Get out that Multimeter

[rollo]

  So did ya ever check your chassis voltage to determine if the PC is wired correctly ? First disconnect all ICs and speaker cables then test one component at a time. You will need a cheater plug with equal sized blades so you can reverse the polarity for TWO readings. Plug the component in and turn it on. Place the negative probe to earth ground, then the positive to the outside of the RCA jack [ input] and take a reading. Reverse plug and remeasure. The lowest reading indicates the correct polarity.
  The lower the better ? Yes and NO. It would most desirable to have the same voltage present throughout but that ain't happening to often. So just make sure that your source component is as close to the preamps voltage [ always lower] What you do not want is a higher voltage than the next component. A lower voltage will not fight against the voltage of the next component.
  So recently performed the exercise and to my suprise the CDP was very low but used the higher value instead. The results much quieter and more information retrieval. Try it.


charles

[Triode Pete]

Be careful with a cheater plug...grounded circuits (3-prong) should remain grounded in the end....

[melgross]

It's a very dangerous game to play with power outlets. I hope no one will be recommending that the plug be reversed in the socket and the ground, if any, be removed.

[richidoo]

It's not dangerous if you understand what you're doing and have a good reason. Audio is a fine art, not limited by National Electrical Code.  Rollo is just recommending the buster as a tool to look for design flaws. Product engineers are not always as insightful as audiophiles.

You don't want to leave your equipment powered through a ground buster though. You would lose the safety ground which activates the circuit breaker with or without neutral.

[tmazz]

Rollo is just recommending the buster as a tool to look for design flaws. Product engineers are not always as insightful as audiophiles.

I'm not sure that I would call having the proper A/C polarity and ground reference a "design flaw" even if it does sound better with the plug reversed. Anyone who has sat for a PE exam can tell you that there are always a number of questions on Engineering Ethics. And one of the most overarching concepts driven home in the Engineering Ethics section is that an engineer's number one priority must be the health and safety of the users of the products he or she is designing. Given a choice of making a design change that would sound better but at the same time run the risk of connecting the hot side of the A/C feed to the chassis where someone could electrocute themselves or set up a situation where a short in the unit could draw unlimited current from the mains without tripping a breaker, any engineer worth a dam would pick safety every time.

Getting "sound to die for" is a cute saying, but I really don't think any of us want to play that game for real.

[rollo]

I'm confused then. When a two prong plug comes with a component and the correct orientation is NOT marked how is it grounded ? The other puzzling thing is some manfs recco lifting of the ground, PS Audio CAT, Lector. Why would they impose a liability on themselves if it was so dangerous. Mel, Tom ?
   I am curious not defending any position.


charles

[tmazz]

Ah, but the standard two prong plug is indeed marked.. Look carefully and you will see that the neither the blades, nor the slots on a standard 15a receptacle are the same size. It only goes in one way.

Also Simply lifting the ground is very different form flipping the plug with a cheater cord. In one case you are removing the third conductor (ground) connection from the  and simply relying on the neutral to act as the ground reference for the unit. This is not necessarily a bad thing if that is how the unit was designed in the first place. Many hand held power tools are designed with a technique called double insulation and they are perfectly safe to us with a two prong AC connection.  However, when you flip the polarity on the plug what you are actually doing is connection the hot side of the AC to what is now the ground reference of the unit.
remember , the unit is designed for safety's sake so that the case is always at ground potential so if there is ever any kind of short the current will take the easiest path to ground and therefor would not go through and person touching it. If you reverse the plug and you connect the hot side of the circuit to the place that should be providing the safety ground you run the risk of providing the ground yourself by touching the unit (Especially if you are in a basement mancave where is gets damp or can flood leaving you standing in a wet spot.)

Now this of course would not happen when the unit is operating properly, but can come into play when something goes wrong internal to the unit (and what is the precedent for a tube going bad and frying some other componets with it?

I guess the point is that even at 120v commercial AC is nothing to be taken lightly, it fights back, sometimes with tragic results. By flipping the cord you are putting yourself in a situation where you can be flying without a net. You can get away with is plenty of time, but it only takes that one second......

It is just something that I am not comfortable doing or recommending to others.

[richidoo]

There is no need to fear electricity if you understand it and take precautions. If you don't understand it, don't mess with it, but you will miss out on Charlie's discovery.  If you understand the danger then you are able to explore safely, and that is fun.

Leaving the ground buster in the circuit for normal operation is unsafe no matter which polarity sounds better. But if you swap the hot and neutral at the transformer or in the power cord as Charlie suggests and maintain safety ground, it's not dangerous to swap hot and neutral. It is illegal to do it in the wall outlet.   

SAS preamps have a polarity switch on the back for this purpose. Sometimes the difference is audible. It was not audible on my dedicated line. But on a shared line where neutral has more wire nuts or a bad connection somewhere raising it's impedance, it might benefit to swap the polarity. I don't understand how it could improve the sound, but rollo is offering a possible reason, which intrigues me to try his test. 

Some audiophiles lift the ground on their amps and source to allow the preamp to be the ground reference for the whole system. The technique might lower noise. But then safety depends on whether chassis ground is connected to signal ground - by design it may not be, and how much you trust the ground wire in your interconnects and all those solderjoints, nuts and bolt star grounds, cheap RCA connectors. I insist on safety ground on every component, unless it is double insulated like my Sansui tuner. It has equal width plug blades which was the norm for all appliances in '79 when many houses still did not have 3 prong outlets. I know it was tested safe and certified for legal importation from Japan.

While on the subject of polarity, it's a good idea to test all of the outlets in your house for correct polarity and working safety ground. Especially if your house was built during the housing bubble when "less experienced" workers probably did the wiring and inspector was too busy to check every outlet. Could be the polarity is wrong at the wall, or ground has come loose with changing seasons.

[pmkap]

A little background on what Rollo is getting at -
http://www.boundforsound.com/tweak.htm
http://www.audioasylum.com/audio/tweaks/messages/3/36909.html

As noted in the above references, the use of a cheater plug is for diagnostics only, not as a permanent fix for ground loop hum/noise. The object of the above is to minimize reactive leakage coupled to the chassis/safety ground. Safety grounds stay. By minimizing that capacitive/inductive coupling to safety ground, one attempts to minimize current noise on the safety ground(s). Balanced (technical) power is a more purposeful and effective way of doing this. As long as the fix is to reverse (or not) the polarity of the power transformers primary, after going through the proper extant fusing and switching, there is no harm, no foul.
The dreaded ground loop hum that we all dread largely a result of the lack of any standards in connecting single ended signals between our kit, and the multiplicity of connections from safety to signal ground. See-
http://www.audiocircle.com/index.php?topic=19860.msg177365;topicseen#msg177365

FWIW,
Paul

[etcarroll]

"While on the subject of polarity, it's a good idea to test all of the outlets in your house for correct polarity and working safety ground. Especially if your house was built during the housing bubble when "less experienced" workers probably did the wiring and inspector was too busy to check every outlet. Could be the polarity is wrong at the wall, or ground has come loose with changing seasons. "

How is this done.

Just got a multi-meter for antidipated diy projects, but haven't used it yet.

Also, my home is a McMansion, I've already realized cheapest components used throughout. And the wall outlets are all 0.58 cent specials, I found that when my 'fridge quit on me and I replaced the outlet and fuse/trip at the fuse box. Was looking for a new receptacle at HD, found a row of them with the proper manu. name, but none matched what I had in my hand.

Then saw a ratty box on the floor full of what I was holding, at 0.58 a pop. Sheesh.

[richidoo]

Sounds familiar!

Get one of these from any good hardware store or the borg.
http://www.amazon.com/50542-Receptacle-Tester-Improper-Indicator/dp/B002LZTKIA


Test every outlet in the house. And do it again every couple years. With temperature cycles a borderline connection can work loose over time. 95% of problems you can fix it yourself easily by tightening outlet terminal screws, and redoing the wirenuts with 7 wires in there. In shared circuits a bad testing outlet may be caused by another outlet closer to breaker. Test the whole string until you find a good one, then you know where to look first.

If you call the homebuilder or the installing electrician they will come fix it for free. If they are a moron, threaten to call the town building inspector, as he screwed up too.

Good luck!

[tmazz]

If you call the homebuilder or the installing electrician they will come fix it for free. If they are a moron, threaten to call the town building inspector, as he screwed up too.

If the guy who initially installed the service didn't do it right the first time, I'm not sure I would trust him on the rebound. Circuit polarity is easy enough to check yourself and I for one would feel much safer if I eyeballed it personally. However, you do need to follow the safety rules. Most importantly, NEVER work on a hot circuit. Especially if you think it might be improperly wired. Kill the breaker before you even take off the outlet cover. If you don't know which breaker covers that out let you can use a digital circuit snooper.



http://www.amazon.com/Reliance-Controls-THP110-Digital-Circuit/dp/B000IF9KBC/ref=sr_1_10?ie=UTF8&s=hi&qid=1269011159&sr=1-10

You plug the smaller of the two pieces into the outlet and the other piece gets run over your breakers and finds the proper breaker by detecting the tone being sent by the other piece. (Some units require you to make multiple passes over the breakers to zero in on the right one - be sure to read the instruction for your specific model.). Once you find and open the breaker, recheck the outlet with the receptacle tester before proceeding to make sure the circuit is actually dead - belt and suspenders.

Once you remove the outlet cover and pull out the receptacle make sure that the wiring is connected in the proper places. On standard polarized replicable the hot lead (the black wire) should be connected to either the push in connection on the side of the smaller of the two blade slots or to the darker (usually brass) of the connection screws. The neutral (white wire) is connected to the push in by the large blade slot of under the lighter colored screw (usually silver). The ground connection (either a bare copper or green insulated one) is connected to the green screw. (see illustration below)



So the connections should be black to brass, white to light and ground to green.  While you have the outlets out always take the opportunity to  tighten up all of the connections (push and pull on the screwless connections to make sure they are still tight and do a torque check on all the screws.Remount the outlet in the box, and replace the cover. When you have finished with all of the outlets, reset the breaker and check the outlets once more with the receptacle tester. If you still have a polarity flip even with all of the outlets on the legs visually verified than the miswiring is in the breaker box itself. The breaker box is not a place to be playing around if you don't know what you are doing. My suggestion is that if you needed to read these step by step instructions to check the outlets you would be much better off having an electrician check the breaker box for you.

For more information about wiring outlet boxes you can go to:

http://www.inspectapedia.com/electric/Electrical_Outlet_Installation.htm#bannertop

[richidoo]

Good info Tom.

In production building (McMansions), "helpers" (often of questionable qualification, and legal status) are used to pull the wires, and often do basic hookup too. But when there is a trouble call, someone with proven diagnostic, repair and communication skills is needed so a better qualified tech will come for that.  Of the dozen or so faults I have had in 5 years I could have fixed any of them myself. I have one outstanding that requires digging to fix an outdoor lamppost. There is no continuity in the underground leg. I will gladly outsource that one to the "electrician" that installed it.