How can I chance output port to input port


Hello. I have just bought a macbook pro 13'' (new, so: OS X 10.8) and would like to plug my guitar to the computer. I have just the audio output port (wich is called audio in/out in tech specs) and id i go to System Preferences/Sound when guitar plugged to it it does not have the possibility to chance it to input. So how could I plug my guitar to the "output" port or is it even possible. Is the fault in my cable (instrument cable-3.5mm plug). Thank you :)
It's as simple as you can read in the little user guide that came with your MacBook Pro:
Connect external speakers, headphones, or digital audio equipment.
You can specify audio analog line in functionality, to support line-level microphones and audio equipment, by selecting Audio In in the Sound pane of System Preferences.
I don't think you will see how to change to your own guitar input, unless you have that input plugged in.
And, you should see the built-in microphone listed as an input. Click on the drop-down to change from microphone to your own line-level input.
yea, well that exactly is the problem. I don't have it listed there. And i've been googling, and several other people are having the same problem. It's like the option has been removed from 2012 model, but it should be possible, becouse it's called line in/out port. :(
Do you live near an Apple store?
Check out a new MacBook Pro there (or take yours in), and see if someone at the store (like a genius) can show you how that works (or maybe show you that it won't work.

I can see where you might need to try an external interface for that, such as a USB box like a Griffin iMic - or Tascam US-122/144 or numerous others.
Yea I think that would be the best the best solution :). I've checked too the iMic but wouldnt like to pay 40€ just for that. But thats kinda strange that apple would remove such property. :D thank you
You do need a device that is designed for audio, to help assure that input levels are matched properly.
That's not going to be free...

I don't think that Apple has "removed such property".
When you click the "Input" tab in the Sound pref pane, you should be able to adjust the level for the built-in microphone.
And, you should be able to set the input for line level there, too.

Are you saying that the "Input" tab does not appear at all in the Sound pref pane?

You can also boot to your hardware test, and check if there is any hardware problem reported.
Boot to that test by restarting while holding Command-D