MacBook Bass issue

Discussion in 'MacBook' started by anon16, Nov 20, 2010.

  1. anon16 macrumors newbie

    Joined:
    Dec 26, 2009
    #1
    Chances are this is in the wrong place but I'm not sure where else I should post this.

    Whenever my MacBook has the charger in, there's constant 'drone' of bass from the subwoofer that my laptop is connected to, but as soon as I take the charger out the noise stops..

    Is there any way to stop this from happening (ie moving the cables round?) or is it just something I'll have to live with?

    Ta
     
  2. Blue Velvet Moderator emeritus

    Joined:
    Jul 4, 2004
    #2
    I've found the Apple power supplies to occasionally cause interference and unwanted noise. You may also have a ground loop.

    1. Have you tried moving the cables?
    2. Is the hum just on the subwoofer or can you hear it when you plug headphones into the Mac or anywhere else in the chain?
    3. How is the sub-woofer connected to the Mac?
    4. Is the sub-woofers mains lead plugged into the same mains sockets as the Mac's power supply?
     
  3. anon16 thread starter macrumors newbie

    Joined:
    Dec 26, 2009
    #3
    1. Yes
    2. Just tried it with headphones too and can hear it through those as well.
    3. There's a cable that goes to a volume and on/off control, which goes straight to the sub-woofer.
    4. They're plugged into different sockets, though they both run from the same mains if that makes sense (sorry if I have not used the correct language but I hope you know what I mean).
     
  4. blackburn macrumors 6502a

    blackburn

    Joined:
    Feb 16, 2010
    Location:
    Where Judas lost it's boots.
    #4
    I guess it's stupid but swapping "polarity" worked for me in the past. Looks like your listening to a 50Hz sin wave doesn't it?
     
  5. Blue Velvet Moderator emeritus

    Joined:
    Jul 4, 2004
    #5
    OK. With the headphones in and the power supply plugged in so that you can hear the hum, does the hum stop if you unplug the sub-woofer from the Mac?

    Hmmm.

    What country are you in? What do the mains plugs look like? Three pins or two?
     
  6. anon16 thread starter macrumors newbie

    Joined:
    Dec 26, 2009
    #6
    Yeah, there's the same problem with headphones. And I'm in the UK so 3 pins.
     
  7. blackburn macrumors 6502a

    blackburn

    Joined:
    Feb 16, 2010
    Location:
    Where Judas lost it's boots.
    #7
    Have you tried to unplug other devices from the mains (like the subwoofer itself)? Can you try with another magsafe adapter?
     
  8. Blue Velvet Moderator emeritus

    Joined:
    Jul 4, 2004
    #8

    Thought so. The third bottom pin on the plug goes to electrical earth and it sounds like you have a ground or earth loop. A solution might be awkward as I don't want to recommend that you put yourself at risk of electrocution.

    Does the mains plug on the sub-woofer have a plastic pin at the bottom of the three pins? Like so:


    [​IMG]


    Or is it three metal pins?
     
  9. anon16 thread starter macrumors newbie

    Joined:
    Dec 26, 2009
    #9
    It's three metal pins.. Anything that can be done? (doesn't sound promising :()
     
  10. Blue Velvet Moderator emeritus

    Joined:
    Jul 4, 2004
    #10

    First, try plugging the mains plugs of the Mac and the subwoofer together into one double-plug adapter and then into the mains if you have one of these:

    [​IMG]
     
  11. anon16 thread starter macrumors newbie

    Joined:
    Dec 26, 2009
    #11
    Don't have one of those but have an equivalent extension lead with 4 sockets and that's worked! Thank you!!
     
  12. Blue Velvet Moderator emeritus

    Joined:
    Jul 4, 2004
    #12

    No probs at all, anon16. Really pleased it worked out once we narrowed down exactly what was going on. You've put a smile on my face. :)
     
  13. skunk macrumors G4

    skunk

    Joined:
    Jun 29, 2002
    Location:
    Republic of Ukistan
    #13
    BV, I need a good electrician. Fancy a rewiring job on a four bedroom house? :)

    I like your new 'tar.
     
  14. anon16 thread starter macrumors newbie

    Joined:
    Dec 26, 2009
    #14
    And mine. Thanks again.
     
  15. Blue Velvet Moderator emeritus

    Joined:
    Jul 4, 2004
    #15

    Heh. Bonfire Night was a couple of weeks ago. :D

    Not in the slightest qualified or insured. Just some audio stuff I remembered from one of my previous secret lives running a little college radio studio. If the star arrangement hadn't worked, with all mains running to a common earth, then we might have been struggling. :eek:
     

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