Ultralink "flow arrows" on sub cable mean what?

Discussion in 'Accessories, Cables, and Remotes' started by John Walker, Jun 2, 2003.

  1. John Walker

    John Walker Agent

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    My sub came with this cable and the dealer pointed out the arrows on the cable suggesting it was directional. So what? Are these arrows supposed to "point" toward the sub, the receiver, or north? There isn't anything in the package literature to suggest they mean anything.

    Baffled (not infinite)

    John
     
  2. Matt_Doug

    Matt_Doug Stunt Coordinator

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    The arrows point in the direction of the signal flow i.e. toward your subwoofer. Directional cables have a shield made of foil or braided metal, each or both sometimes with a bare metal wire that is bonded to the drain wire or connector barrel at one end of the cable only. That end has to be at the source of the signal else the shield will be defeated, hence the arrows. Some cable manufactures also say the arangement of the molecules of the metal conduit make it directional. I'm not sure how valid that claim is.
     
  3. Bob McElfresh

    Bob McElfresh Producer

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    The other very valid issue is having the shield NOT connected at the destination end removes ground-loop hum.
     
  4. John Walker

    John Walker Agent

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    Yes I understand ground loop issues. I thought if there was something to the arrows it would have been documented in the packaging - oh well.

    The thing I don't understand is how many conductors are in the coax? I thought coax was one center conductor and one or more layers of shielding. If there are multiple layers of shielding are they not electrically connected (i.e. touching)? If so, and the shield is only connected at one end, how does the cable work? There would appear to be only one conductor connected to both RCA plugs. How do the electrons flowing along the line-level cable center conductor complete their path back to the amp? (Surely not through the 110ac neutral!)

    Confused.

    John
     
  5. Kevin C Brown

    Kevin C Brown Producer

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  6. Bob McElfresh

    Bob McElfresh Producer

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  7. Steve Carlo

    Steve Carlo Stunt Coordinator

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    Basic physics says that an electric field is established by flowing any current through a wire. It also says that if you have a shielded wire arrangement that no external fields will be able to get into the signal carrier to disrupt its signal.

    Not connecting the external shield to the ground will by definition make an antenna, just watch your signal go crazy then.

    As for directionality of molecules??? Never heard such a COS in all my life, molecules have directionality, but metals are not molecules in the same way that a polymer is for example. No directionality, a metal will conduct in either direction equally. They are a dispersal of nuclei in a sea of electrons. But having said that I do not know the make up of the more "advanced" shielding methods and they could well impose some directionality.

    *walks away pondering how this might be the case*
     
  8. Matt_Doug

    Matt_Doug Stunt Coordinator

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    John. basic coax design is a center conductor and a shield/ground bonded to the rca connector barrel at both ends. Directional cables add a second conductor for ground duty and lift, float, or disconnect the shield from the connector barrel at one end. The arrows point in the direction of the lifted end which should only be connected to the inputs of your a/v gear. This arrangement prevents any emi/rfi noise picked up along the length of the cable from reaching the inputs of your sensitive audio/video equipment. To add; cable makers do crazy stuff (and charge crazy money) for extra ground condcutors, extra shielding, exotic dielectrics(insulation) and weird geometries like twisted pair and litz...etc but only for audio cable cause video cable requires a constant 75ohm impedance which is only possible with your basic center conductor and shield/ground. ironic isn't it.
     

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