Audio static from 2010 MP

Discussion in 'Mac Pro' started by macstatic, Sep 6, 2013.

  1. macstatic macrumors 65816


    Oct 21, 2005
    Is anyone else experiencing static noise from the Mac Pro line out?
    I hear what I can best describe as random white noise which I can hear even if I turn the volume all the way down.
    If I say scroll up or down in a browser window, hold down a key (to repeat) or even just type I get additional noise. It stops when I stop scrolling or typing.
    Why is this happening and what can I do about it? I'm on a Mac Pro 5.1 (2010) with OSX 10.6.8.

    PS: I remember having a similar problem with a Powerbook where strangely using "TextEdit" generated a lot of random digital noise out of the speaker!
  2. slughead macrumors 68040


    Apr 28, 2004
    I have the same problem, I believe it's electromagnetic interference from the video card / other internal components.

    You can try buying a more insulated audio cable or making sure the cable stays away from other EMR sources, but it may not work. Digital (eg Optical) is the only way to be 100% rid of interference.

    I bought a really good cable to go from my Mac to my PC, but my PC's GTX780 releases horrible, loud interference when playing games.
  3. N19h7m4r3 macrumors 65816


    Dec 15, 2012
    You don't happen to have an external audio card, or DAC to plug in to see if the issue stops do you?

    Slug is right about the interference, although I can't say I've ever noticed that on any of the system's I've built or used before.
  4. macstatic thread starter macrumors 65816


    Oct 21, 2005
    No, I don't have any audio interface connected.
    The line-out goes into my monitor (has built in speakers), and now and then I attach my headphones into the monitor's headphone jack. That's when I really notice that noise.
    I'll see about the cabling, although everything appears fine to me.
  5. DJenkins macrumors 6502


    Apr 22, 2012
    Sydney, Australia
    You have what is called a ground loop.

    Google it, there are some good explanations out there.

    Happens mostly when people use powered audio monitors (speakers).

    Basically you have electricity that doesn't know where to go, and instead of finding it's way to ground (earth) it's trickling back up into your system and causing interference.

    There are simple devices out there that break these ground loops. I'm using the Behringer HD400 hum destroyer and it works great.

    It's not a mac pro problem, any PC or DJ equipment can have the same issues and it plagues many users.

    You can try and get better quality cables, plug your monitors or computer into different wall outlets further away etc. but the most guaranteed way to get rid of it is to get a ground loop isolator like I mentioned.

    Good luck!
  6. slughead macrumors 68040


    Apr 28, 2004
    Only $30! that is awesome. However, in my case, since the interference is actually created by the device it is plugged into (and not downstream), would that work?

    Edit: I wonder if I could just remove the metal motherboard bevel or put a small washer to insulate the miniplug... hrmmmmm
  7. DPUser macrumors 6502a

    Jan 17, 2012
    Ground loops occur when there are differing paths to ground with varying impedance and generally cause a 60 cycle hum + harmonics.

    If the problem is a ground loop, it can often be eliminated by plugging all AC powered devices into the same wall outlet, accomplished by using a power strip. Hum-isolators generally use transformers which, depending on their quality, can degrade sonic performance.

    I have experienced very stubborn ground loops with certain Yamaha USB-interfaced keyboards that were resolved by creating custom USB cables with the shield and ground wire severed. MIDI interfaces use optical isolation to avoid these issues.

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