Ground Loops - Eliminating System Hum and Buzz

[Speedskater]

a] Does the TV have a 2 pin or a 3 pin AC power plug?
b] How is the TV audio connected to the hi-fi:
RCA, XLR, digital or HDMI?
c] is the TV plugged into the same AC power strip as the hi-fi?

 

[TLS Guy]

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?

The problem arises form non linear power supplies.

In times of old all home electronics consisted of a power transformer, rectifier, smoothing caps, and sometimes an inductor. They were linear power supplies.
The problem is those power supplies are bulky and use expensive components, and are now used pretty much only in power amps.

These days switching power supplies are used, or what is often called pulse modulated power supplies. These divide the power into pulses, they are efficient and use many more but smaller components. If one were not used in your TV it would not be slim and thin. These supplies are also used in class D amps, like those in subs and other class D amps.

The problem is that these pulses also feed back down the AC cord. Normally that is not of any consequence. However, in your power amp, the laminations in the power transformer which control eddy currents are not properly 'potted'. In other words they are somewhat loose and can vibrate. In any system that vibrates there is a resonant frequency, just like a clock pendulum. Now it is your bad luck that the pulses from your TVs switching power supply happen to be the frequency that excites the resonance in that improperly 'potted' power transformer in your power amp.

I suspect that the power cord you are using for your TV is likely not the original. Often devices that use switching power supplies come with a blocking device, which is a 2" or so cylinder in the power cord. This is tuned to those pulse frequencies and blocks them.

If you don't have the original power cord, you can try this generic solution. That is a link to a two pack, and you should clamp one onto the power cord to your TV close to the TV, and the other on the power cord to your power amp, close to the unit.

If that does not work then the power transformer of your power amp needs to be replaced. Just for the record, a properly designed and built power transformer core should never vibrate and resonate under any circumstances, no matter what is thrown at it. So the primary fault here lies with the power transformer of your power amp.

 

[pinifinina]

a] Does the TV have a 2 pin or a 3 pin AC power plug?
b] How is the TV audio connected to the hi-fi:
RCA, XLR, digital or HDMI?
c] is the TV plugged into the same AC power strip as the hi-fi?

Hi @Speedskater , here are the answers
1. The TV has 2 prong power plug
2. The TV normally connected to receiver via HDMI. But like I said before, when I test my power amp hum issue, I disconnect the HDMI from the TV, so nothing is connected to the TV, the moment the TV is power on, my power am hums.
3. Yes, the TV plugs into the same power strip as the power amp. I’v tried other power outlet in the same room, it is the same, I think they are all connected to the same line.

 

[pinifinina]

The problem arises form non linear power supplies.

In times of old all home electronics consisted of a power transformer, rectifier, smoothing caps, and sometimes an inductor. They were linear power supplies.
The problem is those power supplies are bulky and use expensive components, and are now used pretty much only in power amps.

These days switching power supplies are used, or what is often called pulse modulated power supplies. These divide the power into pulses, they are efficient and use many more but smaller components. If one were not used in your TV it would not be slim and thin. These supplies are also used in class D amps, like those in subs and other class D amps.

The problem is that these pulses also feed back down the AC cord. Normally that is not of any consequence. However, in your power amp, the laminations in the power transformer which control eddy currents are not properly 'potted'. In other words they are somewhat loose and can vibrate. In any system that vibrates there is a resonant frequency, just like a clock pendulum. Now it is your bad luck that the pulses from your TVs switching power supply happen to be the frequency that excites the resonance in that improperly 'potted' power transformer in your power amp.

I suspect that the power cord you are using for your TV is likely not the original. Often devices that use switching power supplies come with a blocking device, which is a 2" or so cylinder in the power cord. This is tuned to those pulse frequencies and blocks them.

If you don't have the original power cord, you can try this generic solution. That is a link to a two pack, and you should clamp one onto the power cord to your TV close to the TV, and the other on the power cord to your power amp, close to the unit.

If that does not work then the power transformer of your power amp needs to be replaced. Just for the record, a properly designed and built power transformer core should never vibrate and resonate under any circumstances, no matter what is thrown at it. So the primary fault here lies with the power transformer of your power amp.

Thanks for the explanation @TLS Guy . The power cord from my TV is original. It doesn’t have a blocking device on the power cord. I might try your method and see how it goes.

 

[TLS Guy]

Thanks for the explanation @TLS Guy . The power cord from my TV is original. It doesn’t have a blocking device on the power cord. I might try your method and see how it goes.

It won't cost you much. I suspect there is a good chance it will solve it, or at least reduce it.

 

[saqib]

Success... or at least a measure of it

I thought some more about grounding, that maybe the recepticle is not grounded--it is an old house afterall. I have a protected power strip that I have all the power cords plugged into, and this power strip has indicator lights for "protected" and "grounded". While the "protected" light is always on, the "grounded" light is never on.

So I tried a test. I plugged the power strip into a much newer recepticle that was installed a few years ago (in a different room). The grounded light came on. Therefore, that seemed to indicate that the recepticle I'm using for the A/V components is not grounded. So I used an extension cord to connect the power strip (and thus all the A/V components) to the newer, grounded recepticle. Voila! The hum was reduced significantly, although there was still a very light hum present. I then unplugged the satellite power from the grounded power feed and plugged it into the older, ungrounded recepticle. The hum was eliminated completely. Cool.

BUT... Now I have to figure out how to ground the recepticle that is used for the A/V components. Oh joy.

It sounds like you’ve done a great job troubleshooting the grounding issue and identifying the source of the hum! Grounding plays a crucial role in eliminating unwanted electrical noise, and your approach to testing different receptacles and isolating components is spot on.

Here’s a quick breakdown of what likely happened and why your solution worked:

1. Old Ungrounded Receptacle: The receptacle in the older part of your house is not grounded, as evidenced by the power strip’s "grounded" light remaining off. Without proper grounding, electrical interference and hums are more likely, especially in sensitive A/V equipment.
2. Grounded Receptacle: By connecting the power strip to a newer, grounded receptacle, you provided a proper ground path for the power strip and the connected A/V equipment. This significantly reduced the hum but didn’t completely eliminate it, likely due to other factors, such as the satellite power source.

 

[saqib]

You’ve just connected your system and there’s a buzz or hum that won’t go away. You’re running your gear through power conditioners and you’re beating your head against the wall trying to figure out what’s up. Congratulations - you've just entered The Ground Loop Zone...Several weeks ago I was pulling my hair out after I installed a new component into Reference System 3 for review. It was an amplifier that came with a three-prong power cable. Immediately after placing the amp in my system a very noticeable 60Hz hum starting pouring from my speakers.

If this has happened to you the chances are it’s a ground loop between your Cable TV and another component in your system (like an amplifier or powered subwoofer). Now, how do you solve it? Check out this article for a surprisingly helpful way to combat this common problem.

[Read About Combatting Ground Loops]

To solve a ground loop issue, especially one caused by a cable TV connection, try the following steps:

1. Disconnect the Cable Line: Temporarily disconnect the cable TV line from your system to confirm if it’s the source of the hum.
2. Use a Ground Loop Isolator: Install a ground loop isolator specifically designed for cable TV lines between the cable input and your equipment. These devices break the ground loop without affecting the signal quality.
3. Check Power Connections: Ensure all your components are plugged into the same grounded outlet or power strip to avoid creating multiple grounding points.
4. Reconfigure the Setup: Try connecting components in different power outlets or configurations, isolating the device causing the hum.

If these steps don’t resolve the issue, consulting an electrician to evaluate your home’s electrical grounding system might help. Ground loop hums are common but manageable with the right

 

[highfigh]

To solve a ground loop issue, especially one caused by a cable TV connection, try the following steps:

1. Disconnect the Cable Line: Temporarily disconnect the cable TV line from your system to confirm if it’s the source of the hum.
2. Use a Ground Loop Isolator: Install a ground loop isolator specifically designed for cable TV lines between the cable input and your equipment. These devices break the ground loop without affecting the signal quality.
3. Check Power Connections: Ensure all your components are plugged into the same grounded outlet or power strip to avoid creating multiple grounding points.
4. Reconfigure the Setup: Try connecting components in different power outlets or configurations, isolating the device causing the hum.

If these steps don’t resolve the issue, consulting an electrician to evaluate your home’s electrical grounding system might help. Ground loop hums are common but manageable with the right

Or, if the cable feed hasn't been grounded properly or it's not providing adequate connection, CALL THE CABLE PROVIDER AND HAVE THEM FIX IT because not grounding the feed is an electrical code violation.