[mythtv-users] Hum on analog audio to TV

Gabe Rubin gaberubin at gmail.com
Tue Oct 21 21:08:47 UTC 2008


On Tue, Oct 21, 2008 at 1:17 PM, James Crow <james at ultratans.com> wrote:
> I have two Myth systems currently running. Both are connected by analog
> audio to RCA inputs on the TVs. My master BE/FE works great. 720P and
> analog stereo. My secondary FE (no BE on this box) is having an audio
> issue. It is connected to the TV at 480P component with analog sound.
> Whenever the Myth box is turned on there is an audible buzz from the TV
> speakers. I have tried switching from the built audio to an external USB
> audio device and the symptoms persist. Does anyone have any
> recommendation of things I can try to fix this?

This is likely a ground loop.  Is the audible buzz kind of high
pitched or just staticy (if the former, it most likely is a ground
loop).  Do you also see a horizontal band go down on the tv screen?
That would also be a sign of the issue.  I assume you have a coax
cable going into the FE that is giving you the issues (if not, then
the below solutions probably don't apply).  If you do, try unplugging
that while hearing the buzz, and see if that eliminates it (if it
does, the solutions below may help).

There are ways to reduce the ground loop, by getting better grounding,
or having your cable company fix it (not likely).  I used to take an
extension cord with a three-prong plug, stip the ground wire out and
tape that around the coaxial cable that was going into my myth box and
plug the plug into the wall.  It did not eliminate the buzz, but it
reduced it significantly?  You may also be able to get a power
conditioner that you can plug your coax into, but never tried those.

The easiest solution is to go all digital with the audio if you have a
digital receiver.


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