The usual way to connect a 3-pin XLR to a 1/4″ TRS (AKA stereo jack plug) is to use the following pin allocation:
- XLR pin 1 to 1/4″ plug sleeve
- XLR pin 2 to 1/4″ plug tip
- XLR pin 3 to 1/4″ plug ring
This wiring configuration gives you a balanced mono audio cable.