Ground Loop Question


Just curious about this....

What exactly is a ground loop and why does it affect the stereo like it does? What exactly is happening to cause this? I'm a little rusty on electrical but i know the basics and terms. I would assume a ground loop is actually where a ground gets fed back into itself and maybe oscilates and causes the hum? or am i totally reaching here?

My buddy's ol man has a pretty decent mid-level system that is PLAGUED by this Hum. He has a MONSTER 3600 stage 3 power filter and the hum is still there.

Better yet, when he turns on the lights the hum gets WAY worse. (not a dimmer switch either) Normally i would attribute this to bad power, but shouldnt the stage 3 filter be clearing this? Does this sound like it could be a ground loop?

What are some common causes of ground loops and some common fixes?
slappy
When two or more components are connected to a common ground through different paths, a ground loop occurs. Current flow through these multiple paths can cause noise or a 50Hz/60Hz hum.

To eliminate ground loops, all signal grounds need to go to one common point. When multiple grounding points cannot be avoided, you must isolate the signal and grounds of each ground point from the other.

Some components do not really need to be grounded directly; so eliminating the ground connection on that component will also solve the problem. An AC "cheater plug" is a quick fix, and/or an easy way to test each AC connection and locate the offending connection.

A power filter or conditioner by itself will not solve a ground loop hum.
See,http://www.epanorama.net/documents/groundloop/index.html

Previous thread: Is cheater plug safe with grounded monster power?

See also, http://aikenamps.com/StarGround.html

greg
HI SLAPPY, FIRST OF ALL IS THE HUM COMING FROM THE SPEAKERS OR A COMPONENT? IF IT IS COMING FROM SAY THE AMP OR PREAMP IT IS QUITE POSSIBLE THAT THERE IS A DC PROBLEM THAT'S CAUSING THE TRANSFORMER TO HUM. FOR MONTHS, I HAD A HUM PROBLEM WITH MY PIONEER SX-1980 RECEIVER. MY HUM WAS LOUDEST WHEN STREET LIGHTS WERE ACTIVATED. DUKE POWER CAME OUT AND CHECKED THE STREET LIGHT/S CLOSEST TO MY HOUSE AND COULD NOT FIND ANY PROBLEM. POWER CONDITIONERS HAD ABSOLUTELY SO AFFECT ON THE HUM. AS A LAST RESORT, I DECIDED TO TRY THE HUMBUSTER FROM PS AUDIO AND IT WORKED IMMEDIATELY. NO FURTHER PROBLEMS. HOPE THIS HELPS. KEEP ME POSTED.
Does he have the stereo hooked to the TV? If so, disconnect the coax and see if the hum goes away. If it does you can get a ground break for the coax.
Maybe this will help.

Pass Labs Ground Loop Hums

Cheers,
John
the hum is coming from the speakers, there are several groups of lights in the basement where the rig lives, one of these sets if you turn them off the hum drastically decreases.
He has a lot of stuff hooked up, a turntable, DVD player, CD player, VCR, Tape Deck, digitital cable box, and everything runs through his MONSTER HTS3600 power conditioner.

I think i might try getting a couple cheater plugs and just disconnecting everything and bringing everything back in one at a time. All of his cables are MONSTER cables and somewhat decent ones at that, the power and audio is all run together with no attention to placing the audio/power at 90 degree angles(drawback to using a mass market retailer for an install). I guess one way to isolate if it is the transformer in his reciever (pioneer elite 36 model) would be to disconnect everything and try the radio with nothing else hooked up. He does have an HDTV with the audio from the cable box being fed to the reciever, i think he is using COAX or Fiber. will take a better look sometime.

This guy's system is a pretty decent mid-level system, i know that he is completly happy with his choice of gear, but im sure he would appreciate getting rid of that hum.

Thanks for all the responces, i think i have a good strategy as to how to get rid of this hum.
I have a similar problem, with audio humming caused by several-different devices IF the 3-wire powercords are plugged into 3-wire outlets. My solution is as above--float the ground pin with some kind of cheater plug. While you're doing this, try to orient the remaining 2 wires to achieve the lowest voltage (measured to a grounded outlet centerscrew) on the chassis (with all signal cables disconnected). I've seen up to c. 60vac on a chassis when the remaining 2 sprongs are oriented the wrong way.

BTW, HUM from ground loops is caused by 60Hz AC-power current flowing between components thru the SIGNAL cables and somehow modulating that hum into the signal-carrying circuits. Understand that floating the 'green-ground' pin leaves some of that voltage previously drawn to some ground still on the chassis.
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Sugerbrie is correct, single-point ground is ideal way to isolate ground loops. To further improve ground loops, a ground lift is the best.
I had the same problem with my HDTV system using a Krell HTS connected to a Pioneer Elite DV-38 CD/DVD player and a Pioneer Elite PRO-730 RPTV. The CD/DVD player was connected to the TV via a component video cable (RGB). Absolutely terrible hum when the HDTV cable box was connected. The hum was coming from the HDTV cable box, to the TV, then the CD/DVD and eventually pre-amp/amplifier. The problem was eventually eliminated by replacing the copper coax digital interconnect between the Krell HTS and Pioneer Elite DV-38 with an optical interconnect, no hum at all now. I also had some success using a #XA-63400 ground breaker ($7.45 from www.hometech.com ) between the cable box and TV.
I purchased used a Pioneer Elite Receiver VSX 95 that has a hum throught the speakers and the headphone output. This hum is present with all other source components disconnected. The hum does not increase in volume and becomes masked by the music. The AC plug is two pronged and does not seem to have an effect when placed in one way or the other in the electrical outlet. There are no dimmers in the room and this problem occurs in no matter what room outlet the Receiver is plugged into.

This seems like a grounding problem. Is there a simple fix or complex fix that can be done by someone with limited to mayber moderate experience in tinkering with electronics.

Thank you for your time and assistance in helping me. My email address is: lawdogesq@excite.com
check to see if your receiver has 3prongs instead of 2. If so, the 3rd prong maybe pulling in the 60 cycle hum from your cable TV...regardless if any of your componens are switched on or off. As a test try uppluging your cable TV and see if the problem goes away. If disconnecting the cable does the trick then a group loop isolator will solve the problem. The part number for the isolator is VR-1FF. I puchased one (49.95) on ebay last month and it worked like a champ....good luck!