This tuning version of passive tuning board, the main function of the input audio signal for high and low frequency adjustment, and then sent to the amplifier board to enlarge The principle of the product is that the audio signal is directly filtered through the RC filter to get the desired high and low sound through the RC capacitor. The tone board does not need power supply, but the volume after processing will be much smaller. Product Name: Passive tone board Adjustable items: total volume treble bass Number of channels: 2-channel Knob spacing: 22.5mm Socket type: XH2.54 - 3P size: 56 x 28mm Material:plastic colour:green Package Contents: 1 x Passive tone board Only the above package content, other products are not included. Note: Light 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.