pre amp tube switch

Discussion in 'Amps and Cabs [BG]' started by FunkySpoo, Jul 17, 2002.

  1. FunkySpoo

    FunkySpoo Supporting Member

    Feb 6, 2002
    I replaced my GT 12ax7a that I think comes standard in the SM400 with a Ruby Tube 7025 STS. It's really interesting how different pre amp tubes can change your tone. This tube really warmed up the tone and mellowed out the top end I always thought the SWR highs were a little brittle sounding. This Ruby tube has alot more gain also. I'm guessing that's the reason my amp seems a bit louder than it used to. Anybody else have any experience with these Ruby tubes? It's not a 12ax7a so I'm wondering if it might mess something up by using it in place of a 12ax7a.
  2. CS


    Dec 11, 1999
    I think its a lower gain valve.
  3. FunkySpoo

    FunkySpoo Supporting Member

    Feb 6, 2002
    Could be. I know nothing about tubes. It just seems louder. Maybe it just sounds fatter so it seems louder. Either way it sounds pretty good. Any problems with it not being a 12ax7?
  4. 44me


    Jun 17, 2002
    Bedford, NH USA
    I’m fairly certain a 7025 is an old industrial number for a 12AX7. The typical gains should be the same. I think what you are hearing is the difference between two slightly different tubes. It’s amazing how changing a single tube can alter the character of an amp. There is no problem using either of these two in place of each other.