AC Polarity and the reduction of noise and hum

[DaveC]

I actually don't think it is very clear . I had to read it a few times to figure out what he is saying and what is trying to be accomplished.

Turns out what he is saying may make things worse, not better. Let me explain.

What he is trying to do as Folsom correctly explained, is to take advantage of one of the leads in the input transformer leaking more into the chassis than the other, say through proximity or construction. That by itself can be a good thing. As Folsom again correctly says, if there is such kind of "polarity" then it is best resolved by changing the wires internally. I doubt that high-end equipment makers would leave this stone unturned but maybe some do.

The reason this can be beneficial is that if the source equipment has higher ground potential than your target (say between pre and power amps) then that current flows from source to destination in unbalanced (RCA) connection causing 50/60 Hz originated hum. So it seems that lowering the leakage in every gear would be a good thing but it is not. Read again what I said: what flows is the differential between equipment which will never be zero. So what you want to do is to get that differential to be the lowest, not the individual leakage voltage. If you measured the first gear and it is at say, 50 microvolts and the second at 60, and then you swapped leads and got one to 30 and the other to 10, you are worse off. In the first case the differential was 10 microvolts, the second, 20. So you doubled the voltage which then doubles the leakage current and doubles the hum.

The biggest issue here is that almost all of our equipment comes with three prong cables. Swapping the hot and neutral with a cheater plug requires eliminating the ground which takes away the safety redundancy in your equipment. Should one in a million chance thing happen with the hot lead coming loose and touching the chassis, and said gear is connected to other gear that is grounded, lots of things could short out and cause fire, etc. And if all of them are floating, now you could electrocute yourself.

A better solution than any of this -- assuming there is a problem -- is to use balanced connections. Then it doesn't matter what the chassis voltage is.

I agree with everything except balanced being better and chassis voltage not mattering in balanced equipment. Balanced is not better in home systems for various reasons we've discussed, IME the potential benefits of balanced do not manifest in home systems and you're left with an overly complicated system that cancels even-order distortion and not odd, so it sounds dry and mechanical in comparison. Also, the gear never treats each phase exactly the same resulting in more distortion. A properly setup single ended system is FAR better for a home system imo.

BTW, I have ~105 dB midrange horns, you can stick your head inside and hear nothing and that's with three pieces of SET amplification all connected using unshielded, single-ended RCA cables. Using balanced gear in a home system is trying to fix a problem that doesn't exist and making things worse in the process.

 

[DaveC]

Not in all EU countries (Shuko's also have an asymmetrical ground connection for some specific countries), but mostly yes!

Is there a fuse/breaker on both hot and neutral then? A fuse should blow either way but it's always on the hot side, if it's on neutral there's still going to be the possibility of a hot wire touching chassis and just waiting for the circuit to be closed!

 

[amirm]

Yes, it is so unclear that people will probably misinterpret as it seems to me you and others did.
The cheater is only used to determine the lower leakage position.

Nope. You can't physically reverse the polarity of a three-prong cable without it. It plugs in only one way otherwise.

BTW, we will eventually disagree on this issue, as you will just consider the 50/60 Hz hum, not the non scientifically proved wide band grounding issues.

The technique is for reducing ground leakage due to chassis potential difference. That current changes to the tune of 50/60 Hz.

The chassis ground is for safety and only for safety. It is a huge myth to think it has to do with noise.

 

[amirm]

BTW, I have ~105 dB midrange horns, you can stick your head inside and hear nothing and that's with three pieces of SET amplification all connected using unshielded, single-ended RCA cables. Using balanced gear in a home system is trying to fix a problem that doesn't exist and making things worse in the process.

We are OK on this too . I too run unbalanced when it is the only option or it is not an issue as you mention. In other cases like my sub in my theater there is massive hum with unbalanced so I run balanced there.

 

[Folsom]

Not exactly true, at less if the manufacturer exports to Europe. Schuko mains plugs are not oriented and manufacturers must consider that any of wires can be hot or neutral. Just rewiring the power cable (or in our case, rotating the power plug) is enough.

BTW, mains power systems and codes are different around the world - no universal rules on this subject, except minimizing leakage current.

In apparatus that have more than one transformer a perfectionist could think about following your suggestion - re-wiring each of them separately for low leakage. But than probably he would find that changing the magnetic coupling of them was causing hum, manufacturers usually optimize for this aspect!

Thanks, I corrected it to "least impedance" which I knew I meant but the hands typed something else

BTW there's a chance more leakage could have an unintended benefit in some cases, believe it or not. Consider that during a listening test with a cheater plug you have no ground for the leakage, so preference isn't related to leakage actually in that case. Either way if anyone is into this please do it correctly internally or have someone do it that knows how to do it. It's at your own risk. I'm sure many people online would help with pictures to verify what you're doing is presumably safe looking but it's still your own risk.

 

[microstrip]

Nope. You can't physically reverse the polarity of a three-prong cable without it. It plugs in only one way otherwise.

Surely. It is why it was clearly explained that people had to open the plug and re-wire it, how to do it and its consequences. If we were unlucky molded plugs had to be cut and replaced. Audiophiles carrying this type of optimization will probably be using after-market power cords and plugs, and will never consider using cheaters permanently.

The technique is for reducing ground leakage due to chassis potential difference. That current changes to the tune of 50/60 Hz.

The chassis ground is for safety and only for safety. It is a huge myth to think it has to do with noise.

No, it is not. It aims at reducing wide band absolute leakage current to ground, tout court. Have you read the extra care and resources some audiophiles take with ground, using special rods and techniques? Again, it is for believers, not for 50Hz skeptics.

Yes, unfortunately it is a huge myth that introduces noise in real life audiophile equipment, just what we debate most of the time in WBF. Probably not in your world. And no, I do not have blind data to prove anything, you do not need to ask!

 

[microstrip]

(...) Consider that during a listening test with a cheater plug you have no ground for the leakage, so preference isn't related to leakage actually in that case. (...)

Again, no one wants to carry listening tests with cheater plugs. The cheater is only used for the short time measurement. If you then want to carry listening tests you should use two proper cables with ground.

And this optimization should be carried to ALL equipment, otherwise we risk increasing the current through the signal ground wires.

Properly carried this technique is SAFE. It is no where related to often referred craziness of operating equipment without mains ground.

 

[Folsom]

And this optimization should be carried to ALL equipment, otherwise we risk increasing the current through the signal ground wires.

That's a bit complicated to say because not all transformers are the same. My preamp's connections don't follow the same orientation as my amplifier's. They're made by the same manufacturer but the dot* that indicates phase relationships isn't an indicator for how it's wound necessarily in relation to parasitic qualities. You can check the actual ground current if you please, however. But I use my ears to determine which is better. As I said before, it's possible for leakage to be your friend in some cases. Hum isn't necessarily destructive on playback sound - obviously it has to be at a low level so you don't go crazy.

BTW my amplifier transformer does indeed have a preference for the wiring, which is the difference between flatter and smoother rounded tones and a little bass. So the effect is real, for anyone wondering.

Using cords with swapped L & N for testing sound preference, with a ground, is only slightly safer since you're still bypassing the fuse/breaker until you make the appropriate internal switch after listening (for all you reading, it's not a permanent solution to change the powercord wires).

 

[amirm]

No, it is not. It aims at reducing wide band absolute leakage current to ground, tout court. Have you read the extra care and resources some audiophiles take with ground, using special rods and techniques? Again, it is for believers, not for 50Hz skeptics.

Again it is nonsense. The ground wire going all the way back to your service entrance has very high impedance and would not remotely do what you and others think it does.

The connection is called safety ground and that is all it is. It is a redundant path to your mains entrance at which point it connects back to your neutral wire. No noise is being dumped into the "ground" after those dozens of feet much less through that poor connection to earth no matter what you do.

Audiophiles resort to many things because they use their lay intuition rather than understanding of the electrical engineering involved. That they do doesn't amount to hill of beans in an informed discussion.

So let me repeat: the ground wire in your equipment is there to save your life. No audio equipment better be designed to rely on it for anything else. Don't substitute your gut feeling for how things work. You are liable to waste money, and or risk your life.

 

[microstrip]

Again it is nonsense. The ground wire going all the way back to your service entrance has very high impedance and would not remotely do what you and others think it does.

The connection is called safety ground and that is all it is. It is a redundant path to your mains entrance at which point it connects back to your neutral wire. No noise is being dumped into the "ground" after those dozens of feet much less through that poor connection to earth no matter what you do.

Audiophiles resort to many things because they use their lay intuition rather than understanding of the electrical engineering involved. That they do doesn't amount to hill of beans in an informed discussion.

So let me repeat: the ground wire in your equipment is there to save your life. No audio equipment better be designed to rely on it for anything else. Don't substitute your gut feeling for how things work. You are liable to waste money, and or risk your life.

We agree, it is apparently an "electrical nonsense" as you say, but it is the same kind of "electrical nonsense" as power cables and other devices that allow us to tune our systems to sound great, and you do not accept and deny. And yes, I and many others in this forum with a science and technological backgrounds use our gut feelings to get our systems performing as we want, because we know of the limitations of science and technology, and also because most times the so called "science and technology" experts do not have anything to offer to please our sound quality preferences.

Great to know that you know that the ground wire in our equipment is there to save our life. Nothing else to add. People have the information, those interested can research on the subject as there were many articles on this subject in the past.

And yes, my central heating system should not depend on plug orientation. But it is 6ºC outdoor, so it is not the time to teach it about theory of symmetrical mains, tube warmth is not enough to keep me comfortable!

 

[microstrip]

(...) Using cords with swapped L & N for testing sound preference, with a ground, is only slightly safer since you're still bypassing the fuse/breaker until you make the appropriate internal switch after listening (for all you reading, it's not a permanent solution to change the powercord wires).

Just to remember that if equipment is CE certified - and most international manufacturers export to Europe, the equipment must be designed for aleatory neutral/phase. Otherwise it will not enter EU. Probably it is why my old cj equipment has a single pole breaker and the current one has dual pole breakers.

 

[amirm]

We agree, it is apparently an "electrical nonsense" as you say, but it is the same kind of "electrical nonsense" as power cables and other devices that allow us to tune our systems to sound great, and you do not accept and deny.

Sorry I am not here to deal with your protests of what you do or don't do in life. I am here to explain things technically and when you say I am wrong, I will explain why that is not the case. To wit, I have tens of thousands of dollars in instrumentation in my lab. Not one of them says to do anything with earth ground to make to perform to their guaranteed specification. Most sensitive radio equipment works in airplanes with no connection to the ground whatsoever. Ditto for anything running on batteries.

A ground wire is just a duplicate neutral wire. It is there to trip the circuit breaker should the hot wire come loose inside your equipment and touch the conductive case. It is not even needed if your case is not conductive (or any other connection to it). It is purely a safety thing. It was never put in there for anything to do with noise.

Your argument was around broadband noise. To shunt such a noise you need an extremely short path to *power return*, internal electrical ground. The path from the chassis to your breaker panel and then to some rod stuff in dirt has no prayer of doing anything. That rod is there to guard against incoming surges. Should a lightning hit the wires leading to your house, it provides a way for it to complete its path through said ground bar instead of using your home wiring. The lowest impedance path wins because electrons will follow the path of least resistance.

The "ground" of interest with respect to noise is inside your equipment and under the control of the designer. And that ground is the return current for the power supply. Ground loops can get created there if one is not careful, impacting more sensitive parts of the equipment. A high-end designer with far less stress over budget can easily design robust ground planes that deal with these issues. And at any rate, it is all his job to do so. Such equipment connected to ordinary AC outlet using generic cables measures superbly to noise levels that are laboratory grade. And thousands of times lower than any threshold of hearing.

These are the facts micro. They don't change because you wish them to as to justify what you have bought for erroneous reasons.

And yes, I and many others in this forum with a science and technological backgrounds use our gut feelings to get our systems performing as we want, because we know of the limitations of science and technology, and also because most times the so called "science and technology" experts do not have anything to offer to please our sound quality preferences.

You are mistaken micro to conflate this topic with others. There is nothing fancy here. Understanding this topic requires knowing the simplest rules of electricity flow and ohm's law. That understanding unfortunately escapes many engineers let alone hobbyist with enough techno lingo to be dangerous, pun intended.

You have to repeat after me. The chassis ground is for safety. Put that out of your vocabulary for any other purpose. It is a redundant line back to the circuit breaker and as such, it can't perform any magic whatsoever.

 

[microstrip]

(...) The lowest impedance path wins because electrons will follow the path of least resistance. (...)

(...) And thousands of times lower than any threshold of hearing.(...)

Just noticed that I have nothing to debate or learn from you. I was considering electromagnetic waves, not electrons.
Thanks for remembering our eternal divergence on thresholds. Bye.

 

[Steve williams]

Just noticed that I have nothing to debate or learn from you. I was considering electromagnetic waves, not electrons.
Thanks for remembering our eternal divergence on thresholds. Bye.

 

[YashN]

To wit, I have tens of thousands of dollars in instrumentation in my lab.

Doesn't mean you actually know how to use them properly.

All that means is you can throw away a lot of money at these, that's all.

 

[DaveC]

Just like the ground wire on single ended IC cables, the chassis ground may serve more than one purpose and in some gear it's connected directly to signal ground, so it may float with the signal and then it certainly may have an effect as it's part of the return signal path, and so are the ground wires in the power cables. So it's really not as cut and dried as you think Amir, and the standards for grounding components are not complete, designers do it in many different ways. Also consider that in electrical systems isolation does not mean a brick wall so attempts by designers to isolate grounds is partial.

Basically, safety ground may also be signal ground and be part of the return signal path, and while this may be prevented to some extent it won't be perfect. Theory based on ideals and real life sometimes don't quite match up...

 

[RogerD]

Glad I stayed out of this one.

 

[FrantzM]

Just noticed that I have nothing to debate or learn from you. I was considering electromagnetic waves, not electrons.
Thanks for remembering our eternal divergence on thresholds. Bye.

We stick to our opinions for various reasons. On Audiophile matters, it is all good
It is snot so benign for matters of LIFE and DEATH. When it comes to electricity and in particular of safety ground and other lifesaving concepts, the audiophile life and that of people he/she cares or at the very least should care about, are the issues. Accepting the facts would have been the wise thing. Some prefer to debate just for the sake of being right right putting in that sense the lives of less knowledgeable people in harm's way. That is Very unfortunate.

 

[mcduman]

i live in the schuko land and here are my measurement with normal and reverse polarities.

Normal Reverse Result
(Volts) AC AC
Transport 110.3 114.0 ?
DAC 114.5 110.6 Change
Pre 39.2 84.8 ?

1. I did not measure current but was surprised the voltage reading was as high as 100v.
2. One unit showed a lower reading with inverted polarity so i changed its orientation and indeed it was noticeably better this way. (bass, stage depth, attack)

 

[microstrip]

We stick to our opinions for various reasons. On Audiophile matters, it is all good
It is snot so benign for matters of LIFE and DEATH. When it comes to electricity and in particular of safety ground and other lifesaving concepts, the audiophile life and that of people he/she cares or at the very least should care about, are the issues. Accepting the facts would have been the wise thing. Some prefer to debate just for the sake of being right right putting in that sense the lives of less knowledgeable people in harm's way. That is Very unfortunate.

Unfortunately Frantz you choose the poor moment and subject to snipe someone in WBF. The original advice and recipe are absolutely safe and have been used by many audiophiles for more than 30 years.

I appreciate your constructive posts, but please explain me why reversing neutral and phase in a grounded plug in modern systems is a dangerous think. Europeans do it every day in their houses many times at 230V AC!

And yes, I know that in prehistorical times there was no separate ground wire and neutral was often used as ground, and some equipment dis not use power transformers and connected neutral to ground. Fortunately these days are gone, many people died because of it.