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electret mic preamp gain
electret mic preamp gain
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Old 23rd September 2012, 02:01 PM   #1
emosms is offline emosms  Bulgaria
diyAudio Member
Join Date: Sep 2010
Default electret mic preamp gain

how to control the gain/sensitivity in the following schematic?
I thought it is R2 (1M) but it is biasing resistor, not a feedback like in opamp.
So, is it the R1 (4k7), load resistor for the fet transistor inside the electret mic capsule?
Best Regards
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Old 23rd September 2012, 03:02 PM   #2
DUG is offline DUG  Canada
diyAudio Member
Join Date: Jan 2003
Location: mississauga ontario canada
One way would be to replace R3 with a pot and connect C3 to the wiper

Generally if the mic is a two wire then R1 is external, three wire then internal.

Find the data sheet for your particular mic...or get one that you can find a data sheet for. (IMO)

Not all piezo mics have the same supply and load resistance requirements.
Doug We are all learning...we can all help
"You can't stop the signal, Mal. Everything goes somewhere..."
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Old 23rd September 2012, 06:53 PM   #3
emosms is offline emosms  Bulgaria
diyAudio Member
Join Date: Sep 2010
the electret capsule is 2 wire, I played with R1 - put a 10k pot.
At 10k goes up, at 0k goes away... just some unpleasant hum
but around 1k or 510 it has a low sensitivity and still clean signal - needed to pick a loud source like drums
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