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SVT 3 Pro Tube Gain problem

Discussion in 'Amps and Cabs [BG]' started by rykuzushi, Nov 7, 2013.

  1. rykuzushi


    Jan 24, 2013

    For some time I have a problem with my amp. After start-up, while the mute button is on, turning the Tube Gain to 0 I hear louder noise like lamps were "burning" but nothing is happening inside the amplifier. The sound stops when I set Tube Gain to 5 or above.
    Once encountered a situation when playing on instrument, the volume level balanced from 0 to normal sound.
    Do you know what is the reason? Will replacement the lamps help?
  2. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Replacing the tubes might help, but it could just be one tube that needs replaced. If I'm not mistaken, the tube gain is only related to the two driver tubes. Try replacing each tube one at a time with a known good tube and see if you find a culprit.
  3. rykuzushi


    Jan 24, 2013
    thx for reply. Ampeg service support said exactly the same. I think I will try with the replacement of the tubes and see if it will help.
  4. nukes_da_bass

    nukes_da_bass Banned

    Feb 19, 2006
    west suburban boston
    Also keep in mind, early versions of this amp had FET bias issues which caused unwanted distortion- which is why I ultimately ditched mine!
  5. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    That would mean it's distorting at all volumes, which I don't believe the OP's is doing.
  6. hodgy


    May 5, 2004
    Bothell, WA
    Customer Support- Ampeg/ Line 6
    LOL, yes this is exactly what I told him earlier this week.
  7. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    Yes.... adjusts plate voltage for power amp tubes.

    I'm not 100% "getting" the problem..... But I think he is having a noise that probably sounds like the wind blowing, when tube gain is set to lower settings.... and it stops when set to higher settings.

    "Tube gain" really means "amount of plate voltage reduction", so at maximum effect, the voltage is lowest.

    Therefore it seems noise is occurring with max plate voltage. Yes, could be a tube, could be something else, too.

    Tubes are easy, so the advice to change them is good.

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