I have an Asus Xonar U7 usb sound card and it works except for the microphone input which isn't recognized at all by pulseaudio. The "Input" tab in the sound settings is completely empty. I've tried using pavucontrol but the U7 is only listed there as an output, not an input.
It works on Windows and I'm having this problem on two separate computers (running Ubuntu 14.04 and Linux Mint 17).
The device is listed by arecord -l:
card 2: U7 [Xonar U7], device 1: USB Audio [USB Audio #1] Subdevices: 1/1 Subdevice #0: subdevice #0
If anyone else is using the Xonar U7 then it would be great if you can confirm that it's working (or not) with audio input.
The farthest I've come is to get Audacity to record something (although very very low) by setting default audio device to Alsa in gstreamer-properties. Since my main use is Skype (which uses pulseaudio) this doesn't help very much.
alsamixer looks like this: