Hi, I've had intermittent problems with my headphone port since I've had my iMac 27" late 2013 but today the headphone port seems to have bitten the dust. The internal speakers are fine, but whenever I plug in headphones or a stereo via 3.5mm jack, once a sound occurs within OS X (music, notification noise, etc.) it produces a very loud, constant buzz. No audio whatsoever. Then after perhaps 30 seconds-2 minutes, the sound will stop. Has anyone got any idea what the hell is happening? Have I got a faulty headphone port?