power cord interference

Discussion in 'Home Theater Projects' started by EduardoBonifaz, Dec 11, 2003.

  1. EduardoBonifaz

    EduardoBonifaz Stunt Coordinator

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    I´d read and heard alot about interference and electric "noise" thata affects video and audio signals, so tit´s recommended not to place together the power cords and the audio and video cable, my question is, does it really matter the distance between the power cords and the audio/video cables? you know in most equipment racks it´s not possible to separate them much, some devices have the power cors on the left side, others on the right, and the audio/video inputs and/or outputs sometimes on the middle of the device, so I can´t figure a way to effectively separate them, using decent isolated cables, do you think it´s really and important matter to care about cable distance and separation?
     
  2. Bob McElfresh

    Bob McElfresh Producer

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    Yes it is important.

    The power wires generate a small electromagnetic field at 60 hz around them.

    The interconnects have a 'shield', but this shield connects to the ground of the electronics.

    Run them together and you have just introduced a 60 hz noise into what should be 0.000 volts (your ground reference).

    Try this:

    - Put the receiver on the lowest shelf. This puts the speaker wires away from everything else, and lets them flow out with minimal drop.

    - Look at the back of your equipment. Pick a side for the power cords (left/right) and run all the cords to that side. Use velcro strips to secure them down the side of the rack. They are usually stiff enough to hold their shape. Note: Put a A/B/C label on each power cord right as it comes out of the box, and at the plug end. This makes it easy to tell which is which at the power-strip end.

    - Leave all the interconnects to dangle down the middle of the rack. You can loosly bundle them with some more velcro, but this is not necessary.

    This should give you several inches of separation for parallel runs, and yes, some of the power cords will touch the interconnect, but at a 90 degree angle. This minimizes the interaction.

    Hope this helps.
     
  3. EduardoBonifaz

    EduardoBonifaz Stunt Coordinator

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    thanks for the tips Bob, is there a minimal distance suggested?
     
  4. Brian OK

    Brian OK Supporting Actor

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    Bob is correct. A MINIMUM of 3" SEPARATION is the general rule.

    A great tip is to go to the hardware store and buy a package of the gray foam tube used to insulate hot water pipe to literally "make" that separation between wires a physical one.
    These tubes usually come in 4' lengths, purchased individually or in the aforementioned 4/pack. Great for separating wire runs. You can treat 90 degree intersections with short cuts of it and shield all your wires to your desire.

    Looks like hell, but if it is all behind your rack, and out of sight, who gives a whoot.

    BOK
     
  5. Chu Gai

    Chu Gai Lead Actor

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    OTOH, you could always separate them and then visually observe what happens to your image as you literally put them on top of each other. How close are the power cords and video cable going to that monitor you're typing on? See any problems?
     
  6. Wade_Kennerson

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    I am having a similar interference issue, but I am not sure how to solve it. The interference comes from my cable lines and only effects my HTPC output. The interference doesn't show up through my DVD or other video sources. I have tried re-cabling all the cable lines with shielded wire from Home Depot, but it still persists.

    I think the video problem extends from the VGA cable running to the transcoder. It is just a simple patch cable. It doesn't have one of those inline cylindrical thingies.(Technical, huh?) Would somehow creating a cable with one of those make a difference?
     
  7. Chu Gai

    Chu Gai Lead Actor

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    well you can head down to the Shack and pick up some snap-on RFI beads and at least if it doesn't work, you get your money back.
     

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