Where Does Ground Loop Isolator Get Installed?

Discussion in 'Archived Threads 2001-2004' started by James Edward, Jan 28, 2003.

  1. James Edward

    James Edward Supporting Actor

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    I have a ground loop hum; I bought an isolator from RadioShack, and am not sure where in the audio chain to put it. I have an obvious hum from my sub, and also(though not as loud) through my 5 speakers.
    The isolator has L/R RCA jack inputs and outputs. The only place I have L/R analog inputs is at my sub and from the set-top box to the TV.
    I only ask this because moving my equipment to make changes is a real hassle; I'd like to get it right the first time.
    And does anyone with experience with isolators know if they adversely impact either the sound of the sytem or picture quality?
    Thanks for any answers...
     
  2. Bob McElfresh

    Bob McElfresh Producer

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    I hate to say this, but there could be several sources of hum in your system:

    - CATV coax
    - DSS Coax
    - Receiver->self-powered sub
    - Receiver/Processor -> amp

    Each problem has a different solution.

    That "isolator" would only work on say the Receiver->Sub connection. It WONT work for the CATV box->receiver because you also have a VIDEO feed that could be the source of the humm.

    Do this: get to hum to occur then un-screw the CATV coax to your system. Does the hum stop? If so then the CATV coax is the problem. Follow this link Fixing CATV Hum .

    Get a "cheater plug" from the hardware store (to convert a 3-prong cord so it fits into a 2-prong outlet). Get the hum to happen then TURN OFF THE SUB, un-plug the sub and install the cheater plug on the sub power cord, then plug it back in and turn on the sub. Does the hum stop? If so you have 3 choices:

    - Try using that isolation adaptor on the subwoofer cable
    - Continue to use the 'cheater plug'
    - Get a new subwoofer cable with arrows on it. (These cables do not have the shield connected to the RCA plug on the destination end and this breaks the ground-loop).



    Hope this helps.
     
  3. James Edward

    James Edward Supporting Actor

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    Thanks Bob-

    OK- I should have been more specific. The hum is definitely being generated by my satellite dish connection. I went over every piece, plugging and unplugging, etc., and the guilty party was the coax connector from dish to set-top box.
    Would the cable fix work for the dish also?
    Thanks
     
  4. Lee Bailey

    Lee Bailey Second Unit

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    James, where is the Sat Cable grounded at outside? If there is no ground wire on it, you need to have one installed. It needs to be tied to your electrical ground of the house. The CATV fix will NOT work on your sat setup. There are voltages that have to be passed to power the LNB on the dish.
     
  5. James Edward

    James Edward Supporting Actor

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    The installer has a ground wire attached to the metal conduit of my electric meter, same spot where cable was grounded. Could I do anything to make a 'better' ground?
    Thanks.
     
  6. Gregg Roszkowski

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    James,

    I had the same problem. Lee is saying that you need to connect a wire (ground) to the electrical system of your house. That is, the cable coming off of the feed horn must be connected to the common ground. Pick the nearest outlet and take the screw out of the face plate. Connect the ground from the cable(or dish) to this screw and screw it back into the outlet. Do this and you will have no more Hummmmmmmmm.

    Gregg
     
  7. Lee Bailey

    Lee Bailey Second Unit

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    Gregg is correct. As for the current ground connection outside, the cable really should be connected inside your breaker box on the ground strip that the rest of the house uses. To do that will require you to drill a small hole through the bottom(if it is accessible). You can get an electrician if you want, and have them drive a new grounding rod into the ground for you, and connect it to your panel as well.
     

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