3.Whether E17K can decode for smart phones with Apple or Android system?

A: The E17K was designed chiefly as a USB DAC for computers;  it has not been purposely designed for use with smartphones and we make no claim that it would work.  For USB decoding from smartphones, you may try turning off USB charging on the E17K and then connecting it to your smartphone with a USB OTG cable, but we cannot guarantee that it would work.