DAC

TI Audio DAC THD+N SNR
PCM5102A FiiO E17K Aspen 2
PCM1798 FiiO Kunlun E18
High end PCM1792A FiiO X5 MP3 music player

Cirrus Logic
Flagship CS4398 FiiO X3 2nd gen

iFi Nano iDSD LE

Head-Fi review of USB audio on the go!
Headphone Amplifier, Digital Analog Converter

audioengine D3 24-Bit DAC no android, ios
audioquest dragonfly series - mobile compatibility Red, Black, android OTG, not 1.2
Cozoy Astrapi USB OTG
Schiit FULLA 2  Andorid, iOS
Meridian Explorer2  no android, ios
HRT dSp Android, i-dSp iOS
FiiO K1 no smartphone
FiiO i1 for iOS devices