Why Should I not do This..Use Video switching for SPDIF

Discussion in 'Archived Threads 2001-2004' started by Richard_s, Feb 2, 2003.

  1. Richard_s

    Richard_s Second Unit

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    This probably applies to all receivers mine is the Yamaha HTR-5550.

    Ok this is an ODD question for sure.

    I have three SPDIF co-ax I want to hook up to my receiver (but it only has 1 CO-ax input). Now I looked and I can get a manual three input 1 output switch. What I wanted was somehthing automatic.

    Since each avdio input has an associated Video input I tried plugging the SPDIF into the Video-in and the Monitor output I looped back to the CO-ax SPDIF input.

    Given the specifications of the Video in/out I did not expect this to work.

    I tested the system with AVIA and hooked up this way the 5.1 works fine and there was no setting differences from when the SPDIF was hooked up without using the Video switch. Volume level is identical and sounds exactly the same.

    OK I know there is something bad about doing this like maybe I will burn something out or the sound must be distorted I just am not listening critically enough.

    If this is OK to do it is an ideal solution as it will switch the respective CO-ax using the receivers remote. DVD switches to DVD SPDIF and v_aux switches to my DIVX players SPDIF output for example.

    Would really like some advice on this as I really do not want to ruin my Receiver if that is a risk.

    Thanks ALL
     
  2. Luke_Y

    Luke_Y Second Unit

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    Richard, it should be just fine. An often overlooked solution. As a matter of fact, one of the home theater mags was recommending this to a letter writer a while back and I couldn't quite get my mind around it at the time. :b To satisfy my curiosity I looked into it some more and have read that it is a perfectly acceptable solution that most don't even think of.
     
  3. Jeff Kohn

    Jeff Kohn Supporting Actor

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    That's actually a really good idea, I'll have to keep it in mind if I need additional coax inputs in the future.
     
  4. Richard_s

    Richard_s Second Unit

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    Thanks

    My reason for concern even though it does work is that if I use an ohmeter it does not short the input to the output so its not a direct bypass. It must have some circuit between the input and the output.

    I just figured that a video signal for composite was higher than that of an SPDIF signal. Is this correct I could not find the specifications nor do I really understand the video spec which is 1 volt peak to peak 75 ohms.

    Just want to be sure its safe.

    Thanks again
     
  5. Bob McElfresh

    Bob McElfresh Producer

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    Richard: listen to the sound for 15 minutes. If you dont experience any drop-outs, you are home free.

    Video cables/connections need to be made with 75 ohm coax and plugs.

    SPDIF cables need to be made with ... 75 ohm coax and plugs

    (They had a common-as-dirt Video cable in mind when they came up with the SPDIF specification.)

    So it should work fine.

    Look at the Inexpensive HD Switching thread. They have switches that respond to remote-control signals so when you press "DVD" on your receiver remote, the switches also flip.

    These switches also have a neat feature with respect to digital-audio:

    Each input have coaxial & optical inputs.

    The output has both coaxial & optical outputs.

    All the inputs are converted to both optical and coaxial output. This would allow you to feed your receiver with coaxial, but have 4 optical sources. Cool huh?
     
  6. Richard_s

    Richard_s Second Unit

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    Thanks very nice devices. At least I have an alternative.

    I will try the video-in method for a while it at least sounds like its safe to try.

    I will try some music with wide dynamic range and see if I get any clipping or dropouts did not think of that but the few minute test I did souded great.

    My receiver has 3 optical inputs so I am set there when I get some optical digital devices. My older DVD player and my Divx box that I am putting together both have co-ax unfortunately (bad planning I guess). I am also finally getting a cable box from ATT that also has the SPDIF co-ax output (took me a year to get that item). So now I have three Co-ax and one input.

    Looks like either using the video switched in the reciever or one of the devices from your thread will do the job so I should be all set.

    Appreciate the help
     
  7. AaronBatiuk

    AaronBatiuk Second Unit

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  8. Richard_s

    Richard_s Second Unit

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    Thanks All

    I knew I came to the right place after all everyone here helped me put together my system in the first place and I have been extremely pleased with it.

    Thanks for the specification help that teaches me alot. I understand the capacitive coupling makes absolute sence now I am comfortable with setting things up this way.

    [​IMG]
     

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