Edit: Updated. Valid for Live 8 to 11.
If you simply want to use the built-in sound card, the process is pretty straight forward and you can skip the first two steps. If you have an audio interface, read on as there's a little more to take care of.
- Check the manufacturer's website for the latest driver (some offer none though) and possibly a control software. Download and install if available.
- Connect your audio interface to the Mac (via USB or Firewire most likely) and to a power source if needed (most do). Then switch it on. Check the manual if there are any other setup steps necessary.
- Start Live and go to the Preferences > Audio. The shortcut for it is Cmd + ,.
- Make sure Core Audio is chosen as the Driver Type.
- Choose either the built-in input or the one of your audio interface as Audio Input Device. You can also choose the built-in microphone, but then do yourself the favour and use headphones. Otherwise arming a track will greet you with some nasty feedback.
- Choose the built-in output or the one of your audio interface as Audio Output Device.
- You can activate the needed mono and/or stereo in- and outputs under Input and Output Config respectively. (Note: Since Live 10 it's possible to label them for convenience.)
- Choose the Sample Rate as needed. It's not saved with the Live Set, but is set universally so beware if you tend to switch, e.g. between live and studio. You can set the Bit Depth in Preferences > Record/Warp/Launch.
- A Buffer Size of 512 seems to work for most. Or you can try to find a setting that gives you low latency without audio drop outs. This should always be a power of 2 (64, 128, 256, 512, 1024 and so on) to avoid issues with the driver of the interface.
- Now you should be all set. If you're using an audio interface, don't forget to plug in headphones or connect it to speakers.
One last tip:
If your audio interface is off, Live will default to No Device as Audio Input Device and Built-In Output as Output Device. You need to change it back manually in the Preferences.
Anything to ask, add or remark? Just leave me a comment.
There are plenty more Ableton Live tutorials where this one came from.