This is a mini audio mixer with four 3.5mm inputs, one 3.5mm AUX output, and a 3.5mm headphone jack output. It can mix signals from CD players, musical instruments, portable recording devices, video playback devices, and more. When connected to a USB power source, the built-in audio amplifier chip functions, amplifying the mixed audio signal for a louder sound. No external power supply is needed. However, the sound will be quieter. I have used this with a Switch, PC output, and smartphone output. I am now focusing on sound quality, so I am selling this. Audio interface with four knobs, and master volume control. - Model: Audio Interface - Number of Knobs: 4 knobs - Output Terminals: 1/4 inch output terminal - QC Pass: QC PASS 06 - Master Control: Master volume control Thank you for viewing.