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  1. #1

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    Default Klipsch Synergy Sub-10 and the mysterious ground loop adventure.

    Finally got around to swapping out all of the old HT gear with the new.
    Wires all nicely managed, everything plugged in and located in the rack.
    Fire it all up and...oh yeah baby!
    Everything works and sounds great. I play through some Blu-Rays, listen to some music, throw a couple of games on the xBox at it.
    HUGE improvements across the board.

    I shut everything down and get ready to head to bed for the night.
    As I am walking through the living room, I notice a steady hum at about 60hz coming from the vicinity of my front sub.
    I know the sound of that evil bastard, Ground Loop Hum.
    It is getting late, so I begin some quick basic troubleshooting. (each step was performed independently. So after each test, everything was returned to original state)

    1. Pull interconnect at sub. Hum is gone.
    2. Pull interconnect at AVR. Hum is gone.
    3. Pull the cable from the dish. Hum persists.
    4. Swap sub interconnects around. Doesn't matter. Hum persists in same sub.
    5. Connect ground from my surge suppressor to chassis of both amp and AVR. Hum persists.
    6. At the sub end, I ground the "shield" connector of the interconnect to the center screw of the outlet it is plugged into. Here is where it starts to get weird. Hum goes away completely with gear turned off but power to gear. Turn gear on, hum is back but even louder.
    7. Ground shield of interconnect on AVR side directly to the common ground on the surge suppressor. Hum diminishes slightly but is still there.
    8. Plug sub into same outlet the rest of the gear is connected to. Hum persists.
    9. Jump the shield side of the sub interconnect to the "negative" terminal of the nearest speaker wall plate. Hum disappears completely. No sound quality issues, speaker sounds fine. Voltage readings on the speaker terminals are normal.

    So there you have my weird and wild adventure with my ground loop nemesis.
    I am not comfortable grounding the interconnect in this manner.
    One thing I did notice is that the hum fluctuated while unplugging and plugging in the interconnect at the wall plate on the AVR side (AVR->Interconnect->Wall Plate->Coax through the wall->Wall Plate->Interconnect->Sub)

    Tomorrow, I think I will pull the wall plate and verify that the coax isn't loose on the terminal.

    Other than what I have tried, anyone else have any thoughts?
    "Unwad those panties and have a good time man. We're all here to help each other, no matter how it might appear." DSkip
    I may have an addiction... RTA-15TL, SDA 2, LSi25, LSi15, LSi9, LSi7, LSiCx2, LSiFX, LS/FX, RT/FX, DSW MP2000...and that's just the Polks...

  2. #2

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    a] How many powered subs are in the system?
    b] Do the subs have 2 pin or 3 pin AC plugs?
    c] Does the AVR have a 2 pin or a 3 pin AC plug?
    d] Have you tried removing all surge suppressors and power conditioners?
    e] Have you tried running a good unbalanced interconnect (like the Blue Jeans Cable LC-1) straight from the AVR to the sub? (no wall plates)

  3. #3

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    [a] How many powered subs are in the system? 2 Klipsch Synergy Sub-10. One located up front and a second back beside the sofa. Switching them back and forth, the hum doesn't follow leading me to believe that the issue lies with the coax running to the front sub in the wall.

    b] Do the subs have 2 pin or 3 pin AC plugs? Both have floating grounds. (2 pronged plug)

    c] Does the AVR have a 2 pin or a 3 pin AC plug? AVR is floating ground as well.

    d] Have you tried removing all surge suppressors and power conditioners? AVR was plugged directly into the wall, bypassing the surge suppressor. Hum persists. I can't conveniently remove the line conditioner as it is an in-line, hard wired unit.

    e] Have you tried running a good unbalanced interconnect (like the Blue Jeans Cable LC-1) straight from the AVR to the sub? (no wall plates) Simple troubleshooting step that I overlooked. I have Audioquest Copperheads running to the wall plates on each side but have not yet tried the direct connection. I have a ~25ft "decent" Monster Cable sub interconnect I will try tonight. Was actually surprised I still had this thing as I tend to boycott Monster quite passionately.

    Some good suggestions there. When I installed the line conditioner, I checked the output line for "noise" with an occilloscope and it tested out great. I am beginning to think that it is either the coax in the wall up front or the ground for that specific subwoofer port. Less likely to believe the ground though as the hum follows the interconnect between ports.
    "Unwad those panties and have a good time man. We're all here to help each other, no matter how it might appear." DSkip
    I may have an addiction... RTA-15TL, SDA 2, LSi25, LSi15, LSi9, LSi7, LSiCx2, LSiFX, LS/FX, RT/FX, DSW MP2000...and that's just the Polks...

  4. #4

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    Sorry to hear of your frustrations, ZLTFUL. If you can't find any solutions through the discussions here, you might want to take the time to read through this. Good luck on getting the issue resolved.

    http://www.jensen-transformers.com/a...%20seminar.pdf

    Tom
    In search of accurate reproduction of music. Real sound is my reference and while perfection may not be attainable? If I chase it, I might just catch excellence.

    The best way to enjoy digital music reproduction is to never listen to good analogue reproduction.

  5. #5

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    That was an awesome read, treitz.

    I ended up tracking the ground fault to a loose coax connector at the wall plate.

    No more hum and no funky ground.
    "Unwad those panties and have a good time man. We're all here to help each other, no matter how it might appear." DSkip
    I may have an addiction... RTA-15TL, SDA 2, LSi25, LSi15, LSi9, LSi7, LSiCx2, LSiFX, LS/FX, RT/FX, DSW MP2000...and that's just the Polks...

  6. #6

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    No problem, ZLTFUL. You can actually thank Speedskater. He offered it to me on another forum for something completely unrelated. Glad to hear that you got the issue resolved.

    Tom
    In search of accurate reproduction of music. Real sound is my reference and while perfection may not be attainable? If I chase it, I might just catch excellence.

    The best way to enjoy digital music reproduction is to never listen to good analogue reproduction.

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