This is a stereo audio mixing board with four audio inputs mixed into one stereo output (Four Input, One Output). It can directly drive headphones or connect to an amplifier; the interface is a 3.5mm stereo socket. The working power supply is DC 5V12V (DC 5.5 x 2.1), and the amplification is approximately 2 times. Each potentiometer individually controls the volume of each channel, and the volume levels do not affect each other. The quiescent current is approximately 8mA, and it uses an NJM3414 low-voltage, high-current operational amplifier. The maximum driving current is 70mA, which easily drives earphones and external amplifiers. Color: Blue. Material: Metal. Package Contents: 1 x Audio Mixer. Only the items listed are included; other products are not included. Note: Light reflection and differences in display screens may cause slight variations in the color of the item shown in the picture compared to the actual product. Measurement error allowance is +/- 13 cm.