USB Extenrnal Sound Card Stereo 3.5mm Interface Multi Mode Design Multiple EQ Sound Conversion Audio Adapter Item Type: USB Extenrnal Sound Card Model: AM-U004 Material: Aluminum Alloy USB C Function: Computer USB2.0 Input, Connected to Desktop or Notebook USB Interface EQ Key: Short Press to Switch Between Three Kinds of Sound Effects (Default Sound Effect; Music Sound Effect; Movie Sound Effect) Headphone Hole: Connect Stereo Headphones Headset with Microphone: Connect Headset with Microphone Microphone Connector: Connect Wired Microphone 3 x USB: 3 USB Hub Interfaces (when the USB Interface is Connected to the Headset, the Microphone and EQ Have No Effect) FL  FR: Stereo Output Mode Coaxial: Coaxial Audio Output, Connected to the Power Amplifier with Coaxial Interface For Toslink: Optical Fiber Audio Output, Connected to the Power Amplifier with Optical Fiber Interface Volume: Analog Audio Volume Adjustment (Increase Clockwise and Decrease Counterclockwise) Compatible System: For Windows,  for OS X, for Linux and Other Systems