VoCore2 audio noise

jab
 
Posts: 6
Joined: Fri Sep 30, 2016 3:52 pm

VoCore2 audio noise

Tue Jul 25, 2017 10:26 am

On VoCore2+dock, when I plug in headphones and microphone, there is audible noise even if no recording or playback is running. This noise is present in recorded file with arecord. I tried different headphones&mic and also different pieces of VoCore2.
Any ideas what causes this noise and how to fix it?

Vonger
 
Posts: 564
Joined: Sun Oct 19, 2014 6:00 am

Re: VoCore2 audio noise

Tue Jul 25, 2017 3:12 pm

It is the on board blue antenna crosstalk with the audio chip.
To fix this, one way is to remove on board antenna then use an external antenna, another way is to change its factory setting, make antenna power output lower, 100mW -> 10mW.
But also will reduce wifi signal strength.

jab
 
Posts: 6
Joined: Fri Sep 30, 2016 3:52 pm

Re: VoCore2 audio noise

Tue Jul 25, 2017 7:28 pm

Thanks for reply. These factory settings are defined in Linux drivers or at higher (or lower) level somewhere? In case wifi is not needed at all, simply removing wireless drivers from Linux would be sufficient to solve the problem, right? And do you think shielding audio connector would help?

Vonger
 
Posts: 564
Joined: Sun Oct 19, 2014 6:00 am

Re: VoCore2 audio noise

Wed Jul 26, 2017 1:49 pm

if you do not need wifi, just call "wifi off" or add "disable 1" in to /etc/config/wireless, that will disable wifi.

jab
 
Posts: 6
Joined: Fri Sep 30, 2016 3:52 pm

Re: VoCore2 audio noise

Tue Aug 08, 2017 9:16 am

Thanks, disabling wifi helped to get rid off most of the noise, but there is still significant noise from other parts. You "hear" the device when e.g. writing to SD card. Besides, there is very big DC bias in captured sound (see attachment). So I think, there are two distinct issues: crosstalks and bias. I wonder if at least one of them can be solved by codec configuration? Or is it in hardware connection, pre-amplifier settings and so? I'm not experienced with audio stuff much...
Attachments
vocore2_dcbias.png
vocore2_dcbias.png (30.22 KiB) Viewed 322 times

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