Your friend here is a simple piece of wire with an alligator clip on each end; probably a couple of them.
Try the different grounding schemes, tying pin one to the shell at one end, both ends, or all ends of the cable.
Every connector you add increases the probability of a noise problem (generated through mis-wiring or a wrong connection scheme)
You have a connector at the console/preamp end, one at the wall going into the studio, another at the wall coming out in the studio then two on the mic cable.
Now, find out where the EMI is coming from.
Start with only the console or mixer or preamp fired up and start switching things in.
If it's coming in on the power line, you'll hear it on the board before anything else is turned on.
Are you in your own building or sharing space with other businesses?
Try some of the above.
Let us know what you find out.