3. Buttons and ports instruction of M21

What are the differences between the two USB ports at the bottom of the M21?

The port marked "USB3.0 supports" functions such as data transfer/charging, USB HOST, and USB OTG. The port marked "POWER IN" only supports charging/power supply and cannot be used to transfer data to a computer.

Note: The POWER IN port only supports PD2.0/3.0 fast charging, while other types are recognized as normal charging. When connected to PD3.0 fast charging via the POWER IN port, the maximum charging current can reach approximately 3.5A.

How to use the multifunction button?

1. In Player mode: Add to Favorites (default option), Play next song randomly (randomly play the next song according to random play rules), Play/Pause, Delete currently playing song, Switch filter (cyclically), Switch equalizer (cyclically), Enter USB DAC Mode, Enter Bluetooth Receiving Mode, Lock screen/Wake up, No function

2. In Bluetooth Receiving mode/USB DAC mode, the multifunction button is forcibly set to: No Function.

Note: This button only responds in Android mode/Pure Music mode, and some functions only apply to FIIO Music.

The input priority between 3.5mm and 4.4mm headphone ports

The output will be given priority in the order of insertion.After connecting to the 3.5 port and then connecting to the 4.4 port, the sound will still come out of the 3.5 headphone port.

For better output effect, two headphone ports are not supported to output at the same time.

What are the contacts on the back cover used for?

It's the signaling contact between the M21 and the tape case.

What TF card is recommended for M21?

Theoretically, the M21 supports TF cards up to 2TB. The Sandisk SD card is recommended.