How to connect microphone mono to stereo power amp
You probably need a pre-amp first. That power amp will probably require &quot;line level&quot; input, i.e., a signal over 2 volt peek to peek, although you might have a sensitivity knob where you might get the sensitivity lower. But if that picks up a microphone signal is questionable, the voltage level may be too low and impedance not matched. That is why microphones have different inputs on HiFi equipment and stage sound equipment have a sensitivity gain control to deal with guitar pick-ups and microphones. A power-amp is intended to just blast a normalized leveled and mixed signal to full power ear-destroying boom blast levels as desired.
As for mono / stereo, microphone inputs would normally be mono, unless you have two microphones or a &quot;stereo microphone&quot; (which is two microphones in one.) Since you are already having a low level, if you divide it up over 2 channels of a stereo input, you effectively reduce the mic level even more, to half of its already insufficient level.
Of course there are passive and active microphones, the active ones would have a battery inside and they might or might not produce line levels. There are also power amps with sensitivity/gain controls that can be dialed very sensitive. So your mileage may vary and success with one pair of equipment isn't a refutation of the general points made here.