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.