Access to microphone gain adjustment.

[drewgates]

The v1 PCB does not permit sufficient access to the microphone's gain adjustment potentiometer, which is located on the back of the mic PCB. This problem might be averted by using a different microphone module, or by moving the mic-out trace to enable a hole to be drilled through the PCB (which would enable a small screwdriver to make adjustments.

In the present version, we have found that bending the microphone module away from the board, while less than ideal, allows access.