Square dance speakers, with a microphone shouting, the sound is normal, is inserted into the memory card, can not play the song, only a very small da ~ da ~ da ~ current sound!

Microphone shouting, just use the analog circuit of the PA part.

Memory card more digital circuitry, digital circuitry part of the card must first read out the data and converted into audio signals and then sent to the analog circuit of the PA part of the final after the speaker to broadcast the sound.

So when something goes wrong with the digital circuitry, the card can't play the song.

Check with your computer to see if the card is defective? Is there still not a song inside the card? And could the card not be loaded properly?