1.This is a stereo audio mixing board with four audio inputs mixed into one stereo output. (Four Input.One Output) 2.It can directly drive the headphones or connect the amplifier, the interface is 3.5mm stereo socket. 3.Each potentiometer individually controls the volume of each channel, and the volume does not affect each other. 4.The power supply is DC 5V-12V, and the magnification is about 2 . Tips: not include the Power supply. 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 earphones and external amplifiers. Please use low ripple power supply, please use shielded cable for audio cable. colour:blue Material:metal + plastic size:108x43mm Package Contents: 1 x stereo audio mixing board Only the above package content, other are not included. Note: Light and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.