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1935 Mini Electret Microphone Question
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1935 Mini Electret Microphone Question

by Korsakovsky on Thu Jul 29, 2021 10:28 am

Hi! I'm trying to build a microphone that could be plugged directly into a guitar-tuner pedal.

Basically building a microphone into a 1/4" audio plug.

This one seems to be high-impedance and wouldn't need a preamplifier, and could therefore be plugged directly into a tuner-pedal.

What I can't tell is if it would need power?

https://www.adafruit.com/product/1935

Thanks!

Korsakovsky
 
Posts: 23
Joined: Mon Jun 18, 2018 1:42 pm

Re: 1935 Mini Electret Microphone Question

by adafruit_support_mike on Mon Aug 02, 2021 12:09 am

That's just the electret element: basically a jfet whose gate is controlled by a film of electrically charged plastic. The FONA has all the remaining circuit for an electret preamp, so you can get away with connecting the mic straight to the board.

All microphones need preamps in one way or another. The sound-to-electric conversion just isn't powerful enough to produce big signals.

We don't have any preamps that would fit in a 1/4" plug, but making one as a freeform circuit wouldn't be too hard. You could use our MAX4466 breakout as a design reference:

https://www.adafruit.com/product/1063

Change the layout so it's longer, and you can make it narrow enough to fit in a 1/4" audlo plug.


Power could be a bit of a problem. Most mics use phantom power, meaning both lines connected to their output sit at about 12VDC. Then the cable has a GND line, and the preamp draws its power from the offset between the signal lines and GND. If you can do that, you'd just need a small voltage regulator to drop the line offset to 3.3V for the preamp. Again, that won't be difficult because most simple linear regs come in packages the size of a grain of popcorn.


If you don't have the option to use phantom power, the next solution is to build in a battery. That will consume more space, but coin cells are pretty good these days. You can probably even tear apart some cheap wireless earphones to get a LiPo that fits in a tight space.

adafruit_support_mike
 
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Re: 1935 Mini Electret Microphone Question

by Korsakovsky on Mon Aug 02, 2021 11:49 am

Thanks very much for that!

And for such a detailed reply.

I very much appreciate it.

Korsakovsky
 
Posts: 23
Joined: Mon Jun 18, 2018 1:42 pm

Please be positive and constructive with your questions and comments.