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Dimmer and Video

Discussion in 'Sound, Music, and Intercom' started by blademaster, Dec 7, 2005.

  1. blademaster

    blademaster Active Member

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    Occupation:
    Automation Engineer
    Location:
    Mountain Home, AR
    At my church we have our computer, DVD, and VCR right next to our light dimmers. And on the 20ft or so dual RCA line we come to the board we have a 60cycle hum and i want eliminate it. Any ideas
     
  2. farmerjo1111

    farmerjo1111 Member

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    The two things to check is that your sound power is properly grounded and it is a sheilded cable. Also check that your not pluged into the same power pannel as your dimmers.

    Dustin Strobush
     
  3. avkid

    avkid Not a New User Fight Leukemia

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    If possible I would switch those RCA cables out with some balanced 1/4 inch TRS cables.
     
  4. bdesmond

    bdesmond Active Member

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    Last I checked consumer playback gear is an unbalanced source/input...
     
  5. avkid

    avkid Not a New User Fight Leukemia

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    I was never told what kind of playback gear this is, so I included if possible, say it has the ability use such connectors. Another idea is to use high quality shielded RCA with gold connectors such as:

    http://www.monstercable.com/productPage.asp?pin=105
     
  6. AVGuyAndy

    AVGuyAndy Active Member

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  7. soundman1024

    soundman1024 Active Member

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    The first thing to do is to try to figure out what is causing the problem. Before buying other gear it may be worthwhile to try putting a different DVD/VCR/CD player on the cables you are using currently that has been used somewhere without having a hum and see if it is the device. I doubt it is the device, but if it is possible to know for sure it isn't the device that helps to troubleshoot.

    I would like to second avoiding Monster Cables. They are severly overpriced. Furthermore RCA is still an unbalanced signal so it isn't likely that it would prevent the buzz. Something to remember with cables is its fine to have a gold-plated connector, but signal will always be subject to the weakest link. Not only is the output on must devices aluminium. Furthermore with "gold plated" connectors what is behind the gold probably is the weakest link. I agree with AVGuyAndy that a DI is prehaps a good method to use. Personally I would advise a Whirlwind pcDI. You can Froogle for one, they are about $120. They have a minijack (1/8in) input, as well as RCA in and thru on one side, and 2 balanced XLR outputs on the other side as well as a 20dB pad. That may solve the issue, if that doesn't it is probably that you don't have clean power. The best think I can think of to test that is to run an extension cord from another circuit and run all audio equipment on a different circuit. The DVD/VCR, board, anything after the board (EQ/Dynamics/DSP), and anything else that is in the signal flow at that time on a different circuit. If that solves it then you know it is a power issue. I guess an easier way would be to unplug unused equipment to see if that makes the hum go away. To do that only have whats necessary to play the DVD/VHS plugged in. See if there is a hum. If there isn't plug things in till it appears. When the device is found that causes hum you know that device needs to go on another circuit. Keep going till you know everything plugged in doesn't cause noise.

    Sorry about the lengthy post.
     
  8. bdesmond

    bdesmond Active Member

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    Heh. Andy and soundman1024 covered this pretty well. Monster cables and the gold plated stuff is all overpriced marketing driven crap...
     
  9. RonaldBeal

    RonaldBeal Active Member

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    2 likely causes:
    RFI Leak from the dimmers and PC
    or
    Grounding problems

    Turn the dimmers off (turn off the breakers, kill the power)
    Is the problem still there?
    Is it present but in a reduced state?
    Turn off the PC
    Still have a problem?
    If you've done this, and still have hum, you are most likely looking at bad grounding.
    Make sure All the components are on the same power supply, and grounded.
    physically isolate the chasis of the components so they are not touching each other (eliminate potential ground loops)

    These are just some starter ideas.
    let us know how it goes
     
  10. blademaster

    blademaster Active Member

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    Occupation:
    Automation Engineer
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    I would love to put all the circuits on the components on the same circuit but unfortunmately the way we have our lights set up is that each set is on its own breaker s o that means that we have like 8 diff breakers for lights. The pc isnt the problem, i know this because at one point it was stolen and we still had the problems. And its not the DVD/VCR because we still had that problem after those got stolen as well. I will try the power lights off idea though and look into the DI as well. Thanks you guys
     

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