Hi, Macbook 12" Retina has 1 headphone jack.
Can we use it for a Microphone input ?
I want to connect Guitar to that port - without any sound card, and I do not want to use the USB port.
MacBook, macOS High Sierra (10.13.3)
The 12" MacBook Retina can use the headphone jack as an audio input. I've done this a couple of times before by connecting an audio source to the MacBook via a male to male audio cable. Be careful that your guitar doesn't over drive the headphone jack. You will definitely need to adjust the input volume to account for how "loudly/softly" the guitar is sending it's audio over the cable. Also, you might want to look at an Apple iPhone headphone jack to see what the end that plugs into the MacBook will look like, as ZaZo mentioned earlier.
Hope this helps!
I've seen a mixed bag on this. I found this on Macworld.com.
The MacBook Air has a single headphone port, which should be more accurately called the “headset” port. Like the headphone port on iOS devices, this jack supports audio input as well as output—with this caveat: The microphone or headset in question must be of the three-ring variety, just like Apple’s headsets (and their compatible brethren).
So, works for Air, may for rMB. Probably better luck with bluetooth or USB C, which you stated you didn't want to use.
Macbook 12" Retina: Can I use headphone jack for Microphone input
