What solution do folks use for the dreaded BFD hum? - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 330 Old 09-30-06, 02:47 AM
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Re: What solution do folks use for the dreaded BFD hum?

The cheapest solution I found, which also worked the best/easiest, was to buy XLR ground-lift adapters. I think they were $7/each (one per channel as necessary, not all channels since I still want the ground level between my processor and amp to be equal) from Sweetwater.
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post #12 of 330 Old 09-30-06, 06:36 AM
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Re: What solution do folks use for the dreaded BFD hum?

Quote:
was to buy XLR ground-lift adapters
Most people use RCA unbalanced though..... Can't lift that ground
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post #13 of 330 Old 09-30-06, 04:33 PM
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Re: What solution do folks use for the dreaded BFD hum?

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brucek wrote: View Post
Most people use RCA unbalanced though..... Can't lift that ground
I see that sweetwater has a plethora of adapters and couplers that might work if a ground lift works. Could you attach a rca(f)/xlr(m) adapter to a xlr(f)/xlr(m) ground lift coupler into the BFD and use the 1/4" jack/rca(f) as the output to the sub woofer? It would be a cheaper option compared to a transformer/humx? if it works...... Will the amount of different attachments screw with the signal?
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post #14 of 330 Old 09-30-06, 04:52 PM
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Re: What solution do folks use for the dreaded BFD hum?

Quote:
Could you attach a rca(f)/xlr(m) adapter to a xlr(f)/xlr(m) ground lift coupler into the BFD and use the 1/4" jack/rca(f) as the output to the sub woofer?
Well, you always have to remember a basic rule in electronics, that no signal can flow in an open ended circuit. You need to create a loop for current to flow. In an unbalanced interface, there is only a single unbalanced line that requires a return path, and that's the ground. You can't break that path - no amount of adapters can break that rule. The shield in a balanced circuit isn't a return path, so you are allowed to lift it. Not the case with a single ended circuit.

I suspect the Hum-X to be ineffective. You really need a device that is placed in the audio circuit itself, such as the DC1...


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post #15 of 330 Old 09-30-06, 07:28 PM
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Re: What solution do folks use for the dreaded BFD hum?

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brucek wrote: View Post
Well, you always have to remember a basic rule in electronics, that no signal can flow in an open ended circuit. You need to create a loop for current to flow. In an unbalanced interface, there is only a single unbalanced line that requires a return path, and that's the ground. You can't break that path - no amount of adapters can break that rule. The shield in a balanced circuit isn't a return path, so you are allowed to lift it. Not the case with a single ended circuit.

I suspect the Hum-X to be ineffective. You really need a device that is placed in the audio circuit itself, such as the DC1...


brucek
Got it!
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post #16 of 330 Old 09-30-06, 11:31 PM
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Re: What solution do folks use for the dreaded BFD hum?

Quote:
brucek wrote: View Post

I suspect the Hum-X to be ineffective. You really need a device that is placed in the audio circuit itself, such as the DC1...


brucek
Gotta question your quick assumption there Bruce given that we all know that lifting the power line groung with a cheater solves the problem it's just that it is not a good thing to do from a safety standpoint. If the HumX device is able to do what it says: "Hum X filters out unwanted voltage and current in the ground line that cause ground loop hum while simultaneously maintaining a solid, safe ground" then it would seem to me to be the best solution. Anyways I have one on order so I'll let you know in a week or so.
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post #17 of 330 Old 10-01-06, 12:11 PM
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Re: What solution do folks use for the dreaded BFD hum?

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Gotta question your quick assumption there Bruce given that we all know that lifting the power line groung with a cheater solves the problem
Yeah sorry, I answered quick because I have concerns over these devices. I have no doubt it likely does the job. But we all know there is no way to eliminate that ground loop hum at the plug/receptacle without lifting the safety wire or inserting components into its path.

Those components have to be able to support the entire 120volt AC current to ground in the event of a failure in your equipment. They must support that current until the breaker trips. This requires quite high wattage components. Do they fit into that little device? Does the device have UL certification? If so, where are the specification sheets on their site. All I read is advertising hyperbole.

I'm more comfortable recommending line-level components.

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post #18 of 330 Old 10-01-06, 12:54 PM
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Re: What solution do folks use for the dreaded BFD hum?

Hmmm, I thought as Dundas did not having to insert something in the signal path would be preferable, and so have been using the HumX with great success, but...after reading bruceks' comments may need to rethink this.

Any thoughts on the suggested converting BHD balanced out to unbalanced RCA?

RG
post #19 of 330 Old 10-01-06, 01:19 PM
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Re: What solution do folks use for the dreaded BFD hum?

Quote:
Any thoughts on the suggested converting BHD balanced out to unbalanced RCA?
Can you explain what you mean? The BFD has both balanced and unbalanced capability on the output already. If you have a hum, you could try the DC1 that was mentioned..

Again, I have no experience with the HumX, so I was just asking questions about its safety. I couldn't find any testing reports or specs on the site or otherwise....

brucek
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post #20 of 330 Old 10-01-06, 01:27 PM Thread Starter
Mitch
 
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Re: What solution do folks use for the dreaded BFD hum?

I was reading some other stuff about ground loop hums and one suggestion was to ground your cable TV service to the same place as the power ground.

My humming is clearly related to my cable TV because once I disconnect the cable TV, the hum goes away. My cable TV service is grounded outside where it enters the house. But, that ground is not the same as used for power.

So, I was considering adding a coax grounding block where the cable enters the house and then running ground wire to the water pipe where my power ground is. My coax entry and my circuit breaker box are basically colocated. So, it's not as if I'm running the ground wire any further than the power ground wire.

If I understand the root cause of ground loop hums, this seems like it will remove the voltage potential that is causing the hum. But, I would like to hear from the experts before I pull the trigger on this.


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