Audio composite cable Vs. component cable

Discussion in 'Beginners, General Questions' started by Mike Rowles, Dec 10, 2003.

  1. Mike Rowles

    Mike Rowles Auditioning

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    I finally finished installing my projector. The salesman sold me composite cable (yellow, white & red terminals) for the video singal from amp to pj.
    Is this the same as video component cable (r,g & b terminals). Im happy with the picture quality but will it get better or is safer with component?

    Thanks for any advice.
     
  2. Rick_Brown

    Rick_Brown Second Unit

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    Component is way better quality than composite. Stick with it!
     
  3. JamesCB

    JamesCB Second Unit

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    A little confusion here?

    The yellow, red and white terminals are:
    Yellow = composite video
    Red = right audio channel
    White = left audio channel

    While the component video is the red, blue, and green cables carrying video only. These are the video connections you need to use.
     
  4. Michael Reuben

    Michael Reuben Studio Mogul

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  5. Bob McElfresh

    Bob McElfresh Producer

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    Hi Mike. Welcome to HTF! [​IMG]

    As James pointed out, Red & White cables are for audio and audio cables can be made with any of the popular impedences of coax: 50, 75, 110, 300.

    Note: all video cables are made with 75 ohm coax. (Component cables are just 3 composite cables in a bundle).

    But - cable makers often use identical 75 ohm cables for the L/R/Video bundles. This is why they are sometimes used as inexpensive component cables. The problem is - you cannot tell by looking at the cables if they are all 3 video cables or not.

    If your dealer sold the L/R/Video bundle he either:

    - Knows that all 3 cables are 75 ohms
    - Does not know what he is doing.

    Do you have a store that sells component video cables with a 30 day return policy? If so, buy a set of component cables and try them in place of the ones the dealer sold you. If you see a difference, take the originals back and ask for real component cables.

    Use some bright movie with constrasting colors like Austin Powers/ Finding Nemo and freeze a frame. Then try the 2 different cables. Pay attention to long, straight lines of contrasting colors to see a difference.

    Hope this helps.
     
  6. Ted Lee

    Ted Lee Lead Actor

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  7. Rogozhin

    Rogozhin Stunt Coordinator

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    I'd have to go the-"he does not know what he is doing" route.

    I'd never sell composite over component especially if it's for any kind of hi res applications.

    rogo
     
  8. Mike Rowles

    Mike Rowles Auditioning

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    Thanks Bob Elfresh, my question was obviously worded too vague, but you hit the nail on the head. Thanks for making it all clear.
    The salesman had a projector himself so im hoping he "- Does not know what he is doing". Hoping!
    The only problem i have is that now the pj is all installed, to run another cable in parralell for the tests would mean i'd have to drill many holes throughout the house again. As the cables are 20m long wife would not be happy.
    If each cable is 75 ohms... what if i unattatched the cables at both ends, (amp & pj) got a female-female connector, and joined two together at one end and at the other end with a multimeter checked for 150 ohms between the two. Or is there another way to check the leads are video coax?
    Sorry, i hope this makes sense.
    Thanks again for any help guys.
     
  9. Allan Jayne

    Allan Jayne Cinematographer

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    Measuring impedance requires equipment much more sophisticated than a multimeter. I believe that impedance is the resistance to a 1000 Hz alternating current, while a multimeter uses direct current to perform its measurement.

    You will get a picture by using the red/white/yellow cable set. It is just that the quality of the cable is unknown so the picture quality cannot be predicted.

    A composite cable can work just right for component video. Another important criterion is bandwidth, in megahertz. Just because a cable is 75 ohms does not mean it has enough bandwidth.

    Video hints:
    http://members.aol.com/ajaynejr/video.htm

    Regular DVD video (interlaced) needs 7 MHz bandwidth, composite or S-video or component.

    Progressive scan needs twice that, or 14 MHz.

    HDTV needs 37 MHz although you can get away with 25 MHz for 1080i since no HDTV set will reveal the difference.

    But for each cable or other piece of equipment I suggest aiming for at least twice the above bandwidth figure since when connecting up several pieces, the net bandwidth will be lower. How much lower cannot easily be predicted so experts just state a safety margin like two times.
     
  10. Bob McElfresh

    Bob McElfresh Producer

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    So the cable is already run?

    Let's work this out:

    Problem: 3 conductor cable could be 3 video cables, or a L/R/Video cable with the L/R cables not being 75 ohms. How do we tell?

    Do this: get a good test-pattern up with lots of straight lines & contrasting colors.

    Make a little chart that says what cable is going to what connection on both sides so we can restore the original setup.

    Now - change what connection is made by the YELLOW wire to some other set of output-input connections. Remember you have to do this at BOTH ends.

    You should now have 1 disconnected set of connections and 1 disconnected wire - hook these up.

    Now look at the test-pattern. Did it change in any noticible way? If not, then all 3 cables are identical => all are video cables.

    Theory: if the yellow cable is DIFFERENT from the R/W cables, shifting this cable to a different set of inputs should change the picture. If it does not this means all 3 cables have the same impedence.
     
  11. ChrisWiggles

    ChrisWiggles Producer

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    Back to the original post. You mention RGB?

    I'm confused if your projector even takes component. MAny do not, and only take RGB. In which case you'll need a transcoder.
     
  12. Mike Rowles

    Mike Rowles Auditioning

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    Thanks Allan Jayne your website is awesome!

    Cheers Bob I did tests on many 'test pattern type' screens and all looks good. Woohoo!

    But now for the bandwidth dilema : Do I

    A) just rip this cable out and throw it back at the salesman, go to another store and buy a good expensive one or
    B) now that i know it IS a component cable and im happy with the picture quality - assume the bandwitdth is ok and everytime i watch it wonder if the quality could be just a little better with a new cable.

    Ok i think i just answered my own question.

    in reply to chriswiggles i only mentioned r,g,b as an abbreviation for the colour of component cable terminals.
     
  13. ChrisWiggles

    ChrisWiggles Producer

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    OK, but just so you know, RGB is it's own video transmission method, which is different than component video. That's the only thing that threw me originally.
     
  14. Chu Gai

    Chu Gai Lead Actor

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    Ummm...no. What you do is make a stab at determining what the bandwidth of your cable is and compare it to the bandwidth that you need times 3. If your bandwidth exceeds your needs, then you're in 'the zone'. Your dealer should have this information. If not, he may have the diameter or effective diameter of the center conductor. Get back with that and let's take a look.
     
  15. ChrisWiggles

    ChrisWiggles Producer

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    Whoa, how did we get talking about cable bandwidth?

    This is beyond the original question which was just whether the cables were 75ohm. We don't know that they are.

    Bob's suggestion is a good one.

    The only thing we are trying to figure out is whether all three cables in the bundle are the same (and 75ohm). They may well be, they may not. The bandwidth is a TOTALLY separate issue...If you've got a 50ohm audio cable with OODLES of bandwidth, it really doesn't mean sqaut, you'd not want to use it for video.
     
  16. Chu Gai

    Chu Gai Lead Actor

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    At a 40 or so foot length, if they weren't 75 ohm cables, he'd have video issues. IOW, try estimating the length of the signal from the frequency that you're using and then compare that value to the length of cable being used.
     
  17. Allan Jayne

    Allan Jayne Cinematographer

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    Try each of the cables one at a time, connect the Y jack of the DVD player to the Y jack of the TV and leave the Pb and Pr jacks empty.

    Set the DVD player to progressive scan.

    Play the 200 TVL resolution test pattern on AVIA.

    If you see the full horizontal resolution (upright resolution wedges clear down to the narrow end) the bandwidth of the cable should be adequate. If you don't see ghosting and you see full horizontal resolution the impedance should be correct (75 ohms). (It is possible the cable is good even if you do see a slight amount of ghosting or resolution loss since the root of these problems could be elsewhere. It just takes some skill and perhaps other cables to compare with to make a final judgment.)
     
  18. Mike Rowles

    Mike Rowles Auditioning

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    Thank Allan Jayne thats a cool test. Unfortunatly i havent got a progressive dvd player, theyve only just become part of the market here in Oz.
     

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