I have a Lectrosonics M140-MC - Cardioid Lavalier Mic with Micro Mini Connector (2.5mm) that is used with a Lectrosonics Long Ranger 4 - Wireless Integrated Public Address Speaker and Microphone System (Basic System). We keep going thru the mics so we tried a less expensive mic. It still works however now we must use the aux input volume control instead of the normal volume control. The mic is plugged in the same location in the wireless unit. So the question is what is causing the switch in vol control when we switch mics?