Woo Audio 2nd gen WA7 Fireflies Headphone Amplifier/DAC in Silver High Performance 100% Vacuum Tube Design Headphone Amplifier with DAC 24-Bit, 384kHz ESS SABRE DAC for high resolution audio playback Ultra quiet 1/4" and 3.5mm (for IEM) headphone outputs, Hi/Lo Impedance switch Multi-functional switch for USB input, RCA input, and RCA output for D/A mode Available in Black or Silver color. External Linear power supply. Teflon tube sockets, High clarity glass top for tubes protection