Re: [Gumstix-users] Overo audio input, microphone volume

[Morten L. <mor...@gm...>]

Hi Markus

2010/9/26 Markus Svilans <msv...@ae...>

>  Dear gumstix-users,
>
> Recently I've been experimenting with audio on the Overo Air with Tobi
> board.
>
> Audio playback works, using aplay and wav files.
>
> When I tried recording with a microphone, the volume was extremely
> quiet, and was not usable at all. With "arecord | aplay" I could hear
> some quiet static only when I blew directly onto the microphone.
>

Is your microphone an electret one? They require a bias to work properly.

The audio input on the tobi board is a line level input and is not able to
bias an electret microphone, the mic_main_mf and mic_sub_mf on
the connectors of the gumstix are able to bias a microphone, but these are
not routed on the tobi board.

Alternatively you could try and connect that input to a line out of an mp3
player
or similiar and see if you get any signal.

If you connect a "normal" microphone it will most likely require a lot of
gain because of the input impedance of a line input is much lower than the
impedance of a microphone input.


> The alsamixer program didn't offer any options to boost the mic input
> level.
>

Try amixer, i find it easier to find the right parameters.


> What should I do to make the mic recording levels usable?
>
> Thanks,
> Markus.
>
>
>
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regards Morten Larsen