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SVT 2PRO owners question

Discussion in 'Amps and Cabs [BG]' started by Rickenmonster, Sep 1, 2013.

  1. When I power up my amp I hear a quick hum. Volume off-no input. Doesn't happen with my SVT CL. Bias it fine-no warnings and everything works. Amp sounds great. Does anyone else hear this when powering up? Is it just a nuance of this particular amp?
  2. Is it a hum from speakers or just the amp itself?
  3. skychief


    Apr 27, 2011
    South Bay
    Yep... I hear it on mine.

    No worries.

    Its just the secondary windings of the OT gettin ready to dance.
  4. WretchedExcess


    Jul 29, 2013
    Yep. Transformer hum on startup (that does not come out of the speakers) is normal as long as it goes away. It's an artifact of inrush current. If it doesn't go away, and if you hear it through the speakers, then it's a different problem and you might want to re-balance your bias to minimize hum on the amp's output.

    The amp has another idiosyncrasy -- it can emit a loud BANG! when you're coming out of standby, where the top panel can flex and pop when the B+ transformer gets energized. If you've never heard the bang before, unscrew the top bolts to loosen the cover, leave it sitting on top, and cycle the amp off, wait a few minutes and turn it back on. You'll hear it when you come out of standby. The first time I heard it, it scared the bejeezus out of me!

    There's a thread around here somewhere where I posted pics of how I fixed the bang-on-standby problem. I'll see if I can find it.

    edit: found it. see next post
  5. WretchedExcess


    Jul 29, 2013
    Here's the Wretched Mod for the Bang on Standby problem. It's pretty simple. It amounts to putting a pair of adhesive-backed neoprene strips on the top of the trannies so that when the transformers energize and bang the top cover, they bang on neoprene padding (quiet) instead of the transformer laminations (loud and scary!).


  6. Yes. The bang. Thanks for the input, guys. A load off my mind. Love this amp.
  7. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    I'm assuming the neoprene won't set on fire...?
  8. I'm not going to do anything about the bang. As long as its not harming my amp I can live with it. My amp makes some much louder noises-ones that I love.
  9. WretchedExcess


    Jul 29, 2013
    Yeah, that would sure be a disaster, wouldn't it?

    I'm not too worried about a fire -- the transformers don't get hot. This amp also has forced air cooling, and it's constantly blowing ambient air up from the bottom chassis, so it passes in between the two transformers, and flows over the power tubes and out through the grille on the back. It doesn't get anywhere near as hot as a Fender-type amp that doesn't have a fan. My Super Twin runs a lot hotter.

    FYI they make those high-temp rubber rings that people snap around tubes. They're made of Viton and they can handle the full heat of contact with the power tube envelope. So if you're worried at all about heat, use high-temp viton rubber sheet.