Dual channel input and output, used to control small signals, between the and the front stage or between the front stage and the power amplifier, string in the audio loop to control the volume. 3.5mm, two interfaces, the internal use of 09 potentiometer. Balance knob is to adjust the volume of the left and right channels, due to the passive circuit conditions, balance adjustment only in the main volume knob below 80% of the adjustment curve is relatively smooth. Colour:black Material:Metal Size:. 87 x 38 x 38mm Package Contents: 1 x Volume Controller Amplifier 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.