【1】 3 wire method

(1) There is no gain because a signal is FET SOURCE output.
(2) It may have a positive phase output signal from positive sound wave.

NOTE: Shown resistor is recommended value when DC voltage is +5V.

 

【2】 2 wire method

(1) This method can have approx.10dB gain because of FET DRAIN output. 
(2) It might have unevenness in output level because of FET gm difference.
     It may have a negative phase output signal when it has a positive sound wave.

NOTE: Shown resistor is recommended value when DC voltage is +5V