Hiss in audio while using headphones on Macbook

Discussion in 'MacBook Pro' started by hari-bhari, Jan 8, 2008.

  1. hari-bhari macrumors regular

    Joined:
    Jul 4, 2007
    #1
    When using my standard iPod headphones with my macbook I can hear a hiss in the audio signal. It is the same level regardless of volume, but it is to the point where I can tell whether the audio port has been shut on or off. For example, if there is no sound playing, there will be no hiss whatsoever. Then if I adjust my volume controls for example, the audio port pops on, I hear the blip sound of the volume control, and then I can hear hiss for about 5 seconds in the background after which the port shuts itself back off (presumably to conserve power). Funny thing is that I just got a new logic board last week and this issue was present both before and after. So is it normal, or does replacing the MLB not replace the integrated audio chip somehow.
     
  2. mad jew Moderator emeritus

    mad jew

    Joined:
    Apr 3, 2004
    Location:
    Adelaide, Australia
    #2
    Do you have external speakers or other headphones you can test the port with? It could be something as simple as a bit of dirt/dust stuck down the hole.
     
  3. thomaschina03 macrumors newbie

    Joined:
    Apr 9, 2008
    #3
    I have the same issue with my Macbook. A google search turned up an explanation: apparently it is due to interference from putting the audio circuitry in close proximity to the other electronics. I've worked in theatres where this happens on a larger scale with the PA picking up a hum from the mains wiring!

    The problem goes away when you connect headphones or speakers with a high impedance, although they will drain the battery faster.
     
  4. alphaod macrumors Core

    alphaod

    Joined:
    Feb 9, 2008
    Location:
    NYC
    #4
    That's interesting, Sennheiser HD555s have an impedance of 120 ohm compared to the 50 ohm on the Apple headphones and the hissing gone. The hissing is worse on my Shure E500 :(
     
  5. Blubbert macrumors 6502

    Joined:
    Nov 1, 2006
    #5
    The apple headphones have a 50 ohm impedance? That is a really high number. My Sennheiser CX300's have an impedance of only 16 ohm, and the HD280's have an impedance of 64 ohms.

    I mention this because on the CX300's, the noise from the headphone jack is noticable and annoying, and on the HD280's it is not audible at all.
     
  6. thy macrumors newbie

    Joined:
    Dec 8, 2008
    #6
    hd280

    I even have the hiss on my sennheiser hd280 which is 64 Ohms.
    I will try to hook it up to a mixer with an higher impedance. Maybe that will help.
     

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