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MAX9814
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MAX9814

by stuartiannaylor on Sun Aug 02, 2020 1:15 pm

Electret Microphone Amplifier - MAX9814 with Auto Gain Control

I am starting to really like this little the only thing I can fault it on is the choice of tC of 100nf.
You can also change the Attack/Release ratio, from the default 1:4000 to 1:2000 or 1:500.
I understand 100nf was chosen as its center of table 2 of the datasheet https://datasheets.maximintegrated.com/ ... AX9814.pdf
So what happens like the product info you give you end up just leaving the input floating to get the max AGC attack/release time.

Even now the longest AGC attack/release time is still extremely fast and reactive for voice patterns.
I swapped out CT for a 680nf and wow it does work a lot better.

So I did a bit of googling and generally with AGC 1-2 secs attack is a norm and here is what Shure say, just to back my tinkering.

Note that the AGC is not meant to have a short attack time. A long attack time of 1-2 seconds or more is appropriate. The decay time should also be several seconds. If attack times are too short, the AGC responds too quickly and the benefit of the speech detector is lost.


The 100nF, 0.24, 120, 480, 960 of CCT tATTACK, A/R = GND, A/R = VDD, A/R = UNCONNECTED

Puts it in a A/R where unconnected it just about becomes useful for AGC.

Would be so good as it would incur no further cost if Cct was swapped to say 680nf or even 1uf to garner an actually working A/R range for AGC

stuartiannaylor
 
Posts: 15
Joined: Wed Feb 06, 2019 1:15 am

Please be positive and constructive with your questions and comments.