The ST-MPA24 contains two identical phantom power circuits and a common power supply input. If only one mic input is to be converted for phantom operation, only one circuit needs to be used. Each circuit has a mic input and a mic output. Phantom voltage appears on each of the mic input terminals. There is no voltage on the mic output terminals. Therefore, the ST-MPA24 can convert any existing mic input into a phantom powered input.

Module operation is from a 24 Vdc ground referenced power supply. The ST-MPA24 has an internal pass transistor-regulator filter circuit which permits this incoming voltage to be adjusted to the desired phantom voltage, up to 92% of the supply input voltage. A multi-turn trimming potentiometer is provided to reduce the phantom voltage if desired. In the default fully clockwise position, the ST-MPA24 provides "P24" 24 Vdc phantom voltage conformant to IEC 61938.