[mythtv-users] Hum on analog audio to TV

[Allen Edwards]

get a piece of wire and touch both the chassis of the PC and the RF ground
on the coax input on the Tv and see what happens.
You might also try reversing the plug on the TV into the power outlet.

I had to do lots of things to eliminate ground loops caused by the RF Coax
going to all parts of the house.  I made sure everything was grounded from
the same point.  You can pick any point, just make sure everything uses the
same point.  I ran wires to the TV antenna and the TV and the projector and
the amps and the TV from this same single point.  For wires going to other
rooms where this was not possible, I isolated the coax by making a circuit
that had a small capacitor in both the center conductor and ground and
connected the coax going to the other room through that device.

Might take some experiments but like the other poster said, disconnect
things until it goes away and you will know where to work.

Allen



On Tue, Oct 21, 2008 at 6:28 PM, Tom Lichti <tom at redpepperracing.com> wrote:

> William wrote:
> > James Crow 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?
> >>
> >> Thanks,
> >> James
> >>
> >>
> >>
> >
> > Several other people have mentioned ground loops and they are on the
> > right track but are offering the wrong solution. If you can go digital,
> > do so and you will be surprised how good it sounds. If you must use
> > analog audio then you may want to buy or build a isolation audio cable.
> > There is a good page about how to make one here
> >
> >
> http://www.epanorama.net/documents/groundloop/audio_isolator_building.html
> >
> > Its simple enough that most people can handle making their own if you
> > have the tools. I did not research commercial versions but I am sure
> > they exist. Another option would be a UPS type power supply acting as a
> > central power distribution hub with computer up-time benifits. Be sure
> > to put the tv on one of the filtered jacks not one of the backed up
> > jacks. Most UPS's dont like the power spike tv's make when starting.
> >
> >
>
> Perhaps an even easier fix (as in my case) would be to make sure that
> the cable line coming into the house is properly grounded. Mine was not,
> as soon as I grounded it, the hum went away. Certainly one of the
> easiest and cheapest things to try.
>
> Tom
>
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