What is this AC Ground loop crap

[nandi_nokuri]

It is reallly annoying that we spend our hard earned money, only to find out we have to spend more. I have the ATI AIW 7500, and I have rolling white almost transparent lines on my television when using the tv out. Plus when using the audio-in and s-video part, I hear an annoying humming noise. From what I can gather these are all evidence of ac ground looping. Is this just in old houses and apt. ?

[gll99]

Do you suspect that your house or apt AC connections are not properly grounded.

Do you have 3 pronged plugs on your appliances, tv,vcr and computer and are the wall plugs 3 pronged.

If yes then its unlikely that you have a general grounding problem.

That would not eliminate a specific device problem if the ground wire or connection was faulty or one of your cards was touching inside your case.

It could also be caused by a bad video connector cable from your TV-out to the TV. RF interference from a motor or florescent light could give a similar result. This used to be very common with antenae signals when even the generator (before alternators) from a car parked outside near the window would cause a rolling interference band to appear on the TV.

Try running it though the vcr first. If that is your current setup then reverse it and go to the tv first just to see if it changes the pattern.

Lastly (unless you have one ready at hand) change the video cable between the tvout and the TV.

[nandi_nokuri]

Thanks Gll99

The video probably to my card was fixed when I went hooked a composite through a vcr. However the buzzing sound I noticed with the audio cords, was present when going to the computer and also simply connecting it my stereo. I think I have to some further investigation and moving stuff around. But thanks again for explaing ground looping

[thxkid]

Is your stero in any way also hooked up to your TV and or Cable or Satelite or dish, I had a line problem with a hum also and found out its one of the coxial lines coming from my dishnet, replaced the cable and all is well.

[walkinthru]

Go to teh store and buy 2 75/300 ohm transformers. They come in various shapes but one popluar shape is a female threaded connector on one end and pigtail antenna lead on the other. $3 each. Connect the pigtails together. Either solder or screw the lugs together. Just get tehm fixed together tightly.

That leaves you with an adapter tha now has a threaded female connector on each end. Connect this between your TV set and your cable feed. You will need another short piece of co-ax to do so.

Your hum will go away. You do indeed have a ground loop. Your cable or Sat dish is grounded at one source and your household wireing at another. The above device forms an isolation transformer for about $6. RS part # 15-1140 or 15-1296 or a combination of the two

Cable -- 75/300---300/75---TV

Adios

[The village idiot]

Here is a "picture" of what Walkinthru described:



coax cable connector-----<== ==>-----coax cable connector

This is also my recommendation to fix your hum problem.

[greddyrps13]

I tried the above method, and i still have the hum/buzzing. I am not using a satellite or cable source. i am using a powered antennae. What could be wrong? I even lowered the line in recording level.

[Lamont Cranston]

I ran into a ground loop problem whe recording from a satellite receiver. The computer was in one room and and the receiver is in another. Both use the 3 wire plug with the 3rd or green wire going eventually to the driven ground (rod driven in the ground). The satellite dish and the coax also go to the gound. Gound loops are multiple paths to ground. In this case the ground loop was created when I added the audio cables from from the computer sound card and the audio out on the satellite receiver. The ground shield on the audio cables. Since all the ground paths are not at the same potential you can have current flow which appears as a low level input signal on the audio cable. In the ideal installation the ground wires for each outlet in your house would star off of one point at your computer but that is not the case. I solved the problem by connecting satellite receiver to the same wall outlet as the computer using a 3 wire extension cord and disconnecting the ground from the dish antenna while I was making the recording. The background noise or hum went from -30 db to -90 db.