MBP 15" 2011 audio hizz/hum on line out

Discussion in 'MacBook Pro' started by de.user, Mar 15, 2011.

  1. de.user macrumors newbie

    de.user

    Joined:
    Apr 5, 2010
    #1
    I have a problem with the Line-Out from the new 15" MBP. If I connect my ear/headphones to the audio output I can hear a hizz/hum. The volume of the tone does not change if I change the audio volume and does not go away if I play music.

    I have tried it with B&O A8 earphones and B&W P5 headphones. I also unplugged any cable. The hizz/hum get a bit more silent if I remove the USB and minidisplay plugs, but it still there. Only if I remove the MagSafe plug the hizz is gone. I already tried the 3 and 2 pin power cable.

    I wonder if it is due to the low impedance due to the earphones? I will try to connect the MBP do my stereo.

    Does anyone else expirence this problem?
     
  2. ender land macrumors 6502a

    Joined:
    Oct 26, 2010
    #2
    Are you listening to iTunes?

    I've had this issue a few times on my stereo system when using the audio out on my MBP and I can "replicate" it by using the equalizer in iTunes. For whatever reason the equalizer appears to introduce a fair bit of noise into the signal.

    The native volume on the laptop does something similar to me - if you can, increase the volume in whatever you are listening to (iTunes/groove shark/etc) to maximum and that should let you lower the volume on the laptop and reduce noise.

    If the power cord is the cause, I'm not sure what to tell you. I'm assuming you are keeping the actual headphone cord far from the magsafe cord?
     
  3. DustinT macrumors 68000

    DustinT

    Joined:
    Feb 26, 2011
    #3
    If it is the power cord you could just use the laptop on battery when you need to get rid of the hiss.
     
  4. de.user thread starter macrumors newbie

    de.user

    Joined:
    Apr 5, 2010
    #4
    I do not use iTunes or a equalizer. I used VLC, Quicktime etc. You can already hear the problem if the output is activated. So for example if you change the system volume you hear the hizz/hum. It is also there if you play music.

    It is really odd, it only disappears if all plugs are removed. If just the power connection is removed the noise stays. The cable from the headphones do not cross any cable.

    This is more worse than the silent hizz/hum/metallic sound from the 07 SR MBP which disappears if music is played. There was not such noise even when all connections are used.

    I will do some more tests but I wonder if someone else has the problem on the latest 15" model?
     
  5. grayh0und macrumors newbie

    Joined:
    Mar 1, 2011
    #5
    Maybe try a pram reset? I had an early 2008 MBP with this problem and that fixed it.
     
  6. de.user thread starter macrumors newbie

    de.user

    Joined:
    Apr 5, 2010
    #6
    OK, I finally tracked down the problem. I have tested it on my stereo and TV. It is not the new MBP.

    The problem is the Powerline adapter. It transfers network data over the mains. The adapter itself is plugged into the outlet and then MBP and monitor follows. There is a filter in the adpater to filter the noise out. But it seems that it is not good enough.

    If I remove the two Powerline adapters the hum/hizz is gone. The adapter causes also interferences on the signal cable from the monitor. This is the reason why the noise became better with MagSafe adapter only.

    So I am happy that I do not need to return the MBP. I will try a different brand for the powerline adpaters or try to change the network structure so that I do not need these adapters.
     

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