Where I work we routinely need to connect random laptops, both PC and Mac, to our mixing board usually at a distance of about 30' away.

Generally we will be connecting to both a projector in the middle of the room and a sound board in the back, hence the long run.

We usually use some arrangement of 3.5 mini to either xlr or rca for these setups, but occasionally we get a lot of noise/interference in the line.

Is there an industry standard or more reliable way to run these setups?

2 Answers 2


I'd say you really need a balanced line converter.

Google will find dozens.

Keep the unbalanced connection as short as possible & run the rest balanced.
Simply connecting mini-jack to XLR does not balance the signal, it just runs one wire 'empty', making the potential for interference even higher

Once balanced, you can run the cables for far further than you need with no additional interference.

There's a theory lesson here & a full Wikipedia page on it - explaining how & why it works better at suppressing signal degradation & interference.

  • DI box, audio line isolator, etc. Feb 6, 2015 at 23:13
  • Would something like this work?
    – apaul
    Feb 10, 2015 at 1:57

I always had good luck using xlr. When I had any issues before 99% of the time it was an internal ground issue with the laptop. Unplugging power usually made it disappear but also meant it wasn't plugged in. If the laptop had a cable with a ground sometimes a short extension with the ground pulled fixed it too. If all else fails and it sounds like a grounding issue, investing in a cheap usb audio device might be worth having around.

Maybe try direct box or adapter with transformer? (Honestly no idea if that would do it... all of our adapters had transformers anyways)

What kind of interference? That would help narrow it down.

  • I've had the grounding issue you're describing with a few laptops. Not sure what kind of interference it is, sounds like a hum or buzz not sure if that helps at all.
    – apaul
    Feb 6, 2015 at 3:54
  • Do you run a power cable along with the audio cable? That can cause a hum/buzz issue. Occasionally I've had issues of a buzz only showing up when also connected to a projector (unplugging the vga/dvi/hdmi made it disappear). Now I'm thinking about it I eventually had a friend solder an isolation box together and I permanently mounted it in the lecterns we used. It's literally two 1:1 transformers (one per channel) in a small RadioShack box with a 3.5mm Jack on each side. That will stop the ground loop too. Won't fix a buzz from a power cable that runs with it, but amazingly handy.
    – user12912
    Feb 6, 2015 at 6:04
  • The last option is always crank the laptop volume and make your signal/noise as big as possible. Not exactly the best plan, but if you have no other option it can ease the pain
    – user12912
    Feb 6, 2015 at 6:07
  • I can't stress enough that using a power extension cable without the ground on any device is a bad idea. Use a DI box with unbalanced/balanced converter and lift the ground there instead (that should only affect the audio line, not the entire electrical system).
    – user9881
    Feb 7, 2015 at 18:01
  • I agree, but if you don't have a di box handy it's a last resort fix
    – user12912
    Feb 7, 2015 at 21:17

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