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Thread: 75ohm cable for digital out? Optical vs Coax

  1. #1
    FLAC
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    75ohm cable for digital out? Optical vs Coax

    I was sitting with a trusted techie shootin the poop and we discussed optical vs coax digital transmission. He brought up a couple points that I would like to discuss - get some feedback. Let me toss a disclaimer out... I do not know if the following comments are factual, yet they make sense.

    Optical vs Coax

    -Point made: Coax is a better medium for transmission as the optical has a delay. He pointed out that the switching required for light on/off tends to be slow and often times comes at the expense of a delay, especially in normal conumer grade gear.

    Coax Cabling

    -Point made: Requires a 75 ohm video cable compared to normal interconnects. Non 75 ohm cables can cause significant signal degredation where the square waves begin to curve and lose definition.



    Conceptualy these points make sense but I would like to hear from the masses if they agree/disagree. I can tell you that i have always ran coax but I have used non 75 ohm cables. I swapped it out for a 75 ohm cable and i do not hear a bit of difference. Maybe my original cable was good enough quality? Maybe it was a 75ohm cable and i didnt realize it.

    Your thoughts?

  2. #2
    FLAC
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    Last time I checked, electricity and light were the same speed in a vacuum. The DAC sitting behind the input is where the delay would come, not the cable itself. Also, optical signals are totally immune to RF and EM radiation.

  3. #3
    FLAC
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    But to produce that optical signal requires the extremely fast pulsing of the light (optical source). That pulse is an off/on to some bulb. His comment was that the switching on/off is not as fast as the digital data transmission rate of the same on/off (in that case 0 and 1) in the coax. This is not the limitation of the fiber cable but the low quality components in the fiber output. If this is in fact true, what happens if the the light cant turn on/off fast enough? would it queue or skip over that portion all together?

    I'm theorizing of course

  4. #4
    Maximum Bitrate v8 scimitar's Avatar
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    your right if it was actually a bulb but it isnt there isnt a delay like a bulb would have as in switch on build to brightness switch off. This would actually be an analogue signal because of the considerable (in data transmission terms) time. If you look at the end of a fed optical line all you will see is light as the human eye cant detect the frequency. So as regarding a delay, there is no more delay in conversion than there is in a coax link and an optical can handle a masive amount more bandwidth than a coax can, which admitedly isnt important when it comes to hooking amps and stuff together.
    over a short distance ( a few meters) you would never pick up the difference between the two so long as the RF in the area is resonably clean. Start to increase that distance to the 10's of meters and you will start to hear the optical being clearer, manly because the coax is starting to pick up some trace RF noise. Then you get into the big distances where optical wins hands down but thats irelevant to what your doing and more data transmisions, although your digital sound at the end of the day is still data.

  5. #5
    FLAC
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    Right, there's a solid state light, LED, that pulses way faster than the human eye can conceive.

  6. #6
    Maximum Bitrate v8 scimitar's Avatar
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    or laser in the big boys toys

  7. #7
    Low Bitrate
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    Yeah, a lot of the time they use a laser diode because its solid state and fast.
    Hey Laserlips, your momma was a snowblower!!

  8. #8
    FLAC
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    Quote Originally Posted by adaminc
    Yeah, a lot of the time they use a laser diode because its solid state and fast.
    LED = Light Emitting Diode = solid state

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