The board uses six disassemble amplifier tubes(used), 4 responsible for the left and right channels, the other two connected to BTL circuit for subwoofer use, wiring is simple, especially for DIY. Working : AC double 18-24V 100W transformer output power: 3*80W Max subwoofer output: 120W Max Left and right channel output: 100W+100W Load impedance: 8ohm Frequency response: 20Hz-30KHz Distortion: 1% Size: 158 x 167 x 42MM Channels: 3 (2.1) Model Number: 2.1 240W Feature: Audio Amplifier Board 2.1 Channel 240W color:Photo color Material:plastic Package Contents: 1 x Karaoke Reverb 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 a little different from the real thing. The measurement allowed error is +/- 1-3cm.