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I am building a Bluetooth audio receiver as an embedded system with the CHIP sbc (single board computer) from getchip.com. Pretty similar to Raspberry Pi, runs Debian Jessie, too.

I am using the onboard 3.5mm jack as an audio output. I configured PulseAudio to receive the Bluetooth audio and redirect it to the ALSA sound driver. Everything works flawlessly except for static noise on the output. Directly after boot there is a medium loud sum in the few hundred Hz region. It´s always in the background, even if I play something via bluetooth or locally via CLI. The interesting part is that it disappears after exactly 10min and 10sec after powerup, so I think exactly 10min after the startup of PulseAudio or ALSA. I couldn´t find a reason for it.

  • I tried the tsched=0 fix in /etc/pulse/system.pa
  • I unloaded the module suspend-on-idle in /etc/pulse/system.pa

And by the way, I´m running PulseAudio in system-mode, as I´m using it as an embedded system and not a multi-user configuration. I hope I get help from you anyway ;-)

Maybe you have an idea where this noise could come from? It has to be some sort of software configuration issue, otherwise it wouldn´t disappear after exactly 10mins.

I´ll add the PulseAudio and ALSA configuration files later this day.

Thanks in advance!

PhoGGy
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  • Sorry but this is a programming site so this question will be deleted. – Mike Jul 13 '16 at 06:24
  • Hey Mike! Why isn´t this question a programming issue? I´m pretty sure it can be solved by programming or by customizing the program someone else wrote by using the configuration files. Please correct me if I´m wrong with that. – PhoGGy Jul 13 '16 at 06:51
  • It doesn't look like your programming is the cause of the problem, but some background task on your PC. Have you tried this on a different PC? – Mike Jul 13 '16 at 06:55
  • I tried it on a few of those CHIPs, each of them has a fresh installation of Debian Jessie. That´s why it can not be a specific background task, as I didn´t add anything to the system by myself. – PhoGGy Jul 13 '16 at 06:57

1 Answers1

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Fortunately I solved the problem on my own:

The C.H.I.P. from NextThing has a 3.5mm TRRS jack, which does not only output stereo audio but component video as well. Now if you plug in a standard 3.5mm jack, the ground pin does does interfere with the component video connector.

Thats why there was this humming noise on the audio output. And thats why it disappeared exactly after 10mins, because the screen idle time is 10min, I think.

So I have to admit, that it was indeed not a programming question as it was a connection issue. Thanks anyway for the quick answer!

PhoGGy
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