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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
 

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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.
 
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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! :dunno:

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Can you explain what you mean? The BFD has both balanced and unbalanced capability on the output already.
brucek
The BFD manual states that the outputs are balanced and recommends using balanced devices. The BFD is no different from any other balanced device, in that you can ground one side and use it with unbalanced devices, halving the impedance. While this may work fine in some systems, others will have problems with it. The only certain way to avoid ground loops due to kludged unbalanced connections is to use a balancing transformer or an active device designed to modify the output configuration. Transformers are the logical choice for low frequencies like we use with subs.
 

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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?
Robert,

I'm don't see where lcaillo's post refers to adapters or cables. He said the proper way to eliminate the problem is with a transformer - and he's correct. I backed this up in my post where I suggested any of the in-line solutions suggested in the Guide would work by using transformers or differential amps. You do have to be careful to not purchase a transformer that is so cheap that it suffers a poor low frequency response.

Either the DCI-ALHI or the Ebtech Hum Eliminator would be fine. Personally, I like Jensen transformers. Some people just make their own with Jensen transformers or they purchase them in a box like this or this.
Jensen supplies this type of proper spec sheet. Why can't the others? I suppose that's why Jensen products are so **** expensive.
MarkerTek for $120.....or mono MarkerTek for $95............... :)

brucek

EDIT: I should be mentioning the Jensen isolator for subs which has better low frequency response.
 

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Bruce,
The HumX patent application appears to be number 20040264712 which can be seen at:
http://appft1.uspto.gov/netahtml/PTO/srchnum.html

In addition to the BFD I also have a hum problem with an HDMI connection between my Panasonic projector and Denon receiver. I have not seen any signal path solutions for HDMI.
The HDMI connection is just one of the ground paths that exist in your system. Look for a solution elsewhere by improving the ground at some point or isolating one. Chances are that the problem is something else and breaking that connection is just one of several that relieves the problem.
 

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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!
The HumX patent application appears to be number 20040264712 which can be seen at:
The patent documentation shows the device to be exactly as I indicated before. It uses the standard method of inserting (parallel back to back diodes) in series with the safety ground. Using the fact that the flow of current that causes hum is usually quite low, it is easy to see that if you place a device in series that inhibits that flow until a small breakdown voltage is reached, then no current will flow and the hum problem is solved.

A single diode has a breakdown of 0.7volts and two would have a breakdown of 1.4volts, etc. You need two sets in parallel with opposing polorization, since this is required to pass AC current.

This is the standard principle used in marine galvanic isolators to block AC and DC currents from reaching a boat connected to shore power. It eliminates corrosion of the boat hull etc.

Anyway, this is great as long as those diodes are rated to pass a steady state current long enough to trip a breaker on the hot line. A 120voltAC dead short can pass enormous current. It can easily be a few hundred amps depending on your service. The breaker should trip fairly quick. It must trip before those diodes blow. Most high current diodes are the variety that require bolting to a heat sink to achieve their rating. But then, they must pass that current for long periods of times. The diodes in the HumX only need to pass that current long enough to trip a 15 or 20 amp breaker. Hopefully the diodes that are jammed into that little device are spec'd to achieve that. I'd feel confident if it had a UL or CSA sticker on it. Either way, the HumX is sure better than a cheater plug.

You also have to realize that if the BFD is connected to a device that has a safety ground, then the shields of the interconnects will pass the current in the event of a BFD failure and trip the breaker. In fact, that's long been a trick to eliminate ground loops and its resultant hum. Choose a central device that everything is connected to (such as a processor), and then cheat every other device except the processor. The theory being that the interconnects will provide the path to safety ground through the one device that is safe. This is a horrible idea though, since some unsuspecting person may have the interconnects pulled off and a fault may occur and electrocute them. Don't use this method.

The best and safest method is to plug in the three prong plug to the wall and if there is a hum, solve it at the line level.........

brucek
 

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I'm going to buy an isolation transformer for this purpose very soon.

Is the Ebtech Hum Eliminator significantly better than the Art Cleanbox II?
 

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I haven't any experience with these two products, but the specs they publish show the low frequency response of the Art CleanBoxll to be better. That's important for a sub application.

The HUM Eliminator shows down 0.5dB @ 20Hz. We don't know what the 10Hz value is.
The ART shows 0.5dB @ 10Hz.

These transformer based hum devices generally would use an "input" type transformer. This is evidenced in the ART spec with it's large insertion loss with low input impedance loads. This would mean it is a good idea to install it very close to the load amplifier. Probably a good idea anyway, because since it allows balanced or unbalanced connections. I would run a long balanced interconnect from the BFD to the ART box and then a very short RCA unbalanced interconnect to the power amplifier (unless your amp is balanced input - then use that)...........

brucek
 

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I have a balanced interconnect from the BFD to a Carvin amp. No problem there.
The noise is in the connection between the Denon receiver and the BFD.
I should install the Cleanbox close to the receiver, right?
 

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The noise is in the connection between the Denon receiver and the BFD.
I should install the Cleanbox close to the receiver, right?
Well, since you'll be running balanced from the cleanbox to the BFD, and unbalanced from the receiver to the cleanbox, you would think that the distance from the receiver to the cleanbox should be shortest, but I don't feel that it would be best here.

My reasoning being that the output impedance of the cleanbox demands that the output cables be the shorter ones, although the worst that will happen with long lines after the cleanbox is that it will act as a low pass filter and lower transient response.

Either way, your BFD must be located close to the reciever, no?

brucek
 

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Actually, after rethinking this, I would definitely place the Cleanbox close to the BFD and run the longer unbalanced lines to the cleanbox from the receiver.

The cleanbox's job is reject noise. Even though the line feeding it is unbalanced, the common mode rejection will be very high since transformers tolerate the mismatched source impedance very well.
The short lines on the output of the cleanbox will offer the lowest distortion and overall insertion loss.

brucek
 

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I guess it's a useful discussion for others, but silly for me to debate.
My BFD is sitting next to my receiver, literally touching it.
Two 18" cables will do the trick.
 

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HELP!

HELP!

I bought the ARTcessories CleanBOX II and hooked it up. It made a terribly loud hum!

I connected my recievers subwoofer pre-out to the CleanBOX II with a cable that has an RCA jack on one end and an unbalanced 1/4" TS jack on the other. I connected the CleanBOX to the BFD with a balanced 1/4" TRS cable. I powered up the amp and it hummed very loudly. What did I do wrong?

The connections on the CleanBOX II are confusingly labeled in that one side is labeled input and the other side is labeled output, but a painted line seems to indicate that the inputs are connected, which seems not to be the case as I have tried connecting the cables all ways.

Help!
 

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Most people use RCA unbalanced though..... Can't lift that ground :)
How about this duo? This combined with a cheater plug?

Will this work? I've found the gfci elsewhere for about $12. $12+cost of a cheater plug could be a cheap solution to eliminate ground loop hum.... Any comments?

What I found is that the GFCI works the same as the ground(3rd prong) with one difference....If there is a ground fault, you won't know until you touch it and get a slight shock before it shuts power off. If the BFD isn't bypassed with the cheater plug a ground fault would blow a fuse or circuit immediately without touching it.
 

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I connected my recievers subwoofer pre-out to the CleanBOX II with a cable that has an RCA jack on one end and an unbalanced 1/4" TS jack on the other. I connected the CleanBOX to the BFD with a balanced 1/4" TRS cable. I powered up the amp and it hummed very loudly. What did I do wrong?

The connections on the CleanBOX II are confusingly labeled in that one side is labeled input and the other side is labeled output, but a painted line seems to indicate that the inputs are connected, which seems not to be the case as I have tried connecting the cables all ways.
This is a stereo unit, so there are two inputs and two outputs. The funny line between the two seems dumb for sure.

Anyway, since we presume this is a transformer device, you can remove the ground reference at its input and simply use the differential input.

Does the sub amp hum with just the BFD and cleanbox connected without the receiver connected?

Are you able to make your own cables?

brucek
 

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Thanks for helping, Bruce.

There is no hum at all if the receiver is not connected to the input of the CleanBOX.

I don't make cables, but I could always order a custom one from a local shop if I needed to. What could be wrong wtih the way it's hooked up now?

(Maybe some bonehead bought this unit and fried it with an amplified signal and then returned it to the store. ???)

Here's what I tried and got the very loud hum.

 
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