13. How to connect the M17 to an external decoder? Does it support USB audio digital output?

The M17 supports USB audio. The setting steps are as follows.
1. Enable "USB output" in FiiO Music app of the M17.
2.Use an OTG cable to connect the M17 and the external decoder.
3.Open FiiO Music app or other music applications to use the M17 as a USB digital output device.

It supports most of the decoding devices on the market. For those unsupported, you can turn off the USB output in FiiO Music app, or unplug and re-plug the USB device after quitting the FiiO Music app. If it does not work, please contact us by sending an email to support@fiio.com for further help.