Apple - MacBook Pro (mid-2012) Microphone Input
All PowerBook and MacBook models support analog audio in via the headphone jack.
In your specific case, it is possible to use external microphone on MacBook pro and Air 2012 Models.
It looks like Apple has redesigned it to be a multifunction plug, without telling us in plain English. What they do say is you can use the Apple iPhone headset with microphone! Now that is a Hint !
Since there are multiple options to connect a microphone lets take a look.
1 - For stand alone microphone with cable you could use a USB connector type or Audio to USB converter.
2- You could use a BlueTooth type microphone/Headset.
3 - And last not least, you could actually use your Headphone (as marked) the 1/8 inch plug, but NOT with standard audio plug.
Here is the how: The plug is like the headphone port on iOS devices, this jack supports audio input as well as output—with as described in Apple specification.
Looking under the hood of Apple "About this Mac" you get the answer (it says it does support it).
The microphone or headset in question must be of the three-ring variety, just like Apple’s headsets. The fourth pin (ring) is for the microphone !
OK, what now? Lets assume you insist on using your microphone!!!
Get the 3.5mm 4 Position to 2x 3 Position 3.5mm Headset Splitter Adapter - M/F
... this headset splitter adapter breaks the audio port out into two distinct ports - one that can be used for a microphone input connection, and the other for connecting external (output) speakers.
I found stores in Europe (for about €10), but sure you can find it where you are.
I post my solution hoping it can help someone.
I've have a MBP mid-12 13in, with the so-problematic unique audio jack. I'me sure that external&internal usage is possible because of the iphone headset test.
So I bought the TRRS cable, and my first tests fails: I got an external audio detected, but no luck with the internal line.
Then, I found an amazon comment about the cable, solved:
- First, connect your external and internal lines to the Y cable
- Second, connect the Y cable to the MB
- It should take a couple of seconds to be recognised as an external mic
When I trying it fails again. But I've found the trick:
- The internal line must be a microphone
- So after being detected by the MB as an external mic, you can unplug the mic and connect anything else (an iphone)
- Note: I've can only testing with a cheap non-powered computer mic
The Griffin iMic is probably the most commonly touted solution for this "new" problem. This way you can monitor through the headphone jack, and the USB headphone jack also....I would assume. Maybe it's one or the other, however.
Either way the digital solution may improve signal quality also. There are other cheaper versions of the iMic but it seems Griffin was like "Hey Apple, want to make a computer that's missing stuff so we can make some more money?"
http://store.griffintechnology.com/catalog/product/view/id/623/?gclid=CLKDicGj1b0CFQaTfgodJqUAVA
If the link breaks just look up griffin iMic. It appears B&H currently sells it for $23.78
I've also seen similar products via https://www.google.com/#q=usb+to+3.5mm
I hope this helps with the "no line-in" problem on the 13" MacBooks and the new 27" iMacs. As well as the "My line-in doesn't recognize my mic" problem.
Alternatively try that 3.5mm 4 Position to 2x 3 Position 3.5mm Headset Splitter Adapter - M/F that Buscar mentioned above.