This is a stereo audio mixing board with four audio inputs mixed into one stereo output. (Four Input.One Output). It can directly drive the headphones or connect the amplifier, the interface is 3.5mm stereo socket. The Working Power Supply DC 5V-12V DC5.5 x 2.1, and the magnification is about 2 times. Each potentiometer individually controls the volume of each channel, and the volume does not affect each other. The quiescent current is about 8ma, and the NJM3414 low-voltage and high-current operational amplifier is used. The maximum driving current is 70ma, which easily drives various earphones and external amplifiers. color: blue material: metal Package Contents: 1 x Audio Mixer Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.