SABAJ Audio D2 Audio DAC with Headphone Amplifier Silver Color Main function:USB/Optical/Coaxial input and 3.5mm/RCA output Headphone amplifer build in DAC Compatible with headphone ranging from 32ohm to 300ohm. Fitting:Micro USB line and OTG line USB input:16bit-24bit/32kHz-96kHz(asynchron), Optical,Coaxial:16bit-24bit/32kHz-192kHz Build in headphone amplifier function,Portable Headphone Amplifier,you can also use the 5V charging treasure Charging It has Smart Volume Memory,If you do not change the input mode,You do not need to repeatedly adjust the volume