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BFD hum....???


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10 replies to this topic

#1 of 11 Cam McFarland

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Posted July 04 2004 - 01:49 PM

Besides not being able to figure it out, every time
I turn on my BFD, my sub gets a loud hum.
All of my HT stuff is plugged into a Monster Bar power conditioner strip.
Gotta get rid of it before I can try to figure the dang thing out.

Any ideas....???

#2 of 11 Felix_F

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Posted July 04 2004 - 02:19 PM

You're getting a ground loop. Put a cheater plug on the BFD. A cheater plug coverts a 3-prong power cord into a 2-prong. You can get one at Home Depot, etc.

#3 of 11 Cam McFarland

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Posted July 04 2004 - 02:34 PM

will do Felix....thanks

#4 of 11 Wayne A. Pflughaupt

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Posted July 05 2004 - 09:52 AM

Cam,

Defeat the ground of an electrical plug at your own risk.

Regards,
Wayne A. Pflughaupt

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#5 of 11 Cam McFarland

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Posted July 05 2004 - 12:30 PM

Wayne.....what else can be done???

#6 of 11 Felix_F

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Posted July 05 2004 - 01:10 PM

I'm not Wayne, but since I directed you toward the cheater plug solution, perhaps I can give you some other options, too. Please keep in mind that your BFD was humming, because it was grounded "twice," if you will - once through its 3-prong plug and once through the interconnect. The odds are that your cable TV connection is carrying the other ground potential, causing a hum when the BFD is grounded, as well. By removing the ground on the BFD, you may also be deleting the chassis ground, so you'd stand a chance of being electrocuted if you spilled a glass of water inside the unit, as an example, and then stuck your hands in it. Too, keep in mind that many manufacturers include a ground-lift switch in their designs - Bryston as an example.

If you don't feel comfortable with lifting the ground on the BFD, and you've unplugged your cable TV connection to make sure that it is causing the hum, you have a couple of solutions at your disposal. You can get a purpose-built device to strip your cable hookup of its ground. Mondial used to sell such a product for ~$100. Or, you can get a pair of baluns, tie them together and filter the ground from the cable connection that way. I can only say that in my 20+ years of being involved with audio, both as a hobbyist and as a one-time professional, I've never heard of any mishaps caused by lifting the ground on a piece of gear in a ground loop situation. YMMV.

Felix

#7 of 11 Wayne A. Pflughaupt

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Posted July 05 2004 - 01:32 PM

What Felix said; Posted Image

Make sure your CATV or satellite feed is properly grounded at house ground stake (which should be at the breaker box). If it’s grounded anywhere else, you have the potential for a ground loop which only occurs when you have more than one path to ground, as Felix noted.

However, often you can get a ground loop in spite of proper grounding. Do search on the DIY and Advanced Projects Forum and the Speakers and Subwoofers Forum for “ground loop” and you’ll get back lots of information on dealing with ground loops.

Quote:
Too, keep in mind that many manufacturers include a ground-lift switch in their designs - Bryston as an example.
I’ve never seen this on anything but equipment with balanced sends, and it only lifts the signal ground from the chassis, not the electrical ground.

Regards,
Wayne A. Pflughaupt

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#8 of 11 Felix_F

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Posted July 05 2004 - 01:43 PM

Quote:
I’ve never seen this on anything but equipment with balanced sends, and it only lifts the signal ground from the chassis, not the electrical ground.

You're right. I should have been more clear in my post.

Best,
Felix

#9 of 11 Cam McFarland

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Posted July 06 2004 - 12:45 AM

thanks guys......I think I need to go lay down now.....lol

#10 of 11 Henry Wai

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Posted February 20 2006 - 05:31 PM

Cam

If you don't like/can't sleep because of the cheater plug idea, you can also use the Ebtech Hum X, to get rid of your hum, I bought mine at Audiomidi.com for $49.00

#11 of 11 chris_everett

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Posted February 21 2006 - 03:07 AM

FYI, people have been electrocuted and killed because of lifted safety grounds. If your device has a gound fault (for whatever reason), and you grab the signal line.....ZAP.....

The safety ground is there for a reason. Don't bypass it!!!
--Chris Everett





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