A Question About HUM

[pucho812]

I am sure this has been asked, but in case it hasn’t, would it be possible to take photos of the set up? Would it be possible to take photos of you testing it? And would it be possible to get an audio recording of the noise in question?

 

[NoisyIndividual]

No you are not. The current flows from the transformer, down the live wire, through the device, and back to the transformer via the neutral.

Cheers

Ian

yes but the neutral then also flows down the ground because of the error in connecting it so.
The Neutral and ground are now in parallel and current will flow through both.

This means current is forced through the Ground loop which is supposed to be free of such things.

 

[ccaudle]

The current flows from the transformer, down the live wire, through the device, and back to the transformer via the neutral.

But neutral is tied to protective earth at building entrance, so if PE is also tied to neutral at the device then there is a second path down the live wire through the device, down the PE, and back to the transformer where PE and neutral connect at the service entrance.

 

[NoisyIndividual]

That was my point from the beginning.


Not only is this an Earth Loop, but there is in fact current flowing in it, which will modulate all the Earthed equipment connected to it, which will cause all sorts of mayhem that defies all logic.

Well here is the logic.

 

[abbey road d enfer]

So if you connect Neutral to Ground, are you not then sending some Neutral Return current though the ground wire? And this current will have a 100 Hz component? So the entire ground buss has 100Hz on it?

I'm no electrician, that is not my field at all, but I can't see the flaw in this logic.

Yet.

Current circulates in a closed loop.
Joining two conductors does not automatically result in current flowing.

 

[NoisyIndividual]

The neutral is carrying the same current the live is.
If you parallel a piece of wire to it, current will flow through both, it's just 2 parallel resistors.

In the case of a linear supply/bridge rectifier, current charges the caps twice per cycle, so you get 100 Hz noise artifacts on the current now flowing through the ground everything is connected to, which is supposed to be clean and NOT have any current flowing through it at all.

 

[Cqwet Dbdfte]

So if you connect Neutral to Ground, are you not then sending some Neutral Return current though the ground wire? And this current will have a 100 Hz component? So the entire ground buss has 100Hz on it?

I'm no electrician, that is not my field at all, but I can't see the flaw in this logic.

Yet.

In this context there is no AC mains "neutral", just like your stove, A/C, water heater, has none. US 117V AC has neutral, but not 220 - 240V 50Hz used in EU.

 

[Khron]

US 117V AC has neutral, but not 220 - 240V 50Hz used in EU

Really? I could've sworn that in the EU, the neutral is bonded to mains earth at the electrical panel, and it was the US system that was weird...

 

[Cqwet Dbdfte]

The 3-pin 220V outlets in EU has two "hot" and one protective ground.
In the US the 3-pin outlets has one "hot", one "neutral" and one protective ground.
The protective ground carries no load current, that would be a "ground fault", but at no load has the same potential as "neutral", (as they are both connected back to the 240V transformers center tap, out side the building.)
Using a GFCI outlet reduces the risk for electric shock and should be installed in kitchens, bathrooms, garages, and outside, as mother earth and water pipes are bonded together, typically with a long copper plated steel rod, to protective ground in the AC outlets.
But you already knew this, sorry...

 

[Khron]

The 3-pin 220V outlets in EU has two "hot" and one protective ground.

And that statement is based on... what, exactly? I guess that's why those neon-based voltage checkers light up when you poke them in either terminal of the mains socket. Oh wait - no they don't...

Maybe I'm weird, but "hot" implies both terminals are active. I'm quite sure if ypu probed between earth and live you'd see the mains voltage, but not between neutral and earth, so... In my book, that pretty much means neutral is not "hot. If anything, it's what the name says - "neutral".

The protective ground carries no load current, that would be a "ground fault", but at no load has the same potential as "neutral", (as they are both connected back to the 240V transformers center tap, out side the building.)
Using a GFCI outlet reduces the risk for electric shock and should be installed in kitchens, bathrooms, garages, and outside, as mother earth and water pipes are bonded together, typically with a long copper plated steel rod, to protective ground in the AC outlets.
But you already knew this, sorry...

That rest of it is indeed true, although preferred terminology is protective earth, precisely to avoid confusion with "circuit ground".

(Later edit)
https://en.wikipedia.org/wiki/Electric_power_distribution#Regional_variations

 

[NoisyIndividual]

I think this is why I suggested checking the Neutral, in case Warm Audio have done something to it.

 

[Walrus]

This video will fully explain UK Protective Earthing systems, start at 2 minutes....

 

[abbey road d enfer]

US 117V AC has neutral,

Yes.

but not 220 - 240V 50Hz used in EU.

Eurovoltage inded has a neutral.
However, due to the fact that many houses use unphased wall sockets, all equipment with PE has to be designed as if both legs were "hot".

 

[abbey road d enfer]

I think this is why I suggested checking the Neutral, in case Warm Audio have done something to it.

What could they have done that would explain 100Hz hum?
Try to have the start of the beginning of a theory.

 

[NoisyIndividual]

What could they have done that would explain 100Hz hum?
Try to have the start of the beginning of a theory.

I've already done that.

 

[Cqwet Dbdfte]

Yes.

Eurovoltage inded has a neutral.
However, due to the fact that many houses use unphased wall sockets, all equipment with PE has to be designed as if both legs were "hot".

I would not recommend anyone in EU to find a "neutral" in a wall socket and tie it to Protective Ground to find a 100Hz problem, especially if you don't possess even a basic DMM

 

[NoisyIndividual]

Er, the Neutral is already tied to Protective Ground.

 

[DaveDC]

Mains voltage is 50 Hz. Mains current is 100 Hz. Current flows only at the voltage crests as the main filter caps recharge. That happens twice per cycle.

 

[NoisyIndividual]

Dave, you are correct as I also said. And if you feed this current down the Earth buss with it's 100 Hz noise, you are probably going to experience 100 Hz artifacts.

 

[Cqwet Dbdfte]

Er, the Neutral is already tied to Protective Ground.

Yep, at the mains panel or at the transfomer. The unphased EU sockets you would have to measure which one is neutral, as both protective ground and neutral would carry a load, so using a light bulb etc would not be helpful as you could introduce a ground fault, possibly tripping a GFCI mains breaker.
Besides, a 100Hz problem would unlikely be a ground loop issue.
OP's problem smells like a regulation issue.
Would consider 50/60Hz a "hum" and 100/120Hz and its harmonics a "buzz".