Ground Loops - Eliminating System Hum and Buzz

[highfigh]

'josh' the DC part of your post is totally incorrect. Planet Earth works the same way with DC as with AC. In the past, we didn't see much high voltage DC in contact with Earth. But now some electric cars have high voltage batteries and in an accident, the safety worker have to be careful not to electrocuted.

With electric cars and even electric tools, I'm more concerned about the Lithium batteries going off like a small rocket. The local SnapOn guy was charging a Ryobi battery in his former garage, near his former SnapOn truck filled with former tools, his former pickup truck, his former Camaro and the Alpha Romeo he inherited from his dad. The new garage isn't quite done.

 

[joshk03]

Speedskater & TLS Guy, perhaps you could update your last posts? The mistake has been corrected.

 

[Speedskater]

Speedskater & TLS Guy,
....................................
Speedskater, they work the same, but should never be connected together.

In a hi-fi component, the AC Safety Ground is connected to the chassis and the DC supply common (aka ground) is also connected to the chassis.

 

[NorseMythology]

I get a nasty POP when I turn my bathroom exhaust fan off, I get some feedback when I turn the lights on and off in the bathroom but not like the exhaust fan. Any ideas?

 

[Speedskater]

There are suppressor circuits for that type of POP. But the parts are tricky to purchase and install.

Use a long extension cord to power your hi-fi from different circuits in your home. (as a test)

 

[highfigh]

In a hi-fi component, the AC Safety Ground is connected to the chassis and the DC supply common (aka ground) is also connected to the chassis.

Sometimes. There's plenty of gear that uses a two prong AC plug. In that case, the ground only meets the AC neutral inside of the breaker panel although this can be different in various countries.

 

[fabiocz]

How much volts is considered less/more dangerous in ground loop ?
Example:
3v = low ?
20v = high ?

 

[bikdav]

What can be done about computers? My BUZZ noise comes from the desktop PC. Actually, I have 2 desktop PCs. I tried both of them on my system and they both emit that same BUZZ. I even tried another amplifier. That didn't solve anything.

 

[kenwstr]

What can be done about computers? My BUZZ noise comes from the desktop PC. Actually, I have 2 desktop PCs. I tried both of them on my system and they both emit that same BUZZ. I even tried another amplifier. That didn't solve anything.

I recently installed a new AV specked PC in a PA system that I maintain. So, I did a lot of R&D for the spec and how best to connect it into the PA system. Turns out that while PC audio has definitely come a very long way over the last decade or so, it is still not comparable to a good CD player unless you spend an insane sum on filtering and isolation etc. Part of the problem is the USB power. However, you can still get a good result on a budget of a few hundred by paying simple attention to basic filtering and electrical isolation.

As far as my research revealed, best practice is to use an external DAC rather than the computing devices sound card and headphone jack. While there are some very good shielded internal DACs available, this is still not best practice. An external DAC gets this process out of the PC case and away from interference effects and power noise that PC's are generally riddled with. Oddly enough USB is still considered very highly for PC audio despite it being very old tech. I used a Trip-Lite U023 USB cable because of the high shielding and ferrite chokes that suppress a degree of noise from the PC. The DAC itself is a Radial USB-Pro. This incorporates further noise filters, capacity to accept high res audio, audio transformer and ground isolation (eliminates potential ground loop hum). I am using a standard lossless uncompressed bit stream (less than the DAC's capacity). The DAC's balanced output is from it's internal audio transformer which allows PC/DAC ground shield to be isolated from the PA ground shield (ground lift). This is a relatively inexpensive pro audio DAC but up there in quality and durability. It was a convenient option to connect with the mixing desk's balanced XLR inputs and provide electrical isolation at the same time. I have listened to music from this DAC directly into my HD650 phones and it is equivalent to anything I have heard from any digital source and I am eminently pleased with the result for the money.

You could probably find a similar device with single ended audio outputs or use a balanced to unbalanced (single ended) converter.

At home, I use an Essence HDACC to connect all my digital sources into an analogue stereo system. This does not in itself provide ground loop isolation though but I am not using it to connect computers to the stereo. For that, I would have to use and audio transformer between the HDACC and the analogue Stereo system. So basically, the options are either a DAC with an output & ground shield isolation or use a separated audio transformer if ground loop hum exists.

Both perform very nicely IMO however, to get the same kind of filtering and isolation as I have with the PA, but in an unbalanced or single ended solution, in a high end HiFi solution would generally take separate components (filters, isolator, USB power conditioner....) and add up to a premium price. Which is why many people are ditching computer audio in favor of audio specific devices to serve digital music into high end DACs. Perhaps something like a music server or smart player connected to a network drive or simply a streaming service. The only advantage I can see offered by a computer is the convenience of playlists. Where I am, that's about $2500 AUD to setup a full HD AV PC and external DAC with appropriate filtering and electrical isolation. That's a big investment for that playlist function alone.

 

[highfigh]

What can be done about computers? My BUZZ noise comes from the desktop PC. Actually, I have 2 desktop PCs. I tried both of them on my system and they both emit that same BUZZ. I even tried another amplifier. That didn't solve anything.

It's possible that the buzz may be from the display or a power supply. Is the computer close to the amplifier, or in another room? If the latter, run an extension cord from the outlet powering the audio system to the computer and if the noise stops, you have a ground loop. If possible, it may be necessary to use a separate ground wire to connect them.

 

[Jenzard]

Hello there, forgive me...I am new as of today! Thank you!
So to my question. What if you have a static sound coming thru speakers. not blown, but sounds staticky and it is intermittent? We have replaced all of our cables/speaker wires with sheilded cables as of late. I keep thinking my AVR is on its way out, but would this be intermittent? OR does this sound like a ground loop issue? I am patiently or not so patiently...waiting for my new Amplifier to get here. (This is a first time for me). Super Excited...But I fear that I will be amplifying my problem. Any thoughts are much appreciated.

Jenzard

 

[Audioluvr!]

The problem with ground loop issues is that an electrical engineer designs a fantastic system, then some idiot builds it based on a schematic not knowing the laws of amp design. Basically every ground wire needs the EXACT same length. If you have an amp or pre that you LOVE the sound of then it needs a qualified technical engineer to review and repair. Luckily for me I know of one locally. Rolland of Hi-Tech Audio in Stevenson, WA. is a master of this kind of stuff. I'm sure there are others in your area.

Good help isn't cheap. Cheap help isn't good. Pick one.

 

[Speedskater]

What if you have a static sound coming thru speakers. not blown, but sounds staticky and it is intermittent?

That's not a ground loop. A ground loop has a low frequency hum or buzz sound.
You might have an interference problem. Try turning different items on your home on/off and see if the noise follows.
Things like hi-tech lighting, HVAC, TV's & Set Top Box's, Wi-Fi and appliances.

 

[pinifinina]

Hey everyone, first time poster on audioholics. I also put my conundrum on the AVS forum as well to try to get as much advice as possible, so if you see my post on there then just ignore it. I'm just looking for a little help in determining how to correct a potential ground loop problem in my system.

My HT setup consists of a Marantz SR7009 AV receiver connected via the pre-outs to an Outlaw Audio Model 5000 power amp - these 2 components are running a 7.1.4 atmos setup using a 7.1 base-layer of Pioneer SP-PK52FS Andrew Jones speakers and 4 Atlantic Technology IC-6 OBA ceiling speakers for the atmos. My other relevant components are an LG OLED C6 display and an Oppo UDP-203 disc player, as well as a Samsung Time Warner digital cable box and a BIC F12 sub.
I do not believe my issue to be super complicated but since some of the symptoms are confusing (at least to me, lol) i thought i should reach out to the pros on this forum for some advice on how to proceed.
I did research and troubleshoot this on my own for about 2 weeks prior to posting on this thread so allow me to explain the issue: For my 2 rear atmos ceiling speakers i am getting a plainly audible hum from those 2 speakers only. I suspect the issue to be a voltage potential difference between my Marantz AV receiver and the Outlaw power amp but i need clarification on this.
I first discovered the humming issue when the only components i had connected to my AV receiver were the HDMI audio-only for my Oppo player and the HDMI coming from the cable box; the Marantz was connected to my LG C6 OLED tv via the main HDMI out from the Marantz. I use the 5 channels on the Outlaw amp to power the front L/R/C channels and my 2 rear ceiling speakers.
Initially i unplugged the co-ax cable cord and the HDMI cord from my Samsung digital cable box to see if that was the problem but the hum remained. Next, (and i left it this way) i tried plugging both the AVR and the Outlaw amp into the same power socket (the socket outlets were verified to have proper grounding) but there was no change. Since the AVR has a 2-prong power cord and the Outlaw amp is a 3-prong i plugged them both into a surge protector power strip but this also had no effect. The last thing that i tried was to connect the metal chassis of the Outlaw amp to the metal chassis of the Marantz AVR w/ a single cord of 16-gauge speaker wire, and this approach did finally cut the volume of the hum coming out of those 2 speakers by about 70%, however, there is still a slight hum present that is audible during quiet movie scenes. This is how i arrived at my suspicion of a possible voltage potential difference between the AVR and the amp. If that is the case then i'm assuming that properly grounding all the components to a single point will address that issue.
Now, here is the strange part: any time i watch a movie that has a Dolby Atmos soundtrack the hum essentially disappears and the atmos track works/sounds great, but if i watch a movie with any other kind of soundtrack - i.e. a DTS-X track, etc. - the slight hum reappears. Also, if i select the input on the Marantz AVR for my Samsung digital cable box (HDMI in - Sat/Cable) the hum once again essentially disappears and i get the normal upscaled atmos output "Surround" mode for my tv channels as i should and it works fine.
Any advice on how to better isolate/proceed with removing the remaining light humming noise is much appreciated!

Hi Cheyne,

I know its been 4 years now, but may I know if you have resolved your issue? I have similar but not exact situation as you have. Initially I have just a AVR (receiver with 2 prongs plug) running 5.1, the speakers are dead silence when nothing is playing. But after I added a 5 channel power amp (which has 3 prongs plug), I hear all sorts of noise coming out from my all 5 speakers. My front speaker is 3 way design, I can hear zzzzzz.... coming out from the tweeter, hummmmmm...... from my mid and low drivers. So I began my frustrating noise hunting exercise.

I started with isolating my power amp by unplug everything on my power amp, except for the speaker cables and speaker. It is pretty much silence when the power amp is ON, not completely dead silence, but pretty good. Then I added my receiver to the power amp via 5 RCA interconnects..... just slightly worse, just a little, I can definitely live with that. Then I start adding my sources one by one, i.e. apple TV, internet TV streamer (no antenna just LAN cable), Wii game console, blue-ray player and TV (HDMI OUT from receiver to TV ARC HDMI). All of these are using HDMI cables. The more source I add to my receiver, the more buzz and hum comes out from my speakers.

All of my equipment has 2 prong plug except for the power amp. This means everything is grounded via my power amp. I thought this is a good thing? Because from what I understand is the system should only have 1 ground point. But then how come I'm still having this buzz/hum issue? Or is it my issue is not related to the ground loop? But to do with... faulty equipment design? Is it that my equipment or sources I should say is generating noise itself and hence got amplified by the power amp?

I've also noticed all of my equipment is leaking some electricity to its chassis, is this normal? When I unplug the power cord from my power amp, my whole system is energized. I can sort of understand that because I have remove the only ground point of the entire system. I can get electricity shock if I touch something and also feel tingling when I glaze by finger on any equipment (my sources and TV). I then use a multi-meter and measure a screw of the receiver chassis, I get 6V (I can't remember if it is AV or DC). Is this normal?

Initially I was thinking maybe it is my power amp, because it is the newest addition to my system. I noticed the toroidal transformer of my power amp actually makes a hum noise itself when my system is ON. Could this be the cause? Does the toroidal transformer normally hums? However, when there is nothing connected to the power amp (i.e. I remove all of the RCA), I can barely hear it hum.

Thanks guys, please if anybody has any idea how I can resolve this, I'll be a very very happy man!

 

[TLS Guy]

Hi Cheyne,

I know its been 4 years now, but may I know if you have resolved your issue? I have similar but not exact situation as you have. Initially I have just a AVR (receiver with 2 prongs plug) running 5.1, the speakers are dead silence when nothing is playing. But after I added a 5 channel power amp (which has 3 prongs plug), I hear all sorts of noise coming out from my all 5 speakers. My front speaker is 3 way design, I can hear zzzzzz.... coming out from the tweeter, hummmmmm...... from my mid and low drivers. So I began my frustrating noise hunting exercise.

I started with isolating my power amp by unplug everything on my power amp, except for the speaker cables and speaker. It is pretty much silence when the power amp is ON, not completely dead silence, but pretty good. Then I added my receiver to the power amp via 5 RCA interconnects..... just slightly worse, just a little, I can definitely live with that. Then I start adding my sources one by one, i.e. apple TV, internet TV streamer (no antenna just LAN cable), Wii game console, blue-ray player and TV (HDMI OUT from receiver to TV ARC HDMI). All of these are using HDMI cables. The more source I add to my receiver, the more buzz and hum comes out from my speakers.

All of my equipment has 2 prong plug except for the power amp. This means everything is grounded via my power amp. I thought this is a good thing? Because from what I understand is the system should only have 1 ground point. But then how come I'm still having this buzz/hum issue? Or is it my issue is not related to the ground loop? But to do with... faulty equipment design? Is it that my equipment or sources I should say is generating noise itself and hence got amplified by the power amp?

I've also noticed all of my equipment is leaking some electricity to its chassis, is this normal? When I unplug the power cord from my power amp, my whole system is energized. I can sort of understand that because I have remove the only ground point of the entire system. I can get electricity shock if I touch something and also feel tingling when I glaze by finger on any equipment (my sources and TV). I then use a multi-meter and measure a screw of the receiver chassis, I get 6V (I can't remember if it is AV or DC). Is this normal?

Initially I was thinking maybe it is my power amp, because it is the newest addition to my system. I noticed the toroidal transformer of my power amp actually makes a hum noise itself when my system is ON. Could this be the cause? Does the toroidal transformer normally hums? However, when there is nothing connected to the power amp (i.e. I remove all of the RCA), I can barely hear it hum.

Thanks guys, please if anybody has any idea how I can resolve this, I'll be a very very happy man!

You have a classic ground loop. You do have more than one ground. Your LAN cable has a ground and this is the likely culprit. Do you have cable TV as well? So the first thing to do is unplug any Ethernet and cable or satellite TV cables, and see if the hum stops. Then report back.

If this does stop the hum we will need to know exact details of your home Ethernet and cable systems, especially how that are grounded at the entry to your home.

Ethernet and cable TV systems are by far the most common cause of ground loops.

 

[pinifinina]

Thanks TLS,
I've tried disconnect my TV antenna cable between my TV and the wall socket, it didn't help. But now you've mentioned LAN cable, I do have 3 LAN cables connected to my system, my AVR, apple TV and TV box streamer. I will test it today by disconnecting them and see what happens. Thank you.

 

[highfigh]

Hi Cheyne,

I know its been 4 years now, but may I know if you have resolved your issue? I have similar but not exact situation as you have. Initially I have just a AVR (receiver with 2 prongs plug) running 5.1, the speakers are dead silence when nothing is playing. But after I added a 5 channel power amp (which has 3 prongs plug), I hear all sorts of noise coming out from my all 5 speakers. My front speaker is 3 way design, I can hear zzzzzz.... coming out from the tweeter, hummmmmm...... from my mid and low drivers. So I began my frustrating noise hunting exercise.

I started with isolating my power amp by unplug everything on my power amp, except for the speaker cables and speaker. It is pretty much silence when the power amp is ON, not completely dead silence, but pretty good. Then I added my receiver to the power amp via 5 RCA interconnects..... just slightly worse, just a little, I can definitely live with that. Then I start adding my sources one by one, i.e. apple TV, internet TV streamer (no antenna just LAN cable), Wii game console, blue-ray player and TV (HDMI OUT from receiver to TV ARC HDMI). All of these are using HDMI cables. The more source I add to my receiver, the more buzz and hum comes out from my speakers.

All of my equipment has 2 prong plug except for the power amp. This means everything is grounded via my power amp. I thought this is a good thing? Because from what I understand is the system should only have 1 ground point. But then how come I'm still having this buzz/hum issue? Or is it my issue is not related to the ground loop? But to do with... faulty equipment design? Is it that my equipment or sources I should say is generating noise itself and hence got amplified by the power amp?

I've also noticed all of my equipment is leaking some electricity to its chassis, is this normal? When I unplug the power cord from my power amp, my whole system is energized. I can sort of understand that because I have remove the only ground point of the entire system. I can get electricity shock if I touch something and also feel tingling when I glaze by finger on any equipment (my sources and TV). I then use a multi-meter and measure a screw of the receiver chassis, I get 6V (I can't remember if it is AV or DC). Is this normal?

Initially I was thinking maybe it is my power amp, because it is the newest addition to my system. I noticed the toroidal transformer of my power amp actually makes a hum noise itself when my system is ON. Could this be the cause? Does the toroidal transformer normally hums? However, when there is nothing connected to the power amp (i.e. I remove all of the RCA), I can barely hear it hum.

Thanks guys, please if anybody has any idea how I can resolve this, I'll be a very very happy man!

Look at the power inlet on your receiver- it should have three pins. If it does, you're using the wrong power cord.

 

[pinifinina]

Alright, I’ve tested with the LAN cable unplugged, and it didn’t help much. The best solution is still unplug all HDMI cables from my AVR to get the lowest buzz and hum. For example, when I’m watching apple tv, I unplug my tv streamer box, blueray player and wii console. I have no other solution.

@highfigh the power socket at the back of my AVR only has 2 pins, not three, I assumed this means there is no ground?

 

[highfigh]

Alright, I’ve tested with the LAN cable unplugged, and it didn’t help much. The best solution is still unplug all HDMI cables from my AVR to get the lowest buzz and hum. For example, when I’m watching apple tv, I unplug my tv streamer box, blueray player and wii console. I have no other solution.

@highfigh the power socket at the back of my AVR only has 2 pins, not three, I assumed this means there is no ground?

It means the chassis is connected to the neutral, which is typical for source devices like CD/DVD/BD players and small streaming devices like Roku, AppleTV, etc.

What brand and model of AVR and power amp? Is the amp plugged into a different outlet for power? This matters.

Do you have Cable TV? If so, disconnect the coax from the cable box and it may stop the hum. If it does, call the cable TV provider and have them send a tech out to do their job which, in this case, is to make sure the cable feed is properly grounded, according to the National Electrical Code specs. The first link shows the actual requirements-

Article 800: Communications Circuits

Because Art. 800 has its roots in telephone technology, it addresses telephone and related systems that use twisted-pair wiring. The telephone utility typically provides the twisted...

www.ecmweb.com

Communications Systems Grounding Rules

www.ecmag.com

 

[pinifinina]

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!