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Ampeg SVT Classic Hums with nothing plugged in

Discussion in 'Amps and Cabs [BG]' started by JG WORLD, Apr 1, 2009.



    Apr 1, 2009
    I am having a Hum problem with my SVT Classic. It makes a hum with nothing plugged into the input, It gets louder when you turn the gain up and the eq changes the hum too. Is there a way a user can determine if this is a bad solder connection to the ground on the input jack or do I need to take it to a service technician to see weather this is a bad filter cap or input grounding problem.

    has anyone else experienced this problem with an SVT Classic?

    If so what did you do to isolate the problem or determine what was wrong?

    Amp has been used about once a month for the past few years.
  2. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    The input is grounded when nothing is plugged-in. A bad ground will cause some hum like that, but probably insane hum when you plug in an instrument.

    Sounds possible that there could be a loose connection, bad filter capacitor, etc in the power supply filter. Also the first tube is supposed to have a DC filament supply, but something could be messed up there.

    Getting louder when gain is up suggests it is getting into first stage , but humming with gain down suggests it isn't JUST in the very first stage.

    You might try swapping the first tube with the other one just to see if there is a change.

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