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?

4 Answers 4


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.
  • 9
    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
    Commented Feb 17, 2017 at 14:59
  • Don't think you can configure QuickTime, it sounds like a latency problem What device are you connecting? Commented Feb 17, 2017 at 20:50
  • 1
    the delay is bad Commented May 13, 2018 at 1:46
  • I can confirm this adds a significant delay. The on-screen meter responds to sounds almost immediately, but I don't hear them until several hundred ms later. The latency seems to be added by Quicktime.
    – Josh
    Commented Aug 17, 2020 at 22:52

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

  • I also found delay using this method :( Commented Apr 7, 2020 at 2:08
  • Any tips on preventing feedback when used for Karaoke? Commented Feb 14 at 16:40

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.

  • 2
    The free app: LineIn worked for me, up until I upgraded OSX to 10.14 mojave- now it doesn't work.
    – user313267
    Commented Dec 8, 2018 at 1:15

A bit late to the party but I’ve stumbled on a solution on another StackOverflow website that led me here: http://jsfiddle.net/jib1/7ejwaxkc

It works wonderfully as an audio passthrough. Took me ages to find... phew!


EDIT: Found out the solution isn’t perfect: it’s mono. :(

  • 1
    While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes.
    – grg
    Commented Mar 12, 2021 at 22:18
  • @grg Ah yes, good point. Thanks! (I’m a total newb, as you may have found, haha... 😄) Commented Mar 12, 2021 at 23:08

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