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Biasing an Ampeg SVT2 (non pro)

Discussion in 'Amps and Cabs [BG]' started by smo, Mar 27, 2013.

  1. Hi all,
    Hoping some of you tube-amp guru's can help me out!

    So I have my SVT2-nonpro at home staring blankly at me.
    It's depressed.:crying:
    Recently got it serviced, only the amp tech has rebiased it a bit colder than it was before.
    Unfortunately, that sweet-spot I love has disappeared and the amp is a whole lot cleaner than it was before.:bawl:

    My question is fairly simple - once I get the amp nice and hot after some intense use, I got out my multimeter and measured the bias at 60mV.
    Gievn that it's colder than it was before, would going up to 70mV be okay?
    I wouldn't be wanting to go super hot or anything, just slightly, to get the amp driving the same way it used to.
    Good Idea?
    Would I be damaging anything?
    Any precautions I need to take?

    Cheers guys.
  2. creis2


    Nov 11, 2011
    Cambridge, MA
    Don't SVT's have a bias adjustment outside of the amp with red and green lights.

    If it's internal, and done with a pot and test leads, I would recommend bringing it to a tech. Or pay someone to teach you.

    Why? One wrong move can kill you. Especially when that beast is on.

    Even when a tube amp is off and unplugged, they often hold enough voltage to kill you. There's a proper way to decharge it.

    I'm a frugal DIY'er, down to changing the circuit panel in my home, rebuilding an engine on my car, fixing all my home appliances, etc. I consider myself more technically inclined than the average person. Due to the dangers and the ability to screw up the amp, I leave it up to the tech.

    It's a great thing to learn, but you should have someone teach you hands on.

    If you know what you're doing (your tech) a bias adjustment is easy and quick.

    Why not bring it to your tech and ask to bump up the bias? The same happened to me, I brought it in and my tech bumped it up for me at no charge.
  3. Primakurtz

    Primakurtz Registered Nihilist Supporting Member

    Nov 23, 2011
    Denver, Colorado
    The non-pros do not have lights. They do have external bias points & instructions.
    To my knowledge, you can push the bias a bit. It may or may not sound better at 70mv, and your tubes may age faster, but I doubt you will fry them.

    IME, guitar amps usually sound better run slightly hot, but bass amps are often better a little cold, especially if you hit the front end with a boost.
  4. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    Considering that the II has the same setup as the SVT, and also the same correct bias of 72 mV, you'd be doing about exactly right.

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