FET conversion project

According to the manufacturer of this microphone it uses a Field Effect transistor and was the first microphone in history to do so beginning in 1965 when it was released.

 

I just found this cool coupling capacitor calculator for tailoring low end frequency response.
https://www.v-cap.com/coupling-capacitor-calculator.php

 

I just found this bypass Capacitor calculator.
http://www.learningaboutelectronics.com/Articles/Bypass-capacitor-calculator.php#answer

 

I did some experiments today.
I changed the pull-up resistor to 1000k and I changed out both coupling capacitors for different values.
1uf and 47uf switchable between the two.
Noise cancelling doesn't seem to work well.
Back to the drawing board.

 

Original Telex Turner RK56 vs Electret with 1uf blocking cap. Hard to beat the Telex Road King 56.