DiegoHG:
Or is there a way to connect all of the amplifiers to these same pins? If yes, how?
All of the amplifiers and the SD Card use MOSI MISO and SCK. And each of them also needs its own CS pin so that the Arduino can signal which one it wants to communicate with.
But I need pin 5 for the SD card
I did not say Pin5. I said the 5v (5 volt) pin.
...R