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5532 1st order bandpass for electret mic preamp

Question asked by ITPhoenix on Nov 26, 2012
Latest reply on Dec 11, 2012 by ITPhoenix

I found the capacitors that give the desired response.  The mic runs straight into the non-inverting, with R1 at 50k and R2 at 10k in the negative feeback loop.  It works perfectly but when I attempt to increase the gain by increasing the value of R1 but does not gain as it should, even at 100k.

 

I had tried the awesome SSM2219 and had no problems with the one-resistor gain adjustment.  I was able to pick up dogs barking two block away with just the window in the room open. So does the resistor combination have to change for extended gain ranges or are the caps influencing the feedback?

 

The band is about 500-3500Hz, first order.  The application is a speech recognizer which requires the substance of 300Hz-10khz.  However, the electret's frequency response is not flat, and begins to rise substantially after 3500Hz.  The lows are being attenuated to reduce background noise, and also the highs to some extent, but this particular electret takes a dive after 10kHz anyway.

 

Any pointers will be appreciated.

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