AR directional cables -- where's the arrow supposed to point?

Discussion in 'Archived Threads 2001-2004' started by MarcVH, Jan 14, 2003.

  1. MarcVH

    MarcVH Second Unit

    Joined:
    Dec 26, 2001
    Messages:
    324
    Likes Received:
    0
    Just bought a set of Acoustic Research Pro II RCA interconnects to hook up a new external amp to my receiver. I'm normally not into cables but I figure this is a place where it makes sense to spend a bit more than Radio Shack grade.

    Anyway, the cables are directional. There's an arrow on the cable labeled "SIGNAL PATH", so I assumed that meant the arrow would point in the direction of the signal, in this case from the receiver's pre-out to the amplifier's input.

    However, the hook-up guide included says to "position arrows so that signal path points toward input." This seems to suggest that it goes the other way, I guess? I find this phrasing counter-intuitive.

    Looking at the connectors themselves, it appears that the shielding is soldered to the sleeve on the "from" connector (that the arrow points away from) but it is not connected to anything on the "to" connector (that the arrow points toward.) In directional cables, which side is supposed to have the shielding connected?

    I suppose I should just go with what the instructions say, but I find it a tad confusing. Can anyone confirm I'm getting this right? Thanks!
     
  2. Mike Matheson

    Mike Matheson Second Unit

    Joined:
    Jul 15, 2000
    Messages:
    416
    Likes Received:
    0
    Those arrows are there for the benefit of the little electrons. They help them figure out which way to go when they get confused. Sort of one-way street signs.

    BTW, you're right--the end with the shielding grounded (your "from" end) should be connected to the signal's source component. Maybe that manual was translated from another language? Like electrical engineering or something? My guess is that the "input" they refer to is not relative to the cable itself (i.e., which component is feeding an input to the cable), but rather in terms of which component is receiving an input (via the cable). Geek-speak I guess.
     
  3. Chu Gai

    Chu Gai Lead Actor

    Joined:
    Jun 29, 2001
    Messages:
    7,270
    Likes Received:
    1
    If a cable has a shield, there’s three ways it can be implemented on the cable itself.
    1. it can be grounded at one end
    2. it can be grounded at both ends
    3. its not grounded at either end so it’s ‘floating’

    If your cable is either 2 or 3 its irrelevant as to how it goes on due to the fact it’s symmetrical. Of course if the manufacturer of the cable in those cases is saying something like the wire itself has a preferred electron flow they’ll put an arrow on the wire somewhere. In those cases, return the wire if possible, as this is a clear indication that you’ve paid too much for the wire, seeing that such a statement is pure BS.

    If it’s #1 then generally there will be either an arrow or a marking on the cable. The general convention is that the arrow points in the direction of signal flow which implies that the shield is grounded at the source. In other words, if you’ve got a cable going from your preamp to your amp, the preamp connection will have the grounded shield and the arrow will be pointing towards the amp.

    Mike is right though about electrons being stupid though. At one time people thought electrons were massless, now we know they're clueless and respond well to cable cookers. kind of like boot-camp for electrons.
     
  4. brucek

    brucek Second Unit

    Joined:
    Dec 29, 1998
    Messages:
    335
    Likes Received:
    0
    Marc,
    If you disassemble one of these directional cables, 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 conventional method of transmitting a single ended low level signal across a high impedance connection.
    The circuit on the directional cable is completed by connecting one of the "pair" to the center pins and the other conductor of the "pair" to the cases of the RCA connector (ground). Now you have your completed circuit.
    The shield is connected only on one end, to the case (ground) of the RCA. The rather weak theory is that any RFI or EMI will be picked up by the shield and passed to ground (Mmmm, current flow in an open ended piece of wire - interesting). Anyway, 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, you know the theory is flawed. Because, even if you did buy into that theory, and you believed that the shield will transfer the noise it picks up to the end of the cable where the shield is connected to the grounded end, then what would stop this noise from traveling in the ground conductor inside the cable over to the equipment it's connected to? [​IMG]
    brucek
     
  5. Bob McElfresh

    Bob McElfresh Producer

    Joined:
    May 22, 1999
    Messages:
    5,182
    Likes Received:
    0
     
  6. Chu Gai

    Chu Gai Lead Actor

    Joined:
    Jun 29, 2001
    Messages:
    7,270
    Likes Received:
    1
    i'm sorry, they're not stupid, just intellectually challenged [​IMG]
     
  7. MarcVH

    MarcVH Second Unit

    Joined:
    Dec 26, 2001
    Messages:
    324
    Likes Received:
    0
    Thanks for the info. I suspect you're right, that when they say "points toward the input" they don't mean the input to the cable, but rather the jack labeled "input" (which in my case is on the amplifier.) I still say the phrasing they use is confusing though.

    I share some of the skepticism about whether it really matters, but I figure I should at least try to get it right in case it does. I didn't buy the cables because of the directionality, but because I'd gotten the impression they were among the better interconnects in their price range. Is there any consensus on better RCA interconnect cables for under, say, $25?

    I'm familiar with ground loops and will keep an eye out for them, and in this case I am indeed connecting between two amps so the concern seems well-placed. I've already had to filter out a ground loop from the cable TV line, and my wife won't abide by hearing any more humming and whumping.

    Anyway, thanks for the help.
     
  8. Chu Gai

    Chu Gai Lead Actor

    Joined:
    Jun 29, 2001
    Messages:
    7,270
    Likes Received:
    1
    well at least you can try them both ways, right?
     
  9. brucek

    brucek Second Unit

    Joined:
    Dec 29, 1998
    Messages:
    335
    Likes Received:
    0
     
  10. Bob McElfresh

    Bob McElfresh Producer

    Joined:
    May 22, 1999
    Messages:
    5,182
    Likes Received:
    0
    Bruce - I think we are in agreement, but have experienced different cables.

    You talk about a twisted-pair wire encased in a shield. I think this is an audiophile "Twisted Pair" cable with a shield. I've never taken one of these apart.

    I have taken an ohm meter to a COAXIAL directional audio cable intended for subwoofers. I believe the AR Cables that Marc is talking about are coaxial constructed.

    These directional-coaxial cables do not connect the outer part of the RCA plugs at the 'destination end' to the shield. And it does solve the ground loop problem as we have recommended them to many members with the dreaded "subwoofer hum" problem over in the Speakers fourm.

    So I think you and I have simply had experiences with different designs of interconnects.
     
  11. PaulT

    PaulT Supporting Actor

    Joined:
    Oct 28, 2002
    Messages:
    932
    Likes Received:
    0
     
  12. Keith Mickunas

    Keith Mickunas Cinematographer

    Joined:
    Dec 15, 1998
    Messages:
    2,041
    Likes Received:
    0
    I just bought one of the Accoustic Research Pro series stereo interconnects. I'm not sure if its the same model mentioned above, but it is a twisted pair cable. I've unscrewed the ends and I found on one end the white wire and the braided shield appeared to be soldered to the outer portion of the RCA connection. On the other end only the white wire is connected, and there's an extra layer of rubber between that clamp that holds the RCA connector to the cable and the cable itself.

    I do have a hum caused between my satellite and Samson amp. Would using one of these cables from the receiver to the amp solve this hum? Or do I need a regular coax where the shield isn't connected? And where can I find one of those? I have a Monster digital coax cable (I was young and naive) that claims to be uni-directional, but when I unscrew its ends the solder connections look identical. Would it be enough to take a standard coax RCA cable and disconnect the braided shield from the connector?
     
  13. MarcVH

    MarcVH Second Unit

    Joined:
    Dec 26, 2001
    Messages:
    324
    Likes Received:
    0
    Thanks to the various posters, and the cable seems to work fine. I haven't done extensive double-blind testing with both directions or anything, but as far as I can tell it seems to be less of a source of noise than either the receiver or the amp.
    The cable I have is AR Pro 2; sounds like you have Pro 1, but I believe they're pretty similar. The connectors on mine are as you describe.
    Not sure the cable will entirely eliminate a ground loop hum in the scenario you describe, but hey, it's worth a try. If your loop was with cable TV, I'd suggest getting one of these but they're not designed to handle the high frequencies of DBS. There must be some similar device which can, though.
    If you want to isolate the receiver-subwoofer link and the cable doesn't suffice, you could try a similar Jensen device but there's got to be a cheaper way to solve the problem.
     

Share This Page