Electret microphone to speaker circuit

Thread Starter

PhoenixRisen

Joined Dec 16, 2020
2
Below is the circuit I created. I'm trying to to get the electret microphone to amplify through the PAM8403 amplifier into the 4Ohm 3Watt speaker. The PAM8403 has an operating value of 2.5V-5V, claims to work with speakers from 4-8Ohms, and speaker power from 2W-8W. Did I get connect something wrong or is a part (possible multiple) a dud?

Circuit Diagram.jpg
 

Thread Starter

PhoenixRisen

Joined Dec 16, 2020
2
Hello,

An electret microphone needs some power to work.
Read the following pages for more info:
https://www.epanorama.net/circuits/microphone_powering.html
https://sound-au.com/articles/mic-electret.htm

Bertus
Thank you for the quick reply, so to make sure I understood correctly: Not only does the amp need a power supply. The electret microphone needs a power supply as well. Based on parallel voltage, would the electret microphone be able to use the same battery pack? Connecting the amp and electret microphone, in parallel, to the battery pack?
 

Wolframore

Joined Jan 21, 2019
2,183
electret microphones are condensers... they need what's called phantom power not just amplification. It can be supplied as simply as using a resistor tied to VCC.
 

Audioguru again

Joined Oct 21, 2019
2,374
The Chinese amplifier has absolutely no detailed spec's. The datasheet for the PAM8403 IC shows that external resistors are used to set the voltage gain but the Chinese amplifier assembler did not say the resistor values or the gain. The gain is probably too low for a microphone.

EDIT: I forgot that with the mic and speaker near each other then the amplifier will produce acoustical feedback howling and squealing.
 
Last edited:

Audioguru again

Joined Oct 21, 2019
2,374
electret microphones are condensers... they need what's called phantom power not just amplification. It can be supplied as simply as using a resistor tied to VCC.
An electret mic uses electret material to provide 48VDC to bias the condenser in the mic but it has a Jfet impedance converter that needs to be fed about 0.4mA through a resistor at the mic output. The resistor should be fed a filtered voltage.
 
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