Can anyone suggest a circuit as to how I can add an amplifier to an electret mic without requiring a seperate power supply? I.E. convert the first circuit into the second? Pull up resistor, voltage, and coupling cap can not change.

 

Something like this?
or missed the question

 

3.3V would power a discrete transistor amplifier or an IC amplifier.
https://www.mouser.co.uk/Semiconduc...tional-Amplifiers-Op-Amps/_/N-4h00g?P=1yzmlzm

 

Something like this?
or missed the question

That does not provide bias for the Electret mic. And no, I can't run a separate Vcc line.

As further info, I've got a Baofeng UV-5R. These are know for low audio levels (put the unit right up to your mouth and talk loud - if your nose is not touching the unit the audio will be insufficient). FIgured I'd go with an external mic/speaker, but reports are that this has the same problem. Would like to be able to go into the mic case and add an amplifier without having to add batteries to the mic.

 

3.3V would power a discrete transistor amplifier or an IC amplifier.
https://www.mouser.co.uk/Semiconduc...tional-Amplifiers-Op-Amps/_/N-4h00g?P=1yzmlzm

For power, I have available 3.3 VDC with a 3K resistor in series. Need to same voltage source/output line to supply power both to the electret mic and the amplifier.

 

No amplfier can work without a power supply.

 

I made this a while back and works great for a chip recorder needing a 32mV input. But for the life of me, I don't see any way to power it and output the audio on the same wire.

 

A slight variation of post #2 will allow the Electret to be biased ...

 

The amplifier would get power from that 3.3v/3K source. Was thinking of something like this, but I am having trouble getting enough current to the mic element without loading down the amplifier section until there is no gain left. [edit: The +3.3 volt source should be shown inside the transceiver block]

 

I made this a while back and works great for a chip recorder needing a 32mV input. But for the life of me, I don't see any way to power it and output the audio on the same wire.

Won't the 47uF on the mic output completely remove any audio?

 

I made this a while back and works great for a chip recorder needing a 32mV input. But for the life of me, I don't see any way to power it and output the audio on the same wire.

I've only got 1 wire and ground coming out of the transceiver. This circuit would require a separate power source.

 

Yes AlbertHall. I goofed drawing the schematic. The 47uF belongs at the top of the resistor.

 

If you had a dynamic microphone you could use a transformer, but with an electret mic you're going to need a voltage source.

We might figure out how to get power and audio on the same conductor. Can you get clean voltage that can be used to power the preamp?

Have you looked for a microphone with better sensitivity or a built-in preamp?

 

Attached a schematic snippet. (I'm pretty sure the wiring on the external mic jack is not quite right) Looks like I might have a separate +3.3 volt source available through R71, depending on whether or not it is brought through the cable up to the hand held speaker/mic I ordered. (This will be the mfg recommended external speaker/mic). If I do have that +3.3 volts available at the mic, I might go as far as to try using a SSM2167. Should have the mic in a couple days.

 

The connections to J1 are shown incorrectly.
Pins 1 & 2 are swapped. Pins 3 & 4 are swapped.