Turning our attention to the FET input board, we will replace the 470 pF input coupling capacitor with a film type, remove the 560 pF pad cap, and cut 2 of the pins on the pad switch. These pins will connect to the very high impedance mic capsule, so they will be isolated from the PC board.

With parts removed, the board looks like this. The hardest part is snipping out small sections of switch leads. Small nose wire cutters are required. The 1 G ohm resistor will be reinstalled. It was removed for access to the switch.

With a new film capacitor and the resistor reinstalled, a wire is soldered from the input terminal to the cut outer lug of the switch. Now we’re ready to attach the wires from the capsule and reassemble the mic.

The backplate wire goes to the same hole on the PC board as before and the front diaphragm wire goes to the same standoff terminal. The wire from the back diaphragm goes to the center terminal of the switch. The switch connects the back diaphragm either to backplate (cardioid) or to the front diaphragm (omni).

Front

Back

The last little job is a label for the switch. Could be neater, I admit. Sound sample here.

Finally, quick frequency sweeps.

First, omnidirectional, 2 mics.

Second, cardioid, 2 mics.

5 Hz resolution, no smoothing.