I have a 2011 21.5 iMac 2.5 i5 running 10.7.4 i have it set up in my office with an mini display to HDMI to my TV. never had issues until tonight. any audio source on my iMac produces a crackle sound behind (Netflix, iTunes, DVD). almost like it is distorting. it gets louder and softer as the audio flucuates. and then when audio signal stops it stops as well. i have troubleshooted it and isolated to just the HDMI output (internal speakers and fire wire studio monitors work fine) and only HDMI inputs on my TV (Xbox and TV ant work fine) i have: switched HDMI cables (twice) switched mini display/HDMI adapter switched HDMI inputs on tv rebooted 4 times switched every setting in Audio Midi Setup again i was just using this yesterday and no issues whatsoever....to my knowledge nothing has changed.... please help!