Wiring for stereo mic using MAX9814

Electrical Engineering Asked by M. Stern on January 2, 2022

My goal is to test some algorithms for sound localization, so I connected two microphones (MAX9814 boards from adafruit) to my soundcard. In the future I want to use four channels.

I wired them like here.

The problem is that while both microphones work individually, when I connect both of them, the signal of each microphone end up in both channels at the same time. Probably this is due to some cross-talk, because I share the same 5V DC supply. Can anyone explain how to do the wiring of two (or four) microphones and avoid this kind of cross-talk?

This is my wiring right now:


GND, +, Gain and Out go to the MAX9814 board, L- and L+ go to the first channel of my sound card (MAYA44 USB+) via a coax cable with chinch connector, and R- and R+ analogously to the second channel.

Edit: The wiring as shown above is ok. Following the advice of the accepted answer I switched to shielded cables to connect to the sound card. Additionally I reduced the length of all other cables as much as possible.

2 Answers

The cause of the "problem" is really simple, and there's not much you can do about it.

If you have two of these things together in any normal sized room, they will both "hear" the same sounds.

The output of both microphones will look similar because they are picking up the same sounds.

With the automatic gain control (AGC) that the MAX 9814 has, even the output levels will be similar.

There's nothing wrong with your modules, and you are almost certainly not getting noticeable crosstalk electronically.

The 9814 may not be the best choice for sound localization.

The AGC may distort the signals in ways that interfere with the correlation methods normally used for localization.

The AGC will certainly interfere if you try to do localization based on the sound volume.

Answered by JRE on January 2, 2022

You ought to understand how the chip works as a preamp. It has variable gain with AGC and attack/decay rates.

I suggest you should be using STP cable with a grounded shield.

The microphone isolation is more about acoustic pressure isolation and focus than electrical connections.

If the mikes have passive rear cancellation for far field, you will have problems in phasor acoustic measurements even with equalization.

Answered by Tony Stewart EE75 on January 2, 2022

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