This seems like a simple thing but I find lots of confusion around using line-in on an imac. I have 2 ports on the back of my imac purchased new Dec of 2011 and running latest ios. One is the headphone and the other is a bizarre icon but apparently a combined audio in/out. All I seek to do is record speech with a headset (into camtasia studio). I have seen reports that you must have an amplifier on a microphone to utilize line-in on the mac. Another report said that you must utilize a 3 pin to 4 pin adapter like this: http://www.amazon.com/gp/product/B004SP0WAQ/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1 I purchased that adpater but the line-in still does not seem operational (using either port on the back of the imac). And yes i've been to settings both dictation and speech and sound, and regardless, the headset does not appear to be active using line-in. Can the imac accept line-in input to record speech? Do I need an amplifier? Is the adapter truly supposed to work? Any help greatly appreciated!