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Well, if I use cheater plugs on the BFD of my system as well as on my plasma TV, I get slight hum with my cable feed connected.

If I disconnect my cable feed from the wall outlet, without cheater plugs, I get no hum.

So clearly my problem lies within my cable feed. The moment I hook or even touch the coax to the wall outlet I get hum through all of my speakers.
 

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The moment I hook or even touch the coax to the wall outlet I get hum through all of my speakers.
You need to check if the cable is properly grounded to your house ground. This is usually done where the cable enters the home near the service panel.
 

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I already have Comcast coming out today between 4-6pm as this symptom is present on all my coax jacks :)

Up until I started getting serious about my home entertainment, I never understood what made my bedroom subwoofer make a crazy loud hum if I jiggled the cable the wrong way.

Now I believe that also is a 60hz hum being transmitted, as I have those devices also plugged into the coax (cable internet) in one way or another.
 

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A special thanks to brucek, wayne, and HClarkx for their help in my humming problems.

These links also proved to be useful in both understanding what a ground-loop actually is, as well as troubleshooting methods to resolve them.

http://www.audioholics.com/tweaks/connecting-your-system/ground-loops-eliminating-system-hum-and-buzz

http://forum.ecoustics.com/bbs/messages/34579/180767.html

http://www.epanorama.net/documents/groundloop/home_solving.html

I ordered the Jensen transformer, and I'm hoping to put it where my CATV coax comes into my condo, before the splitter sends it to my 3 rooms. That would solve the problem at all ends, otherwise I will settle for getting my main entertainment system fixed.

-Jason
 

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So my Jensen transformer arrived today.

Basic rundown of the symptoms:

1) With cheater plugs not installed on my 3-prong devices, I had audible hum from subwoofers and satellites if the cable coax was connected to the TV.

2) With a cheater plug on the TV and Behringer, I still had slight hum when the coax cable was connected.

3) With cheater plugs and no cable coax, I had zero hum.

4) Without cheater plugs and the cable still disconnected, I had zero hum.

With my new MFW-15 subs, I still had a VERY slight hum if the Behringer was connected and the coax was also connected.

I installed my Jensen transformer as the first device after my coax feed enters my condo, before the splitter that connects my bedrooms/living room to the main feed.

I then went over and turned on all my audio devices, and only have an audible HISS at near-reference volume, which can easily be attributed to the noise-floor being amplified.

I HAVE NO HUM!

The Jensen Transformer worked like a pro for me. :)
 

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I do not know if this has already been posted in the thread(frankly, it's a long thread and I don't intend to read all of it), but Behringer has a new passive ground loop isolator. It also has balanced to unbalanced conversion. I have not had one to measure, so I can not comment on it's frequency response.

Behringer HD400

http://www.zzounds.com/item--BEHHD400

-Chris
 
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I just hooked up my BFD/amp setup with my new sub and got the hum. I have a Belkin PureAV power console where my cable TV connects as well. I had my BFD connected to a separate strip, but after reading some of this thread I tried plugging it in to the Belkin and the hum is gone. I don't know where my ground loop was, but this fixed it.
 

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Mark Seaton had mentioned in another forum regarding a thread on hum: "Markertek sells their house brand of TecNec cables for very reasonable prices. If you order XLR-RCA terminated cables, they are wired correctly, and very fairly priced.."

When he says "wired correctly" I am assuming he means pins 1 and 3 bridged at the rca end?

Also within this BFD/REW guide it again mentions Markertek and this particular cable which appears to be the same one that was referenced by Mark Seaton.

Has anyone purchased this and confirmed this is indeed wired correctly (pins 1 and 3 are bridged) demoting the notorious hum?
 

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Has anyone purchased this and confirmed this is indeed wired correctly (pins 1 and 3 are bridged) demoting the notorious hum?
The urls you mention show a typical 1/4" TS phone plug at one end and an RCA at the other. There is no pin 1,2,3 on a 1/4" phone plug. The phone plug can be a type TS (tip/sleeve) or a TRS (tip/ring/sleeve).

In the case of a BFD, we want to use the 1/4" TS phone plug (as shown in your url). This essentially shorts the ground and the minus differential amp together, which would be equivalent to shorting pin 1 and 3 on an XLR connector.

This would be the correct connection, but would do nothing to reduce hum if you were experiencing it.

brucek
 

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The urls you mention show a typical 1/4" TS phone plug at one end and an RCA at the other. There is no pin 1,2,3 on a 1/4" phone plug. The phone plug can be a type TS (tip/sleeve) or a TRS (tip/ring/sleeve).

In the case of a BFD, we want to use the 1/4" TS phone plug (as shown in your url). This essentially shorts the ground and the minus differential amp together, which would be equivalent to shorting pin 1 and 3 on an XLR connector.

This would be the correct connection, but would do nothing to reduce hum if you were experiencing it.

brucek
So the cable I linked (TS to RCA) wouldn't offer me any more value over my existing RCA cable to RCA->TS adapter?
 

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Removing hum.
The only way to remove hum with a cable would be to build a cable that uses a pseudo balanced configuration.

This involves buying a 1/4" TRS plug and wiring it to an RCA connector using two conductor shielded cable as shown below.

See how the positive (+) of the RCA connects to the Tip (+) of the TRS, and the ground of the RCA connects to the Ring (-) of the TRS, and the shield of the TRS connects to the shield of the cable without a connection back to the RCA.

This removes the physical connection between the RCA device chassis and the BFD chassis, which reduces the ground loop considerably. There is still noise rejection realized from the balanced configuration in the BFD, since noise rejection basically relies on matched impedances at the two inputs of the differencial amplifier stage. The impedance of the positive differential amplifier will be that of the previous stages output impedance, while the negative differential amplifier will be at ground or zero impedance. The mismatch still offers decent noise rejection.

Note that you require two conductor shielded cable to use this configuration, and that depending on the severity of the ground loop, this may not offer enough help.

pseudo balanced.jpg

brucek
 

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So the The easiest way to build this cable might be to buy an XLR to XLR or TRS to TRS cable and then remove one of the XLR or TRS ends replacing it with an RCA connector wiring the RCA connector appropriately as documented in the image above?

This would fit the requirement around having a cable with 2 conductors with shield and you're half there having the cable already bound with either an XLR or TRS connector on one end. I am assuming there wouldn't have to be any changes made to the XLR or TRS end as the main change in wiring occurs at the RCA termination.

Correct?
 

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Rolls HE18 Buzz Off Hum Eliminator

I bought a Rolls HE18 "Buzz Off" hum eliminator at my local Guitar Center last week and I am very happy with the results.

I had a pretty noticeable hum that I was chasing down and decided to try a hum eliminator. I have read of many people having good luck with the ART Cleanbox II but couldn't find any local. I was able to find one of these in stock so I decided to give it a try. It has completely eliminated the hum and the response curve is unchanged (measured with REW). I also like the fact it has standard RCA inputs/outputs in addition to the 1/4" inputs/outputs.
 
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