Fine Tunes #10 letters part 2
Editor: As an electrician and audiophile, I thought I should correct some errors in Jonathan Scull's recent comments on grounding ("Fine Tunes," March '99, p.51). According to the National Electric Code, the neutral is the grounded conductor, whose job it is to carry the current back to ground. The "ground" is actually the equipment-grounding conductor and has no electronic purpose whatsoever. The sole purpose of the grounding conductor is life safety.
If a short were to occur in a piece of equipment, the chassis might become energized, and you might become the circuit's path to ground as you adjusted volume on your way from the shower. Or if another conductor were nearby it might arc, starting a fire. Second, by providing a low-impedance path to ground, it should ensure that the protective breaker or fuse will blow, opening the circuit. The ground does nothing whatsoever if all is well with the wiring and the piece of equipment. Thus, "a good ground" contributes nothing whatsoever to sound quality.
Some of the confusion comes from the common use of "isolated ground" outlets for computer circuits. An isolated ground outlet is one in which each outlet has its own ground wire. The reason to do this has nothing to do with actual performance. IG outlets are installed because the building owner fears that fault current will be backfed through the ground to other digital devices, potentially doing damage to devices separate from the first device.
When I am wiring a box, I attach the grounding conductor to a metal box, to conduct current away from that box in the event of a short circuit. Grounding clips are fine for that job, but I always run the same wire to the outlet, without splices, to ensure a good ground. Splices must be carefully made, as they always create a possible short.
In my opinion, most neutral problems are caused by a loose connection somewhere. The key to a good, safe ground is that you have a grounding conductor to conduct the current away in the event of a short. If you do not have a grounding conductor, then by code the outlet must be replaced by a ground-fault circuit interrupter (GFCI), or protected by one. A GFCI simply compares hot with neutral, and opens the circuit if an abnormal difference appears, which is what would occur if your radio fell into the bathtub.
How you ground depends on where you are. In my Columbus, Ohio home, moist soil makes a single ground rod fine. In dry, sandy soil such as Arizona, a ground ring may be required, and local codes will reflect that. In a Manhattan high-rise, I would seek building steel if I needed to ground something (usually a transformer). In new steel buildings most of the steel pillars are cad-welded to their own ground rods, so you can be assured of a good ground.
Most residential current is 120/240V single phase, where a single phase from the transmission line feeds a center-tap transformer. "Two-twenty" is sort of a catchall term that averages 120/208 three-phase circuits. Three-phase power is virtually unknown in residential wiring, unless you are Bill Gates—or perhaps Jonathan Scull, though his Manhattan high-rise might still have a single-phase panel, fed from a transformer. (Most commercial or large buildings bring their power in at at least 277/480V because it offers significant savings in running motors, lights, and such. Transformers convert power to 120/240 1x or 120/203 3x for outlets.)
Neutral distortions produced by digital components should be negligible in any home application. For commercial electricians like myself, the problem is that while power goes in as a wave, computers, electric light ballasts, and the like shoot it back out the neutral with the wave bearing harmonic products. If you have a large number of such devices connected to one circuit, the harmonics sometimes sum and overload the neutral. The usual solution is to pull a larger neutral.
That solution is probably not possible for the home audiophile. Homes are wired by stapling Romex (rubberized conductors, type NMR) to your studs. In a commercial building, I pipe between outlets. But the good news is, upsizing is almost certainly unnecessary. Digital components draw very little power; three or four won't make a difference. Even if the harmonics sum, the resulting currents will not approach the current rating of your neutral wire, particularly if you have a circuit or two dedicated to audio/visuals. If you are worried, the easiest solution is to have a circuit added. But do remember that the neutral comes after your component, and modern buildings are wired in parallel. I doubt if harmonics are an issue to the average audiophile. But do make certain you have adequate power available to drive your devices. Power amplifiers are the beasts to worry about here, as everything else draws next to no current. If you own a big Levinson or Audio Research, you might want to think about giving it its own circuit.
One last thing about outlets: Hospital-grade receptacles are less likely to arc if you pull a live plug. But how many of us pull the plug without first shutting off the equipment? The big difference between cheap 39-cent outlets and commercial-grade outlets is simple mechanical ruggedness. Grounding holes are particularly prone to breakage. For audiophiles who often make changes, that matters. But the cheapies will provide power just fine, so I use spec-grade only for my stereo and one or two other spots, like the kitchen. Cheapies are fine elsewhere, and probably fine everywhere. But then I don't have to pay an electrician to change one if it breaks.—David L. Wyatt, Jr., Columbus, OH, firstname.lastname@example.org