This morning I was using my new JawBone Bluetooth headset to make a Skype call. The quality was bad and therefore I decided to switch to my headset. The result was better, but still not what I was looking for. At the end I took the time to really understand, where the sound is coming from and to my big surprise I found out that the line-in jack is not working with normal headsets.

On the Mac you need a mic (or a headset) with "power" (e.g. a USB mic or a pre-amp mic).

Conclusion: I have stored away my headset and will use the built-in speaker/built-in mic to make calls. In case I need privacy I will just plug in my iPhone earbuds. That sounds like a/the winning configuration. But that also means that I do not have a solution for environments with a lot of background noise. Maybe I need to go back and need to find out why the quality with the JawBone was bad in the first place.