I had the mics plugged into the CA 9100 preamp. I can't change the mic wires because they're permanently connected to the mics.
This sounds crazy but if I plug in some grado labs SR60 headphones directly into the output of the preamp, crank up the gain, it sounds like I have a walkman. However, if I wrap the microphone wires around the preamp itself, then the radio station goes quiet.