1. #1
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    Default Have to lay some mic cables across/over a power cable

    I have to lay some mic cables across a power cable in my studio at least for quite a while. Can I wrap the power cable in something to prevent it from interfering with my mic cables? Like foil tape or something? What will stop the interference from getting out? plz dont laugh at my "dumb" question
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    Default Re: Have to lay some mic cables across/over a power cable

    Cross the cables at 90 degrees and you should be OK.
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    Default Re: Have to lay some mic cables across/over a power cable

    someone is going to shout at me for this but you will probably even be fine running them parallel. i do it all the time at work for when we run power, audio and vision to/from a lectern.

    keep in mind your XLR cable is (hopefully) balanced and shielded...
    Last edited by Brendo; February 9th, 2012 at 02:06 PM.
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    Default Re: Have to lay some mic cables across/over a power cable

    It will obviously depend on the quality of the cables, and of course the signal is balanced, right?

    If it is not balanced, do not even think about it...

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    Default Re: Have to lay some mic cables across/over a power cable

    As Brendo already said...

    There are already a couple of fundamental concepts at work there in the mic cables.

    One is the shield wrapped around the thing, connected to ground.

    The other is that the whole basic idea of balanced lines is that if any kind of electromagnetic field induces currents in the conductors, they cancel out at the destination. That's really the whole point of balanced connections.


    If everything is working as it should, this should not be a problem. The two basic concepts there exist because the real world can be a bit messy and complicated, and electromagnetic debris can be flying around, so clever humans cooked up these ideas to deal with this by taking any kind of induced currents and effectively neutralizing them. A whole bunch of audio activities could be really messy business otherwise.


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    Default Re: Have to lay some mic cables across/over a power cable

    If the signal running down those cables is UNBALANCED, you may have an issue. If it's not, you should be fine.

    Also it usually takes a fair amount of current to induce some serious hum into a cable, so if the only thing hanging off that power cable is a tuner, you definitely don't have much to worry about. If it's the main 3phase feeder for the whole building, I'd be a little more worried.


    Someone I know once told me that wrapping a mains cable in any sort of shield may be a bad idea (something about capacitance?), but I have no idea how much truth is in that.

    And yeah, if you can keep them running at 90 degrees to each other, that will help, but it sounds like you're running them next to each other.

    Good quality mic cable helps, too.
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    Default Re: Have to lay some mic cables across/over a power cable

    If you have to run the mic cables parallel to the AC power cables for any distance you could run the mic cables in a soft steel pipe. No the pipe does not need to be grounded for this to work.
    Or you could run the AC power cables in the pipe, but then the NEC rules get a little tricky.
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    Default Re: Have to lay some mic cables across/over a power cable

    ahh, I will try putting a meter long pipe around the AC cable, where the cables cross. I do notice some noise with balanced cables, and less with quad cables, if the power cable has a lot of current going through it. I just want to be extra careful and not have to worry about interference.

    So I didn't hear anything about the foil tape, will that work? It will be less bulky than the pipe idea, if it will work. I am in my parents basement so I have cables running all over the place, I cannot really get proper cabling routing installed in the walls or anything. Would I have to ground the foil?
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    Default Re: Have to lay some mic cables across/over a power cable

    It really needs to be soft steel, that a magnet will stick to. Foil be it aluminum or copper works best at radio frequencies.

    Anything involving the AC power line has to follow the regs.
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    Default Re: Have to lay some mic cables across/over a power cable

    It really needs to be soft steel, that a magnet will stick to. Foil be it aluminum or copper works best at radio frequencies.

    Anything involving the AC power line has to follow the regs.


    The best thing to use would be something called mu metal. It is a electromagnetic shield material that is used to block magnetic field interference. Get a small sheet or foil tape of it and turn it around the power cable at the intersection point. You will need at least 4 to 6 layers of foil for it to be effective.
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    Default Re: Have to lay some mic cables across/over a power cable

    The price of "mu metal" has gone thru the roof! When doing something like a mic pre-amp circuit, it's a great solution. For power line problems it's over-kill. A piece of plumbing pipe or a fence post should work fine.
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    Default Re: Have to lay some mic cables across/over a power cable

    The price of "mu metal" has gone thru the roof! When doing something like a mic pre-amp circuit, it's a great solution. For power line problems it's over-kill. A piece of plumbing pipe or a fence post should work fine.
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