Hi learning,
first off, what is a "PA" microphone?
Microphones are normally capacitive (Electret) or inductive (dynamic).
Most today's main boards with integrated AF-amplifier don't have a mic preamplifier. Using the windows voice recorder you get a very weak signal only when shouting into the microphone.
Here are schematic and PCB layout for a PC-Mic-Amplifier.
T1 must be a BC550C (hfe > 600)
AF-OUT connects to the outer pin of the 3.5mm stereo plug and Ground connects to the sleeve.
Boncuk