Buzzing sound from subwoofer (ground loop), what is the best solution?

Discussion in 'GENERAL AV Discussions' started by MinusTheBear, Aug 4, 2008.

  1. MinusTheBear Audioholic Ninja

    MinusTheBear
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    I moved my system into the t.v room and at first when I was listening to music everything was fine, then all of a sudden I noticed a very loud buzzing sound coming from the subwoofer, I shut down the c.d player and the receiver and the subwoofer was humming. I flicked the switch off on the back of the sub and the hum went away, I turned it back and the hum was present again. Great groundloop:mad:. I am pretty sure the subwoofer and the HD satellite box are the culprits. A cheater plug came with my sub and decided to use it. The depth of the cheater plug is not as long as the 3 prong plug of the sub cable and only fits half way into the cheater plug...so I took some eletric tape and taped over the exposed part of the prong and plugged it IN (is this safe)....NO HUM! Great the cheater plug worked!

    I know cheater plugs are not a permament solution due to saftey issues (especially when it does not even fit properly).

    So my question is what would be the best product to buy to fix this ground loop problem I have with subwoofer and the HD cable box?

    Thanks
  2. DD66000 Senior Audioholic

    DD66000
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    You need a coax isolator, call your cable company, they will put one on your incoming coax line. They will probably charge you for a service call. Or you can buy a ISO-MAX VRD-1FF Cable TV Ground Isolator for $50. Go with ever is cheaper, the cost of the Jensen or the cable service call.
    http://www.cs1.net/cables/jensen_transformers.htm
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  3. j_garcia Audioholic Jedi

    j_garcia
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    $50?!@!!@#% for an inline isolator? THAT IS A RIPOFF. You can get the same exact thing from www.partsexpress.com for $9.00 PN# 180-075. It isn't like it does something fancy, all it does is remove the ground.

    The simplest way to check for this issue is to disconnect your incoming CATV line. If it is ground loop hum, it will most likely go away when you disconnect that incoming line. Your cable company should be able to fix this as well, as it means you have a bad ground on the line within your home - I complained when I had the same problem and they eventually got around to fixing it, but the product I listed above fixed mine just fine in the meantime.
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  4. MinusTheBear Audioholic Ninja

    MinusTheBear
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    The note on the end of the product description says it Interferes with digital cable, cable modem, and satellite TV operation.

    I am running a HD digital box hooked up to satellite. How much would I be sacrificing using this? What product would work that would not affect the quality of the incoming signal?
  5. MinusTheBear Audioholic Ninja

    MinusTheBear
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    I just went to that site and this will work for a digital cable box and should not filter out any channels or degrade the signal. Here are the specs:

    Improves audio/video quality by reducing 60 Hz ground currents

    2 MHz to 1300 MHz bandwidth spans VHF/FM/UHF/CATV spectrum

    Low VSWR helps prevent digital cable channel degradation

    Capacitive based design minimizes broadcast channel interference

    Meets FCC Part 76 Regulations for CATV systems

    Any thoughts??
  6. j_garcia Audioholic Jedi

    j_garcia
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    I did not try it with an HD box, so I can't answer for certain. I just know that my sub didn't hum after that. I'd call PE sales or support and see if they can tell you if they or any customers have tried it with your box. My guess is, it will be fine - they are of course going to put that as there are likely cases where it does cause issues.
  7. Adam Audioholic Jedi

    Adam
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    Hey, Bear. Someone asked about this about a week ago, and I mentioned that maybe using a surge protector/power conditioner that includes coax inputs/outputs might work - and he said it did. However, it did make it so that his on-demand didn't work with his cable, so he was going to get one of those isolators.

    Anyway, I mention it because you could try running your cable lines through a surge protector/power conditioner to which you've plugged in your components if you already have one. For at least some surge protectors/power conditioners, this provides a common ground. This suggestion is assuming that you've taken John's advice and disconnected the cable line to see if that's what is causing the hum.
    Adam,
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  8. MinusTheBear Audioholic Ninja

    MinusTheBear
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    I just looked at the surge protector that I have the subwoofer and cable box hooked up too and there is one coax cable input labelled sat/cab in and another one labelled tv/dss out. My coax cable from the satellite outside comes through the wall and that is plugged into the HD box. How would I do what you suggested above? This is a safe solution if it would work, correct? Thanks:)
  9. Adam Audioholic Jedi

    Adam
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    What I would try first is to connect a cable from the wall jack to the "sat/cab in" jack on the surge protector, then connect another cable from the "tv/dss out" jack on the surge protector to the HD box.

    This should be perfectly safe. You're just routing the cable line through a surge protector. If it doesn't eliminate the hum, or if it screws up the HD signal, then it's not the solution - but it doesn't take long to try it out. :)
    Adam,
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  10. MinusTheBear Audioholic Ninja

    MinusTheBear
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    Cool, I will give this a try. This is exactly the steps I am going to take, so please tell me if I will be doing anything wrong.

    1) Remove the cheater from the 3 prong cable (subwoofer), plug the 3 prong back into surge protector.

    2) Disconnect coax cable from cable box and connect that cable to the sat/cable in on the surge protector.

    3) Grab a coax cable that is lying around the house and connect one end to the TV/DSS out on the surge protector and the other end into the HD cable box.

    4) Test to see if hum exists.
  11. Rickster71 Audioholic Spartan

    Rickster71
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    I'd try to trace your cable line outside and look for the cable grounding block.
    Make sure it's connections are tight and that it has a ground wire leading to a water pipe ground, or to a ground rod; and that those connections are tight and corrosion free.
    Even though the cheater plugs and ground lifters get rid of the hum. They are band-aid fixes.
    Cable companies are notorious for bad grounds at the pole.
    The surge protector idea is good too.
    I route the cable line through a surge protector / line conditioner, along with having a proper ground before the cable enters the house.
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  12. Adam Audioholic Jedi

    Adam
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    That is exactly what I would do.

    Please let us know if it works for you. Thanks!
    Adam,
  13. ougrad02 Audioholic

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    I am the person who Adam was speaking of who had this problem recently. When I used the surge protector the hum was gone but the on demand didn't work. I then ordered the jensen cable isolator and another one made by holland. Both eliminated the hum but some of my hd channels didn't work. Anyway, I finally have the hum gone and all channels working. What I ended up doing is taking the cable ground wire from the grounding block and running it to the service grounding rod for the house. This put them both on the same ground and eliminated the hum. The surge protector or isolators may work for you. I'm sure every situation is different. For what its worth the holland isolator is much cheaper ($12 range) and people that I talked to about my problem had said they had success with it.
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  14. bandphan Banned

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  15. MinusTheBear Audioholic Ninja

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    I tried routing the cable to the surge protector but that did not work :(, the hum was exactly the same, no more, nor less. I had these exact same sound compononents (speakers, receiver, subwoofer etc) hooked up in my bedroom with no problem ( for video I had the system hooked up to a computer monitor for videogames, no television or cable box up there), moving the system downstairs i subtracted the computer monitor, the only additions made were a television and a cable box and ....hummmmm. The only 3 prong equipment I have hooked up in the system is the t.v and the subwoofer. I re-installed the cheater plug (this time I got it in all the way) and the hum went away....currently have that installed. BTW I am not getting any interference on the t.v just buzzing from the sub.
  16. Alex2507 Audioholic Slumlord

    Alex2507
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    I have a Calrad RF isolation transformer from BJC. This is kind of messed up but the little piece of paper that came with it describes the unit as analog. It goes on to say that due to the reflection coefficient it will not work properly at the frequency extremes used in digital cable and broadband cable modems. None of this was mentioned on their site. I'm pretty sure that the limitations of the device will be addressed on the site at some point.

    Bottom line is that I got to learn something and I'm passing it on. This isn't a rant or anything like that. It's simply the source of the info.

    PS. I'm rootin' for ya.
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  17. TLS Guy Audioholic Overlord

    TLS Guy
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    You can't use an isolator with a satellite system, as it won't pass the phantom DC powering voltage.
  18. Rickster71 Audioholic Spartan

    Rickster71
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    Exactly! Well done.
  19. j_garcia Audioholic Jedi

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    I have two line conditioners and neither of them removed hum. It does NOT give you a common ground point, since the problem occurs prior to the unit itself. The problem is the ground on your incoming cable is not good or non-existent. All your cable company will do if this is the case is exactly what ourgrad02 said - move the ground to a better location.
  20. MinusTheBear Audioholic Ninja

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    I found out the source of the hum and got rid of it:D! A set of component cables hooked up from the television to the dvd player were the culprit. I just assumed it was the cable box because that was the only addition to the setup, but I overlooked the fact I used a set component cables that came with the HD box (I am using DVI instead) for the video for DVD player. So today I unplugged the HD box and unplugged the television, hum was gone. Plugged back in the television hum from subwoofer, so then I started removing the DVI cables, optical, RCA to 3mm from the t.v and still humming like a bastard, then I removed the component cable, and viola! Hum is gone! Good riddance ground loop:):D:p!

    Thanks again everyone for your help!

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