I recently traded my ipad for an Macbook Pro 2010 13". The macbook wouldn't start at first so i changed the harddrive. Now everything works except the headphone jack. There is sound but it sounds awful. After some fixing i discovered that the left or right channels phase is inverted (the sound waves is upside down). so if i pan the sound in system preferences to left or right the sound will sound okay EXCEPT that the sound becomes mono. im a music producer so i really need the stereo sound to work perfect for mixing and mastering. the wierd thing is that some speakers and headphones work good and the rest sound awful. its kinda 50% chance that the phase is invertet in one of the channels. some speakers dont even give out a sound! i've tested 6 headphones and 4 speakers with it. i think its the hardware but im not sure. i would really appreciate any help i can get! have a nice day!