Ground Loop Hum (Multiple sources of noise detected)

[Sylar]

It has been a while since I have used my system and over the weekend I tried to use it. I ran into stubborn static noise emitting from my speakers, what I suspect to be a ground loop issue.
I have debugged it to a certain degree and found multiple potential sources for the noise.

The setup looks like in the image.

• What changed recently
  • Desktop PC Motherboard was replaced (HDMI output fried).
  • UPS #2 is just 2 months old and it is an Online UPS (Online UPS - Output power always provided from battery).
  • UPS #2 was repaired and the power board was replaced - MOV burst (Spike is the suspect as per service personal.).
• When I disconnect either 1 OR 2-AND-3 (See in Red) there is significant change in the noise levels.
• Removing all 3 (1, 2 AND 3) eliminates noise.
• With UPS #2, when I run it off battery, all noise is eliminated (This is an online UPS).
  • On mains Power and noise is back. Switched this on and off multiple times with same result.
  • Used UPS #1 in-place of UPS #2 with PC switched off, and noise is eliminated. UPS #1 is a Line Interactive UPS.

How do I fix this one?
I wouldn't say it is driving me nuts. It is making me think

Note:
HDMI Splitter is being used as I had an issue with PC motherboard and it has created an HDMI issue with 2 of my receivers, and I realized what changed in the past was the darn motherboard (Long story short, I will be replacing my PC motherboard with a new one as it was replaced in warranty for the second time!! This is the prime suspect of the HDMI issues on my receivers).

 

[ban25]

Things to try:

- Try taking one of the UPSes out of the chain. Just run with UPS 1 or UPS 2, not both.
- Try unplugging the PC HDMI from the splitter to see if that removes the ground hum.

PCs are a nightmare of ground loops, coil whine, fan noise, etc., so you may be tilting at windmills here.

 

[TLS Guy]

It has been a while since I have used my system and over the weekend I tried to use it. I ran into stubborn static noise emitting from my speakers, what I suspect to be a ground loop issue.
I have debugged it to a certain degree and found multiple potential sources for the noise.

The setup looks like in the image.

• What changed recently
  • Desktop PC Motherboard was replaced (HDMI output fried).
  • UPS #2 is just 2 months old and it is an Online UPS (Online UPS - Output power always provided from battery).
  • UPS #2 was repaired and the power board was replaced - MOV burst (Spike is the suspect as per service personal.).
• When I disconnect either 1 OR 2-AND-3 (See in Red) there is significant change in the noise levels.
• Removing all 3 (1, 2 AND 3) eliminates noise.
• With UPS #2, when I run it off battery, all noise is eliminated (This is an online UPS).
  • On mains Power and noise is back. Switched this on and off multiple times with same result.
  • Used UPS #1 in-place of UPS #2 with PC switched off, and noise is eliminated. UPS #1 is a Line Interactive UPS.

How do I fix this one?
I wouldn't say it is driving me nuts. It is making me think

Note:
HDMI Splitter is being used as I had an issue with PC motherboard and it has created an HDMI issue with 2 of my receivers, and I realized what changed in the past was the darn motherboard (Long story short, I will be replacing my PC motherboard with a new one as it was replaced in warranty for the second time!! This is the prime suspect of the HDMI issues on my receivers).

View attachment 66314

First of all, power amplifiers should never be run from UPS units. Their power is too great and variable. That means that receiver should not be powered from UPS units either. UPS units are best to protect fragile unis packed with processing chips. Power amps are much less vulnerable to AC perturbations. That is another of the downside of receivers versus separates.

So, job one is to get rid of the UPS units powering the receiver and those power amps.

HDMI splitters are not recommended. Plug your PC into the receiver and not the TV. That is the way it should be.

If the PC still causes trouble suspect the power supply. When I replaced the motherboard in my HTPC I had to change the power supply. I had been persuaded to use a Microcenter branded power supply. I traced the noise problem to that power supply. When I took it back, the guy at the counter told me those were coming back in large numbers. So I bought the top of the line Aurum Gold power supply. I had always used these previously. That solved the problem right away. The Microcenter power supply had an internal ground loop. Open up your PC and make sure all grounds were reconnected and making good contact.

I bet if you do all that, you will have success.

 

[Speedskater]

While it's true that UPS's and some power conditioners can have serious problems with big audio amplifiers, most of these problems only occur at very high volume levels.

 

[highfigh]

It has been a while since I have used my system and over the weekend I tried to use it. I ran into stubborn static noise emitting from my speakers, what I suspect to be a ground loop issue.
I have debugged it to a certain degree and found multiple potential sources for the noise.

The setup looks like in the image.

• What changed recently
  • Desktop PC Motherboard was replaced (HDMI output fried).
  • UPS #2 is just 2 months old and it is an Online UPS (Online UPS - Output power always provided from battery).
  • UPS #2 was repaired and the power board was replaced - MOV burst (Spike is the suspect as per service personal.).
• When I disconnect either 1 OR 2-AND-3 (See in Red) there is significant change in the noise levels.
• Removing all 3 (1, 2 AND 3) eliminates noise.
• With UPS #2, when I run it off battery, all noise is eliminated (This is an online UPS).
  • On mains Power and noise is back. Switched this on and off multiple times with same result.
  • Used UPS #1 in-place of UPS #2 with PC switched off, and noise is eliminated. UPS #1 is a Line Interactive UPS.

How do I fix this one?
I wouldn't say it is driving me nuts. It is making me think

Note:
HDMI Splitter is being used as I had an issue with PC motherboard and it has created an HDMI issue with 2 of my receivers, and I realized what changed in the past was the darn motherboard (Long story short, I will be replacing my PC motherboard with a new one as it was replaced in warranty for the second time!! This is the prime suspect of the HDMI issues on my receivers).

Ground loops usually don't cause static, but oxidation in controls that can move does.

WRT "Online UPS (Online UPS - Output power always provided from battery)."- what brand and model are you using and how are you providing power from battery at all times?

Also, use one device of that type when possible. Small load stuff can be powered via a non-filtering power strip, to allow connecting everything through the main one. As mentioned, power amps, especially with high power output capability, shouldn't be powered by surge protectors that don't have the ability to send all of the energy the amps need without current limiting. These amplifiers can draw enough to stress the capabilities of the protection without you knowing because it happens quickly and meters don't necessarily show it when it occurs.

You might want to find out if the PC's power supply is sending the noise.

 

[TLS Guy]

Ground loops usually don't cause static, but oxidation in controls that can move does.

WRT "Online UPS (Online UPS - Output power always provided from battery)."- what brand and model are you using and how are you providing power from battery at all times?

Also, use one device of that type when possible. Small load stuff can be powered via a non-filtering power strip, to allow connecting everything through the main one. As mentioned, power amps, especially with high power output capability, shouldn't be powered by surge protectors that don't have the ability to send all of the energy the amps need without current limiting. These amplifiers can draw enough to stress the capabilities of the protection without you knowing because it happens quickly and meters don't necessarily show it when it occurs.

You might want to find out if the PC's power supply is sending the noise.

PC ground loops are a very different animal. The Buzz is not the usual buzz, but at these frequencies: - There are peaks at 333 Hz, another at 666 Hz, a smaller one at 1000 Hz, plus a few at other harmonics. Those are the usual suspects. That is what I was dealing with. The tip off was there was some static on the TV at times, and above all the movement of the mouse arrow was erratic and had a fuzzy tail when moved. That is what led me to suspect the PC power supply, after I made a careful check of the internal grounds. No issues at all since changing the power supply.

In the OPs case my top suspicion is an internal ground loop in his PC.

As far as UPS units, I absolutely do not favor powering power amps via UPS units, especially if the power supplies of the amps are unregulated. I favor unregulated power supplies. All my power amps in my three systems are unregulated. The only downside is slight but insignificant reduction in power output into lower impedances. For instance my 909s deliver 150 ohms per channel into 8 ohm loads, but 250 watts per channel into 4 ohm, rather then 300 watts. However in terms of spl. that difference is totally insignificant. Unregulated power supplies are cheaper, give far less trouble and as long as they have large power caps deliver power fast when called to do so.

I talked with Peter Walker about this over the years, and he was strongly in the unregulated camp for power amps. I think part of this was his correct obsession with reliability.

 

[tillerman6]

It has been a while since I have used my system and over the weekend I tried to use it. I ran into stubborn static noise emitting from my speakers, what I suspect to be a ground loop issue.
I have debugged it to a certain degree and found multiple potential sources for the noise.

The setup looks like in the image.

• What changed recently
  • Desktop PC Motherboard was replaced (HDMI output fried).
  • UPS #2 is just 2 months old and it is an Online UPS (Online UPS - Output power always provided from battery).
  • UPS #2 was repaired and the power board was replaced - MOV burst (Spike is the suspect as per service personal.).
• When I disconnect either 1 OR 2-AND-3 (See in Red) there is significant change in the noise levels.
• Removing all 3 (1, 2 AND 3) eliminates noise.
• With UPS #2, when I run it off battery, all noise is eliminated (This is an online UPS).
  • On mains Power and noise is back. Switched this on and off multiple times with same result.
  • Used UPS #1 in-place of UPS #2 with PC switched off, and noise is eliminated. UPS #1 is a Line Interactive UPS.

How do I fix this one?
I wouldn't say it is driving me nuts. It is making me think

Note:
HDMI Splitter is being used as I had an issue with PC motherboard and it has created an HDMI issue with 2 of my receivers, and I realized what changed in the past was the darn motherboard (Long story short, I will be replacing my PC motherboard with a new one as it was replaced in warranty for the second time!! This is the prime suspect of the HDMI issues on my receivers).

View attachment 66314

 

[tillerman6]

I don't have any UPS equipment in my setup, but I do run a power amp for a second set of main speakers. The other day I noticed a hum after some re- cabling and I noticed that my Yamaha 5.1 AV receiver power cord does not have a ground wire. ( just a 2 prong plug) On the other hand, my commercial grade Yamaha P2250 power amp DOES have a ground wire. So this means that the RCVR is not grounded except maybe thru some rca jacks. So I ran a wire between the power amp chassis and the RCVR chassis (AM antenna ground) and the hum is gone!
You probably have some 60 cycle noise coming from one or both ot those UPS units too, but strapping your Crown unit to your RCVR could not hurt anything. _ Be sure to shut everything off first! LOL!

 

[Sylar]

First of all, power amplifiers should never be run from UPS units. Their power is too great and variable. That means that receiver should not be powered from UPS units either. UPS units are best to protect fragile unis packed with processing chips. Power amps are much less vulnerable to AC perturbations. That is another of the downside of receivers versus separates.

So, job one is to get rid of the UPS units powering the receiver and those power amps.

HDMI splitters are not recommended. Plug your PC into the receiver and not the TV. That is the way it should be.

If the PC still causes trouble suspect the power supply. When I replaced the motherboard in my HTPC I had to change the power supply. I had been persuaded to use a Microcenter branded power supply. I traced the noise problem to that power supply. When I took it back, the guy at the counter told me those were coming back in large numbers. So I bought the top of the line Aurum Gold power supply. I had always used these previously. That solved the problem right away. The Microcenter power supply had an internal ground loop. Open up your PC and make sure all grounds were reconnected and making good contact.

I bet if you do all that, you will have success.

The mains power supply is extremely unreliable in our country, I barely know anyone who run equipment directly, and if connecting directly to mains they usually run into issues very quickly. Equipment is always run with some kind of a protection in between. I can unplug the Amps from the UPS and run directly from mains. But there is no way I will risk running my receiver directly. FYI the UPS is 2KV capacity.

Ground loops usually don't cause static, but oxidation in controls that can move does.

WRT "Online UPS (Online UPS - Output power always provided from battery)."- what brand and model are you using and how are you providing power from battery at all times?

Also, use one device of that type when possible. Small load stuff can be powered via a non-filtering power strip, to allow connecting everything through the main one. As mentioned, power amps, especially with high power output capability, shouldn't be powered by surge protectors that don't have the ability to send all of the energy the amps need without current limiting. These amplifiers can draw enough to stress the capabilities of the protection without you knowing because it happens quickly and meters don't necessarily show it when it occurs.

You might want to find out if the PC's power supply is sending the noise.

It is a 2KV APC online UPS.
I think I might run with your suggestion and unplug the amps from the UPS while keeping the receiver on UPS.

You might want to find out if the PC's power supply is sending the noise.

How do I figure this out?

 

[Sylar]

I disconnected everything and started from scratch again.
I made some changes based on suggestions above, and did some more tests.
1. Removed the splitter.
2. Replaced HDMI cable from PC to Receiver.
3. Removed power amp for front speakers and connected directly to receiver.

Here is what I observed,

• I also replaced my PC with a laptop. Noise remains.
• With zero RCA connections (Sub pre-out is disconnected and power also disconnected), I have zero noise.
• I reconnect subwoofer, and plug the subwoofer Crown amp, but DO NOT switch it on. I have noise. I switch it on & I have same noise.

At this moment, it looks like as soon as I connect RCA to any of the crown amps I get the noise.

 

[TLS Guy]

I disconnected everything and started from scratch again.
I made some changes based on suggestions above, and did some more tests.
1. Removed the splitter.
2. Replaced HDMI cable from PC to Receiver.
3. Removed power amp for front speakers and connected directly to receiver.

Here is what I observed,

• I also replaced my PC with a laptop. Noise remains.
• With zero RCA connections (Sub pre-out is disconnected and power also disconnected), I have zero noise.
• I reconnect subwoofer, and plug the subwoofer Crown amp, but DO NOT switch it on. I have noise. I switch it on & I have same noise.

At this moment, it looks like as soon as I connect RCA to any of the crown amps I get the noise.

So, you now know where your ground loop is. So the issue is a potential between the grounds of the receiver and power amps. So you will have to bond the grounds together and preferably have everything plugged into the same ground. I strongly suspect that the UPS units are the origin of these ground loops.

I also have three UPS units in my AV room. All three are bolted to metal racks and the photograph below shows how the racks are bonded together.

It only takes the most minute resistance between grounds to make a fearsome racket. Keeping complex systems dead quite is a major engineering challenge.

 

[tillerman6]

Just having the racks that the equipment is sitting on bonded to each other does not solve the problem because there are usually rubber feet on all the components- which defeats the bonding. It might be a little hard to find a suitable point on the receiver to run a small 14 or 16 gauge wire (lamp cord is fine), but it was needed to get my ground loop problem fixed. I found an AM antenna connector with a clamp release latch on it and used the ground side of that for the receiver ground. I never use the AM or FM radio anyway. The other end went to a bolt on the back of the power amp. That's all the bonding that is needed unless you have more than one amp hooked to speakers. And by the way- anything that is hooked to speakers is the only thing that can make any hum, so if you can stop it by bonding the chassis of everything with a speaker wired to it, then you have got it made.

I think if my receiver was built with a 3 wire power cord, none of this noise problem would have ever happened!
{I have all my amps plugged into the same surge supressor) but even that was not enough to stop the hum until I added that single wire between the RCVR chasssis and my auxilliary power amp chassis (which does have a 3 wire power cord)


The other thing is - why do you need UPS for your system? if the power goes out you have the UPS making warning noises anyway and that is going to wreck your next 15 minutes of music anyway!

I would just take them out of the system and use them for your computer if you want, but they have no place in a stereo system IMHO.

 

[TLS Guy]

Just having the racks that the equipment is sitting on bonded to each other does not solve the problem because there are usually rubber feet on all the components- which defeats the bonding. It might be a little hard to find a suitable point on the receiver to run a small 14 or 16 gauge wire (lamp cord is fine), but it was needed to get my ground loop problem fixed. I found an AM antenna connector with a clamp release latch on it and used the ground side of that for the receiver ground. I never use the AM or FM radio anyway. The other end went to a bolt on the back of the power amp. That's all the bonding that is needed unless you have more than one amp hooked to speakers. And by the way- anything that is hooked to speakers is the only thing that can make any hum, so if you can stop it by bonding the chassis of everything with a speaker wired to it, then you have got it made.

I think if my receiver was built with a 3 wire power cord, none of this noise problem would have ever happened!
{I have all my amps plugged into the same surge supressor) but even that was not enough to stop the hum until I added that single wire between the RCVR chasssis and my auxilliary power amp chassis (which does have a 3 wire power cord)


The other thing is - why do you need UPS for your system? if the power goes out you have the UPS making warning noises anyway and that is going to wreck your next 15 minutes of music anyway!

I would just take them out of the system and use them for your computer if you want, but they have no place in a stereo system IMHO.

Stop spouting absolute BS. You need to go on everyone's ignore list.

 

[highfigh]

The mains power supply is extremely unreliable in our country, I barely know anyone who run equipment directly, and if connecting directly to mains they usually run into issues very quickly. Equipment is always run with some kind of a protection in between. I can unplug the Amps from the UPS and run directly from mains. But there is no way I will risk running my receiver directly. FYI the UPS is 2KV capacity.

It is a 2KV APC online UPS.
I think I might run with your suggestion and unplug the amps from the UPS while keeping the receiver on UPS.

How do I figure this out?

One way to isolate the noise source is by moving it away from the rest of the system, but only if it's radiating the noise. If it's adding the noise to the power, you could power ONLY the computer with the UPS using the battery and inverter and the UPS' power cord disconnected- you'll need to find a way to connect the rest of the system's power cords so the system is still connected the same as before and the only difference will be in how the computer is powered.

The HDMI board fried- how? Power surge? If so, don't assume the computer's power supply wasn't affected.

It's 2024- why would a developed country have a power system that's as unstable as you say? That's inconceivable, to me. That would be a nightmare.

 

[highfigh]

Just having the racks that the equipment is sitting on bonded to each other does not solve the problem because there are usually rubber feet on all the components- which defeats the bonding. It might be a little hard to find a suitable point on the receiver to run a small 14 or 16 gauge wire (lamp cord is fine), but it was needed to get my ground loop problem fixed. I found an AM antenna connector with a clamp release latch on it and used the ground side of that for the receiver ground. I never use the AM or FM radio anyway. The other end went to a bolt on the back of the power amp. That's all the bonding that is needed unless you have more than one amp hooked to speakers. And by the way- anything that is hooked to speakers is the only thing that can make any hum, so if you can stop it by bonding the chassis of everything with a speaker wired to it, then you have got it made.

I think if my receiver was built with a 3 wire power cord, none of this noise problem would have ever happened!
{I have all my amps plugged into the same surge supressor) but even that was not enough to stop the hum until I added that single wire between the RCVR chasssis and my auxilliary power amp chassis (which does have a 3 wire power cord)


The other thing is - why do you need UPS for your system? if the power goes out you have the UPS making warning noises anyway and that is going to wreck your next 15 minutes of music anyway!

I would just take them out of the system and use them for your computer if you want, but they have no place in a stereo system IMHO.

Rubber feet do nothing to defeat bonding, which is connecting all of the chassis with a wire, preferably one unbroken wire. It's not like wearing rubber soled shoes or boots and touching an energized wire on wet ground. Setting a piece of equipment on metal shelves doesn't affect the ground/bonding.

If the receiver had a grounded power cord, it can increase the likelihood of ground loops, depending on how the system is assembled and configured.

A UPS isn't intended to keep the system going if the power goes out, it's there to make sure everything can be shut down properly rather than dumping sensitive electronics on their heads, as it were. A music server/computer really doesn't like having the power interrupted instantly and they really hate when the power goes out/comes back repeatedly.