I've got a few electret microphones and I tried to make this circuit:
It didn't amplify my sound, it continuously buzzed. Without mic it did same thing. So I probed mic and I saw 0.000v. Also 0mA (shorted).
I tested 5 microphones sitting next to each other, they all had same results. There was a neodymium magnet about 3-4cm next to them. Are they broken? Or is there something else wrong?