3. CLASS A buttons and ports labeled

Front-panel input knob: Quickly switches between analog inputs, each corresponding to the matching input jack on the rear panel.

Front-panel BASS and TREBLE knobs: Hardware controls for bass and treble.

Rear USB port: Dedicated firmware-update port only; it cannot be used as a USB DAC.

12V trigger in/out: Can link power on/off with other external devices.

Red switch on the bottom panel: 110/220V voltage selector, marked with a high-temperature warning—avoid touching this area when the unit is hot.