On 5/4/2017 8:50 AM, chris hermansen wrote:
Jay and list,

On Thu, May 4, 2017 at 8:24 AM, Jay Foster <j...@systech.com <mailto:j...@systech.com>> wrote:

    I have encountered a strange problem.  About 6 months ago, I added
    a USB
    sound adapter and alsa to an ARM based linux system.  I used aplay to
    play wav files successfully.
    Now, the playback has a crackling noise in it.  I can not find
    anything
    that has changed.  A few units still play with no noise, but I cannot
    determine any difference between them and the ones with the noise.

    One odd thing is if I run an application to make the CPU busy while
    playing the audio wav file, the noise seems to go away. Any ideas on
    where to look for the root cause?

    Jay


I have had a similar experience using an AudioQuest DragonFly and a CuBox i4. In my case, errors were reported in syslog. Do you show any errors there?

Do you have any other USB sound cards to try out?


--
Chris Hermansen · clhermansen "at" gmail "dot" com

C'est ma façon de parler.
I have tried 3 different USB audio dongles (all C-Media chip based). No difference.
No messages in /var/log/messages.
I had to put the following in my /etc/asound.conf file to get clean playback when I originally got this working (the CPU is too under powered to do the default rate conversion).

    defaults.pcm.rate_converter "linear"

The noise is also present using 'speakertest -c 2 -t wav'. What bugs me is that this used to work fine, and still does if I make the CPU busy, which seems counter intuitive.
Jay
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