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

[mythtv at derdev.com]

On Thu, 27 May 2010 23:21:24 +0100, Ed W <lists at wildgooses.com> wrote:
>> 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

Delicious irony... The Comcast digital converter box (not a DTA) coax
connection was removed from the TV's input panel and the hum went away. 
Comcast guy had been here at about the last time I watched this FE and he
had swapped that converter box (remember I said this kit was ok for a
while?).

Since this converter is heading to the basement to put onto my BE, I guess
this makes that decision even easier!  THANKS