Ground Loops - Eliminating System Hum and Buzz

[highfigh]

Thanks @highfigh !

so it is normal for equipments like TV, allope Tv and blueray players with their chassis enrgized. Thanks for the info. My AVR is Anthem MRX510 and my power amp is Rotel 1095. I don’t have cable TV, only the normal TV which means antenna on the roof, then the cable run into walls and to my living room.

I wonder if it is my power amp, because when I’m using just my AVR, my speakers are dead silence…Both my AVR and power plug into the same power board, I’ve also tried not using the power board and plug both AVR and power amp straight to a dourble wall outlet right next to each other, made no difference… frustrating!

You should never be able to measure voltage between the chassis of any equipment.

And before you try anything that could be harmful, ignore any advice to use a power plug adapter that converts a three prong power cord to two prongs- that would 'lift' the ground on the piece with the grounded plug and make the chassis electrically 'hot', which could be a lethal situation.

Where are you located? This sounds like it could be a house wiring issue- I have seen outlets wired incorrectly many times, even though they're in the same junction box.

 

[TLS Guy]

Hi-Fi beat me to it. This cheap device from Home depot, will allow to check the wiring of you outlet, safely and easily.

Unfortunately, it appears that the ground plane in your Rotel amp is poorly configured.

Having said that the pro way is always to put the ground at the preamp or mix panel.

If you secure a robust ground lead, and I mean a big one, and connect to the ground of the receptacle securely, and then bond it securely to the turntable ground on the receiver and then use a robust cable from the receiver to the Rotel chassis ground, that likely will solve the problem. Then you could safely use a cheater plug, as long as you never switch the power amp on unless bonded as above.

My first pre/pro was a Rotel and that had an internal ground plane issue as well. I did not keep it long.

 

[pinifinina]

Hi-Fi beat me to it. This cheap device from Home depot, will allow to check the wiring of you outlet, safely and easily.

Unfortunately, it appears that the ground plane in your Rotel amp is poorly configured.

Having said that the pro way is always to put the ground at the preamp or mix panel.

If you secure a robust ground lead, and I mean a big one, and connect to the ground of the receptacle securely, and then bond it securely to the turntable ground on the receiver and then use a robust cable from the receiver to the Rotel chassis ground, that likely will solve the problem. Then you could safely use a cheater plug, as long as you never switch the power amp on unless bonded as above.

My first pre/pro was a Rotel and that had an internal ground plane issue as well. I did not keep it long.

Thanks for the info guys, I am a bit confused now. So I have 2 issues? One is my house wiring issue, and second is my Rotel amp has ground issue? What are those 2 things mean?

What does it mean by house wiring issue? If there is a issue, shouldn't that mean no power coming out from the power outlet?

@TLS Guy what do you mean by there is a ground issue with the Rotel amp? You mean there is a design fault on the Rotel amp? Is a known issue for Rotel amp? I assumes this issue can not be repaired hence why you sold your unit instead of trying to repair it? The amp has 3 pins socket at the back, and the power core is also 3 prongs. My AVR only has 2 pins socket at the back, but it came with 3 prongs power cable, which I find it weird because to me, that ground pin is useless because there is only 2 pins at the back on my AVR...

@highfigh I am in Australia, we have 2 or 3 pin power cable here depending on the electrical goods. When I use a multimeter and measure a screw on my AVR, I got 0.03VDC (red probe touching my tile floor which is concrete underneath and black probe touching the screw), and 6.3VAC (same method). However, if I reverse my polarity, meaning now I use the red probe touching the screw of my AVR and black probe touching the floor, I got 9.3VAC. I am not an electrician so I actually have no idea what these means... all I know is if I have no ground in the system, I get a light buzz on my finger whenever I touch my my system or any cable.

@TLS Guy I have done something similar but not exactly as what you've suggested. When I was doing my testing to solve the ground loop issue, I ran a thin wire from the AVR ground screw to the power amp chassis, while everything is connected, I removed the power cord of my power amp, and I can see a small spark if I remove the wire from power amp and then lightly touching it, whenever the wire touches the power amp chassis I can see a light spark... this indicates to me there is some electricity trying to flow from the AVR to the power amp, correct? When I reconnect power amp's the power cord, this effect disappears, I assumed it is because now the power amp is connected to the ground so all the "leakage" electricity from the AVR now goes to the power amp chassis and then to the ground, whereas before, when I remove the power cord of the power amp, the "leakage" electricity from the AVR flows to the power amp, but got no where to go, hence why I see the spark, am I correct on this? So this means, the AVR has no ground, even though it has 3 pin power cord, but like I said before, my AVR only has 2 pin socket at the back, so there is no point having/using 3 pin power cord.

@TLS Guy so if I understand you correctly, you think I should get a thick cable, take one end and stick it into the ground of a power outlet and then the other end to the AVR ground screw, and then take another thick wire, one end to the ground screw of the AVR, and the other end to the power amp chassis?

Sorry I have many questions on this @TLS Guy and @highfigh , really hope you guys can help me out on this. Thank you

 

[TLS Guy]

Thanks for the info guys, I am a bit confused now. So I have 2 issues? One is my house wiring issue, and second is my Rotel amp has ground issue? What are those 2 things mean?

What does it mean by house wiring issue? If there is a issue, shouldn't that mean no power coming out from the power outlet?

@TLS Guy what do you mean by there is a ground issue with the Rotel amp? You mean there is a design fault on the Rotel amp? Is a known issue for Rotel amp? I assumes this issue can not be repaired hence why you sold your unit instead of trying to repair it? The amp has 3 pins socket at the back, and the power core is also 3 prongs. My AVR only has 2 pins socket at the back, but it came with 3 prongs power cable, which I find it weird because to me, that ground pin is useless because there is only 2 pins at the back on my AVR...

@highfigh I am in Australia, we have 2 or 3 pin power cable here depending on the electrical goods. When I use a multimeter and measure a screw on my AVR, I got 0.03VDC (red probe touching my tile floor which is concrete underneath and black probe touching the screw), and 6.3VAC (same method). However, if I reverse my polarity, meaning now I use the red probe touching the screw of my AVR and black probe touching the floor, I got 9.3VAC. I am not an electrician so I actually have no idea what these means... all I know is if I have no ground in the system, I get a light buzz on my finger whenever I touch my my system or any cable.

@TLS Guy I have done something similar but not exactly as what you've suggested. When I was doing my testing to solve the ground loop issue, I ran a thin wire from the AVR ground screw to the power amp chassis, while everything is connected, I removed the power cord of my power amp, and I can see a small spark if I remove the wire from power amp and then lightly touching it, whenever the wire touches the power amp chassis I can see a light spark... this indicates to me there is some electricity trying to flow from the AVR to the power amp, correct? When I reconnect power amp's the power cord, this effect disappears, I assumed it is because now the power amp is connected to the ground so all the "leakage" electricity from the AVR now goes to the power amp chassis and then to the ground, whereas before, when I remove the power cord of the power amp, the "leakage" electricity from the AVR flows to the power amp, but got no where to go, hence why I see the spark, am I correct on this? So this means, the AVR has no ground, even though it has 3 pin power cord, but like I said before, my AVR only has 2 pin socket at the back, so there is no point having/using 3 pin power cord.

@TLS Guy so if I understand you correctly, you think I should get a thick cable, take one end and stick it into the ground of a power outlet and then the other end to the AVR ground screw, and then take another thick wire, one end to the ground screw of the AVR, and the other end to the power amp chassis?

Sorry I have many questions on this @TLS Guy and @highfigh , really hope you guys can help me out on this. Thank you

I wish you had told us you are in Australia. We really need location to be required to show in all posts. Power is contrived very differently from jurisdiction to jurisdiction. In Australia I find there are even regional differences.
Here is what I find out about Australia.

The ground is the bottom socket, the live on the left and neutral on the right. Your voltage is either 220 or 230 volts single phase. Most places are switching to 230 volts.

Problems can arise if the live and neutral are reversed. So there should be 230 volts between the lower ground slot and the left slot. There should be zero volts between the neutral and ground. If this is reversed then it needs correction pronto, as it is dangerous.

If the socket is wired correctly, then your amp most likely has a poorly designed ground plane. Designing ground planes is an art. It is not uncommon for audio units to have poorly thought out ground planes leading to hum. It is hard to correct, and in your case I have a feeling you may have to dump that unit if what I suggested fails.
If there is even the slightest resistance between any of the internal grounds in a power amp especially, then hum results.

House grounding design is also often an issue. We built this house 2 years ago, and I was fanatical about the design of the house ground plane, and supervised the electricians every inch of the way.

 

[TLS Guy]

I have had one other thought. May be this is radio frequency interference, known as RFI and not a ground loop. The commonest causes these days are LED light bulbs, especially if they are connected to light dimmers. This is very common with the ubiquitous SCR dimmers.

So turn off all LED lights in the house and any associated dimmers. See if this stops the hum/buzz.

 

[pinifinina]

Hi @TLS Guy , if it is the LED light, shouldn't I also hear the buzz/hum noise when I am only using my AVR?

 

[TLS Guy]

Hi @TLS Guy , if it is the LED light, shouldn't I also hear the buzz/hum noise when I am only using my AVR?

No. It is usually leads that pick it up. Belden do make a cable that is resistant to picking up RF. The other thing is how close is your power amp to the receiver. As electromagnetic induction is another possibility. You don't want the units sitting on top of each other. So a good separation is always a good idea.

 

[highfigh]

Thanks for the info guys, I am a bit confused now. So I have 2 issues? One is my house wiring issue, and second is my Rotel amp has ground issue? What are those 2 things mean?

What does it mean by house wiring issue? If there is a issue, shouldn't that mean no power coming out from the power outlet?

@TLS Guy what do you mean by there is a ground issue with the Rotel amp? You mean there is a design fault on the Rotel amp? Is a known issue for Rotel amp? I assumes this issue can not be repaired hence why you sold your unit instead of trying to repair it? The amp has 3 pins socket at the back, and the power core is also 3 prongs. My AVR only has 2 pins socket at the back, but it came with 3 prongs power cable, which I find it weird because to me, that ground pin is useless because there is only 2 pins at the back on my AVR...

@highfigh I am in Australia, we have 2 or 3 pin power cable here depending on the electrical goods. When I use a multimeter and measure a screw on my AVR, I got 0.03VDC (red probe touching my tile floor which is concrete underneath and black probe touching the screw), and 6.3VAC (same method). However, if I reverse my polarity, meaning now I use the red probe touching the screw of my AVR and black probe touching the floor, I got 9.3VAC. I am not an electrician so I actually have no idea what these means... all I know is if I have no ground in the system, I get a light buzz on my finger whenever I touch my my system or any cable.

@TLS Guy I have done something similar but not exactly as what you've suggested. When I was doing my testing to solve the ground loop issue, I ran a thin wire from the AVR ground screw to the power amp chassis, while everything is connected, I removed the power cord of my power amp, and I can see a small spark if I remove the wire from power amp and then lightly touching it, whenever the wire touches the power amp chassis I can see a light spark... this indicates to me there is some electricity trying to flow from the AVR to the power amp, correct? When I reconnect power amp's the power cord, this effect disappears, I assumed it is because now the power amp is connected to the ground so all the "leakage" electricity from the AVR now goes to the power amp chassis and then to the ground, whereas before, when I remove the power cord of the power amp, the "leakage" electricity from the AVR flows to the power amp, but got no where to go, hence why I see the spark, am I correct on this? So this means, the AVR has no ground, even though it has 3 pin power cord, but like I said before, my AVR only has 2 pin socket at the back, so there is no point having/using 3 pin power cord.

@TLS Guy so if I understand you correctly, you think I should get a thick cable, take one end and stick it into the ground of a power outlet and then the other end to the AVR ground screw, and then take another thick wire, one end to the ground screw of the AVR, and the other end to the power amp chassis?

Don't worry about DC voltage unless you're dealing with DC voltage, which you're not- measure AV voltage. Also, the tile floor isn't your ground reference, the dirt outside is, which is why British and others refer to it as 'Earth ground'. EVERYTHING references to the Earth but a building's grounding needs to be done correctly and conditions must be right for it to work properly, so this means the ground MUST conduct electricity well- extreme drought conditions can cause the ground to dry enough that the ground won't do its job.

The circuit tester TLSGuy linked to is great, but doesn't show voltage between devices- however, a simple test light (this can be bought at an auto parts store) with incandescent bulb can. The cables between the AVR and power amp would need to be disconnected, the clip on the test light's wire would be connected to the shield of the power amp and the probe would be connected to the AVR. If it lights dimly, some voltage is present and if it illuminates brightly, try using a different amplifier. As TLS posted, the preamp or, in this case the AVR, is where the ground occurs, not the power amp. You may see people comment about 'star grounding'- this isn't technically used correctly because, while it might make sense to think of the system as a star with one piece as the centerpoint, it's not a physical topology but rather, it's an electrical concept. This is where it becomes confusing- the AVR should be the center of the electrical grounding scheme for the system (that should be grounded, but the rest usually isn't) and it happens to be the hub of most AV systems. Think in electrical terms- there should be no resistance between the device chassis (plural) and the AVR's chassis.

To test your wiring, the tool in the link will be needed in Australia-

Power Point and Leakage Tester | Jaycar Electronics

Test your power points using this versatile tester. It checks most types of power points within 110V to 240V range for correct wiring and trip levels ...

www.jaycar.com.au

BTW- DO NOT stand barefoot on the tile floor when you touch the equipment- if you feel any kind of vibration as you slide a finger along the edge of your power amp or AVR when you're wearing shoes with insulating soles, it means that the chassis of at least one piece is electrically charged (referred to as 'hot'). Standing barefoot or in socks puts you at risk of being shocked, possibly worse- been there (shocked), done that. If you feel this, hire an electrician to check out the wiring in your house or building- your electrical grid uses 230VAC- nothing to mess with. This would be especially lethal if the person touching the 'hot' equipment has a pacemaker for their heart. Concrete conducts electricity well enough that touching live wires or 'hot' chassis could be lethal- always wear rubber soled shoes when working with electricity and never touch anything that's in contact with live wires (or the wires themselves) AND anything that should be, or is, grounded. You would be acting to complete the circuit and that's not where you would ever want to be.

Do you have a switch on a wall that can shut off the power to one of the outlets used for the system? If so, have the wiring tested- when I wrote "been there, done that", it was in reference to the garage at my parents' house- their friend (an Electrical Engineer) had wired the garage electrical service and did it wrong- he switched the Neutral wire on the three-way switches and that made the metal siding on the garage a live part of the circuit because the junction boxes are metal and in contact with the siding. I had also felt the vibration I mentioned as a kid when I would touch the stereo in our basement but never received a shock.

 

[Mr._Clark]

Problems can arise if the live and neutral are reversed. So there should be 230 volts between the lower ground slot and the left slot. There should be zero volts between the neutral and ground. If this is reversed then it needs correction pronto, as it is dangerous.

Just in case anyone doubts that this can happen, a friend of mine just discovered that the live and neutral were reversed in an outlet at his house (this is in the U.S.).

 

[highfigh]

Just in case anyone doubts that this can happen, a friend of mine just discovered that the live and neutral were reversed in an outlet at his house (this is in the U.S.).

That happens much more frequently than many think. It's not a problem for light bulbs and appliances unless the appliance is close to plumbing (pipes, faucets, etc, or other appliances that are wired properly). Many electricians are totally unaware of why this is a problem for AV equipment.

 

[pinifinina]

Hi guys,
Finally got some updates. So I’ve tested my power outlet, everything seems good, the polarity is all correct, no leakage between the active and the neutral and the ground. Turn off the LED lights made no difference.

Finally, I decide to make a ground for my AVR. So I grab a wire and wrap around the ground prong of the AVR power cable, and the other end attach to the ground screw at the back of the AVR. And then..........NO MORE HUM! YES!YES!YES! I am not sure if this is the safest way to do it, but it works! Like what you all said, it is best to ground at the PRE amp (AVR in my case), and this really works! If any of you have a better way to ground a device other than what I did, please share!

 

[highfigh]

Hi guys,
Finally got some updates. So I’ve tested my power outlet, everything seems good, the polarity is all correct, no leakage between the active and the neutral and the ground. Turn off the LED lights made no difference.

Finally, I decide to make a ground for my AVR. So I grab a wire and wrap around the ground prong of the AVR power cable, and the other end attach to the ground screw at the back of the AVR. And then..........NO MORE HUM! YES!YES!YES! I am not sure if this is the safest way to do it, but it works! Like what you all said, it is best to ground at the PRE amp (AVR in my case), and this really works! If any of you have a better way to ground a device other than what I did, please share!

And you wrote that the AVR has a two prong power inlet on the back?

I think this was recommended earlier. Use the screw that holds the wall plate in place by crimping a ring terminal onto the wire.

 

[pinifinina]

@highfighthat that is correct, my AVR only got 2 pins for the power at the back, but it comes with 3 prong power cable, this means the ground prong does nothing as it is not connected to anything. I know it was suggested earlier that it is best to have just one ground and should be at the pre-amp, but I wasn't sure how to do that. Which is why at end I decided to give it a go by doing what I've described in the previous post. I still have my power amp grounded, I did not remove the ground because I don't have anything to do so. I'm planning to try and get a power cord with only 2 prongs and see if it makes a difference. The power cords are all detachable so should be easy. The hum is pretty much gone, but I still got a bit of buzz from the tweeters, not sure if it is internally induced noise from the pre-amp, or other connected devices...hence why wanting to try to remove the ground from the power amp and just have 1 ground on the pre-amp (AVR). Will report back how I go.

 

[pinifinina]

Hi guys,
Its been 2 years now, what a busy past 2 years. I would like to continue on this topic if you all still interested. So, the "hum free" situation didn't stay for long. But I have discovered the hum is actually cause by my TV. What I did is I disconnect everything from my power amp except for the speakers. I power on my amp, there are no mechanical hum from the toroidal transformer. I have disconnect everything from my TV, so nothing is connected to the TV. The moment I turn on my TV, my toroidal transformer in my power amp start humming. I turn the TV off, the hum disappears. I turned on my receiver, apple TV and blueray player one by one and none of them cause the power amp to hum. Hence I concluded it is my TV that is causing my power amp to hum. The question is how and why? I did some research on the web some said the TV is feeding DC offset voltage back to the mains hence can cause power amp to pick that up and cause it to hum? Just to refresh some info on my power amp, it has 3 prongs on the power cable, hence it has a ground. I think this has something to do with it? Any help will be appreciated. Thank you.

 

[TLS Guy]

Hi guys,
Its been 2 years now, what a busy past 2 years. I would like to continue on this topic if you all still interested. So, the "hum free" situation didn't stay for long. But I have discovered the hum is actually cause by my TV. What I did is I disconnect everything from my power amp except for the speakers. I power on my amp, there are no mechanical hum from the toroidal transformer. I have disconnect everything from my TV, so nothing is connected to the TV. The moment I turn on my TV, my toroidal transformer in my power amp start humming. I turn the TV off, the hum disappears. I turned on my receiver, apple TV and blueray player one by one and none of them cause the power amp to hum. Hence I concluded it is my TV that is causing my power amp to hum. The question is how and why? I did some research on the web some said the TV is feeding DC offset voltage back to the mains hence can cause power amp to pick that up and cause it to hum? Just to refresh some info on my power amp, it has 3 prongs on the power cable, hence it has a ground. I think this has something to do with it? Any help will be appreciated. Thank you.

That is really bad luck, and the only solution is a new TV.

The TV must have some sort of non linear pulsed power supply. This is creating pulses in your AC system which just happen to coincide with a resonance in the core of your toroidal transformer. The odds against that are enormous. I would by a lottery ticket with that sort of luck.

 

[Mikado463]

I would by a lottery ticket with that sort of luck.

not a bad idea, I think the 'Power Ball' is up around 1.7 B..........

 

[TLS Guy]

That is really bad luck, and the only solution is a new TV.

The TV must have some sort of non linear pulsed power supply. This is creating pulses in your AC system which just happen to coincide with a resonance in the core of your toroidal transformer. The odds against that are enormous. I would by a lottery ticket with that sort of luck.

Actually on thinking about this, it is your power amp that should be replaced. The transformer should not make mechanical noise under any circumstance. That transformer was not properly "potted". That is a manufacturing defect that surfaces in AC transformers from time to time. Some transformer manufacturers are known for this problem and sometimes there will be defective batch runs.

 

[pinifinina]

Actually on thinking about this, it is your power amp that should be replaced. The transformer should not make mechanical noise under any circumstance. That transformer was not properly "potted". That is a manufacturing defect that surfaces in AC transformers from time to time. Some transformer manufacturers are known for this problem and sometimes there will be defective batch runs.

Thanks @TLS Guy , that is good to know. I do want to point out that when I place my head behind my TV, it does make a descent buzzing noise... Not sure if that helps with the situation....

By the way, does a power am suppose to have 3 prongs power cord? This means everything is ground via my power amp, is that a good thing?

 

[TLS Guy]

Thanks @TLS Guy , that is good to know. I do want to point out that when I place my head behind my TV, it does make a descent buzzing noise... Not sure if that helps with the situation....

By the way, does a power am suppose to have 3 prongs power cord? This means everything is ground via my power amp, is that a good thing?

That all depend on how the power amp is designed. Some are designed for three pin AC cords, and some are designed as so called double insulated units without a grounding plug.

 

[pinifinina]

Thanks @TLS Guy , that is good to know. I do want to point out that when I place my head behind my TV, it does make a descent buzzing noise... Not sure if that helps with the situation....

By the way, does a power am suppose to have 3 prongs power cord? This means everything is ground via my power amp, is that a good thing?

By the way @TLS Guy , if there is defect on the power amp, how come it only hums when the TV is on and not with the rest of my equipment? I would thought if the defect is on the power amp, it should hum with any equipment?