Ask Eddie: From the Ground Up

Oct 1, 2011 9:00 AM, By Eddie Ciletti



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Mix is gearing up to present its longstanding annual Audio Education Guide in its November 2014 issue. Want to have your school listed in the directory, or do you need to update your current directory listing? Add an image, program description, or a logo to your listing! Get your school in the Mix Education Guide 2014.

Q. Why, in the opinion of this author, is balanced power not The Big Solution?

The AC power line is supposed to be a pure, undistorted sine wave, but it is far from that. All “appliances” reflect noise and distortion (buzz) back into both the power line and into the safety ground. The noise sources can be from outside the facility, as well as from every appliance in the facility, meaning each outlet will have a unique noise characteristic. Connecting all that gear together can make for wonderful harmony or a cacophony of intermittent random noises—the misnomered “ground loop.”

When balanced power works—as in, with before-and-after tests as proof—I believe its success is attributable to both a real component and a virtual variable.

REAL. What we expect from balanced power distribution: two signals of equal amplitude but opposite polarity reduce potential hum and buzz radiation from power cables into both safety grounds, as well as into nearby audio cables.

VIRTUAL. BP conceals problems caused by some combination of problematic gear and lack of a fully thought-out wiring and grounding plan. Again, this is one sentence that could be a stand-alone article about why some gear must be modified to reduce both internal noise and its reception of external noise. All cabling is an antenna and it can bring noise into susceptible units.

There are two ways to minimize or eliminate power line noise from outside the facility: brute force or via an uninterruptible power supply (UPS). The former is a marriage of the most sophisticated power-line filter/surge protector you can imagine—the good ones, at least. A UPS essentially converts AC to DC (rectifier) and replaces “filter” capacitors with batteries, from which conventional 60Hz AC power can be remanufactured. Larger facilities can justify the expense, so let’s get back to that “star” ground.

Running dedicated ground wires to isolated ground outlets is a step up from conventional commercial wiring, where the conduit typically doubles as the ground wire. It is, however, inadequate for reducing noise because the power/safety ground travels in the same conduit (physically parallel with the power lines), and as a result gets contaminated by noise in the AC power wiring. (This is also why audio and power wiring should never be routed in parallel.) The shorter the parallel distance, the less radiated noise will be picked up. From my own experiments, running the safety ground outside the conduit allows it to remain clean up to the outlet, but that’s not “electrical code,” and you know how pirates stick to the code.

From here I hope you can see that the most effective way to solve noise issues is to run a dedicated zero-volts ground-distribution system. While it may seem to contradict the purpose of the star-grounding systems, it is perfectly acceptable for the dedicated audio ground to be in parallel with the safety ground. (They both should share the same “root.”) The ZVDS is, by design, so much more substantial. It is the path of least resistance: thick-gauge cable that is as close to zero ohms as possible. Any noises—from safety ground and chassis—are short-circuited to the earth ground. That brings us full-circle, which musically is called D.C. al coda.

I cannot claim recent facility-wide installation expertise, but I do have loads of troubleshooting experience and have done several modifications and experiments to prove my theories. When in doubt and when referring clients, I seek out people like John Klett, who contributed a distillation of his approach as an online bonus to this article. Thank you, John! And enjoy the show!

Feel free to ask Eddie questions at his MixBlog or visit, the virtual homestead.

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