Sony ECM-77 Lav Mic
 

I recently purchase this Lav mic for use with my Sony UWP wireless setup. The mic has a male stereo mini-plug at one end. About three inches from that end there is a small eight-sided plastic attachment (about half an inch long) that is clipped over the wire. It comes off and when it is opened up it appears to have two metal pieces inside that look like bushings from an electric motor. They actually look like magnets.

I have no idea what this is for. Nothing is said about it in the instructions.

Anyone have any idea what this is?

The mic works great and is a huge improvement over the stock lav mic that comes with the wireless transmitter.

Thanks

Curt

It's probably an electrical noise trap. If you look on the cable on your computer monitor and also on the cables connecting scanners, printers, and cameras you'll often find a similar cylinder that the wire goes through. The purpose is to trap radio frequency electrical noise that may be traveling over the outside of the cable that could interfere with the operation of the device(s) at one or the other ends. In the case of a microphone being used with a body-pack radio transmitter you'd want to prevent the RF from the transmitter from leaking up the cable and getting into the wiring of the mic capsule itself.