4 Replies Latest reply: Feb 19, 2013 9:08 AM by lucafromverona
lucafromverona Level 1 Level 1

Since I installed Mountain Lion (july 2012) on my 2009 iMac, my usb ports send an electric shock to my external sound card anytime it starts/stops/reboot.

So my speakers make a sound like "boom" and I'm afraid they will be ruined..how do I control this shocks?

It NEVER happend with Snow Leopard and Lion. iOS always purchased on Mac App Store.

iMac (21.5-inch Late 2009), iOS 6.0.2
  • BDAqua Level 10 Level 10

    Hi Luca,

    Long shot, but...


    Open Audio Midi Setup in Applications>Utilities, see the input & output options & KHz setting there, some things will change it for their own use, then not set it back.

  • lucafromverona Level 1 Level 1

    Thank you for the quick reply. Sadly it did not work . I can only choose between 44100 and 48000 hz but with both situations, the problem is still there.


    It's most like an USB problem I think, it happens wherever I connect the cable (in any of the 4 ports). I think the Mac sends an electric signal (you can listen the speakers or see the leds in the sound card) to all ports while stopping/starting/waking/rebooting. Actually while starting it happens more than one time.


    I would send a video, but I don't know why but my "Insert Video" button is unactive..

  • Eustace Mendis Level 7 Level 7

    The problem you describe could happen if the electric outlets are not correctly grounded.


    For power, your speakers are plugged into an outlet, right?


    Is your Macbook power adapter plugged in to the same oulet? If not, and if it is possible with the power cords you have, try plugging both - the speakers and the macbook power adapter - into the same duplex outlet.

  • lucafromverona Level 1 Level 1

    sorry about the late..btw it is all plugged in the same outlet..plus when i had Lion it did not happen (same mac same table same outlet same room etc)