap and my initial thoughts are I liked the GT 12AX7 better, tho to be fair tubes IMVLE tend to be about as individual as fingerprints so it might just be the particular Ruby tube I'm not liking. I'll give it a few days to let the newness of it wear off and decide if I'm gonna swap back or keep it in there.**
 
#14
Pitbull Growl said:
...Supposedly the 400+ was voiced for cheaper "Made in China" tubes due to the lack of availability of quality NOS tubes in the open market. It's all in the PBG 12au7 swap thread.
Click to expand...

MAMMOTHvolume said:
12at7s or 12ax7s will make much better driver tubes than 12au7s, you need alot more power to push all those valves. a 12au7 will give more "clean headroom" in the sense that it wont push the output valves as hard but it shouldn't give anymore volume
Click to expand...

In stock form, the 400(+) is notorious for getting loud and/or dirty very quickly - the 12AU7 mod definitely helps you get more useful range with the master volume knob. (And also affects the tone controls and even the channel gains IME.)

Psycho Bass Guy seemed to think that this mod was more of a correction, like Mesa was mistaken to use a 12AX7 in that slot to begin with & just too lazy to correct it. I have to wonder about that, though. Especially if they voiced the tone stack around new Chinese tubes. Why go to all that trouble then just shrug off the driver stage?

I suspect the raunchy behavior in stock form was deliberate. I certainly loved the amp that way and am not 100% sure I'm "feeling" this 12AU7 mod. (Got to dig it when you're totally blowing the room away, look down and see your master volume is only at 3. :D)

Good thing it takes about 2 minutes to change back and fourth! I'd advise anyone getting a new set to go ahead and get 4 12AX7s and a 12AU7 so they can try it both ways.
 
#15
I have made some experiments with my 400+.
Compared Tungsol, Electro Harmonix, Sovtek, JJ Tesla on the pre.

All this was done with the same, a bit exausted, Sovtek in the power section with two different cabs:

I ended choosing JJ Tesla, but I may prefer Tungsol once power tubes will be changed.

I tried the AU7 swap, but in the end I prefer 4 12AX7.
 
#19
I think I'm "over" the 12AU7 mod. I've tried it twice now.

It does make the head a lot more friendly to use in more mellow settings. (My micro-head gave the bigger rigs a run for the money when I first got it - looked like it might be time for some Mesa payback. :p)

But on a louder gig the other night, it totally ran out of juice. I had the master at 10 and I was fuzzing out all over the place but still not loud enough. (Think I was distorting some earlier stages but not really pushing the power section.)

I threw a 12AX7 back in and it was back to its old self. Filling the room way up with the master at 3 1/2 & not breaking up nearly as much. That works for me. :bassist:

No harm done, tho - was worth a try.
 

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