Ampeg V4 - swap 12au7 for 12ax7?

Discussion in 'Amps and Cabs [BG]' started by mikopita, Jul 22, 2009.

  1. mikopita


    Feb 22, 2007
    Central Florida
    I'm looking to get less breakup in the preamp stage of my Ampeg V4, and have been thinking about swapping the 12ax7's for 12au7's (I have a bunch of originals from the 50's). I know that it isn't much of a big deal for many manufacturers, but for some reason I'm finding a lack of info on this for old Ampegs either here or in google world. Is there anything I should be wary of/made aware of if I attempt the swap? Has anyone done it, and if so, what were the results?

  2. Jefenator

    Jefenator Supporting Member

    Aug 22, 2008
    That's a popular "mod" (I think of it more as a "swap") with the Mesa 400/400+. I just did it to my mine this afternoon and it seems like I get more sweep from the channel volume knobs before distortion.

    Here's the original thread where Psycho Bass Guy talks about it.

    Not sure if your Ampeg would benefit the same or not.
  3. mikopita


    Feb 22, 2007
    Central Florida
    Thanks for the reply jefenator. I went ahead and swapped out one of the 12ax7's and noticed an immediate difference (I changed the one closest to the back of the amp). Later I'll try the others and will reply with my findings.