I have a microphone distribution switch box in my shack where I route my one single desk microphone to multiple transceivers (ICOM/Yaesu). My question is how do I build a cable for my distribution switch box to connect to a 6400M? Per the 6400M User Guild (Section 4.3.19) it states the plug on the 6400M is a balanced input and to connect the shield (Negative) side of the microphone cable to the RING on the plug and not to the ground shield sleeve of the plug. The switch distribution box has all the cable shields connected to chassis earth ground. It is OK to connect earth ground to the plug RING or do I need to have some isolation of the microphone ground shield when I connect it to the RING of the plug ?