Audio Input not working on 13-inch Macbook Pro Mid 2012 I am trying to connect an audio device (analog synthesizer) to the input of my 13-inch Mid-2012 Macbook Pro running OS X Mavericks 10.9.3. The synthesizer's output is a standard 1/8th inch stereo plug. According to http://support.apple.com/kb/ht3625, I should be able to switch this from System Preferences. However, my screen looks like this even when my device is plugged in:


There is no option to use the audio jack as an input.
How do I connect my device to the audio input?
You missed the first sentence:


  Plug the input audio device into the combination audio port using the
  proper adapter cable.


You can not use your "standard" stereo plug, use Apple specific plug.