Electret Microphone circuit

[xaleks]

Hi there,

I've taken apart a dual electret microphone with the aim of understanding its circuit. The Microphone is powered from a 1.5V AA battery, and is able to switch between Vout(1) and Vout(2) 'Tele' and 'Normal' modes apparently.

I've measured and drawn the schematic in LTSpice to show you what I am up against.

I am aiming to replace the circuit with something that doesn't hiss, but wanted to understand the existing circuit before I move onto its replacement.

The Electret Mic modules in question is the CZ034GU, nothing fancy.

The ceramic capacitors values were marked, but not their units.

Could anyone walk me through the design?


Best Wishes

Xaleks

 

[KlausST]

Hi,

capacitor values you can find in the internet. It is similar to resistors, but in pF.

example:

224 means: 22 x 10^4 pF = 22 x 10000 pF = 220000pF = 220nF

(I marked the "0000" in the same color as the "4", because there are "4" zeroes)

Klaus

 

[xaleks]

Klaus,

Thank you for the info on the capacitors, I'll update the simulation values now.

Xaleks

 

[Audioguru]

The transistors are simple "common emitter" amplifiers. The capacitors block DC but pass audio. R1 and R10 power the Jfet inside each electret mic.