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Exact Function Of Preamp Tubes In Mesa 400+

Discussion in 'Amps and Cabs [BG]' started by slacker, Sep 4, 2002.

  1. slacker


    Nov 27, 2001
    Portland Oregon
    Not as stupid a question as it may first sound!

    What do each of the four tubes in the 400+ preamp section do?

    One, I believe, drives the power section and should not be swapped out (according to a friend who was told by the factory). The other three are safe to experiment with.

    Anyone care to chime in?
  2. I am fairly sure it is just two per preamp. You can get yerself a darn rich and meaty tone by plugging into both channels at the same time; well worth it. Don't sweat any tube swappin'..I used to "roll" mine all the time.
  3. slacker


    Nov 27, 2001
    Portland Oregon
    I may have to go to the factory with this one. I know all 12AX7 types are more or less interchangable, but I remember Mesa being rather firm on *not* changing the "driver" tube, which I believe, is to the far right. I just wanna be sure.

    Thanks, Mad S., I already split my signal, it is a good trick,though. The best of channel 1 (Fatter) and channel 2 (Grindier).

    Any tube recommendations?
  4. One tube should be a phase splitter. The other three should handle the first, second, and third gain stages for the two channels, as well as the FX loop recovery stages.

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