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S-video & Stereo audio over CAT5?

Discussion in 'Electronic Design' started by Racer X, Dec 17, 2003.

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  1. Racer X

    Racer X Guest

    Hi All,

    I'm looking to make a pair of adapters so I can transmit s-video and stereo
    audio over CAT5, and I'm wondering if anyone has any circuit diagrams, or
    links to similar projects

  2. Mac

    Mac Guest

    Sounds challenging. CAT 5 cable has 4 pairs. I believe s-video has three
    signals, and stereo audio has 2. So the obvious solution of using 1 pair
    per signal won't work.

    Would you consider sending audio over its own cable?

    If so, you could probably send the S-video over three pairs in one cable,
    and up to 4 channels of audio on the other cable.

    Next is the impedance mismatch problem. Cat 5 cable has a differential
    impedance of about 100 Ohms. Video wants to see 75 Ohms. You can
    use either a transformer (assuming the DC component of the video singal
    doesn't matter.. I'm not sure about this) , or a video op-amp buffer to
    match the impedance for the video signal. At the receiving end, you
    probably need to convert back to 75 Ohms, which means another buffer or
    transformer. Or maybe you can just put a 25 Ohm resistor in series with
    the 75 Ohm load.

    For the audio, you might get away with just sending it over the cable
    without any matching. Or you could use a high current buffer at the
    sending end and terminate at the receiving end with 100 Ohms.

    You may get some crosstalk on the audio channels.

    Good luck.

  3. Kim

    Kim Guest
  4. "S-Video" is two signals. Luminance(+sync) and Chroma. You would need a
    pair of video to CAT5 converters at each end of the cable. There are ICs
    made to convert video to balanced, and back. Its easy to convert the
    audio with a couple op amps per channel, per end.
    8 days!

    Michael A. Terrell
    Central Florida
  5. Mac

    Mac Guest

    As it turns out, I was wrong about this. S-video only has two distinct
    signals, so you could get S-video and audio on a single run of Cat 5
    cable. Follow Kim's link elsewhere in this thread for a canned solution.
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