I'm still OK with them, and it was worth it, and "they are what they are". Despite their shortcomings, the small module allows a op-amp placed close to the mic. They will still allow me to check R+L phase and amplitude using my PC sound card line inputs.
If I'm inclined to modify more. I would lower the gain (more module mods) down to 5x from 23x (min without mods) to extend the bandwidth up to 100KHz. Then I would add a second stage to my jack+battery board. Its easy to find 3V op-amps with GBW=8MHz.
If I'm inclined to modify more. I would lower the gain (more module mods) down to 5x from 23x (min without mods) to extend the bandwidth up to 100KHz. Then I would add a second stage to my jack+battery board. Its easy to find 3V op-amps with GBW=8MHz.
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Hey sry for bump such an old thread but i'm trying to get rid of the hiss noise of this preamp module, did you advanced some on that way?
If you mean the AdaFruit with CUI CMA-4544PF-W electret mic ....
Capsule Signal/Noise is specced as 60dB. You just have to know that this is re: 94dB SPL (1Pa). Which puts self-hiss around 34dB SPL.
This is quieter than many homes.
It is louder than if you go out in my woods when no cars are on the road.
It is 10dB-20dB higher than good studio mikes, 14dB higher than good hearing aid mikes.
Sensitivity is -44dB re: 1V 1Pa. So 6mV at 94dB SPL, 6uV at 60dB down (the rated noise).
Hmmmm... the MAX4466 self-hiss is 80nV/rtHz which is 11uV over 20kHz. So the opamp is the first bottle-neck, but the mic capsule is not a lot better.
PUI Audio, AOM-5024L-HD-R is $3. It is bigger. It claims 20dB better S/N and also 20dB better sensitivity. Biasing appears same-as the other capsule. A "simple" swap should get you 14dB lower hiss. It dips past 13KHz. Note that it will overload on trumpet, drums, or close to stadium PA.
HD Series Microphones - PUI Audio | DigiKey
A quieter opamp gets close to 20dB better. There are many choices. The jellybean '5532 will work on a *fresh* 9V battery and give self-hiss below mike hiss.
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I'm using a li-ion battery 14500(AA size) 3.7v, very clean source I think.
I know that is not the best opamp for audio but i like it for the size. (just made a 'circuit bend' adding it internally to the Korg Pandora-mini effects processor so i can use a mike for playing my sax ^^)
What i want is to clean more the hiss noise of the module so I can stop abusing the 'noise reduction' effect of the Korg unit, which have undesirable side effects..
Already cleaned the power source decoupling it from the pandora circuit (resistance+capacitor) and got rid of the buzzing added from that circuit to the preamp.
Don't know what more to do to reduce the preamp module inherent hiss, maybe just need to accept it (its not tooo bad really..) because the Max4466 is crap and not designed to professional audio use.
If you know a way please tell me. Thanks so much.
Ps: btw im using another capsule not the trash one of the module, desoldered it and connected a good old nice sounding japanese Audio Technica capsule which i striped from an old hand mic i had. ^^
I will look to the PUI audio module, thanks.
For the 'jellybean' i can't use 9v, just the 3.7v from the 14500 li-ion battery whichs holds perfect in the Pandora casing (and i can't put an step-up module to raise voltage too because that will add too much switching noise).
Have you modified the module filters or gain ?
I modified mine for measurement bandwidth and as long as the THD was around -50dBr I was OK with it because the speaker(s) were no better. My sound levels are probably higher than your application so you might have alot more gain applied.
I run mine from 2xAA batteries but they used to provide +/-1.5V bipolar supply so I get a virtual ground.
I modified mine for measurement bandwidth and as long as the THD was around -50dBr I was OK with it because the speaker(s) were no better. My sound levels are probably higher than your application so you might have alot more gain applied.
I run mine from 2xAA batteries but they used to provide +/-1.5V bipolar supply so I get a virtual ground.
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