The headphone jack supports an monaural microphone input. Here's the only schematic I could find in a quick search. It shows a breakout adapter which breaks out the microphone input onto a separate phone jack.Hey, I was wondering whether anybody knows how to get input from an external mic (using the 3.5 mm) on the rMBP. I know that it was possible on the MacBook Air in the past but I can't seem to get it to work on here. Thanks.