I have got a Macbook Pro 15" that has both an audio in and out port. Now I would like to play the sound from an external device through the speakers of my Mac.

How can I do that? I tried to just plug in the 3.5mm cable from my external device into the audio in port but I simply cannot make my Mac play the sound. However, in System Preferences -> Sound -> Input I can see that the Mac is receiving the signals.

What can I do?


If you don't have Garageband installed you can also use Quicktime.

  1. Open Quicktime
  2. Go to File -> New Audio Recording. You will see the following screen: enter image description here
  3. Click on the little triangle on the right and choose Built-in Input: Line in as shown in the screenshot.
  4. Slide the volume under the record button up until you have the desired loudness.
  • 4
    For me this imposes about 300ms input delay. Is there a way to adjust that delay (perhaps by means of some ´defaults´ setting for QuickTime)? – Henrik Feb 17 '17 at 14:59
  • Don't think you can configure QuickTime, it sounds like a latency problem What device are you connecting? – Saaru Lindestøkke Feb 17 '17 at 20:50
  • the delay is bad – Chaim Eliyah May 13 '18 at 1:46

You can use GarageBand:

  1. Create a new project and choose for example the voice template
  2. Set Monitor to On

  3. Optionally remove the effects from the Edit tab


You can use the SoundSource app from Rogue Amoeba to set your sound on "Play-Thru". Or you can do it in their free Line-In app, which has been retired but can still be downloaded.

  • The free app: LineIn worked for me, up until I upgraded OSX to 10.14 mojave- now it doesn't work. – user313267 Dec 8 '18 at 1:15

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