SABAJ Audio D1 Portable Headphone Amplifier with Build-in DAC Black Color Easy to use ,no need build-in battery.Decoding for PC and phone fastly and directly Compatible with headphone ranging from 32ohm to 150ohm. With optical output can be as a mini digital convertor.3.5mm headphone jack output. With volume button on handsome CNC aluminium cover. Note:when connect with phone,please prepare one piece of OTG cable, NOT fit all of android phone