Originally Posted by alexwhittemore
Interestingly, the shield pin on the mic itself is internally disconnected. Whenever you're shielding wire like that, you want the shield grounded on one side but not the other.
Anyway, I'd spring for shielded twisted pair wire anyway. It's an extra $20 on top of what you'd spend on cheap crap 22 gauge speaker wire from radioshack, and since it's on the mic line, the (substantial) added noise rejection will be noticed by the other end of your call, not you. Do them a favor
This is what I purchased. If the auction URL changes, it's shielded twisted pair wire, 25ft, from a seller named navships. Super high quality, really great stuff. Glad I have 14' left over after doing the install for myself and gjimmy. And for what it's worth, I never get complaints about audio quality on calls from the car
the grounding is done on the MULF side. if my memory didn't fail me, the connector on the MULF side uses pins 1, 19 and 21 with 21 the connection for the shielding.