I think that the problem is a conflict with Big Picture microphone settings and Steam desktop microphone settings, the way to configure the microphone is diferent in Steam desktop and Big Picture
Hello @obedlink, are you still experiencing this issue on an up to date system?
Closing pending feedback.
Nothing extracted yet.
I have a creative x-fi, the microphone of the x-fi is the primary, the secondary is the realtek microphone.
Steam beta perfectly detects the default microphone using pulseaudio (microphone x-fi). but the microphone volume control adjusts the volume of the realtek card.
no matter if I use "change device" or "pulseaudio default"
to adjust the volume of my microphone x-fi I have to use kmix.
summarizing:
Steam uses the microphone x-fi, but adjusts the volume of the microphone realtek
I use Kubuntu 14.04 updated.