[mythtv-users] myth .23 - after upgrade, buzzing/hum on audio all the time

Ed W lists at wildgooses.com
Thu May 27 22:21:24 UTC 2010

> After software (apt) upgrades from 0.22 to 0.23 (and at least one brownout
> of household power) I now receive a consistent white-noise hum/buzz over
> the speakers when the Myth box is the selected audio input.  Regular cable
> on coax input to the same TV does not yield the buzzing/hum.

Is it a mains hum, eg 60Hz in the US, 50Hz in other places?

> What kind of bothers me is that the hum is persistent in mythbuntu even if
> I shutdown Myth FE...

Does it appear the split second you power on the machine, ie even while 
the box is booting?  If so then it sounds like a grounding issue?

If so then start by baselining the issue and unplugging all other 
electronics one by one until you are left with only the PC and telly.  
Be sure to unplug all of these from the PC including any antenna cables, 
etc.  Also check that the coax socket isn't touching the PC chassis and 
creating a ground loop there?

Oh, just to be completely sure - does the hum stay the same level as you 
adjust the PC volume?  Does it increase as you adjust the TV volume?  If 
so then sounds like a mains hum and you have some kind of ground loop..?

Good luck

Ed W

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