One piece is used for parallel bridged bass channel power amplifier output, and the other piece is used for left and right channel power amplifier output. Can support 100W (bass channel) + 50W (left channel) + 50W (right channel) three-channel output.     With external audio source input interface, with pre-amplification, bass crossover processing; bass volume, bass frequency, left and right channel volume, treble, switch/total volume, 5 adjustment potentiometers.     Wide working voltage, power saving design, efficiency as high as 90% or more. You can use switching power supplies with good performance, laptop switching power supplies, rechargeable bottles, or car power supplies, etc...     Anti-shock protection design for booting, no POPS popping sound when booting     The board is a finished board that has been welded and tested. Connect the speaker box according to the diagram, correctly connect the audio input, and connect the appropriate power supply to use.          Direct current: DC12-24V (current 3-4A, or 19-24V/4-5A)     High power requirement: above 20-24V/8-9A     Audio input sensitivity: 600-800mV     Frequency response range: 20Hz-20KHz     Speaker impedance:     Left and right channels: 4-8 ohms     Bass channel: 2-8 ohms     colour: as shown     Material: Plastic + Metal     Size: 101x100x30mm          Package Contents:     1 x Audio Amplifier Board          Only the above package content, other products are not included.     Note: Light shooting 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.