Confusing ground loop problem!

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joeparaski
joeparaski Posts: 1,865
edited March 2012 in Troubleshooting
This seems strange to me. I am trying to trouble shoot a ground loop problem. The amp is plugged into the wall and there is a hum from the speaker.....ok. Then, I happened to plug an extension cord between the same amp and the wall....and the hum goes away! huh! WTH...hum without extension cord and no hum with extension cord....WHY???


Joe
Amplifiers: 1-SAE Mark IV, 4-SAE 2400, 1-SAE 2500, 2-SAE 2600, 1-Buttkicker BKA 1000N w/2-tactile transducers. Sources: Sony BDP CX7000es, Sony CX300/CX400/CX450/CX455, SAE 8000 tuner, Akai 4000D R2R, Technics 1100A TT, Epson 8500UB with Carada 100". Speakers:Polk SDA SRS, 3.1TL, FXi5, FXi3, 2-SVS 20-29, Yamaha, SVS center sub. Power:2-Monster HTS3500, Furman M-8D & RR16 Plus. 2-SAE 4000 X-overs, SAE 5000a noise reduction, MSB Link DAC III, MSB Powerbase, Behringer 2496, Monarchy DIP 24/96.
Post edited by joeparaski on
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  • thsmith
    thsmith Posts: 6,082
    edited March 2012
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    Does amp and EC have ground plug?

    Maybe EC has flipped polarity ?
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  • inspiredsports
    inspiredsports Posts: 5,501
    edited March 2012
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    The cheap "fix" for a ground loop is to use a grey 2-prong grounding adapter on the grounded cord of the guilty component. This takes the ground out of the equation. If you are somehow plugging a 3-prong cord into a 2-wire extension cord, that would do the trick.
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  • joeparaski
    joeparaski Posts: 1,865
    edited March 2012
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    The amp has a 3 prong cord. Plugging it directly into the wall causes a hum in the speaker (the surrounds in this case). Plugging the amp into the wall but adding a 3-prong extension cord made the hum disappear....which is very strange.

    Joe
    Amplifiers: 1-SAE Mark IV, 4-SAE 2400, 1-SAE 2500, 2-SAE 2600, 1-Buttkicker BKA 1000N w/2-tactile transducers. Sources: Sony BDP CX7000es, Sony CX300/CX400/CX450/CX455, SAE 8000 tuner, Akai 4000D R2R, Technics 1100A TT, Epson 8500UB with Carada 100". Speakers:Polk SDA SRS, 3.1TL, FXi5, FXi3, 2-SVS 20-29, Yamaha, SVS center sub. Power:2-Monster HTS3500, Furman M-8D & RR16 Plus. 2-SAE 4000 X-overs, SAE 5000a noise reduction, MSB Link DAC III, MSB Powerbase, Behringer 2496, Monarchy DIP 24/96.
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  • Serendipity
    Serendipity Posts: 6,975
    edited March 2012
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    I am guessing that the 3 prong extension cord isn't grounded properly or has a break in the ground wire.
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  • joeparaski
    joeparaski Posts: 1,865
    edited March 2012
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    That's not it either. I tried a second 3-prong extension cord, same result, the hum diminished greatly. I think it may have something to do with the "winding" of the cord. It's a 25' cord that is rolled up.

    Joe
    Amplifiers: 1-SAE Mark IV, 4-SAE 2400, 1-SAE 2500, 2-SAE 2600, 1-Buttkicker BKA 1000N w/2-tactile transducers. Sources: Sony BDP CX7000es, Sony CX300/CX400/CX450/CX455, SAE 8000 tuner, Akai 4000D R2R, Technics 1100A TT, Epson 8500UB with Carada 100". Speakers:Polk SDA SRS, 3.1TL, FXi5, FXi3, 2-SVS 20-29, Yamaha, SVS center sub. Power:2-Monster HTS3500, Furman M-8D & RR16 Plus. 2-SAE 4000 X-overs, SAE 5000a noise reduction, MSB Link DAC III, MSB Powerbase, Behringer 2496, Monarchy DIP 24/96.
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  • tonyb
    tonyb Posts: 32,906
    edited March 2012
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    Could be a host of reasons, from the outlet itself to the cords ability to shield out interference, quality of the cord, etc. Either way, maybe try a different power cord on the amp or pick up a 2 buck cheater plug and see if that works.

    Chasing down ground loops can be a pain, sometimes you think it's one piece of gear and it could be another thats connected to it. A bad interconnect, cable tv box, or the wall outlet itself. Obviously the hum wasn't always there so try and think of anything you may have changed around.
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  • Serendipity
    Serendipity Posts: 6,975
    edited March 2012
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    Maybe the twist in the cord is resulting in less interference and you are not actually hearing a ground loop hum? Either way, these problems can sometimes be difficult (or easy) to chase down from my experience.
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