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10 metres audio cable going into PC = too long?

Discussion in 'Electrical Engineering' started by Andy, Apr 18, 2006.

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  1. Andy

    Andy Guest

    I am in the UK.

    I would like to take a stereo signal from the line-out of my stereo
    (or TV) to the line-in of my PC.

    The equipment is in different rooms and the audio cable would be 10
    metres. It will be this type:
    http://www.maplin.co.uk/images/full/130i0.jpg

    I don't understand the technical side but is 10 metres so long that
    it might cause audio problems with things like frequency response or
    voltage/current levels and so on?

    Will I need to get some higher specification audio cable to cover
    that distance? I want to keep cost down.
     
  2. I have used similar cable for a similar purpose over longer distances
    with no problems, for general purpose "listening" quality. Buying a
    higher spec cable is only going to give a very marginal improvement - if
    you really are interested in quality, you would link digital ports using
    an optical cable and not use analogue, anyway.
     
  3. You might get unacceptable noise pickup, you might not. Try. You
    might also get hum. Sometimes it responds to simply lifting the
    screen connection at one end, sometimes you need an isolating
    transformer. Or rather a pair of them.

    What's the link for?
     
  4. mc spake thus:
    So how does house wiring work in the UK? Is there more than one
    grounding ("earthing") point? And how is this better?

    (Here, the Merkin practice is to ground the "service panel"--the box
    where the big wires come into the house--to a single ground rod, with
    everything running downstream from that.)

    By the way, this brings up a strange experience I had recently doing
    some wiring. I was working for a guy who owns two houses right next to
    each other, and he wanted to run a cable TV connection from one house to
    the other. I was about to connect the cable in the attic of the house
    that was the source of the signal when I got a little tingle. After
    grabbing a VOM, it turned out that there was about a 20 volt difference
    between the two cable grounds.

    Was this due to power line potential differences, or to cable signal
    potential differences, or something else? The cable guys do their own
    grounding outside, and I don't think they put in any bonds to the
    electric service ground. In any case, the whole project was abandoned
    then and there as a bad idea. (It occurred to me that a cable
    transformer could have solved the problem, but then so could doing the
    thing the right way: just getting both houses wired for cable.)


    --
    Pierre, mon ami. Jetez encore un Scientologiste
    dans le baquet d'acide.

    - from a posting in alt.religion.scientology titled
    "France recommends dissolving Scientologists"
     
  5. Eiron

    Eiron Guest

    Mc doesn't understand ground loops. You can get them between two boxes
    plugged into the same double socket.

    Your tingle was because your equipment is not grounded, and is perfectly normal.
     
  6. Eiron spake thus:
    No, my tingle was because I was holding two cables strung between two
    different houses, each grounded at its end. Doesn't seem normal at all
    to me.


    --
    Pierre, mon ami. Jetez encore un Scientologiste
    dans le baquet d'acide.

    - from a posting in alt.religion.scientology titled
    "France recommends dissolving Scientologists"
     
  7. Don Pearce spake thus:
    I seriously doubt that, because then the potential would have been more
    like 120 volts, right? I think that's grasping at straws: so far as I
    know, PG&E (local electricity dealer) doesn't even supply 3-phase to
    residential customers. In fact, not even in come commercial districts. I
    owned a small business in Berkeley (print shop) until last year, and I
    remember the previous owner telling me about all the headaches he had in
    having PG&E put in a 3-phase converter (in an underground vault below
    the sidewalk outside). So I know that utility lines don't usually carry
    3-phase power, except to large industrial customers.


    --
    Pierre, mon ami. Jetez encore un Scientologiste
    dans le baquet d'acide.

    - from a posting in alt.religion.scientology titled
    "France recommends dissolving Scientologists"
     
  8. There'll probably be 3 phases in the street. houses, or groups of
    houses will be allocated a single phase.
     
  9. tony sayer

    tony sayer Guest

    I
    What they tend to do is supply the area with a three phase line at
    around 11Kv and transform that down and then supply house number one
    with phase one, house two with phase two, three with phase three, four
    with phase one, five with phase two, house six with phase three and so
    on. Its called load balancing between the phases...
     
  10. sQuick

    sQuick Guest

    I am using the exact same cable from Maplin, this is to go from my computer
    to my stereo amp.

    I would estimate it to be 10m-15m in length and I've had no problems with
    noise.

    sQuick..
     
  11. Andy

    Andy Guest

    Does your "perfectly normal" mean:

    "there is no fault and no danger (until the ground is
    actually needed and then will be a danger)"
     
  12. Andy

    Andy Guest

    Thanks to you and everyone else for the feedback. Seems it is
    less of a problem than i was anticipating.

    Actually my cable is not exactly the Maplin one I illustarted but
    a very similar one.
     
  13. Guest

    "Ground" is not all created equal. Dirt sucks as a conductor and you
    can see significant voltage differences between two grounding
    electrode systems. If you are connecting signal lines between two
    buildings be sure you also bond the grounding systems together.
     
  14. Don Pearce spake thus:
    Reread my earlier post above. In it I described the situation where a
    business I once owned needed to have a power converter installed for
    3-phase. This was in Berkeley, in a commercial district, not a
    residential one, and I think it's pretty typical of the Bay Area in
    general, probably the urban U.S for that matter. The power companies
    don't supply 3-phase power even to commercial areas; if someone needs
    it, they put in a converter. (We had a printing press that required it.)
    Most commercial businesses don't need 3-phase power. Large industrial
    customers do.

    I think the converters can be shared, so if a couple or a few
    neighboring businesses need 3-phase power, they can all use the one
    converter.


    --
    Pierre, mon ami. Jetez encore un Scientologiste
    dans le baquet d'acide.

    - from a posting in alt.religion.scientology titled
    "France recommends dissolving Scientologists"
     
  15. Eiron

    Eiron Guest

    Remember the good old days when everything had a 3-core mains cable?
    You could get a ground loop just plugging a tape recorder into an amp.
    The bodger's solution was to disconnect the earth in the mains plug
    and remember always to connect the audio cable to the amp before connecting
    the power. Now everything has 2-core power leads so you get tingles.
     
  16. Eiron

    Eiron Guest

    No. It's normal and legal to have a load of double-insulated equipment
    connected together so the signal ground is floating at roughly half
    mains voltage and can deliver several mA. It's dangerous, in my opinion.

    In the UK, with 240v mains, and adjacent houses on different phases,
    you might have 220v between the two cables in the attic.

    And you can't feel 20v AC unless one end is on your tongue. I just tried it. :)
     
  17. Floyd L. Davidson spake thus:
    It's a device--a big, honking piece of electromagnetic equipment--that
    generates 3-phase power from 2-phase power. In this case, it sits in an
    underground vault beneath the sidewalk, covered by one of them metal plates.
    Apparently not. If you don't believe me, ask PG&E (Pacific Greed and
    Extortion, as they're known around here). They don't run all 3 wires as
    part of their normal power distribution.

    I know this thing exists, because I saw the crews working on the damn
    thing in front of my shop when it malfunctioned and the press stopped
    working.


    --
    Pierre, mon ami. Jetez encore un Scientologiste
    dans le baquet d'acide.

    - from a posting in alt.religion.scientology titled
    "France recommends dissolving Scientologists"
     
  18. Eiron spake thus:
    Some of us may be more sensitive than others. It's a subjective thing,
    after all. Believe me, I felt *something*. Being the paranoid
    electrician type, I let go of that sucker in a hurry! VOM showed ~20v.
    (Dunno whether AC or DC; I'm assuming AC.)


    --
    Pierre, mon ami. Jetez encore un Scientologiste
    dans le baquet d'acide.

    - from a posting in alt.religion.scientology titled
    "France recommends dissolving Scientologists"
     
  19. Arny Krueger

    Arny Krueger Guest

    True for Detroit Edison, as well.
    http://www.homemetalshopclub.org/projects/phconv/phconv.html
     
  20. tony sayer

    tony sayer Guest

    Me too!, virtually every bit of wire string the electricity grid
    together in the UK is Three phase. Only in some remote places will you
    see overhead High voltage in Single phase, and that only is likely to
    serve a signal customer!..

    Can't believe the USA is that different?. I know or hear that they have
    split centre tapped supplies for 115 and 240 volt domestic supplies...
     
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