Eliminating Ground Loop Hum from Subwoofer

Discussion in 'Archived Threads 2001-2004' started by David_Schiller, Oct 18, 2001.

  1. David_Schiller

    Joined:
    Feb 10, 2001
    Messages:
    48
    Likes Received:
    0
    I tried a 3-prong to 2-prong adapter for getting rid of the hum from my Hsu VTF-2 subwoofer (both connected to a Monster power strip or directly to the wall outlet), but this didn't work completely. Any other suggestions?
     
  2. SVS-Ron

    SVS-Ron Screenwriter

    Joined:
    Jun 2, 2001
    Messages:
    1,074
    Likes Received:
    0
    Try flipping the polority of the plug in the outlet too.
    Also, try another signal cable, and if you have it...disconnect the cable TV for a moment.
    All are likely subjects.
    Ron
     
  3. SamRoza

    SamRoza Stunt Coordinator

    Joined:
    Apr 27, 2000
    Messages:
    186
    Likes Received:
    0
    As I've said before David, I tried a cheater when I had the MOST ANNOYING ground loop on earth. It was awful.
    I bought a Monster Power Center HTS5K, and routed the cable through it...the hum disappeared.
    I recommended that another board member buy a power filter with cable connections on it. What'ya know...it eliminated the hum completely!
    I believe he bought a Belkin Power strip, and it worked just fine. It probably cost between $35-50.
    Sam
     
  4. David_Schiller

    Joined:
    Feb 10, 2001
    Messages:
    48
    Likes Received:
    0
    The hum is not as bad when I connect the subwoofer to my Monster Cable AV800 power strip as it is when I connect it directly to the wall outlet. With regard to switching the polarity of the switch, the back of the outlet has a connection for the black wire and one for the white wire. It's O.K. to switch the wires because it's just an AC signal?
    I thought that maybe Radio Shack sold a reasonably priced little device for getting rid of the ground loop hum, but maybe not...
     
  5. MatthewJ S

    MatthewJ S Supporting Actor

    Joined:
    Feb 27, 2001
    Messages:
    584
    Likes Received:
    0
    Cable ground loop isolater might help(@ $3)
     
  6. SamRoza

    SamRoza Stunt Coordinator

    Joined:
    Apr 27, 2000
    Messages:
    186
    Likes Received:
    0
    David, Voltage filters placed inline with my cable didn't affect the hum a bit. I don't think the Rat Shack sells anything that will help you for dirt cheap.
    What I DO know is that if you buy a powerstrip that will filter your cable lines, you can eliminate the hum.
    Sam
     
  7. David_Schiller

    Joined:
    Feb 10, 2001
    Messages:
    48
    Likes Received:
    0
    Sam, I guess I'm a bit confused at the suggestion of running my TV cable through the power strip (I can try this with my Monster Cable power strip). The subwoofer hum occurs even without my subwoofer audio cable plugged in and also even if I plug my subwoofer in a different outlet than the TV. Are you saying that my TV cable signal is causing the hum in my subwoofer?? This whole ground loop issue is very confusing...
     
  8. SamRoza

    SamRoza Stunt Coordinator

    Joined:
    Apr 27, 2000
    Messages:
    186
    Likes Received:
    0
     
  9. David_Schiller

    Joined:
    Feb 10, 2001
    Messages:
    48
    Likes Received:
    0
    Thanks for the advice, Sam. I'll try it tonight. I called Dr. Hsu (Hsu Research), and since I live in Orange County he told me to bring the subwoofer in in case the amplifier was bad. He didn't think the subwoofer should hum if it is plugged into the wall without any audio signal going into it. You can probably guess what happened...I brought it in, he plugged it in and...dead silence. Arrrrrgh!
     
  10. SamRoza

    SamRoza Stunt Coordinator

    Joined:
    Apr 27, 2000
    Messages:
    186
    Likes Received:
    0
    That's a ground loop, sho'nuff! Mine was so bad that when my neighbor would start up their microwave or their hairdryer that I got a loud hum. Movies were horrid, TV was worse...
    When I plugged the cable lines into my Monster power unit, all was well. Never had another problem.
    Sam
     
  11. David_Schiller

    Joined:
    Feb 10, 2001
    Messages:
    48
    Likes Received:
    0
    The TV coax cable did not affect the hum. However, when I changed the switch on my Hsu VTF-2 subwoofer from 25 Hz "Maximum Extension" mode to 32 Hz "Maximum Output" mode, the hum went away. I notice that my Monster Cable power strip shows my Ground is not O.K.; I hooked the power strip to several other outlets around the house, and the "Ground O.K." lights up green. I have this problem in three receptacles that are close together. I verified that my grounding wire is connected to each of the receptacles, so I don't know what's going on. I might have to call an electrician. I don't like the idea of my TV and subwoofer connected to a power strip that isn't properly grounded.
     
  12. LarrySkelly

    LarrySkelly Stunt Coordinator

    Joined:
    Jan 9, 2001
    Messages:
    129
    Likes Received:
    0
    It definitely sounds like a wiring problem, if the gound on the receptacle does not test out ok.
    The other thing that caused this, in a friend's case, was a light dimmer control on the same circuit. He removed the dimmer and the hum weent away completely.
    But your first problem sounds like bad wiring, a discontinuity in the ground somewhere. Check all of the receptacles in that room, and anything else on the circuit (flip the breaker to see what is on the circuit.) If its recent construction they are usually daisy-chained together, in series. Someone may have gotten sloppy and missed a gound wire, in one of the boxes.
    I just moved my system to a different receptacle in the same room, and now my sub amplifier is humming, where if I use the plug 10 feet away it doesn't. No change in cable or anything. So I've got my own detective work to do.
     
  13. David_Schiller

    Joined:
    Feb 10, 2001
    Messages:
    48
    Likes Received:
    0
    Hmmmm...I could be the culprit. The receptacle is under my stairs. 8 yrs ago I knocked out a wall under my stairs to build a little wine cellar and I installed some track lighting. I tied into the wiring from one of the other receptacles (no loose ground wires where wires tied together) and put in (you hit it) a dimmer switch. Can I have both a dimmer switch and a subwoofer (on 25 Hz Max Extension) that doesn't hum? All my ground wires are hooked up to each individual receptacle, but I didn't check the light switches (one regular, one dimmer). Could a light switch mess up your ground?
    Sure would be nice if I can avoid the cost of having an electrician come out!
     
  14. SamRoza

    SamRoza Stunt Coordinator

    Joined:
    Apr 27, 2000
    Messages:
    186
    Likes Received:
    0
    There are 2 main types of Dimmers. One is capacitive, and another inductive. I believe you need to stay away from inductive dimmers because they introduce lots of extra noise in your electrical system.
    THat's what I know about the subject, but I know it doesn't help much. You might want to ASK an electrician, but edon't pay them...just get some advice, because it's a relatively easy switch once you know what needs to be done.
    Sam
     
  15. David_Schiller

    Joined:
    Feb 10, 2001
    Messages:
    48
    Likes Received:
    0
    By the way, my light switch might qualify as being in parallel rather than series since I added it to a receptacle (one receptacle then had 2 black/white/ground wires). Last night I removed that receptacle (it was behind a wall unit anyway) and tied the black/white/ground wires together that lead to the light switch and to presumably some other receptacles. I thought that would solve the problem, but it didn't.
     
  16. David_Schiller

    Joined:
    Feb 10, 2001
    Messages:
    48
    Likes Received:
    0
    I think I'll go to Home Depot first and ask a few questions like you suggest. I took out the dimmer and checked the ground connections in all my light switches to verify everything was tightly connected. I'm still not properly grounded...
    Thanks for the info on the different types of dimmers.
     

Share This Page