1. The rated power supply voltage is supply 65V, and the voltage can work normally at 58---70V (cannot 70V, otherwise it will burn out). If it is a ring cow, because it does not have a voltage regulator function, the voltage will vary. If the power grid fluctuates, use the margin. Do not connect the positive and negative poles of the power supply wrong to avoid burning the board 2. The power supply is recommended to be a DC supply 65V power supply with better filtering 3. The speaker is recommended to use a 10-18 inch 4 ohm-8 ohm speaker 4. Although the audio output has short circuit protection, try not to short circuit 5. check carefully powering on to that the wiring is powering on. The voltage magnification of this board is fixed at 40 . If the output power is not enough, the -amplification will be added according to the situation size:98x43x30mm Material:PCB colour:Blue Package Contents: 1 x Amplifier 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 a little different from the real thing. The measurement allowed error is +/- 1-3cm.