Comment 12 for bug 1171435

you have to use Mic Source

http://cgit.freedesktop.org/pulseaudio/pulseaudio/tree/src/modules/alsa/mixer/paths/analog-input.conf.common

however front panel seem not a defined name for input

and you just have three capture switches instead of capture source control for selecting Mic, line and aux

in virtualbox with enumulated AC97 codes, sound preference show micrphone1 ,microphone2 and the other AC97 inputs such as aux, video, CD and line in