1. The rated power supply voltage is dual power supply ±65V, and the voltage can work normally at ±58---±70V (cannot exceed 70V, otherwise it burn out). If it is a ring cow, because it does not have a voltage regulator function, the voltage vary. If the power grid fluctuates, please 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 dual power 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. Please check carefully before powering on to that the wiring is correct before powering on. The voltage magnification of this board is fixed at 40 times. If the output power is not enough, the pre-amplification be added according to the specific situation size: 98x43x30mm Material: PCB colour: Blue Package Contents: 5 x Amplifier board 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.