audiomacspeakers
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?
Have a look at the free
Inside The Lines
LineIn is a simple application for OS X to enable the soft playthru of audio from input devices. In simpler terms, you can use LineIn to play sound coming in through a microphone or any other device plugged in to your Sound In port, just as was once available with OS 9's "Play input through output device" option.
Aggregate Device
You can setup an Aggregate Device (Audio Midi Setup > Create Aggregate Device), which allows the ability to combine multiple devices of the same model, or to combine multiple inputs and outputs for apps that don't support separate input and output devices. This Apple guide shows how it works and is surprisingly quite easy to setup.
SoundFlower
Another way to route audio to multiple channels and outputs (up to 64) is with the free app/plug-in Soundflower. You can download a ready-to-use version, or compile the source code yourself if you have the desire to specifically modify the application. Soundflower is really excellent for many things — what is up to you.
Best Answer
If you don't have Garageband installed you can also use Quicktime.
File -> New Audio Recording. You will see the following screen:Built-in Input: Line inas shown in the screenshot.