Get rid of electret microphone buzz

So you get an audio module consisting of a preamp running on DC and an electret microphone in a metal capsule, connected by two wire line to the preamp. You plug it into either CCTV camera audio input or microphone socket of your PC and there is a buzz. A loud humming noise. Sometimes it is the hum of 50 Hz (60 Hz I suppose if you are in the States) electric power line,  sometimes it is a loud tearing noise or similar…

01

When you touch the body of the microphone, the buzz is gone. Nearly complete silence! Slight hiss remains, but we can live with that, that’s common…

You look for a solution. You read on-line a lot about audio equipment noises, grounding issues, ground loops etc., but the information is insufficient, superficial and more often than not is provided by incompetent individuals. It does not help the least.

The solution is simple.

Shield the damn thing!

02

Quick and dirty fix:

  • Get some scotch tape.
  • Get some kitchen foil.
  • Tape the scotch over your preamp to protect it from short circuit.
  • Tape a small piece of scotch over the microphone’s terminals for the same reason.
  • Tape over any other bare electrodes just to be sure.
  • Wrap the foil over the whole thing, including the preamp, the wires to the mike and the mike itself. Leave the very end of the wrap open for the mike to hear sounds.
  • Keep the wrap away from any power lines, including the preamp’s own DC power line.

03

Funny enough, but even flat sheet of foil, just placed underneath the set (pic No.2), is suppressing the noise at times. The mechanism of action is not clear to me.

Still, I did not go into research on the details, and it seems that it still works best if all three parts (preamp, wires, mike) are shielded and these shields are electrically connected, with the mike’s shield touching its metal body capsule. Some of it may be overkill, but it always works, and that’s what matters.

Any comments or recommendations?

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One Comment on “Get rid of electret microphone buzz”

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