Connecting a microphone.

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Cosford

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Greetings all,

Been doing a lot of DSP related stuff at university and would like to have a crack at audio visualisation. I'm aware the Audio library has good facilitation for FFT so I'd like to try that out.
My analogue electronics is pretty poor though; any recommendations on a part(s) to use to hook up a microphone to Teensy to perform FFT with? And a circuit diagram ideally?

Thanks in advance,
Cosford.
 
https://www.adafruit.com/product/1063
can go straight to the adc ... is used for fft visualisation reaction type projects.

Edit ... from the website ...

The output will have a DC bias of VCC/2 so when its perfectly quiet, the voltage will be a steady VCC/2 volts (it is DC coupled).

perfect for an adc without additional components
 
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I can't find voltage bias or peak to peak values for that board, but if I'm understanding the schematic correctly then that board is already doing everything you need and could be connected directly. Hopefully someone more knowledgeable about analog sound can weigh in if I'm wrong; the schematic for Cosford's board is at

https://www.sparkfun.com/datasheets/BreakoutBoards/Amplified-Mic-Electret-v14.pdf

Jep, that's ready to be hooked up to the teensy directly. The used OpAmp is 3.3V-compatible and is set to a gain of 100. You could adjust the gain by changing the 1MegOhm resistor (R5). This will drive Teensy's ADC input very well.
 
Excellent. Thanks for the help all. Will see how I go; give me something to procrastinate with over christmas rather than revising for exams. ;)
 
Just a thought... I spent lots of time using a cheap electret mic, and the circuit in the audio library's GUI tool for adc input. It took some fiddling to get the connections right, several caps and resistors, but worked fine as an input to the fft1024 object. I've made a decent pitch detector from it.

I have since moved to the audio board, and the wiring could not be simpler - still using the cheap electret, but no extra caps or resistors or wires. It also offloads any adc work from the teensy, which instead gets a steam of i2s data from the audio card. I also get simplified outputs all wired.

It's pretty slick - ok, that's an understatement. I've also tested the SD input, and plan to use it in my project.

Well worth the money for me.
 
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