BFD trouble-HELP

Discussion in 'Speakers' started by MikeyWeitz, Mar 11, 2005.

  1. MikeyWeitz

    MikeyWeitz Supporting Actor

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    Ok, went out today and bought ratshack rca-1/4 plugs:

    http://www.radioshack.com/product.as...5Fid=274%2D320

    As son as I plug connect my receiver poutput to either of the inputs, I get a humming noise thru my speakers (even before sub is powered on). Both with BFD on and off.

    Did I buy the wrong ones?

    Can I still at least plot my FR today even without BFD plugged in, then ones I get BFD ironed out, jump right into setting filters?

    Thanks!
     
  2. BrianWoerndle

    BrianWoerndle Supporting Actor

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    They create a ground loop hum. I had the same problem when I got my BFD. (And still even when I switched to XLR)

    The easiest solution (although not the best) is to use a cheater plug to lift the ground prong of the BFD.
     
  3. MikeyWeitz

    MikeyWeitz Supporting Actor

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    Could you exapnd on that one?
     
  4. GrahamT

    GrahamT Supporting Actor

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    Dont understand ground loop myself but you can get a "cheater plug" or an isolator from Radion Shack to avoid the problem.
     
  5. Greg Bright

    Greg Bright Second Unit

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    Brian writes:







    And the best solution might be? Because I have hum myself.
     
  6. Max F

    Max F Second Unit

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    Back to Radio Shack you go!

    Same problem here solve by cheater plug (which has just 2 prongs, no ground).
     
  7. JasonCI

    JasonCI Stunt Coordinator

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    The cause of the ground hum is a difference in voltage between two power loops. I bet if you plugged your sub, receiver and BFD into the same outlet or circuit the hum would go away. You can use a cheater plug to remove the ground prong as GrahamT suggested but your sub may be damaged if a power surge occurs without it. Some sub manufacturers (I think HSU and Sunfire do) advocate using them, others do not.

    If you can't plug all of your components into the same outlet you can try searching for an audio isolation transformer or dc voltage blocker to block voltage from being passed through your LFE cable. The cheapest option I know of is from Calrad part #10-78-RCA.

    They're available here for $16:

    http://www.cablesandconnectors.com/01000-01.HTM

    A more expensive option that may be better at filtering out the hum is available from Jensen Transformers ($115). Here's a link:

    http://www.jensen-transformers.com/sub1rr.html

    You may want to call Jensen to pick their brain about your problem. They are much more knowledgeable about ground loops than I, but they're stuff isn't cheap.

    One more thing. If plugging all of your components into the same outlet does not get rid of the hum try unplugging any coaxial cables coming from your antenna, cable box, and/or DTV dish. Any one could be the cause of your problem if they don't share the same ground (or are not grounded at all) as your breaker panel. There may be more than one coax cable contributing to the hum. If this fixes your problem you can then try a coaxial video isolation transformer like this one from Parts Express:

    http://www.partsexpress.com/pe/showd...number=180-075

    Note: Some video receivers like digital cable boxes and DTV dishes require that voltage be passed through the coax line to work. It is best if you can relieve the ground loop problem from the source but you cannot use isolation transformers on DTV dishes or digital cable boxes or they won't work properly! Your only alternative then is to isolate your subs LFE cable with one of the products I mentioned above.

    Ground loops are a real hassle to get rid of, but this should get you started in the right direction.
     
  8. MikeyWeitz

    MikeyWeitz Supporting Actor

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    Cheater plug for the BFD power, right?

    Back to Radio Shack when they open tomorrow.

    Thanks.
     
  9. Max F

    Max F Second Unit

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    Yes, just for the BFD. Should do the trick. Jason does give good advise though its just that the cheater plug is cheap and does the trick. I've tried pluging everything in the same plugin, btw. It's likely from the cable in my case.
     
  10. MikeyWeitz

    MikeyWeitz Supporting Actor

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    Going to get it in about 30mn.
    Then will re-plot my mains + sub, then post the results.
     
  11. Wayne A. Pflughaupt

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    As noted by others, more of than not the problem is the CATV feed, or a sat feed that has been grounded somewhere besides the main electrical stake.

    Regards,
    Wayne A. Pflughaupt
     
  12. Patrick Young

    Patrick Young Stunt Coordinator

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    Sorry to sound stupid. But What is a BFD???[​IMG]
     
  13. David Judah

    David Judah Screenwriter

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    Behringer Feedback Destroyer--it's a parametric EQ for the sub.
     

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