Hi @BradB ,
That board has a common Ground - the two G pads are connected together. But the four ideal diodes are independent of each other. IN1 feeds only OUT1 etc.. To use it as a power “multiplexer”, you will need to connect the outputs to each other:
Make sure all your power source grounds (0V) are connected together
Connect one of the G pads to your common ground
Connect each individual power source positive (V+) to an individual IN pad
Connect the OUT pads together
Power your amplifier from the combined OUT plus common ground
I hope this helps,
Paul