[mythtv-users] Impedance mismatch?

[Stephen Worthington]

On Wed, 04 Mar 2015 21:44:36 -0800, you wrote:

>This isn't strictly a MythTV issue, but I figure some of you might have run into this before.
>
>I have the audio line out on the back of my MythTV box connected to the
>Aux input of my stereo. Works great.
>
>I added my Blu-ray player's audio output to the audio line in of the
>computer. It adds noise. Is this likely an impedance mismatch or could
>it be some other issue with the Blu-ray player?
>
>I used to listen to whatever came out of the Blu-ray player through the
>TV via HDMI. While that introduces no noise, it's also coming out of
>some dinky speakers. Even with the noise the sound track of movies is
>substantially richer going through the stereo.

The most likely cause is a ground loop.  If so, then the noise will be
a mains frequency hum (50 Hz in my part of the world, 60 Hz in the
USA).  As you connect more and more pieces of equipment together, it
becomes pretty well inevitable that you will introduce a ground loop
somewhere.  Does your Blu-ray player have an optical TOSLINK digital
output?  If it does, and your PC has an equivalent input, use that to
feed a digital signal to the PC and have the PC convert it to analog.
That is the best way to avoid ground loops, but it means that you will
only get the audio quality of your PC's digital to analog converter
and it may not be as good as your Blu-ray player's.