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Feedback from my sub - why?

Discussion in 'Speakers' started by peter_i, May 5, 2005.

  1. peter_i

    peter_i Second Unit

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    Hi,
    I've plugged my D-Box sub into my Harmon Kardon AVR125 reciever via the sub in on my reciever and out via a 2 headed RCA cord to my sub. In other words, my reciever only has a single RCA input that I have plugged my powered sub into through a red and black RCA cord due to the fact that my sub out has dual outs (right and left?). I have been getting this horrible humming and feedback coming from my sub now that's getting worse and will only stop once I've stomped on the floor. What can I do? i think it's the 2 rca outs from the sub to the y connector to my stereo possibly? Help, my ears hurt.
     
  2. John Garcia

    John Garcia Executive Producer

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    If it stops when you stomp on the floor, something is loose at one of the connections or inside the amp or receiver, or your sub's amp is dying.
     
  3. MikeLi

    MikeLi Supporting Actor

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    I don't get it.. should you not be plugging to the "into" jacks of the sub. One RCA from your receiver to one on the Sub. You don't need both of them as bass is analog anyway.
     
  4. John Garcia

    John Garcia Executive Producer

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    If the sub turns off because the input signal is too low, you should use both, so some situations do need both connected.

    If the explaination is correct too, you've connected the sub to the INPUT on the receiver, when it should be the OUTPUT on the receiver. I was hoping that was a mistake though.
     
  5. HienD

    HienD Stunt Coordinator

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    What I'm guessing is you have a rca cable connected to the sub pre-out which is then connected to the subs rca in with a y adapter. Don't think that should cause the feedback. Have you tried a good quality shielded sub cable? A good digital coax or video cable should work too.
     
  6. John Garcia

    John Garcia Executive Producer

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    Have you tried a different cable?


    I'm guessing that is what you were trying to ask too?
     
  7. HienD

    HienD Stunt Coordinator

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    Sorry, I meant sub cable. Corrected now.
     
  8. peter_i

    peter_i Second Unit

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    I have the y adapter going into the reciever from the best of my knowledge, my reciever only has one out for the sub and the sub itself has 2 rca ins. Does that sound odd? should I be using both?
    I used just a basic cable for the connection from the reciever to the sub. This is what I was told by many. Should I be using a fancy cable instead? Any thoughts? It used to be fine but started happening recently when I moved to my new place.
     
  9. John Garcia

    John Garcia Executive Producer

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    I wouldn't use one of the "included in the box" type cables, I would use something better, but it really doesn't need to be very expensive. Depending on the length, maybe $20 from somewhere like Radio Shack should work fine. Maybe you could try borrowing a cable from someone just to try it out to see if that's the problem before spending money?
     
  10. Carl P

    Carl P Extra

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    Peter, just to clarify, you should only have one cable coming from one jack out of your receiver. It should say LFE out or Sub out. When you hook up your sub cable to your sub, you can normally hook it to either the L or R Sub in connector on the sub amp. If it really bothers you, you can add a Y connector between the sub cable and the sub and plug into the R and L simultaneously, but it is not necessary.
     
  11. Bryan Acevedo

    Bryan Acevedo Second Unit

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    Maybe you have a bad ground for your tv from your cable company.

    Try unplugging the coax cable from your wall to your tv and see if your sub stops humming.

    This sounds like a ground loop hum and a common source for that is that your cable lines from the cable company are not properly grounded to your common house ground.

    Bryan
     
  12. John Garcia

    John Garcia Executive Producer

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    He says it goes away when he "stomps" on the floor, so I'm not sure ground loop is what it is. It is something to check though.
     

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