Electret Mic Severe Clipping

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bendesign
 
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Electret Mic Severe Clipping

Post by bendesign »

Hi there,

Sorry if this basic question is already covered elsewhere, I could not find it.

I am trying to build a simple system to reproduce my voice at equal volume out of phase through 2 speakers.

I am using 2 x Electret Microphone Amplifier - MAX4466 running into the Adafruit 3.7w stereo amp into two small speakers (also adafruit)

I have hooked it all up as required using a Breadboard and a 2xAA battery pack.

When I connect a 3.5mm jack to the stereo amp and play a music source it sounds great,
but when I connect the mics it is a very different situation.

I either get a constant buzzing or an audio signal with a horrible clipping/clicking sound over the top of it in time with the input signal.

This seems to happen at any gain setting on the mic amps at even the softest speaking.

I have tried all manner of configurations and also with a single mic and single speaker configurations.

Any help would be greatly appreciated!

Thanks,

Ben.

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adafruit_support_bill
 
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Re: Electret Mic Severe Clipping

Post by adafruit_support_bill »

Can you post a diagram of how you have these all connected?

bendesign
 
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Re: Electret Mic Severe Clipping

Post by bendesign »

Here is a diagram I have just drawn.

Thanks.
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adafruit_support_bill
 
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Re: Electret Mic Severe Clipping

Post by adafruit_support_bill »

As drawn, you have the stereo amp gain jumper on the highest setting. There is also a gain trimpot on the back of the microphone board. Start with both at their minimum settings and slowly increase until you reach a workable setting.

Note: Be very gentle when adjusting the trimpot on the microphone board. It is quite delicate and easy to force past the stop.

bendesign
 
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Re: Electret Mic Severe Clipping

Post by bendesign »

Ok, I will have another play with the gain settings. I have tried the mic gain on min right through to max, as well as various power amp gain settings.

That clicking sound I mentioned - would that be simply from overloading the input signal? Also as far as wiring of it goes - I have it wired up correctly?

Thanks again.

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adafruit_support_bill
 
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Re: Electret Mic Severe Clipping

Post by adafruit_support_bill »

The wiring looks correct. The clicking is probably overload as you suspect. The output of both devices is proportional to the supply voltage. Since you are powering them both from the same voltage, there is not a lot of room for gain.

bendesign
 
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Re: Electret Mic Severe Clipping

Post by bendesign »

I added a second set of batteries to power the pre and power amp seperately.

Seems to work a lot better now with the gain on the mic preamp turned down to around a quarter.

Thanks for the help!

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