Not only does the AD-20 not supply power to microphones, but its input circuit can't tolerate microphone powering. If you use any kind of microphone power supply with it, that power supply must prevent any DC from reaching the AD-20's inputs. Not all power supplies do so.
I once made the mistake of taking the AD-20 out for a recording along with a type of 48-Volt phantom power supply that doesn't block DC at its outputs. The AD-20 simply would not put out a signal, and the recording was a total failure. The singer whom I was asked to record has since become quite successful, and she thinks that I'm a complete idiot. And she may well be right--but my point is: Be sure to test the setup at home before taking it to the recording.
--best regards