The first step of this project is to build a Electret Element test board.  I've chosen the Panasonic WM-61A element for this.  A basic circuit to power it is thus:

Here, the resistor is to restrict current flow and seperate the Vcc line from the audio signal, and the capacitor is used to AC couple the signal.

This audio is the fed into an opamp, I'll use NE5534 for this. Its only for test purposes, so doesnt have to be too fancy, just a general low noise one will be fine. The final schematic of the element and preamplifier look like this: