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Arrows on cables --- which way to connect??

Discussion in 'Archived Threads 2001-2004' started by Miguel Stanic, Nov 16, 2001.

  1. Miguel Stanic

    Miguel Stanic Stunt Coordinator

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    With regards to audio/video cables, which way do they connect based on the arrows. For example, I have my component video cables and each of the three cables show the arrows. Do the cables connect with the arrows going into the televesions component connections or with the arrows going into the DVD/Receiver component connections. Also, I've got a sub cable and was advised to connect the cable with the arrows going towards the sub.
    Is the general idea that the arrows should be consistent with them pointing in an OUT to IN fashion. If so, how does Component and SUB connections work? Is it OUT from the receiver and IN to the components (sub and tv in this case) whereby the cables should be installed with the arrows pointing to the TV for component and SUB for the sub audio cable. Can anybody please advise?
     
  2. Jeffrey_Jones

    Jeffrey_Jones Second Unit

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    As I understand it, you want the arrow, or writing on a cable, to flow with the direction of the signal. If you have a signal flowing through a cable into your TV, the arrows should point in that same direction. If the signal flows into the receiver, the arrows should point into the receiver.
    Someone correct me if I'm wrong.
    Thanks,
    Jeff
    PS - Some would say that the idea of a directional cable, especially with lower end cables, is ridiculous. I cannot verify the differences, but I figure it can't hurt.
    ------------------
    My Homepage
    [Edited last by Jeffrey_Jones on November 16, 2001 at 09:40 PM]
     
  3. Brian OK

    Brian OK Supporting Actor

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    By the same token, if you have a cable with no little arrows to be found anywhere, then use the company name/logo end (usually on strain relief tubing or heat shrunk tubing jacket) as the SOURCE connection end.
    If you connect the arrows backwards, then you can only reverse them to the correct way (arrows (signal)pointing away from Source component) during the next full moon ;^).
    Just kidding. Just go with the flow if they are backwards. Usually, the "direction" of signal flow is set when the cables are initially used and broken in. If you change direction after this initial use period, you may be subject to a whole new break-in period.
    This is the way Ray Kimber looks at the issue. Many may disagree, but so be it.
    BOK
     
  4. brucek

    brucek Second Unit

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    Miguel,
    Mmm, directional cables.
    The signal that is present on an audio cable is alternating current (AC).
    This means it swings positive and negative. If the signal will only pass in one direction, then unfortunately this AC signal will be rectified. This means only the positive portion will pass to the speaker. You don't want to listen to what that will sound like.
    Directional cables. Sheer nonsense.
    Well, the fact of the matter is, if you disassemble one of these, you'll find that the coax has a twisted pair in its core instead of the usual single conductor surrounded by the shield. The latter being the accepted superior method of transmitting a single ended low level signal across a high impedance connection.
    The circuit on these claimed directional cable is completed by connecting one of the pair to the center pin and the other conductor of the pair to the case of the RCA connector. Now you have your circuit.
    The shield is now connected only on one end to the case of the RCA. The rather weak theory is that any RFI or EMI will be picked up by the shield and passed to ground. You'll find the arrow pointing away from the shield connection point. Again the theory is that the arrows point away from the source.
    Well, as you've likely guessed if you've taken even a first year electronics course, no signal can flow in an open ended disconnected wire....
    But hey, that's the theory the manufacturer wants you to eat up and if you maybe feel you're picking up a little RFI and you have these crazy directional cables, reverse them and maybe you'll have better results.
    Don't hold your breath though.
    brucek
     
  5. RichardJS

    RichardJS Extra

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    I am going to go out on a limb here, because I do not really know, but I was led to believe that the idea of connecting the shielding at one end only was related to minimizing ground loop effects in the shielding. Any comments?
     
  6. brucek

    brucek Second Unit

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    RichardJS,
    A ground loop occurs when you have a small AC potential difference in the grounds (for various reasons) between pieces of equipment in a system.
    This causes a current to flow in the ground connection between these pieces of equipment and this unwanted signal causes an audible hum. This connection is usually a single ended RCA interconnect. This ground loop current will flow in the shield of a normal RCA connector and in the ground wire of the previously mentioned "directional" interconnects.
    The circuit is made in either case and the ground loop remains. If the circuit wasn't made, you would also not pass any of your audio signal. Directional cables are a marketing gimmick.
    brucek
     
  7. Saurav

    Saurav Cinematographer

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    Is it possible that the shield and the neutral signal line are tied to different grounds on any piece of equipment? I see what you're saying, if they're both at the same ground, then a ground loop should exists with or without the shield-connected-at-one-end cable.
     
  8. brucek

    brucek Second Unit

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    Saurav,
    Well no, on one end of the "directional cable" the shield and ground wire of the cable are connected to the metal case of the RCA connector.
    brucek
     
  9. Saurav

    Saurav Cinematographer

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    OK, that makes sense, and RCA connector only has two connection points anyway.
    Thanks.
     
  10. joe goswami

    joe goswami Stunt Coordinator

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    I see that my fellow Canucks are on the right track here:
    Well folks, here comes the eng. tech. in me. IT DOESN'T MATTER WHAT FREAKIN' DIRECTION THE ARROWS GO!!!
    Want proof :
    > first unscrew (if you can) the metal casing of you RCA connector. The centre conductor is conected to the RCA's centre pin and the ground braid is solder to the outer ring that mates with your equipment.
    > if you have access to a low frequency (10KHz - 10MHz) Vector Network Analyzer, run an S21 & S12 (insertion loss) measurement from lets say 18Hz to 100KHz. The signal will exhibit the same characteristics in both directions. Hell, just reverse the cable ends between Port 1 and Port 2 of the VNA and see what happens - ABSOLUTELY NOTHING.
    And if that's not good enough , then listen to the cables in either direction.
    This isn't a flame type of post Miguel, just don't believe many of the audio/video "black magic" that's out there.
     
  11. Miguel Stanic

    Miguel Stanic Stunt Coordinator

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    Thanks for the responses guys.
    If it doesn't matter, all the better. Nonetheless, this is the way that I've connected. I need to make sure before the drywall goes up as it's all in wall wiring we're talking about here.
    The cables are flowing with the arrows pointing in the "from" and "to" direction described below.
    From receiver to SUB (sub cable connection)
    From receiver/dvd to TV (component video cable)
    From receiver/dvd to TV (S-VHS video cable)
    The last cable is my RCA Audio and Video Composite connection. It's three cables stuck all together with the arrows flowing in the same direction for each. If I want to get this right, do I need to strip the video cable from the RCA Audio L/R cables in order to ensure that I connect them as follows:
    From TV Audio Out to receiver TV In (RCA L/R Audio cables)
    From receiver to TV (composite video connection)
    If I don't strip the video cable, then I'll have either the video or audio flowing incorrectly depending on which one I decide to connect properly. Therefore, I would think that I need to strip the video cable in order to get the arrow pointing correctly.
    Please advise if anything is incorrect or if I'm being to anal about all this. I just want to make sure...that's all.
    thanks
     
  12. Tor Arne

    Tor Arne Stunt Coordinator

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    I totally agree with brucek.
    Every time a "directional-cable discussion" comes along I try to convince people that both analogue audio and video signals are AC (alternating current).
    Don't be fooled by marketing and "this guy who owns this cable-manufacturing company says that this is better". That's why it's so good we have these forums to share knowledge to help avoid these traps.
    TAH
    Norway
     
  13. Jeremy Little

    Jeremy Little Supporting Actor

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    This is directed toward Joe and Tor.
    Apparently you aren't reading. Yes, the arrows DO mean something. As was stated ALREADY in this thread, the cable is grounded on one end, not both. This is to help reduce the chance of getting a ground loop hum. The reasons for this also have been stated. It does matter. I had a sub cable hooked from my reciever to the sub (duh, I know) and I was getting the hum. Now when I hooked it up, someone here stated it didn't matter. I ended up hooking the arrow toward my reciever. Well, needless to say switching this around corrected the problem. But then again, it was probably the way I held my mouth. Maybe it was a full moon or something, too!
     
  14. Brian OK

    Brian OK Supporting Actor

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  15. Ken Bohn

    Ken Bohn Auditioning

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    The theory I see it with the arrows is that the shield should only be grounded to the outer sleeve of the RCA at one end and thus eliminate a ground loop. The source of the signal should have the grounded shield and thus the arrow points downstream from the source. This is the theory for high voltage shielded cable installation and should thus apply in audio cables also as it is still just electrical alternating voltage.
    Grounding both ends of the shield creates a ground loop since both pieces of equipment are grounded as they both use power. Picture a system as essentially three sides of a rectangle with the grounded chassis of each component (and the RCA female plug outer sleeve on each component connected to the chassis) forming the sides. The electrical system ground forms the bottom of the rectangle. As it is now there is no complete loop, now if you connect a RCA cable between the components with only one end grounded at one of the component chassis there is still no loop. Ground both ends of the RCA and you have a solid wire connecting the chassis of the two components and you complete the fourth side of the rectangle and thus a loop.
    This is still not a problem unless you have a potential difference at ground between the two components. However if there is one, then current will flow through the shield from one component to the other and returning through the electrical system ground - a loop. This current flow creates a hum. Current can also be induced in the shield from outside interference and internally by the signal passing through the center conductor.
    I checked out the shield grounding on three sets of RCA's I have with an ohm-meter. The cheap set has the shield connected to the RCA at either end but no direction arrow. A CAN$50 Audio-Link cable with arrows also had the shield connected to the RCA's at either end, as did my Monster CAN$110 for 3' cable and arrows to boot.
    Yeah all my cables with arrows seem to be a load of crap if you ask me however the theory is sound - only one end of the shield should be grounded and that end should be at the source component. Thus greatly reducing the chance of ground loops.
    There is more to shielding than this but that is a quick overview as it pertains here.
    Ken
     
  16. Miguel Stanic

    Miguel Stanic Stunt Coordinator

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    Thanks guys,
    So are my cables connected correctly based on my description earlier. I need to know because I'm drywalling any moment.
    Please let me know how the arrows should go for my sub, component, composite and RCA audio that's running in wall.
    thanks!!!
     
  17. brucek

    brucek Second Unit

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    Miguel,
    If you still wish to comply with the rather silly theory that cables are directional, then you will always have the arrows pointing "from" the source component "toward" the receiving component. i.e CD to PreAmp to Amp.
    Ken,
    Of course, if you measure with an ohmeter there will be continuity on the RCA sleeve on both ends of the cable, just as you will have continuity on the center pins at both ends.
    If not, how would you expect to complete a circuit between two components and get current flow. You cannot complete a circuit with a single wire, a return path is required.
    As I said in my earlier post, the coax used in directional cables has a "pair" of core wires surrounded by a shield. One of the wires is the hot and the other is connected to the sleeves. This completes the circuit.
    The shield is then connected at only one end under the guise that this will reduce extraneous pickup.
    Well, we know that to be nonsense, because as you stated before, current will not flow in an open ended wire.
    The reason this is done in high voltage cables if for safety reasons only to ensure one end of the shield is always at ground protection -it doesn't apply to audio interconnects.
    brucek
     
  18. Saurav

    Saurav Cinematographer

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    The only thing this doesn't explain is how people report that a ground loop hum goes away when they reverse a specific interconnect. This has been reported in this thread, and I've read it in other places too. One possible explanation is that they had the cable loosely connected the first time, but that's a little facetious, IMO.
     
  19. brucek

    brucek Second Unit

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    Saurav,
    You may be a little confused. With respect to a DC signal, if I attach a positive signal to one end of a piece of wire and don't connect the other end to a negative return path to complete the circuit, believe me - there will be no current flow in that wire. Certainly, there will be the total positive voltage available at any point on the wire, but your LED will not light.
    With respect to an AC signal in the audio spectrum the above analysis holds completely true.
    If I increase that frequency into the radio frequency range and I happen to cut your wire to a length which is a function of the wavelength of that frequency, I may indeed convert some of that signal to electromagnetic energy that will surround the wire and it will transmit some of the signal into the air from the metals surface.
    Here though, we are discussing audio interconnects. This is a high impedance connection and as such requires that the audio signal be transmitted on a coaxial wire that is shielded from any external interference as we've discussed. The coax cable used in audio interconnects is a perfect cable to do the job. The center wire carries the signal on its core and the grounded shield provides a current carrying return path to complete the circuit and protect the core signal. A perfect situation. Why upset this situation with running two core wires and a disconnected shield. It provides no advantage.
    How come some people hear a difference when they reverse their cables. Well, some people hear a difference in their systems when they place little wooden beaks around their rooms and others believe cables need to be broken in.
    Good for them..
    brucek
     
  20. Saurav

    Saurav Cinematographer

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