Powering external microphone

lukesaunders · Post by **lukesaunders** » Sat Apr 15, 2017 9:38 pm

Hi guys

I have an EM172 based microphone http://micbooster.com/primo-microphone- ... phone.html which needs to be powered through its 3.5mm stereo lead. This worked fine with the discontinued Cirrus Audio card which provided 2.7v and I really hope that it can be used with the AudioInjector.

Does the AudioInjector card provide any power to whatever is plugged in to the input ports?

And bonus question - does the headphone jack accept microphones as well as headphones or does all input need to go through the RCAs?

Many thanks
Luke

flatmax · Post by **flatmax** » Sat Apr 15, 2017 10:49 pm

Hi there,

The audio injector can support power and get the signal from electret microphones. Electret microphones take power and supply signal from the positive (hot) lead and connect to ground on the negative lead. They typically only have two leads. I notice the site you link to specifies their electret microphone as the em172, their link is repeated here :
http://www.micbooster.com/documents/EM1 ... 202015.pdf

You can plug and power an electret microphone into the audio injector (which doesn't come with an electret microphone onboard) by using the empty footprint marked "Cmic1". The negative ground connector is the one inside the white silkscreen print. The positive (hot) connector is the one in the green area of footprint "Cmic1".

If you have an audio injector and it has a microphone built in, you will have to de-solder that microphone off the PCB to do this. If you have the skills, that is great, otherwise ask a mate to help.

Hope that helps !
Matt

lukesaunders · Post by **lukesaunders** » Sun Apr 16, 2017 12:43 am

Hi Matt

Thanks very much for the reply - much appreciated.

The em172 based mic I have comes pre-wired up like the below to a stereo 3.5mm jack, so it's a stereo mic consisting of two em172s, not a mono.

So what you're saying is that just connecting this to the audio injector input (either the 3.5mm jack or the RCA) won't supply the power through the hot lead and instead I'd need to wire the hot connectors of the two mics directly to the Cmic1.But then the Cmic1 is mono only, so that won't work. Is my understanding correct?

The audio injector I would get would not have the built in mic, so no problems there.

Thanks,
Luke

flatmax · Post by **flatmax** » Thu Apr 20, 2017 9:34 am

Thats right, however I think you should first try wiring up only one mic. Then experiment with two ... I can see issues with trying to wire both mics in parallel to one mic port ... but see how you go !

Matt

Chloenomobelf · Post by **Chloenomobelf** » Fri May 12, 2017 12:26 am

Hi Guys.

I filmed my first video this weekend and the wind noise on it was insane. I would like to mount an external mic in the helmet to reduce wind noise. Any recommendations? Camera is a Ion Air

flatmax · Post by **flatmax** » Fri May 19, 2017 8:19 am

Oh, no recommendations on microphones as of yet, perhaps someone else can recommend that.

Have you tried a wind noise shield for your microphone ?
https://www.google.com.au/search?q=micr ... ise+shield

Not sure how effective it would be ?

thanks
Matt

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