[PLUG] Audio hum when playing Blu-ray movie

[Denis Heidtmann]

Clearly if the frequency changes it is not 60 Hz.  Is there a chance that
it is a feedback of some sort?  I have run into problems when had both the
input and output selected, but do not recall the details as it was a few
years ago.

On Wed, Jun 21, 2017 at 10:10 PM, John Jason Jordan <johnxj at gmx.com> wrote:

> On Wed, 21 Jun 2017 15:45:29 -0700
> Denis Heidtmann <denis.heidtmann at gmail.com> dijo:
>
> >I do not know much about what you describe, but you could answer the
> >frequency issue by recording the sound into Audacity on the laptop.
> >(Assuming you do not have a 'scope.)
> >
> >Is there a chance that the connections which produce the hum include
> >two different AC powered devices with a (not quite) common ground?
>
> Since my original message I have discovered that the hum goes away
> on the desktop if I turn off the right channel in Pulseaudio (the movie
> has only stereo, not 5.1). I have no idea what this means.
>
> I also compared all the settings in Pulseaudio on the laptop to the
> settings on the desktop. I didn't see any differences, except that
> some are different because the two computers have different audio
> processors, plus I don't know what all the settings mean.
>
> As for the frequency, I note that it goes up and down when I change
> settings in Pulseaudio. Even at its lowest it is higher than 60 Hz, so
> I doubt very much that it is related to household AC power. Besides, AC
> power might affect the stereo or the audio cables connecting to it, but
> the computer? After going through the power supply and its rectifiers?
> I could check it out in Audacity, but I doubt that doing so would
> reveal much.
>
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