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 5V-12V DC5.5 x 2.1, and the amplification is about 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 above package content is included; other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture to vary slightly from the real thing. Measurement may vary by +/- 1-3cm.