MKE 2002 output symetrisation

by mat
(france)

hello

I have this old stereo binaural microphone I got in the seventies. I has two electret mics and a little box with the batterie and a little electronic but it has also a stereo din assymetrical output tat is not good for professional use. I have tried just adding a xlr with normal connections but funny noises appear so I had to add a little resistor between ground and cold. Is there not a better way off doing this? looking at the pcb makes me think the is maybe something to do can someone help me?