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Is there any easy way to listen to the input on a mac?

For example, assume I have a microphone hooked up to the input (i.e. line in) of my mac, and I have headphones hooked up to the output of my mac, is there any way that I can hear what I say in the microphone through the headphones?

This is very easy in Windows XP, simply by going to the sound settings for recording devices, checking "Select" on the Line In and increasing the volume. Which makes it so you can hear what is said into the microphone.

It has to be in real time, a solution where you record the input and then playback the output later doesn't help.

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+1 upvote. This is what I needed too. –  therobyouknow Nov 25 '11 at 8:29

5 Answers 5

up vote 32 down vote accepted

Take a look at Rogue Amoeba's LineIn. It is a free application which will allow you to do what you want.

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LineIn can select line-in/mic/digital-in etc, and there are independent volume control. –  deddebme Oct 21 '09 at 5:39
+1 I will check this out too. Favourited. –  therobyouknow Nov 25 '11 at 8:27
delay introduced is significant. I'd love to see a LineIn-like app working with fast ASIO drivers of the available soundcards. –  Serg ikS Aug 28 '14 at 7:07
Rogue Ameoba released version 2.3 on 2014.09.03 that has completely eliminated delay. –  xizor Sep 24 '14 at 23:00

If you're using an older Mac, the application Audio MIDI Setup.app in the Utilties folder (found in the Applications folder) allows* the ability to pass-through input straight to your output.

To do so; click on your input device and then check off the "Thru" checkboxes to pass audio through. However oddly enough I've never seen anyone to get it to correctly work on an Intel based Mac, I've had it work great on some PowerBook G4s however.

The better alternative is to use Rogue Amoeba's LineIn (as said by Richard Hoskins). Personally I use this and find it easier to use.

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You can also use Garage Band. Choose for example the Acoustic Instrument template (the default audio track in it has no effects) and set monitor to on.

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this seems to work just as well as linein, maybe a bit better –  chrismarx Nov 9 '14 at 0:09

With 10.6 (and newer, AFAIK) you can launch QuickTime Player.app and choose File -> New Audio Recording. Then just turn up the volume control that is part of the window that appears. You might hear a bit of white noise when there's no sound and the volume is all the way up but the Rogue Amoeba app does the same thing.

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If you want to play your synth through your Mac audio, Quick Time would not work because of huge delay (latency). LineIn's latency is smaller but still too strong.

So I need to run Logic which is not very practical but it is the only solution I have found so far. This is VERY odd because I am quite certain that it would be very easy to add "Audio Pass Thru" switch as a standard OSX feature.

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