Electret mic pre-amp with AGC (or at least AGC circuit)
Hi there! 🙂
I'm working on one small project - something like spectrum RGB LED cube, and I'm searching, if there is any available pre-amp for electret microphone with AGC (automatic gain control).
I found e.g. MAX9814. The price is not lowest (on eBay) but the gain go low on low frequencies (up to -10dB around 30Hz).
Any other tips? 🙂
Thanks!
Hi there! 🙂
I'm working on one small project - something like spectrum RGB LED cube, and I'm searching, if there is any available pre-amp for electret microphone with AGC (automatic gain control).
I found e.g. MAX9814. The price is not lowest (on eBay) but the gain go low on low frequencies (up to -10dB around 30Hz).
Any other tips? 🙂
Thanks!
Last edited:
For reference you might study how the old cassette recorders did it, 99% of them had an electret driving a so called "ALC" (automatic level control) , another name for AGC .
Not to be copied verbatim, but as an idea with some real world values .
Such cassette recorders did not have a recording volume control, period, because they "self adjusted".
AGC control cell was a saturated transistor padding the signal, very easy to copy and experiment with.
Not HiFi at all, but I guess you want it for some kind of lights control, anyway not a critical Music reproduction job.
Such circuits were so popular that specialized "cassette recorder" ICs, with ALC built in, were made by the tens of Millions, go figure.
This is a Sanyo IC, the ALC control voltage goes to pin 5, is rectified from the output , follow the 680r > 4u7 path:
Just an example , you might try this simple discrete circuit which is just the ALC section, you feed your Electret Mic to it, use the compressed/limited output to feed whatever control circuit you have, you decide bandwidth and gain:
Not to be copied verbatim, but as an idea with some real world values .
Such cassette recorders did not have a recording volume control, period, because they "self adjusted".
AGC control cell was a saturated transistor padding the signal, very easy to copy and experiment with.
Not HiFi at all, but I guess you want it for some kind of lights control, anyway not a critical Music reproduction job.
Such circuits were so popular that specialized "cassette recorder" ICs, with ALC built in, were made by the tens of Millions, go figure.
This is a Sanyo IC, the ALC control voltage goes to pin 5, is rectified from the output , follow the 680r > 4u7 path:
Just an example , you might try this simple discrete circuit which is just the ALC section, you feed your Electret Mic to it, use the compressed/limited output to feed whatever control circuit you have, you decide bandwidth and gain:
Hi,
There are definitely old chips designed to do this,
used for dictaphones, WT's, CB radios and the like.
Generally they have no bass to speak of, purposely
so the time constant of the AGC is not upset by bass.
rgds, sreten.
Also checkout cassette automatic recording level circuits.
There are definitely old chips designed to do this,
used for dictaphones, WT's, CB radios and the like.
Generally they have no bass to speak of, purposely
so the time constant of the AGC is not upset by bass.
rgds, sreten.
Also checkout cassette automatic recording level circuits.
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