Kurt,
You are correct, been fooling around with a couple of these headset for the past few nights, your post fixed my issue, didn't realize till I found this thread that the mic audio was basically balanced, grounding one of the mic lines to pin a fixed it. ow have the headset working on a PRC-174 HF pack radio. Works pretty well except the mic element is very very hot (lotsa gain) The PRC-174 provides B+ on Pin E. So had to modify the connections down in the U329 accordingly. Grounding one side of the mic and the B+ line to pin E. No connection to pin F. Normally in the CX-14379 on AP107 #7 would go the U329 Pin F, moved it to U329 pin E. Also not sure because all my AP107 line came loose and had to kinda figure them out, but am using AP107 # 4 to blue wire (one side of the mic) go to U329 Pin Ground. Not sure about radios that don't have B+ available at their audio connector, will have to get another CX-14379 and modify it for audio connections only, have read that the headset can work un-powered, if so the headset just wouldn't have the ANR function.
Thanks for you post that straightened me out.
Steve
KM4V