1. Register NOW and become part of this fantastic knowledge base forum! This message will go away once you have registered.

Running Speaker Cables Next To Extension Cords

Discussion in 'Accessories / Connections' started by stealthy, Jan 21, 2010.

  1. stealthy

    stealthy Guest

    I havent really had a particular problem with this, but I was told you arent supposed to run speaker, mic or instrument cables next to power cables and extension cords to avoid hiss. How true is this? Any more input on this simple subject?
     
  2. Kapt.Krunch

    Kapt.Krunch Well-Known Member

    As a general rule, you should try to avoid that. Cables can inductively pick up EMI from other cables, and the closer they are, and the longer the run, the more chance of interference. Unbalanced instrument cables, though generally shielded, may be susceptible. Unshielded speaker cables may be. Shielded, balanced mic cables may be a bit less susceptible, but why give your balancing circuits more work than they need to reject extraneous noise?

    There is a lot of info on this subject through a simple search. Basically, it comes down to the following in order of desirability on cable runs:

    1) Keep power and other cables completely apart, as far as possible.

    2) Crossing them at a 90 degree angle is better than running them parallel, because there is less common area to interact.

    3) If you must run things parallel, move things as apart from each other as possible.

    4) The very worst thing to do is to bundle up power, speaker, and line and mic-level cables together.

    You ever see one of those "clamp ammeters" that read current from clamping the probe over a coated power wire without ever actually touching the bare wire? The same reason those work is the same reason it's good to avoid running power and audio cables parallel, too closely.

    Why take chances, if you can avoid them? Give your audio the best chance to sound clean, and don't create possible problems that you may have to spend more time and energy dealing with later, anyway.

    Kapt.Krunch
     
    audiokid likes this.
  3. stealthy

    stealthy Guest

    Very well, thanks for clearing that up
     
  4. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

    Although in theory parallel signal and power lines can induce noise (hum, not hiss) in the signal, it's rarely a real problem in practice. In fact, there are commercially made combo signal and power cables with the two running in a shared jacket for long distances, and I know several experienced live sound engineers who have attached a power extension to their main snake with no audible effects.

    You ever see one of those "clamp ammeters" that read current from clamping the probe over a coated power wire without ever actually touching the bare wire? Did you notice that you have to separate the two conductors and clamp over only one wire to get a reading? That's because the two wires carry equal but opposite current and their magnetic fields are almost completely cancel out.

    Speaker cable is practically immune to noise because its voltage is so high that any noise is simply buried. Microphone cable is pretty resistant because of common mode rejection, effectively canceling out any noise picked up. Guitar cables and unbalanced line cables may be somewhat more vulnerable due to their lower signal voltage and unbalanced format.

    bouldersoundguy.com
     
  5. TheJackAttack

    TheJackAttack Distinguished Member

    I've never seen a live engineer recommend running power cables next to any mic or line level cable. Attaching an extension to the snake is not the same thing as running power either in the snake or along side the snake. The majority of cables I've seen that run "power" and "signal" together are for security camera systems. They may or may not include an audio line but in any case aren't meant for professional audio use. Of course maybe things have changed since I was last on the road but I doubt it has too much.
     
  6. dvdhawk

    dvdhawk Well-Known Member

    Bottom line, avoid it where you can. In the real world doing bar gigs, you can't always avoid it.
    Don't lose any sleep over it, but try to route your high-voltage 18" or more away from the snake, etc. whenever practical.
    Cross them at 90 degrees if you can.
     
  7. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

    Theory vs. Practice

    I was referring to a power extension, attached parallel to the audio snake.
    Things have changed. There's a whole world of combo audio/power cables out there for powered speakers, from ProCo, CBI and others.

    I used to try hard to follow the same rules of thumb suggested but often found it impractical. The simple fact is that, with several thousand gigs behind me, I've never had an issue running a 100' power cable right next to a 100' snake, and I know I'm not the only one doing it.

    bouldersoundguy.com
     
  8. TheJackAttack

    TheJackAttack Distinguished Member

    It likely also depends on how much power you are drawing. The Proco stuff I saw online was a small IEC power cord and a couple of balanced audio lines. Just not much juice there. I had too many amp racks (220 distribution) for that sort of thing. Of course there is a practical difference between most small to medium size bar gigs and a full touring rig. I'd stick with the recommendations of at least 18" separation when at all practical. That said, I can see where the Proco combo cable would be useful for powered speakers in a nice compact rig. I'd still try to keep it separate from my main audio snake multi-pin or not.
     
  9. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

    Yeah, I'd be a little nervous putting hundreds of amps of 220v next to a snake for any distance, but for running power to the mixer and FOH rack at a bar gig there's not much to worry about. Different worlds.

    bouldersoundguy.com
     
  10. sheet

    sheet Well-Known Member

    It is not to avoid hiss. It is to avoid noise from EMF. You should cross cables at 90 degree angles only. There are multiple published studues about the interference between the pairs in cable, like the + and the -. If we really want to get tweeky about it in high resolution monitoring situations, we keep them separate as well.
     
  11. sheet

    sheet Well-Known Member

    There have always been powered sends available in snakes. That doesn't mean that it is proper. There is a butt load of gear sold that is improper. Those powered snakes as they are often called have shielding between the line level and speaker lines, and then between the speaker pairs themselves to avoid EMF issues.
     
  12. stealthy

    stealthy Guest

    Apparently I no longer receive emails when a reply is posted.

    Anyway, it looks like for my application of medium bar sized gigs, I dont have too much to worry about. However keeping it to a minimum, when possible, is goood practice. Thanks everyone.
     

Share This Page