I have tested the several usb audio modules based on popular C-Media chips and all not working in current core. In .config menu during the core building I try to find out and cann't find the real USB audio class support feature. You should understand that current board has only usb ports for external communication. This fact of lacking support such chips as CM108 or another C-Media is very bad.
Using the lsusb I see that audio usb was connected and enumerated. For some of them also the input device created. But no Alsa no pulseaudio don't see the sound card as is.