I can set global shortcuts for audio output (to mute them), which work. However, if I set a mute shortcut for the microphone, the shortcut doesn't work. Shortcuts that decrease or increase the microphone's input levels, on the other hand, do work. I've done some searching and while there seem to be quite a few bug reports and topics on global shortcuts in KMix, I haven't found any on this.

I'm using:
-KMix 4.12.3
-(Arch) linux kernel 3.13.6-1

For now my solution is to create a custom global shortcut for KDE with the following command: "amixer set Capture toggle". This performs the same function (I'd presume) but does not go through KMix, and works.

If you use the D-Bus interface offered by KMix, are you able to use it to mute the microphone?