@ajudhian Recently i have discovered that even without USB Audio Player PRO, i still can use my Alpen 2 as a DAC for my Asus Zenfone. I change the usb otg cable with the cheap one which price is less than a dollar. So the main problem is the usb otg cable, hope this help.

Pardon my english, but i know how to use the Fiio e17k alpen 2 as usb dac for android. First the issue is not on the device it self but on your android. Even when you plug it in the device, android will always use the internal dac to play sound. So i used USB audio player pro app to bypass...