Homemade electret mic power supply

[dusty summers]

I am attempting to make a power supply for a homemade electret mic connected to a 1/4 inch mono jack, which will then be plugged into the power supply. The recipe comes from the Nicolas collins "art of hardware hacking book". A 9v battery is run to a mono socket, then to a 2.2k resister, then a .1uf capacitor and another mono socket. Each mono socket has two soldering points and I am unsure of which goes to the tip and which goes to the sleeve. I am also uncertain of whether or not the socket will run the power from the 9v to the 1/4 inch plug thus powering the electret element. Sometimes, when I blow into the capacitor it seems to pick up sound like a contact mic, does that mean it is receiving power and could be damaged? Or simply functioning that way because it is not recieving power??

[Huntingdon 361]

Originally Posted by dusty summers

I am attempting to make a power supply for a homemade electret mic connected to a 1/4 inch mono jack, which will then be plugged into the power supply. The recipe comes from the Nicolas collins "art of hardware hacking book". A 9v battery is run to a mono socket, then to a 2.2k resister, then a .1uf capacitor and another mono socket. Each mono socket has two soldering points and I am unsure of which goes to the tip and which goes to the sleeve. I am also uncertain of whether or not the socket will run the power from the 9v to the 1/4 inch plug thus powering the electret element. Sometimes, when I blow into the capacitor it seems to pick up sound like a contact mic, does that mean it is receiving power and could be damaged? Or simply functioning that way because it is not recieving power??

This is the way your jack sockets and components should be wired. You should be able to determine which contact is tip and which is sleeve by examining the jack sockets.


If you are still uncertain about anything, feel free to ask again.

[bob91343]

An electret needs no power supply. It's built in. A condenser/capacitor microphone needs a 'phantom' supply but an electret is just that. It's a plastic with a built in charge.

[Mooly]

Originally Posted by bob91343

An electret needs no power supply. It's built in. A condenser/capacitor microphone needs a 'phantom' supply but an electret is just that. It's a plastic with a built in charge.

I have never seen just the electret mic available on it's own. Don't they always include an FET buffer?

http://en.wikipedia.org/wiki/Electret_microphone

[leswatts]

Most of the small panasonic types have a built in fet. The fet is specially designed for that purpose and has increased gate leakage to bias the capsule.

For best results modify the internal circuit from common source to common drain.

You can buy electret capsules without a fet from places like Transound.
These can give very nice performance with a good low noise fet and resistor biasing.

Les