Precautions for use: The board is powered by DC, do not directly input AC, use an AC transformer, and connect an external rectifier bridge and filter capacitor. In addition, the DC power supply should not exceed 50V or less than 20V. It will not start if it is less than 20V. In addition, the output power is related to the power of the power supply, and the power at 50V will be more than 4 times larger than that at 20V. Product name: Audio power amplifier board Total harmonic distortion (+N): Less than 1% Signal-to-noise ratio (): 100dB Input impedance: 20K Output offset voltage: Less than 150mV Voltage gain: adjustable Conversion rate (): 50V/us Frequency response range: 20Hz--20kHz Power supply range: DC20-DC 50V Product : AD827 op amp is used as the left and right channel preamplifier, the dynamics and details are excellent, and the most notes are also revealed. Parameter index: (subwoofer channel) DC=50V, R=4, +N=10%, P=300W When DC=50V, R=6, +N=10%, P=210W When DC=50V, R=8, +N=10%, P=160W When DC=50V, R=4, +N=1%, P=240W When DC=50V, R=6, +N=1%, P=160W When DC=50V, R=8, +N=1%, P=125W Size: 140 x 102mm Material:PCB+metal colour:As shown Package Contents: 1 x Audio 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 picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.