Small signal analysis of dynamic microphone preamplifier circuit
Agreed with jonk and bimpelrekkie. Look at BJT's and if you want to do analysis on simpler terms think of the BJTs as a two port network. Open the collector,base, emitter and short the collector, base and emitter and perform KCL and KVL. Gain is just difference in output over difference in input. For reference look at small signal analysis of Class AB amplifiers and maybe it will lead you to the answer you are searching for.