Binaural input and output are often used to control small signals, between the and the preamplifier or between the preamplifier and the power amplifier, and are connected in the audio loop to control the volume. There are two interfaces: 3.5mm and RCA Lotus. It adopts type 09 potentiometer inside, which has good durability. The balance knob adjusts the volume of the left and right channels. Due to passive circuit conditions, the balance adjustment curve is smooth only when the master volume knob is 80%. Special reminder that this is not an amplifier. This unit does not require power supply and can only reduce the volume on the original basis. color: Black material: metal 4 rca interface input, 1 3.5mm interface input, 1 rca interface input, 1 rca output, 1 3.5mm earphone output; Multiple audio sources can be connected at the same time without affecting each other, can be mixed or output separately; Dc power supply 5-19v, the best use of linear power supply, switching power supply is easy to generate ; At gain, the rca output port is about 2x and the 3.5mm headphone port is about 4x. The 3.5mm headphone port directly drives the headphone The input and output are in stereo 4 volume controls Multiple rca interfaces input at the same time, no switch mixed output Product parameters: Dc power supply: 5-19v (preferably linear power supply, switching power supply is easy to produce buzzing) Port: 3.5mm, rca Usage: control of external volume power amplifier for earphone, plug and play Package Contents: 1 x Stereo 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.