What solution do folks use for the dreaded BFD hum?

[Mitch G]

I'm a big believer in standing on the shoulders of giants.
In this case that means I would like to know what solution folks use for addressing The Hum.

Right now I'm using a cheater plug, but I would like to solve the problem the right way. I saw the links to Jensen and Ebtech stuff, but Jensen has a bunch of different products, and the Ebtech links are qualified with words like "possible."

So, what are you audio giants using to address The Hum?

Thanks,


Mitch

[lcaillo]

The right way is to convert the balanced connections on the BFD to unbalanced that are required by most AV systems using a transformer. You can get them at radio shack for about $14. Using the cheater plug is OK for testing and may never cause a problem, but why not do it right?

[stitz]

this worked great for me, whisper quiet. The cheater plug was definitely louder. It also got a good review at secrets.

http://www.dcispec.com/

[fibreKid]

I use a cleanbox II.

http://www.musiciansfriend.com/produ...4&src=3SOSWXXA

[azjimmy]

I use the ART CleanBoxII

http://www.audiomidi.com/CleanBox-II-P4657.aspx

Worked like a charm.

[azjimmy]

Great minds think alike

[Hakka]

I've never heard of this problem before, my BFD doesn't hum, then again im in Australia on 240v, not sure if that has anything to do with it or not.

I've had a look at the links posted in this thread, could one of those be used to eliminate the ground loop caused by a laptop on mains power?


Harry.

[brucek]

could one of those be used to eliminate the ground loop caused by a laptop on mains power?

Most likely, if it's in the audio chain.

I would like to know what solution folks use for addressing The Hum

In the BFD GUIDE, under the first section "Connecting The BFD", it discusses the solutions to this problem, including several of the products already mentioned. Some use transformers, some differential amps - take your pick... The DC1 that stitz mentioned seems to be a good price and get good reviews. I've never tried it myself.

You want to stay away from inexpensive devices for this application, since their low frequency response are quite poor. The Radio Shack product is particularily bad in this regard.

brucek

[Mitch G]

Just so people don't think I'm a complete idiot, I did see the suggestions in the BFD guide, but there appear to be a hundred Jensen products and the other products are listed in the guide as "possible solutions."
Hence, I wanted to hear some first hand accounts of what people are using.



Mitch

[Dundas]

Has anyone tried the HumX? Not having to insert something in the signal path would be prefered.
http://www.ebtechaudio.com/humxdes.html

[Josuah]

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.

[brucek]

was to buy XLR ground-lift adapters

Most people use RCA unbalanced though..... Can't lift that ground

[tdamocles]

brucek wrote:

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?

[brucek]

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...


brucek

[tdamocles]

brucek wrote:

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!

[Dundas]

brucek wrote:

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.

[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

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.

brucek

[Robert_Gibran]

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

[brucek]

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

[Mitch G]

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.


Mitch

[brucek]

If I understand the root cause of ground loop hums, this seems like it will remove the voltage potential that is causing the hum.

In some cases it will. It never hurts to ground the cable at the service panel. Any difference in potential on the safety grounds at your equipment can cause a hum.

Even though the safety ground is a cold conductor, it can and usually does, develop a small potential, through mutual inductance, wire resistance and various other reasons that can be quite different at each receptacle in your house.

When you plug a power amp into one receptacle and a preamp into another receptacle, the metal cases of these two units can have a small potential difference in their safety grounds which means that this equipment's metal cases are at a slightly different potential. When you connect a single ended (RCA) cable between these two devices, a small AC current can flow in the shield because of the potential difference. This unwanted signal is in the signal loop circuit and can cause a hum. An interconnect circuit has a loop path (completed circuit) that flows through the centre conductor of the interconnect cable and back on the shield. If there is an AC signal on the shield flowing because of the ground difference potential, you'll hear a hum. Breaking the safety ground of one of the two devices removes the potential and the path for the unwanted signal flow...

Exactly the same situation can occur, except usually worse, when you introduce a new ground into the system from cable TV or a satellite. Their ground on the shield may possess a different potential than the ground in your system and current will flow in all the interconnects. Usually by centralizing and bonding all external grounds to the common house ground you're at least giving yourself the best chance of reducing this problem.

With cable, sometimes it's necessary to use an isolator device like this one. They usually work - not by magic, but by using an RF balun or similar device. They are quite safe, albeit a bit expensive.

brucek

[lcaillo]

Mitch G wrote:

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.

Not only is it advisable, it is a violation of electrical codes anywhere in the US to not ground the cable to the a.c. service ground. You should have a ground block at the entry point connected tot he same ground rod that your electrical service is grounded to, not a water pipe. This will likely improve your problem.

You don't have to do it yourself. Your cable provider is REQUIRED to do it. If they refuse contact your county inspector's office or state professional certification board and let them know that they are not properly grounding their installations. You'll get action.

[Robert_Gibran]

brucek wrote:

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..

brucek

I was referring to lcaillo's post, the second in this thread, where he suggests this to be the proper way to cure the problem, apparently with some type of adapters or cables of adaptive nature. This would seem preferable to line source measures that utilize filters or whatever. Would this cure the problem? Apparently lcaillo believes so. Any drawbacks to this? Anyone else tried this approach?

Regarding the HumX, I agree without some data how are we to evaluate the product. Upon recieving the product, which does not include any additional data, I was left wondering if I had in fact just purchased the worlds most expensive cheater plug!

RG

[Sonnie]

Robert_Gibran wrote:

I was left wondering if I had in fact just purchased the worlds most expensive cheater plug!

We need to call out the manufacturer on it if we find this to be true.