Quick question for what I hope might be a simple circuit. I just set up an ultra sensitive electret mic to monitor some bird activity near my residence. There was no AGC used, so when a jet flys close, it sounds like my speakers are going to burn out from the loud sounds. Of course, i suppose I could build an AGC, but was looking for something simpler, maybe something that would mute the audio when a certain audio level is exceeded? Suggestions for such a circuit would be welcome. It would be placed between the mic output and speaker. Thanks in advance.
audio muting circuit at certain threshold?
Jan 11, 2022
Last reply: 4 years ago
2 Replies
formatting link
Is a start. Battery power adds complication.
Peter Wieck Melrose Park, PA
There's an integrated circuit, LM13700, that has this basic function. See figure 17 here
formatting link
That example uses one half the chip, and responds to pulling the 'gain control' pin low when the sound is too loud. The tricky part is, you use the other half of the chip to amplify, rectify the sound from AC to negative DC, smooth the DC with a capacitor, and steal some current from the "Iabc" circuit node while that capacitor stays negative. It's just a couple of capacitors, diode, and a lot of fiddling with resistor values.
Alas, it's an oddball chip, and an oddball kind of design.
Join the Discussion
Have something to add? Share your thoughts — no account required.
Didn't find your answer?
Ask the community — no account required