What solution do folks use for the dreaded BFD hum? - Page 30 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #291 of 330 Old 07-05-12, 02:58 AM
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Re: What solution do folks use for the dreaded BFD hum?

EDIT ON ABOVE POST:
I m using the cheater plug now and no hum anymore. In what situations will the cheater plug be dangerous?
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post #292 of 330 Old 07-05-12, 08:24 PM
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Re: What solution do folks use for the dreaded BFD hum?

If a device is designed to use a grounded a.c. outlet, it usually is not using a dual isolation power supply. If something opens up or shorts that makes the chassis hot, there is no place for the current to go so it looks for another path like through the body of a person touching the chassis or through the grounds on other equipments. If you had a hum, you had current flowing on the chassis ground to that ground on the a.c. line. That path is broken when you lift the ground, so now that current is looking for another path and cannot find one. If the current remains minimal, no problem. If it is high because of a defective device or something wired wrong somewhere in the system, it could be dangerous. If there are any protection devices internally that depend on that ground, such as MOVs, again, lifting the ground prevents this path.

Lifting grounds is just a patch on the problem. The problem should be corrected with a proper adapter or lifting a signal ground rather than lifting the a.c. ground.




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post #293 of 330 Old 11-21-12, 03:41 PM
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Re: What solution do folks use for the dreaded BFD hum?

Will something like this work? A xlr ground lift adapter?
http://www.amazon.com/Hosa-GLT-255-F...lr+ground+lift

I had a hum and it disappears when I unplug the wire going from receiver to bfd. Currently I am using the cheater plug and it fixed the hum problem,however sometimes when I turn on the fan or light in that room I can here a little soft thump in the sub. If this xlr ground lift adapter works is it just doing the same thing the cheater plug is doing or is it a better fix? Would I need 2 of them to go from the bfd to the sub also or just one going from receiver to bfd?
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post #294 of 330 Old 11-21-12, 05:48 PM
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Re: What solution do folks use for the dreaded BFD hum?


The noise you’re hearing comes from the light or fan being on the same electrical circuit as the sub (or possibly because they’re on the same phase), and it’s coming through the power line, not the signal chain. So I’ll be surprised if the XLR ground lift would work. Aside from that, the device you linked designed to work with a balanced signal chain. When you have an RCA to XLR connection, you have an unbalanced signal, so it would only be useful (if at all) if you have a balanced connection between the BFD and your subwoofer.

Regards,
Wayne



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post #295 of 330 Old 11-21-12, 05:56 PM
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Re: What solution do folks use for the dreaded BFD hum?

Is there a better option than this cheater plug?
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post #296 of 330 Old 11-21-12, 07:46 PM
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Re: What solution do folks use for the dreaded BFD hum?


If you’re asking about eliminating hum, any of the options found on this thread are better than the cheater plug, at least from the standpoint of safety. If you’re asking about the pop when lights are turned on, the cheater plug does nothing for that. The best way to solve that problem is to install a dedicated electrical circuit for your system, or lacking that plug all your gear into an existing circuit where there are no lights or fans.

Regards,
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post #297 of 330 Old 01-21-13, 01:55 AM
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Re: What solution do folks use for the dreaded BFD hum?

I tried removing all except the power cable but the hum/buzz still eminated from within my FBQ 1000 not the speakers. I've tried placing the power cable directly into the socket and also tried two other sockets (230V).

I find it a little strange that the hum fix should be placed in the audio path as the hum seem to be an electrical problem. Can anyone explain this to me?

Last edited by spaceape; 01-21-13 at 02:30 AM.
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post #298 of 330 Old 03-06-13, 02:36 PM
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Re: What solution do folks use for the dreaded BFD hum?

My simple solution - connected a small wire from the ground terminal on the back of my receiver (Denon 4311) to the outside metal part of the RCA plug connecting the receiver subwoofer output to the BFD TRS input.
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post #299 of 330 Old 03-06-13, 08:21 PM
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Re: What solution do folks use for the dreaded BFD hum?


With most receivers, the RCA sleeve (signal -) is common with the chassis. So you could probably attach that wire to a screw, which is probably easier than trying to connect something to the RCA plug itself. If there's a phono input with ground post, that would work too.

Regards,
Wayne



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post #300 of 330 Old 05-01-13, 02:23 PM
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Re: What solution do folks use for the dreaded BFD hum?

I have tried many things to get rid of the hum. I have the Lexicon MC12HD sub-woofer output connected to the BFD DSP1124P input. The output of the BFD is connected to a JBL 6290 power amp for the sub-woofer. The original configuration had all balanced cabling and I got a hum. I turned off everything except the BFD and the power amp with no improvement. I have done the following:
changed the connectors to the BFD to unbalanced -- no change
put a ground lifter connecter between the BFD and the amp -- no change
tried a cheater plug on the BFD -- no change

What should be the next attempt?
Any help will be greatly appreciated.
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