noise problem with cable

Some equipment is hot pin 2, other equipment is not. I don't know about your equipment but both manufacturers should have specs disclosing that.

If either hot or ground is reversed between those pieces, either through original design or reversal of signal via your cheater, the problem you describe could occur.

Depending on what conductors are used in the construction of the cable, you may be able to remove the XLR and switch to RCA.

Do you have an MIT dealer around you can talk to? Or just call the factory and ask if that's possible and what it would cost. Even with ship charges it may be cost effective opposed to selling and investing in another cable.