May be, the native USB audio of Android L is not compatible with the Behringer UCA222.
http://goo.gl/x3loEQ
http://www.head-fi.org/t/595071/android-phones-and-usb-dacs/5085#post_10713638
Do you try to connect the Behringer UCA222 to a PC or a Mac?
Also, you could try to connect the Behringer UCA222 to the Nexus 7 using the USB Audio Player PRO, which includes its own USB audio soft-driver.
It should work.
http://www.extreamsd.com/USBAudioRecorderPRO/
| Nexus 7 (2013)
| yes
| May require a reboot with the audio device connected AND the language set to English-US (no kidding!). Google is said to solve this issue.
|
There is a free trial version of USB Audio Player PRO on the Google Play store.
If these tests are successful, the native USB audio of Android L is apparently not yet compatible with the Behringer UCA222.