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Ghost in the SVT

Discussion in 'Amps and Cabs [BG]' started by jdwinva, Jan 12, 2006.

  1. jdwinva

    jdwinva Supporting Member

    Aug 3, 2005
    Leesburg, VA
    My '78 Ampeg SVT seems to be picking up and amplifying the sound of the fan in the amp. In "Standby" it doesn't happen. As soon as the amp is on and not in Standby you can hear an amplfied whirl of the fan. If you turn up Channel 2 it even gets louder!

    I noticed that the amp is picking up other noises too, like when I tap my fingers on the top of the amp it sounds like a drum through the speakers. Is this a microphonic tube maybe??

    Any help is appreciated!
  2. Trevorus


    Oct 18, 2002
    Urbana, IL
    Yeah, that does sound like a microphonic tube.
  3. Plain Old Me

    Plain Old Me

    Dec 14, 2004
    No doubt here that its microphonic.
  4. Microphonic definatly, happened to mf SVTII a while back
  5. tadawson


    Aug 24, 2005
    Lewisville, TX
    With the amp on, gently tap each preamp tube with the eraser end of a pencil. The one that makes the loud noise is the culprit - replace it!

    - Tim