I use HF player by onkyo. But remember, if you have high resolution music files like flac. Or DSD, you'll still need a high res dongle to get the best sound even though the s21 ultra claims to have a high resolution dac chip. I have an astell&kern dongle and it's awesome. When I'm home, I use my astell&kern Kahn alpha with audio technica ath m50x headphones, or hooked up to my mcintosh Ma6100 amp through klipsch heresy 2 speakers.