[Occam]

.....
The AC hot terminal delivers a nominal 117Vac sine wave which is unreferenced to any other voltage level. The AC neutral terminal provides a 0Vac signal which is the primary reference to the connection above.
The earth ground is a safety terminal directly connected to an earthing rod sunk into the actual planet surface at the closest possible point, and with a surface area that can safely ground any current level (200 amps in a residential service) that can be provided.  The above AC neutral s connected to this  terminal at the breaker box in all cases.

Thus, there is no question of misreferencing of the AC hot signal (different voltage levels on the positive and negative swings of the signal), since there is no reference to be miscentered.  The only issue is the (possible) voltage difference between the AC neutral terminal and the earth ground terminal to which every durn thing is ultimately referenced. 

Set your meter on lowest DC volts, put one probe in the AC neutral terminal, the other in the earth ground terminal, and measure whatever (if any) difference there is.  This is your DC offset.  If any, which seems unlikely to me in a residential environment. 

There are some small complications if you live in a big apartment building or something, but otherwise I do not understand why you guyz are getting so elaborate about this (non)problem.

Comments?......

Poinz,

I've 'bolded' where I believe you've gone astray. Even in your island paradise, you, at least vaguely, adhere to NEC (National Electrical Code).  'Hot', single ended power is allways referenced to neutral (throughout the world), and in N.A. implicitly referenced to ground via ground-neutral bonding at its 'point of service'.

Regards,
Paul

PS - Your preamp is lovely, from both an aesthetic and performance perspective.

[Hap]

Set your meter on lowest DC volts, put one probe in the AC neutral terminal, the other in the earth ground terminal, and measure whatever (if any) difference there is.  This is your DC offset.  If any, which seems unlikely to me in a residential environment. 

There are some small complications if you live in a big apartment building or something, but otherwise I do not understand why you guyz are getting so elaborate about this (non)problem.
 
AudioTropic

Hey Poinz,
Your information is solid; Occam also confirms this.  Paul is the guru of power IMO...

Can you elaborate a bit more on the complications of getting rid of DC in a big apartment building; and your possible solutions to this issue.
The apartment building I live in does not have a true earth ground tap to each apartment although there has to be an earth ground rod somewhere on the ground floor.
Have verified this problem with many electricians and a couple of engineers; aparaently this practice met the local building code when the building was built; back in the late 1970's.

[richidoo]

Thanks for the testing method poinz. I have been going on Josh's advice to get a scope, which I haven't done yet either   

I have 8mV on a shared 15A outlet circuit, and 1.5mV on a dedicated 20amp circuit. If I understand your reasoning correctly, the difference between these two is the impedance of the multiple twist connections in the shared line. This effect would multiply many times if neutral had more contact connections like in a large apartment building with multiple service meters/panels. Do I understand this right? Each mechanical connection raises impedance.

So it's the difference in the resistance of the hot neutral and ground connections back to the panel that typically causes DC offset?  This means that a high offset reading suggests bad wiring connection, not necessarily bad utility transformer.  In these days of production built houses instances of shoddy wiring is common. They rely on breakers as a safety net.

Does a line with DC offset from bad wiring burn more electricity when the circuit is active?
Thanks!

[Bob in St. Louis]

George, what's the status Sir?

Bob

[zybar]

George, what's the status Sir?

Bob

Unless I can borrow a fluke meter from somebody locally, I don't currently possess the proper tools to try and take a measurement. 

George

[JakeJ]

hi zybar,

Is there some where you could rent an o'scope?  Know anyone with a kid in a local tech school that might be able to lend a hand and a scope?  I know it's a stretch but a little research would only cost you some time.

Just a couple of thoughts.

Jake

[Bob in St. Louis]

George,
You pay shipping both ways, I'll let you borrow mine.
It's a Fluke 83 if it matters.

Bob

[zybar]

George,
You pay shipping both ways, I'll let you borrow mine.
It's a Fluke 83 if it matters.

Bob

Bob,

If I can't find something local, I will take you up on the offer.

Thank you very much.

George

[Bob in St. Louis]

You're welcome.... Just let me know George.

Bob

[Ethan Winer]

Unless I can borrow a fluke meter from somebody locally, I don't currently possess the proper tools to try and take a measurement. 

Again, you should call in the power company. They'll come out for free and settle this for once and for all. At least I ASSume it will be for free. You'll never know unless you call them.

--Ethan

[zybar]

Unless I can borrow a fluke meter from somebody locally, I don't currently possess the proper tools to try and take a measurement. 

Again, you should call in the power company. They'll come out for free and settle this for once and for all. At least I ASSume it will be for free. You'll never know unless you call them.

--Ethan

Based on previous discussion with the power company, I don't believe they will come out and if they do, I don't believe it will be free.

George

[dhrab]

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[Bob in St. Louis]

Very interesting and informative post Dave. I've learned a lot. Mainly, to have dedicated (conditioned) lines to the audio room.
Although, I'm not sure what you have against your wife having a "BOB".  aa

Bob     <--------Yea, that's right....BOB. 

[Glen B]

Call off the power company, your DC offset is being generated from within you house

DC can also come from outside the house where one shares the same power company transformer/service drop with neighbors.

[dhrab]

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[jules]

Basic question ...

Where half wave rectifiers are in action, do they all use the same "half" of the sine wave or is it pretty much random?

Great thread, thank you.

Jules

[NewBuyer]

This thread makes me wonder all over again, if products like the new version PS Audio Humbuster III would be a good system addition(?)...

[Hap]

Zybar,
dhrab lends some excellent advice on this issue.
Without the availability of a multimeter or scope to measure the actual levels of DC on your powerlines; start with killing all the breakers as suggested by dhrab.  Pulling power cords from all the AC wall sockets could help, but may not be as effective as shutting off all the breakers other than what powers your audio system to see if there is a noticeable difference.

Apologize if it seems like I tried to hijack your thread earlier; not my intention...
That post noting that big apartment buildings has unique issues, etc. caught my attention, as I am in that boat.

I went through similar issues with DC on my powerlines a few years back and there should be a thread here that others provided great advice.
Occam went through great lengths to help me with my DC issues; however for me, the best solution we could come up with was to use devices to minimize the DC offset which put the low frequency hum to a tolerable level.

For my AC issues, products like Humbusters and quietlines did not help much, but since your home is wired to modern electrical code and has a good earth ground connection, these devices may help you.

As dhrab notes, it may just be a matter of identifying the sources that are polluting your powerline and isolating them properly.

Take a look at the magnan audio website; they have some good information about powerlike conditioning.  Some of their DIY devices are a bit unconventional, but do work.

Good Luck

[peranders]

Most DMMs won't give a reliable reading this way from what I've been told.  Mine reads really erractically when doing this.

That is true in most cases. You must know in detail how the DVM measures the voltage in order to judge if the result is trustworthy or not.