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  1. #1

    Long XLR Cable Problems

    Hello again. Thank you all in advance for your help.

    I will be running 2 XLR hard-wired Countryman mics on 25' cables. I am using the phantom power from the camera (Canon XH A1), and I am concerned about any signal loss. I ordered the equipment today, but I am trying to find out if anyone has had any problems.

    Question 1: Will I have poor sound because of the distance?

    Question 2: Will my audio be delayed from the video because of the distance?

    Mitch

  2. #2
    Senior Member SC358's Avatar
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    Question 1: Will I have poor sound because of the distance?

    Question 2: Will my audio be delayed from the video because of the distance?
    No to both questions.
    SC358
    Relationships are based on compromises - behavior accepted is behavior repeated.

  3. #3
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    Quote: mitch
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    Question 2: Will my audio be delayed from the video because of the distance?
    Electrical impulses travel faster through copper than sound travels through air (actually, they travel faster than light travels through air). I doubt this will be a source of trouble.
    Eric Adler (tonsofpcs)
    http://www.videoproductionsupport.com/ Chat at: http://tinyurl.com/vpschat
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  4. #4
    Thank you both for the reassurance. This forum is great!

    Mitch

  5. #5
    Frame of reference: a 150-ohm mic will, in theory, start to lose high frequencies when the cable exceeds 1,000 feet. For a 600-ohm mic it's 250 feet. This is for permanently-installed foil-shielded Belden cable; rubber-jacketed mic cable is actually a little better.

    I say "in theory" because we're talking about a 1-2dB loss at 20kHz. I dare you to hear that, even in a direct A/B test.

    The electrical time delay of a 1,000ft cable is on the order of a microsecond. The smallest time delay a person can detect is on the order of 10 milliseconds, and then only under special conditions. So a 1,000-foot cable produces a delay that's 10,000 times smaller than a person can detect.

    If you're worrying about stuff like this, I think I should warn you: the next thing that's going to happen is somebody's going to try to sell you special audiophile cable that costs fifty times the normal going rate. Do not fall for this scam.

  6. #6
    Yeah, what they said.. for years folks ( some, not all, and I cannot prove this) said that copper mic cables longer than 100 feet drastically reduce the signal... blah blah blah... that's why your mixer has gain knobs, and the company I work for has several 300 foot snakes and no problems, ... so the short answer is no, it should come through just fine for you!

  7. #7
    More numbers, not because you need them, but because when people try to snow you it's nice to be able to snow them right back.

    A microhpone should never be terminated into its own impedance; the actual load impedance should be at least 10 times higher. Thus a 150-ohm mic should not be loaded lower than 1,500 ohms. Let's assume the Canon is designed that way.

    So let's look at this as a voltage divider: the series resistance of 1,000ft of 24-ga. wire is about 27 ohms. Double that (cuz there are two wires in the circuit) and you get 54 ohms for the series resistance. The shunt resistance is 1500 ohms or higher. That works out to a loss of 3.6%, or about 1/3 dB loss, and mind you this is in a 1,000ft cable. The smallest loss an average person can hear in a direct A/B test is about 3dB; a trained ear can hear 1dB and then only with a continuous tone. In a 25-foot cable the loss should be around 1/120th dB. This is equivalent to the voltage drop you get when you plug a night light into a 20-amp AC circuit.

    Too bad so few people go to the trouble of working these things out. A lot of companies make big dollars selling snake oil because of this.

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