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Ground loop hum?

Discussion in 'AV Receivers' started by AaronG, Apr 25, 2003.

  1. AaronG

    AaronG Stunt Coordinator

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    Hi Guys,

    I just hooked up a Bryston 9bst to my system, and I'm getting a major hum.
    I'm using a Denon 3802 as a pre/pro.
    I've tried disconnecting every source from the 3802 and I've tried covering the ground on the 9bst and the hum is still there.
    The hum goes away if I remove the interconnects from the Bryston (the interconnects are new Acoustic Research).
    Any suggestions?

    Thanks,
    Aaron
     
  2. AaronG

    AaronG Stunt Coordinator

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    Anyone?
    I'd love to watch a movie tonight without this annoying buzz!
     
  3. Pamela

    Pamela Supporting Actor

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    Do you have cable TV? There are a lot of problems with cable tv grounding. I had the same problem with my Parasound. I disconnected the cable from the wall to see if that got rid of the hum. It did. I reconnected the cable and put a ground loop isolator on the amp and it took care of the hum. I found out, however, that by running my cable through my Monster surge protector, it also got rid of the hum. I've stayed with that and it's worked fine.
     
  4. AaronG

    AaronG Stunt Coordinator

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    Thanks Pamela,

    I've already tried disconnecting the cable. There is still something else causing it. I've removed all connections to the Denon and unplugged everything in the room.
    The hum is actually louder when I unplug the TV or the satalite box (which are now plugged in to the same outlet as the amp).

    Thanks,
    Aaron
     
  5. Karl_Luph

    Karl_Luph Supporting Actor

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    You don't happen to have a refrigerator on the same cicuit as your wall outlet there? It sounds stupid but I've heard this can cause problems also the cable like the other person mentioned,fan motors and flourescent lights can be a pain. You will eventually find the culprit, it just takes trial and error.
     
  6. AaronG

    AaronG Stunt Coordinator

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    Karl,

    Thank you for the encouragement. No refrigerator - the home theater is on it's own circuits.

    I had tried two other amps, a Parasound and an Anthem. The Parasound had a hum that went away when I removed the cable and the LD player, and the Anthem had no hum at all.
    Is it possible that the new interconnects is causing the problem? They are directional ( I have the flow going from the Denon to the Bryston).

    Thanks
     
  7. Brett DiMichele

    Brett DiMichele Producer

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    Add me to the list that has hum now..

    I have NEVER had ground loop issues untill I added my
    Parasound Halo into the mix.. Now my tube amps are humming
    to thier own tune.

    Remember the scene in BTF where Marty plugged his guitar
    into the large overdrive speaker? Remember the sound of
    that hum? Yep that's what I got..

    Disconnect the RCA's from my amps and it dissapears...

    I am MAJORLY peeved! My Onk as a Pre never had any problems
    but not I can't get rid of the blasted hum!

    I obviously am going to have to rip out every single cable
    and component and start with just the 2 channel stuff first
    and see where the hum is comming from.
     
  8. Legairre

    Legairre Supporting Actor

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    Guys give this a try. My amps are on a different circuit then the rest of my gear so I ran a speaker wire from a screw on the amp to a screw on the pre pro or receiver. Completely got rid if my hum.
     
  9. CurtisC

    CurtisC Second Unit

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    You need to unhook everything from anything,then hook speaker wires to amp,check,then ic's to amp from denon,check,then cd to denon,check keep going till loop located.good luck
     
  10. Chu Gai

    Chu Gai Lead Actor

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    If all else fails, find out where your local Guitar Center is (yellow pages or online). They've got a product called the Hum Eliminator from Ebtech. It sits between your amp and pre. Their return policy is very good if for some reason this does not work out.
     
  11. AaronG

    AaronG Stunt Coordinator

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    Hi Guys,

    I'm pretty sure the hum is between the Denon and the amp. If I have one interconnect attached there is no hum, as soon as a second interconnect is attached the hum comes on.

    Thanks,
    Aaron
     
  12. Brett DiMichele

    Brett DiMichele Producer

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    I spent the day rewiring everything in my setup... Hum
    Gone! *Whew*
     
  13. MikeTz

    MikeTz Stunt Coordinator

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    Aaron:

    Have you tried a "cheater" plug (three prong to two prong adapter-at Home Depot for around a buck)? Put the cheater on your receiver power connector. Don't bother with a power conditioner on the 9BSST, it has a very good internal filter (and most conditioners will starve the 9B of current). Just plug it into your dedicated outlet. I'll spare you the theory and hope this fixes your hum headache.

    One more thing, the 9BSST requires around 18 amps when all channels are driven if its a five channel unit (an unlikely case in most HT installations), so be careful not to plug too many other components (especially TV/projector units) into the that outlet. I hope your 9B outlet is rated at 20 amps.

    Let me know how you do. If this doesn't work we'll try something else.

    MT
     
  14. AaronG

    AaronG Stunt Coordinator

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    Thanks Guys,

    Brett: Glad you got rid of yours. What was causing the problem?

    Mike: Would covering the ground pin with electrical tape do the same thing as a cheater plug? If so, I've already tried it with no luck.

    I just tried reorganizing all the equipment, and even with nothing attached to the Denon, and the Denon not even plugged in, my hum is still there when I attach a second interconnect.

    AAAAAAAHHHHHHHHHH!!!!!

    Aaron
     
  15. MikeTz

    MikeTz Stunt Coordinator

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    Aaron:

    I'd try a real cheater plug, not just tape on the ground pin. Are you saying that with the 9B plugged in and connected to the Denon, but with the Denon unplugged, you still get the hum? If so, try disconnecting the 9B and and making sure that all speaker wire is making good contact with the 9B speaker connectors. As you know the 9B has tricky speaker binding posts. Also make sure your cables are tight on the speaker side. Loose cables cause hum.

    I assume none of your speaker cables have long parallel runs in very close proximity to power wires. If not, after making sure that all connections are tight move your speaker cables and tell me if there is an audible difference in the hum.

    One more thing, some interconnect cables have a directional design. If you have a pair try them instead of the cables you presently use between the Bryston and the Denon. I assume you also have ensured that your interconnects are making tight connections between the 9B and the Denon. Jiggle the RCA ends on both the Denon and the 9B side and listen for a difference in hum.

    Let me know how you do.

    MT
     
  16. AaronG

    AaronG Stunt Coordinator

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    Thanks Mike,

    I'll pick up a cheater plug tommorrow.
    I'm using bannana plugs and, as far as I can tell, everything is tight (I've given each wire a little tug).
    The Denon is unplugged, and as I add interconnects, I get the hum from each speaker as it's interconnect is added.

    Thanks,
    Aaron
     
  17. MikeTz

    MikeTz Stunt Coordinator

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    Aaron:

    Were the Denon and Bryston plugged into the same outlet when you heard the hum? If not try it. Since you are not using the amp section of the Denon, it should draw very little power.

    MT
     
  18. AaronG

    AaronG Stunt Coordinator

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    Mike,

    No good.

    Thanks,
    Aaron
     
  19. Brett DiMichele

    Brett DiMichele Producer

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    Aaron,

    I just had a FUBAR wiring thing going on.. I am constantly
    plugging, unplugging and swaping components and my wiring
    gets real rat's nest like.. So I took about 3 hours yesterday
    to sit down and rearrange everything and the hum is gone..

    I got some velcro straps they use in Server Farms to bundle
    the Cat5 runs and I used that to bundle my power cords and
    rand them down one side of the rack and tried to keep the
    signal and speaker leads as far away as possible. It worked.

    But this is only temporary since I am working on a new
    8 shelf high end design rack at the moment and when it's
    done I am gonna have to do this all over again [​IMG]
     
  20. AaronG

    AaronG Stunt Coordinator

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    Hi Guys,

    I just tried a cheater plug and the hum is still there.
    I contacted Bryston and they said I should bring it in for testing.
    Does anyone know if this sound more like a problem with the amp or with the pre/pro?

    Thanks,
    Aaron
     

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