AC cord polarity?? Does it matter???????

Hsgarch,

Thanks for getting back with me.

Even if the neutral wasn't at zero potential, most domestic voltges provide more than adequate supply for most component DC rails and regulated circuits (+/- 0.5 to 1.0 VAC of the localized incoming supply, which can swing pretty widely throughout the day, and per region).

In most homes, aren't the neutral and "ground" combined within the breaker box? This SHOULD place the N and G at the same potential, thus supplying the proper circuit voltage into the component's isolation x-former.

Now, what happens to so called "leakage inductance" within a non-ferrous chassis (aluminum)? What about components utilizing un-grounded chassis (2-prong cords), or a combination of the two? If none of the component's circuits are electrically grounded to the chassis, what are these stray voltages going to affect? In a ferrous chassis, I can see some 60 Hz magnet issues affecting certain circuits, but not with aluminum. Any minute x-former leakage would stay localized around itself. Right, or what?

I'm just concerned about blanket statements towards these wiring orientation claims, and whether they are indeed audible in most scenarios.

Your responces are always welcome, and I'm not trying to be argumentative. I do have lots of electronic background, but claim to know everything.

Metro, the answer to:

"In most homes, aren't the neutral and "ground" combined within the breaker box?"

Is no. And this is very important to understanding the "leakage" problem oulined in the article you cite above.
The neutral is zero relative to the 120V on each side of it. But it is not zero relative to earth ground.

So depending how the power supply in a component is laid out, connecting one of the two AC plug blades to neutral will result in less ground current leakage through the "neutral" leg of the power supply circuit. As a matter of fact, that is why, as someone described above how to measure for the best plug orientation, they specifically mentioned not to connect the ground pin of the AC plug when doing the measurement. To which I'll add two more rules: turn off the component, and disconnect all other connections to the component (ICs, spkr cables, coax cable or digital feeds, etc) because they may be connected to ground somewhere on their other ends, and you don't want that.

The idea behind this testing procedure is to "force" current that would,in grounded components, ordinarily drain to ground, instead to "leak" through the neutral so it can be measured. And then minimized by choosing the proper plug orientation.

So why is doing this a good thing? Because when everything is hooked back up, some current will drain to ground through the ground leg, and every one of these conditions in your system represents a ground loop which increases the baseline level of hum (and sometimes noise) in the system.

Metro04,
Here is a couple of posts from my thread on AA.
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General Asylum

Pinging Bob Crump, Can you answer a question for me?

Posted by jea48 (A) on May 19, 2005 at 14:13:30

Bob, John Curl said in a reponse to this question to ask you. When you design and build a piece of equipment is there a set rule on the polarity of the power transformer? That is on the primary side of the transformer are the leads such that the neutral is always on an identified lead and the hot on an identified lead on the transformer. I ask because I have read old archives on Agon where some have talked about reversing the AC polarity feed to the unit, switch the hot and the neutral. Does it affect the sound as some have said? Also does the fact that the neutral is at ground potential have any bearing on the design of a piece of equipment?
Thanks,
Jim

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Re: Pinging Bob Crump, Can you answer a question for me? - rcrump 14:27:42 05/19/05 (31)

In Reply to: Pinging Bob Crump, Can you answer a question for me? posted by jea48 on May 19, 2005 at 14:13:30:

>>"Yes this is very important or the bass and focus will be affected...........Put your red lead of a multimeter on chassis ground and the black lead on a decent earth ground, set the meter to ACV and measure the ground potential with the unit plugged in one way and then 180 degrees off (cheater plug) and make ACV readings each way......Gear being tested should be out of the system or readings will get confused.......The lowest reading will be the correct way of plugging in the unit.......Most transformers are marked for the hot side, but best to test them........"<<
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Re: Pinging Bob Crump, Can you answer a question for me? - john curl 19:07:04 05/20/05 (0)

In Reply to: Re: Pinging Bob Crump, Can you answer a question for me? posted by jea48 on May 2, 2005 at 17:57:57:

">>Jim, like it or not, we have to test the transformers, as to how to wire the PRIMARY. NOT secondary."<<
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http://db.audioasylum.com/cgi/t.mpl?f=general&m=382738
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Nsgarch,

Thank you for the informative response, and will look into it further. I did find some interesting articles after posting my last response, but still have inquiries pertaining to non-ferrous chassis having the same effect. Lots of veteran electronic engineers at my work, so I'll get to the bottom of this, yet.

Thanks again...

First, there is no such thing as "zero volts," we just agree to call something zero (the earth) and measure everything relative to it. It is completely arbitrary.

Second, neutral and ground are bonded in the sevice panel and only there. Go to Home Depot and look at a panel. The neutral bar and the ground are bonded. Another term for neutral is grounded conductor.

Third, in a house, circuits are taken off each "hot" conductor, and the currents in the grounded conductors (which are all tied together) cancel each other out. In other words, if, by chance, the currents on each hot leg were exactly equal, the grounded conductor could be disconected from the service neutral (and the ground) and every thing would work. All the current would flow through the hot legs.

Fourth, the reason the grounded conductor measures hot relative to ground is because the conductor has resistance, and there is current flowing through it. Since there should be no current flowing in the ground, and the two are tied only at the panel, there will be a voltage difference at the outlet (but not at the panel).

Fifth, Mr. Holt does not mention, although I am sure he knows, that all power is generated and transmitted as three phase, each 120 degrees apart in time. When each phase has equal current, they sum to zero and there is no net current to flow through the ground. Any current is due to the three phases being unequal and will be small relative to the total current draw. If any significant power is disipated in the Earth, the power company loses money.

The Earth naturally has absolutely enormous currents flowing in it, making the Earth into a giant magnet.

Polarity is a safety issue.