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microphones and the cirrus audio card

soundcamp

I want to use stereo electret condenser microphones with this card. They need a a bias voltage (Plug in Power) of around 5V.

 

The Wolfson only included mono microphone support through the Mic in plug.

 

The comparison table for the Cirrus says it supports stereo microphones through the Line in, and the video introduction to the card mentions that bias voltage is provided for electret condenser microphones, but doesn't give more detail.

 

It would be great to have confirmation of what exactly this card provides in this direction.

 

This is important because it decides if the card enables the Pi to be used as a high quality audio recorder without an additional soundcard - as the Wolfson sadly could not.

 

Thanks

 

Grant (soundCamp)

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  • Hi Grant,

     

    The circuit diagrams for the two cards (old and new) show the difference. You can see a 22k resistor on the L and R input channels connected to the WM5102 MICBIAS pins (described in the WM5102 datasheet). It is likely to be sufficient for any small electret element.

    The WM5102 datasheet contains more info, but according to it, the MICBIAS pins can be software enabled or disabled.

Reply

  • Hi Grant,

     

    The circuit diagrams for the two cards (old and new) show the difference. You can see a 22k resistor on the L and R input channels connected to the WM5102 MICBIAS pins (described in the WM5102 datasheet). It is likely to be sufficient for any small electret element.

    The WM5102 datasheet contains more info, but according to it, the MICBIAS pins can be software enabled or disabled.

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