I used the Fiio M21 for four months, and there's no doubt that this digital audio player is uniquely brilliant — it even has a desktop mode

With the M21, Fiio is showing that it can deliver a fantastic digital audio player on a budget. It still has all the best features of the M23, but it doesn't cost anywhere as much.

source https://www.androidcentral.com/accessories/audio/fiio-m21-this-digital-audio-player-is-uniquely-brilliant