Different USB port specifications
The UDA-1 Stereo Amplifier is equipped with two USB-ports which enable you to connect your smartphone. However, because the front and rear USB terminals on the UDA-1 have different technical specifications, the front USB port does not support Android 9.
Connecting to the rear USB port that supports Android 9
Since only the rear USB port supports Android 9, you will need to connect your smartphone with the supplied USB-B to USB-A cable in combination with an adaptor “USB-A to USB port” on your smartphone.
Make sure to check which USB type your smartphone has before acquiring the right adaptor.