Why would a modern 3 prong power cord amp have a ground switch?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by BluesForDan, Jul 24, 2008.

  1. BluesForDan

    BluesForDan Member

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    Saw a picture of a boutique amp, and it had a ground switch. I thought those were only needed for the old 2 prong cord amps.
     
  2. 3th3r

    3th3r Member

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    To eliminate ground loops? (such when using the three-prong to two-prong plug converters)
     
  3. VacuumVoodoo

    VacuumVoodoo Member

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    Are you sure the ground switch was on the mains ground? If so it's a no-no.
    Does the amp have FX-loop? Ground switch on FX-return is used to break ground loops.
     
  4. mbratch

    mbratch Member

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    The 70's Fender amps are 3-prong and have ground switches with a central N/C position.
     
  5. Blue Strat

    Blue Strat Member

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    Possible noise reduction in rare electrical situations.
     
  6. SatelliteAmps

    SatelliteAmps Member

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    The 70s Fender ones switch works on the extra outlet, which is a 2 prong outlet, not on the electricity in the amp.
     
  7. doublee

    doublee Member

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    I remember that a tech guy was looking at my DRRI a few years ago and remarked that the ground switch wasnt even hooked up, and he surmised it was just for a 'vintage' look.
     
  8. mbratch

    mbratch Member

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    Is he sure it wasn't disconnected by an owner? The Fender schematic shows it connected.
     
  9. DIXØN

    DIXØN Member

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    Yeah some PA amps, mixers, CD players etc have "ground lift" so you can try and fix ground loops. It's dangerous on a guitar amplifier though.
     
  10. doublee

    doublee Member

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    Interesting. I am the only owner so it wasnt touched. Maybe he meant that it had no effect in his opinion....?
     
  11. tmac

    tmac Goldmember Gold Supporting Member

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    IIRC the DRRI shem shows it disconneted. It was just for cosmetic purposes. Not even sure if they do that with the newer reissues anymore.

    Ya know I just checked a DRRI schem at Schematic heaven and it does show the ground switch hooked up... hmmmm....I don't have a DRRI anymore so I can't check for sure now...
     
    Last edited: Jul 24, 2008
  12. doublee

    doublee Member

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    My DRRI is from the early/mid 1990's and yup the tech said it was disconnected when he looked at it a couple years ago. I could pull the amp and look but.......you know...
     
  13. mr coffee

    mr coffee Gold Supporting Member

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    not a touch of solder or wire..:NUTS
     
  14. mbratch

    mbratch Member

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    The schematic at the Fender web site shows it hooked up.

    Having a ground switch for the cosmetics just doesn't sound like something Fender would do. They'd want to save the pennies it cost to put the switch in.
     
  15. Rosewood

    Rosewood Member

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    I've worked on more than a few DRRI amps with no connection at the switch.
     
  16. mbratch

    mbratch Member

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    Interesting. Have you seen any with it connected?
     
  17. brad347

    brad347 Member

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    That's good. It gives you a head start on routing the NFB loop through it so you can defeat it for a different sound but leave the amp essentially unmodified. ;)

    One of my favorite tricks on a Deluxe or Deluxe Reverb.
     
  18. VikingAmps

    VikingAmps Member

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    Yup, DRRI's I've seen have the polarity switch in there just for looks. Never been hooked up. Some amps keep the ground switch there in case the third prong ground connection is broken somewhere. You get a hell of a lot of noise out of an amp with the chassis floating.
     

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