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  1. #1

    audio with strange problem

    hello to everyone,
    Am a having a strange problem coming from our church audio system. I record video in our media room, so i recieve audio signal from audio room. the moment i plug in the audio line to the video recorder, lines will appear on my video monitor. I ve changed the cables twice, yet the problem is still there. can someone tell me what is wrong? my video signal is perfect with audio line connected that mean nothing wrong with video connection. the problem only come when audio line is connected. Surprisingly, this problems sovled it self during most night Virgil and surface during day recording

    Please help me now. I need solution before SUNDAY recording!!

  2. #2
    New Member
    Join Date
    Aug 2009
    Location
    Torrance, CA
    Posts
    1
    Sounds to me like you have a ground problem. Try using battery power for the camera instead if AC power.

  3. #3
    Do the bands move or change? That could indicate interference from an AM radio station. Many AM stations reduce power or change antenna patterns at night.

    If going to battery operation fixes the problem, but you don't want to run on batteries all the time, you will need to get an audio isolation box to go in the audio line. This couples the signal but isolates the ground into two separate circuits.

  4. #4
    I like the AM radio interference theory. An isolation transformer in the audio feed to you may solve it. That may also eliminate grounding problems. It sounds like your audio feed is susceptable to AM interference either way.

    If you could briefly detail the audio chain, maybe it could be pinpointed.

    Things to look for: Long cables (a biggie cause);balanced and unbalanced equipment and devices strung together without devices to match them; improper shielding and soldering of "home-made" cables and jacks; just plain bad connections.

    Blessings.
    'I think my intimate relationship with electronics started as a child when I was playing with a screwdriver and a wall plug, Doc, and...'

  5. #5

    How do I do it

    From replies, I now believe the problem is coming from AM interference because, there is a radio station close to my office (AM/FM) station. My question now is, how do I overcome this interference from the AM radio station. Please explain it in a layman term because am not an expert audio engineer. am only a video director. Thank you for replying and may God bless you all for your assistance
    ausmatte.

  6. #6
    If it's the AM station, I would guess that the interference isn't perfectly stationary - it changes with as the signal is modulated. Can you see the bands in real time, or only when you play back the recording? If you can see the bands in real time, take an AM radio and tune it to the station. Watch the bands as you are listening to the radio, and if they move in synchronization with the sound, that will prove it's the AM station that's causing interference.

    What's happening is that the signal is getting inside the camera, and then it's being "detected" by the internal circuitry. Radio interference is a lot like lightning: unpredictable, hard to trace.

    Isolation transformers are designed to cure power-line related hum, not radio interference. I would try one anyway, because the next step is tricky: you may need to install bypass capacitors inside the camera. That's best done by a trained tech.

  7. #7
    What kind of cable are you using to get your audio signal? It sounds to me like the lines are not sheilded properly, or ther eis just some 'noise' coming in. If you are already using an XLR cable (which you should be for balanced, RF-rejected signal), get a 1:1 isolation transformer. It won't hurt your audio signal, but it will knock unwanted 'noise' out.

    http://www.fullcompass.com/product/290139.html
    http://www.fullcompass.com/product/231502.html

    Going from a sound system to a press feed/breakout area, it is common to need at least one of these to tame noise. Our adapter kits in the audio shop always had a half-dozen or so.

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