Your Favorite AC Outlets

Peter, thanks for providing the link. Mofi, as the link indicates an isolated ground receptacle has no internal connection between the safety ground contacts of its two outlets and any surrounding metal structure, or conduit if present. In a home environment the safety ground contacts would typically be connected through an insulated wire to the central grounding point at the service panel, where safety grounds, AC neutrals, and earth ground are all connected together. A separate path to that ground point is required for the surrounding metal and the junction box, typically via conduit.

So the AC safety ground connections for the equipment are not truly isolated, of course, as that would be a safety hazard. What is changed with respect to a conventional outlet is just the route by which the equipment safety grounds are connected to ground, with the goal being a reduction of the amount of noise that is coupled into the equipment.

There's lots of info (and also lots of confusion) on the web about isolated ground receptacles and wiring. One brief excerpt from this paper by Bill Whitlock of Jensen Transformers, who as you may be aware is a renowned expert on such matters as they apply to audio:

So-called “technical” or “isolated” grounding schemes can sometimes reduce electrical noise in the safety ground system. It is most applicable in situations where conduit may come in contact with building steel, water pipes, gas pipes, or other structures which may be grounded and carrying noisy currents. Special insulated ground or "IG" outlets (generally orange in color) are used, which intentionally insulate the green safety ground terminal from their mounting yokes or saddles. Therefore, safety grounding is not provided by the "J-box" and conduit, but by a separate insulated green wire which must be routed back to the electrical panel alongside the white and black circuit conductors to keep inductance low. Most often, wiring is not "daisy-chained" to outlets on the same branch circuit, so noisy leakage current from one device has less coupling to others on the same branch circuit. However, inductive coupling from phase conductors to the ground conductor (a major source of ground voltage differences between outlets) is not reduced.

Thanks for the implicit compliment, btw, but I am by no means the leading expert here on electrician-type matters. That would be Jea48 (Jim); perhaps he'll see this thread and comment further.

Best regards,
-- Al

Mofi, thanks! In answer to your question: First, the Porter Ports are apparently not isolated ground receptacles, because IG receptacles are required to have a small triangle symbol on their face, and are usually orange in color.

However, if I understand correctly that what is running from the outlet back to the service panel is just a three-wire cable that is not enclosed in metal conduit, and that is connected to nothing else along the way, then it seems to me that you are getting pretty much all of the benefit that an IG receptacle would potentially provide. The idea behind an IG configuration is to avoid connections between the AC safety ground contacts on the outlets and any ground point other than at the service panel, which is what you've got.

A minor point of difference, though, which I suspect is unlikely to be of any practical significance: RF noise picked up by the metalwork of the junction box itself, acting as an antenna, could be conducted onto the safety grounds in your configuration, but might be effectively isolated from the safety grounds by an IG receptacle. RF wouldn't be directly audible as noise, of course, but might have audible consequences by intermodulation or other effects that can occur in the component circuitry.

Also, I'll mention that conduit vs. no conduit can have its own set of pretty much unpredictable tradeoffs. It can be beneficial as a result of shielding effects, but as explained in the Bill Whitlock quote I provided above it can pick up noise from conduit or other metal it comes in contact with, and couple that noise onto the wires it contains.

Finally, if an IG receptacle were to be installed where there is no conduit or other path for the junction box and the non-isolated metal parts of the outlet to be connected to ground, aside from via the ground wire in the cable, from a safety standpoint and I suspect also from a code compliance standpoint the isolated and non-isolated ground connections of the outlet would have to be connected together. Which would essentially convert the IG receptacle into a non-IG receptacle.

Hope that clarifies more than it confuses :-)

Best regards,
-- Al

Slight correction to my previous post. Revise the last major paragraph to read as follows:

Finally, if an IG receptacle were to be installed where there is no conduit or other path for the junction box and the non-isolated metal parts of the outlet to be connected to ground, aside from via a single ground wire in the cable, from a safety standpoint the isolated ground connection on the outlet and the non-isolated metalwork on it and the box would have to be connected together. Which would essentially convert the IG receptacle into a non-IG receptacle. And I suspect doing that would not be code compliant because the triangle marking on the outlet would be incorrect in that situation.

Best regards,
-- Al

How can a person form an opinion on something that they have not experienced? It is then no longer an informed opinion, it is a wild guess.

Or it could be based on technical understanding, technical analysis, or (hopefully well trained) technical instinct.

While I always hold Roxy's opinions in high regard, in this case I must agree with Mapman, whose opinions I also always hold in high regard. An unequivocal, unqualified, absolute, all encompassing statement such as the one I have quoted is tantamount to saying that technically based opinions invariably have zero place in audiophile pursuits. I would disagree with that notion.

One does not have to jump out of an airplane at 10,000 feet without a parachute in order to be qualified to express the opinion that it is not a good idea. Similarly, those with sufficiently good technical backgrounds can SOMETIMES correctly make "a priori" judgments about issues that fall within their areas of expertise.

Furthermore, those who HAVE tried a particular product and express an opinion about it can often be presenting information that has no more value than a "wild guess," not necessarily because they are imagining things, but because they may be attributing the perceived difference to the wrong variable (which is very easy to do in audio, IMO), or because their lack of understanding of the technical aspects of what is going on may mean that their findings would be inapplicable to other systems and circumstances.

Now certainly science, engineering, and technical understanding have a long way to go before they can explain and predict everything about what we hear and how a product or tweak will perform. Any good circuit design engineer will tell you that some things, as a practical matter, can't be analyzed and are inherently unpredictable. So the question becomes where to draw the line between what may be remotely within the realm of possibility, even though it may be counter-intuitive and/or not fully explainable, and what definitely deserves a place in the Twilight Zones of audio. Obviously opinions will differ widely about where to draw that line. But it seems to me that where to draw that line with respect to any specific tweak can and often should be the subject of legitimate debate.

In this case, although I have not personally experimented with audiophile-oriented outlets, as I presume Schipo has not, my opinion nevertheless differs from his, and I do believe that differences and improvements can be realized in many cases via that kind of upgrade. Although I would expect that any such comparisons, if performed in a properly disciplined manner with possible extraneous variables being well controlled, and across a wide variety of components, would provide results that are component, system, room, listener, and recording dependent, and that are not strongly correlated with price.

But I respect his right to express his opinion, and I consider it, along with the claims of some of those who have upgraded their outlets, to warrant legitimate debate, not summary rejection.

IMO. Best regards,

-- Al