Connect like this:
1. Replace the 48-volt to 12-volt DC\/DC converter with a 48-volt ± 12-volt DC\/DC converter.
2, purchase an SD card decoding board, a 7805 three-terminal voltage regulator.
3. Remove the transformer and AC input line in the chassis, install a DC\/DC converter at the position of the transformer, and connect the red and blue thick and soft 48-volt input wires to the input end of the DC converter through the AC input hole. Weld the DC converter to the corresponding positions of positive 12 volts, ground and negative 12 volts at the rectifier output end.
4, the SD card decoding board is fixed at the appropriate place on the edge of the speaker, processing an outward opening, the card opening faces outward, easy to insert the SD card. The decoding board uses a 5 volt voltage, and connects the positive 12 volts inside the machine to the 7805 input end, and connects the positive and negative 5 volts of the output to the decoding board. The decoder board outputs two wires of about 1 volt audio signal, distinguish positive and negative polarity and connect to the audio input terminal of the power amplifier, the left and right channels are connected together, the negative terminal is grounded, and the original signal input wire is removed and not used. 5, turn on the 48V power supply and insert the SD card with MP3 or WMA format songs to listen. 6. After normal, pack the box and hang it on both sides of the rear frame of the car, you can enjoy the music.