Eliminating ground loop with cheater plug

Discussion in 'AV Receivers' started by Mark Daria, Dec 23, 2003.

  1. Mark Daria

    Mark Daria Extra

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    The ground loop on my system caused by my cable tv is really starting to irritate me.

    Now I read in the basics area that this is caused when youre using equipment with the 3rd prong. And it says specifically not to use the 3 prong to 2 prong convertor.

    Anyway, the only piece of equipment I have hooked up that actually uses the 3rd prong is my HTPC. Unplugging it seems to make little difference, so I assume its due to using a power strip that has 3 prongs.

    Correct me if Im wrong, but since none of my components other than the HTPC use the 3rd prong, then its entirely superflous, except to protect the htpc? Basically, if I put the cheater plug on, would I be putting all my components at risk, or just the one with the 3rd prong, the htpc?

    I also managed to eliminate the ground loop in a kind of hack job way before, by having the cable wire so loosely attached that the signal came through, but the surrounding metal wasnt screwed on. Something about me tells me thats a bad idea...

    Anyway, Id really like to eliminate it entirely from my setup if at all possible. If this only puts my ghetto htpc at risk, Im willing to just use the cheater. I could always just plug the htpc in elsewhere.
     
  2. Gene Severn

    Gene Severn Stunt Coordinator

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    It's not a good idea to use a cheater plug or clip off the ground pin on a surge protector. Many protectors use the ground pin as the path to "drain off" any stray voltages.
     
  3. John Garcia

    John Garcia Executive Producer

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    A very bad idea. Your three prong strip is not likely to be the problem, it is your cable that is causing it. Do a search, as there is a very simple inline filter you can try to see if it will remove the problem.

    Your HTPC is not the only thing at risk, everything connected to it is.
     
  4. chung_sotheby

    chung_sotheby Supporting Actor

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    I had the same problem, and it was so bad that cheater plugs only limited the noise, not eliminated it. There are a couple of solutions where a transformer is added to the cable line. One of them is a Ground Guard by Tributaries($99), another is a similar component made by Dayton and available at Parts Express ($15), and the other is something made by Iso Max and available at the Polk Audio shop ($55). I think that all three work about the same, but the Iso Max module has the highest rated bandwidth, so if you have satellite or digital cable the Iso Max is the best bet.
     
  5. Bob McElfresh

    Bob McElfresh Producer

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    Yes... and No.

    There are several sources of hum. One of the more common is having a external subwoofer with a 3-prong cord, and your AV Receiver with a 3-prong cord. The two devices 'fight' over who owns the ground and this causes hum. The solution is to use a cheater plug on one of the cords, usually the subwoofer.

    You want to have 1 device, and 1 device only that is connected to the AC power ground.

    You have a different problem.

    Your hum is caused by the shield on your CATV coax. It is running for hundreds of yards in parallel with 60hz AC power wires and the shield picks up some 60 hz signal. This noise is now connected through the "F" connector to your electronics. This is why if you dont connect the shield to the "F" connector, the problem is gone.

    Use the filter technique to fix this.
     
  6. JackS

    JackS Supporting Actor

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    Ive been using cheater plugs for years. Please don't take this as a rec for their use, but until a few years ago, many amp mfg's openly endorsed them over line conditioners or other equipment that might be effective in eliminating the hum. The smart solution might be to spend the time and/or money and track down the problem and for a few of us who don't mind dangling one foot over the ledge, cheaters work fine. For absolute peace of mind, spend the time and the money necessary. Good Luck
     
  7. Jimmie Lee

    Jimmie Lee Extra

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    I am an electrical contractor, and I have been an audio/videophile for years. I wanted to address the "cheater plug" issues in this thread.

    It is generally not recommended to lift the ground by using a cheater plug. This is not because it can harm the equipment. It is because it could harm you. By lifting the ground on an amplifier for example, you expose anyone coming in contact with that amplifier to a potentially leathal shock. No equipment manufacturer, or installer is going to suggest lifting the ground, as they do not want the liability associated with any adverse consequences of their advice.

    In reality, unless your equipment is defective, or has been greatly abused (dropped onto a hard surface from three or more feet), it is extremely unlikely that lifting the ground will cause an electrical shock. It would also not be recommended that you touch your ground-lifted equipment while standing in water.

    With that being said, how many of you have dropped your amp from the roof onto your concrete driveway? Or, stand in water while touching your amps? Hopefully, not many.

    I have three high-power amps in my system, and I have used cheater plugs on all of them since they were new. Short of completely re-wiring my A/V room (which I keep promising to do someday) this was the only solution to the ground loop hum that my amps love to amplify.

    Is this a risky solution? Not in my opinion. But, this has to be an individual choice.

    I also recommend using an in-line isolation transformer on your coaxial cable to break the ground loop. Try Parts Express (Part #180-075). It costs about $15 and works as well as any of the $100 items.

    Happy Holidays!
     
  8. JimmyK

    JimmyK Second Unit

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    Interesting, considering some amps come with a switch to lift the ground.

    I was having a ground loop problem with a Parasound amp that had a 3 prong plug. Using a cheater plug eliminated the hum. Just to be sure, I took out my trusty meter to see if I could measure any current from the case to ground. There was absolutely none. So in my case, I had no problem using a cheater.

    Interestingly, however, when I purchased a new pre/proc early this year and rearranged my system in a different hookup configuration, I was able to eliminate the cheater plug without the hum returning.

    Jimmyk
     
  9. MikeTz

    MikeTz Stunt Coordinator

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    Cheater plugs fix the symptom not the problem. A properly grounded CATV installation should not produce a ground loop. But many CATV installations do not bond the ground from the dish (and cable ground blocks) to the house ground at the service entrance. If the installer put a ground rod in for the CATV but didn't bond it to the service entrance, then the possibility for a ground loop exists.

    I think Jimmy Lee is correct that cheaters and CATV cable isolators are safe and will often times solve the problem of an improperly grounded CATV installation. I'm an electrical engineer and my cable installer thought I was a real PITA when I made him bond the CATV ground (he used a rod) to my home service entrance. But after he did the ground loop was gone and he had to admit it was the right thing to do.

    MT
     
  10. Wayne A. Pflughaupt

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    Those would typically be pro audio amps with balanced connections. The ground lift is the signal ground (i.e., from the chassis), not the electrical ground.

    Regards,
    Wayne A. Pflughaupt
     
  11. Mike Nep

    Mike Nep Stunt Coordinator

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    Okay, here's something you can try that most likely won't kill you or anyone around you. Anywhere that you split cable tv lines, you open yourself up to some kind of hum. Why? I don't know, but, I do know one thing... Ground it! It's really quite simple. On a splitter there's usually a grounding screw. Secure a copper wire to this grounding screw/lug and then connect the wire to anything conductive that is grounded also. ie: If you're splitter is not inside of the wall like mine, I attached the end to the middle screw that holds my outlet cover on. Yeah, it's ugly but what annoys you more? That horrible buzzing sound that's ruining all of you movie experiences or the sight of a little copper wire on the ground. Also, you can find your cable main and do the same thing at that splitter and screw the ground to the box that covers it from the environment. Give it a whirl... you'll be amazed if it works. Everytime I have a ground loop hum coming from my speakers this is my first tweak... (and usually last). Plus you don't run the risk of killing yourself.
     
  12. Kevin. W

    Kevin. W Screenwriter

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    My solution to my hum/buzz coming from my speakers was to connect some TV coax cable from my Yamaha FM tunner connection to my coax surge connection on my Monster HTS 1000mkII. Works like a charm.

    Kevin
     
  13. DavidLW

    DavidLW Stunt Coordinator

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    Actually using a cheater plug will not leave any equipment chassis ungrounded so long as you still have the RCA interconnects connected and the one piece of equipment with the three prong plug still plugged in at the outlet. All your equipment is still grounded by way of the negative (outside) side of the RCA interconnects. But to be safe never unplug the piece of equipment that is grounded to the outlet and if you're going to be removing all the interconnects from a piece of equipment, unplug it (the equipment you're removing the interconects from) first.
     
  14. Zeal

    Zeal Auditioning

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    David,



    I know this is a old thread but I have a question that I think you could answer. I've been using a cheater plug on one of my mono blocks. I had to unplug some interconnects that was plugged into the pre amp. The speakers then stated to make a loud humming noise that lasted about a minute then stopped. Can you do damage to your speakers and other equipment when this happens?



    Thank You for reading,




    Richard (Zeal)
     

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