Would a dimmer switch cause 60hz Hum?

Discussion in 'Home Theater Projects' started by chris_steltz, Feb 19, 2005.

  1. chris_steltz

    chris_steltz Agent

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    Im getting a ground loop hum and ive tried isolating everything. Ive noticed that when I turn my dimmer switch up it gets louder but when the switch is off I still get the hum just not as loud. Could it be the reostat in the switch causing the feedback?
     
  2. Jack Ferry

    Jack Ferry Stunt Coordinator

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    Chris, could you give us a few more details? What is humming, your audio equipment, display or the lights themselves? Are the lights on the same circuit as your HT equipment? Have you tried running an extension cord to put equip on a different circuit?
    Dimmers can create a great deal of hum. What kind of dimmer is it and what is on that circuit?
     
  3. Elinor

    Elinor Supporting Actor

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    An electronics tech where I work was helping me diagnose an intermittent hum I was having, and he said a dimmer definitely can generate hums. Also fluorescent bulbs. Also having stuff plugged into different outlets.

    I don't think ground loops per se are intermittent, and if it's a dimmer I don't think it's properly called a ground loop.

    Cable and/or satellite connections (even antenna if done improperly) are the most likely culprits of ground loops.
     
  4. chris_steltz

    chris_steltz Agent

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    The humming only occurs when my DIrectv Tivo is hooked up and my amp is on. The directv system is grounded properly and i have tried running everything off different plugs, I have even installed another plug that runs directly off my circuit breaker. This is the only time i get humming even when the dimmer lights are on. Wehn i watch a DVD or play xbox there is no hum but as soon i hook the tivo up to my TV or to my processor i get hum.
     
  5. Bryan Pape

    Bryan Pape Auditioning

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    You have a ground loop caused by a differential in ground between your audio system, your lighting, and your video system. The most likely culprit is the video system.

    Check the grounding of the cable coming into your home. It's likely got a poor ground that's being exposed.
     
  6. Leo Kerr

    Leo Kerr Screenwriter

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    Also, most dimmers are fairly 'noisy' devices, and will be able to induce noise into a lot of things you'd think would be sufficiently isolated. Worst range is typically when the dimmer switch is somewhere in the 40%-60% range, generating some of the strongest RFI.

    Remember, except in (now) rare situations, dimmers work by turning the power on and off rapidly. This clipping of the AC power line, especially near the high-point of the sine-wave, generates tremendously powerful and broad spectrum harmonics that go everywhere.

    Leo Kerr
     
  7. chris_steltz

    chris_steltz Agent

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    My directv is ground solidly im 100% sure of that. What would be the solution to the problem then if it is the dimmer switch?
     
  8. Elinor

    Elinor Supporting Actor

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    Chris, I don't think it's a question of being "ground solidly" it's a question of the DirectTV using a different ground path than the rest of the system. Is it?
     
  9. Bryan Pape

    Bryan Pape Auditioning

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    Exactly. Even if both have excellent grounds, there can be a difference in ground potential between the 2 of them. The fact that when your DirecTV is on you get it and when it's off you don't points solidly to it IMO.

    Where and how is the satellite system grounded? Have you tried tying a temporary chassis to chassis ground between say your audio receiver and your DirecTV receiver?

    The dimmer is likely causing an additional issue or at least exaggerating it. FWIW, try temporarily replacing the dimmer with a standard switch and see what happens (if you feel competent to do this).
     
  10. chris_steltz

    chris_steltz Agent

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    The directv is gorunded outside of my basement to the wall using a grounding block. How would I ground the Directv Tivo to my parasound amp?
     

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