Using a "real" microphone?

[bird_furniture]

Hi all,

I'm working on a project which needs a microphone input. For prototyping, the tiny electret condenser that's recommended for Teensy worked fine, but now I need something with higher audio quality, better rejection, etc. I'm using Teensy 4.0 with the Audio Shield.

I'm fully prepared to cannibalize a "real" microphone, and it seems like my options are as follows:

- use an analog mic, then use an amplifier to bring it up to line level for Teensy's line in
- use an analog mic, then use an ADC to translate it for i2s input
- use a digital/USB mic, and somehow feed that into i2s

Would anyone be able to point me in the right direction here? Surely I'm not the first to need a beefier microphone with Teensy, but I'm having trouble finding other threads on the topic. Any suggestions would be much appreciated!

[weasel]

i think the easiest/cheapest/most convenient solution is also the most common signal chain in professional audio surroundings - get a preamp to push the mic output to line signal levels, your first option. make sure you pick a microphone that does not need 48v phantom power, ie. use a dynamic microphone.

there are plenty of very cheap mic preamping circuits out there, so that shouldn't be an issue. for example the famous 5$ mic preamp.

of course your second option works as well, but depening on the ADC you might still need pre-amping/attenuation to get the mic output in the right voltage range.
third option sounds like an ugly bandaid workaround to me.

[bird_furniture]

Thank you! This is very helpful. I will look into that $5 preamp, seems like the way to go. I'm glad not to have to resort to that third option...

Thanks again!

[ETMoody3]

The chip in the "5$ preamp" is more like $7 but it's still a great circuit.

[alex_vy]

Been reading this thread, since I also plan to hook up a handheld dynamic mic (eg.Shure SM58 or similar).
Why couldn't I just use the mic input on the audio board to connect it to?

[jonr]

You can, although noise may be a concern.

[ETMoody3]

The mic input on the teensy audio shield is designed to allow easy use of common electret condenser capsules.

[ETMoody3]

The mic input on the audio shield isn't just an audio input, there's a biasing source.

[MarkT]

Been reading this thread, since I also plan to hook up a handheld dynamic mic (eg.Shure SM58 or similar).
Why couldn't I just use the mic input on the audio board to connect it to?

Definitely rather noisy, dynamic mics are low impedance and a good mic preamp is needed to get a good
noise figure - otherwise there's little point moving to a professional microphone in the first place. And without
a differential input the EMI/hum pickup would be an issue.