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Preamps: replacing 12ax7 with 12au7?

Discussion in 'Amps and Cabs [BG]' started by Seedouble, Jan 27, 2014.

  1. Seedouble


    Feb 13, 2007
    Hi there,

    I've been using an Alesis MicTube Duo at the end of my chain for recording recently and I think it warms up the sound quite a bit.

    Since it starts peaking at 9pm on the dials, I wonder what would happen if I changed it out for a 12au7?

    I went to a local music shop and the guy said he'd never heard of anyone wanting to do anything like what I was talking about. Besides, he didn't have them in stock anyway.

    Would I really just be making it so I can turn the gain knob up higher? Would there be any real benefits to this "mod" anyway?

  2. BurningSkies

    BurningSkies CRAZY BALDHEAD

    Feb 20, 2005
    Seweracuse, NY
    Do it and find out. or alternately, you could use something slightly more gain than the AU, and use a 5751.

    I like the 12AU7 and the 5751 better than the 12AX7.
  3. scf4003


    May 2, 2004
    I've used a 12AU7 in the preamp section of Marshall, Orange and HiWatt amplifiers to reduce the gain, it works very well
  4. I did just that for one channel on a V4-B, made it more friendly to an active bass. I kind of liked the character of the sound better as a bonus.
  5. wcriley


    Apr 5, 2010
    Western PA
    I swapped a 12AT7 in place of a 12AX7 in the "dirty" channel of a guitar amp and liked the results. Higher gain than an AU, but lower than an AX.
  6. BurningSkies

    BurningSkies CRAZY BALDHEAD

    Feb 20, 2005
    Seweracuse, NY
    B-String suggested that I put a 12AU7 in the V1 of my Fender Twin Reverb to clean up the messy low end it had, and it worked very well. Sounds great now.