Ground Loop Isolation

[LewF]

Beating this dead horse a bit more. The hum on my coach came from a "ground loop" - this occurs when two different sources of 60 HZ power supplying this complex home entertainment system try to equalize their slightly different voltages. This imposes a 60 HZ signal on the audio output and that is amplified and then output to the speakers - therefore the hum. The simple fix is to install a ground loop isolator in the audio lines from the "DVD Output" to the Home Theater amp. I used a Xitel unit I bought from Amazon, it required no gender changing and isolates both the "red" and "white" audio lines. It is more expensive that the Metra unit but I liked its tech specs better, it also needed no gender changing plugs. This fix is so simple I am surprised Monaco is having such a problem finding a fix.

I see other suggestions of installing a very small capacitor on the line to the speakers. This is an old ham radio trick and will shunt RF signals that become superimposed on the speaker input signals - they are essentially a high pass filter that grounds frequencies above a certain value. The signal producing the hum on my coach was a 60 HZ, i.e. basic electric power frequency, hum so high pass filters were not needed and in fact would not be effective.

Hope this doesn't add more confusion to this issue. If have a hum that sounds like the hum from a florescent light then you have a ground loop and need a ground loop isolator.

[LewF]

Beating this dead horse a bit more. The hum on my coach came from a "ground loop" - this occurs when two different sources of 60 HZ power supplying this complex home entertainment system try to equalize their slightly different voltages. This imposes a 60 HZ signal on the audio output and that is amplified and then output to the speakers - therefore the hum. The simple fix is to install a ground loop isolator in the audio lines from the "DVD Output" to the Home Theater amp. I used a Xitel unit I bought from Amazon, it required no gender changing and isolates both the "red" and "white" audio lines. It is more expensive that the Metra unit but I liked its tech specs better, it also needed no gender changing plugs. This fix is so simple I am surprised Monaco is having such a problem finding a fix.

I see other suggestions of installing a very small capacitor on the line to the speakers. This is an old ham radio trick and will shunt RF signals that become superimposed on the speaker input signals - they are essentially a high pass filter that grounds frequencies above a certain value. The signal producing the hum on my coach was a 60 HZ, i.e. basic electric power frequency, hum so high pass filters were not needed and in fact would not be effective.

Hope this doesn't add more confusion to this issue. If have a hum that sounds like the hum from a florescent light then you have a ground loop and need a ground loop isolator.

[Sixpack98]

Lew,
You are absolutely correct. Unless you insert a very tight notch filter, any cap, in series or parallel, will have a huge impact on the sound quality. There are all kinds of ground loop isolators, some good and some bad. The Xitel is used by a lot of home theater installers because it has little impact on sound quality and gets the job done. The solution should have been good electrical enginering practices on Monaco's part to limit the number of grounds or a single ground for the audio/video components and a filtered 12v for the AV stuff.

I don't have a ground loop problem but did have noise introduced by the Magnum inverter/charger with the main culprit the 12v charging side. It only impacted the XM tuner so I bought a 12v filter which stopped that noise. I also put a filter on the 12v input to the Winegard AV switch which reduced the video hum bar on the TV's. Both were cheap filters I bought locally and will probably replace them with a quality filter to feed a separate 12v to the radio, XM receiver and Winegard.