Fine Tunes #7
The mechanical universe tells us that a signal flowing through a conductor creates a magnetic field that expands and collapses at the frequency of the applied signal. This modulated magnetic field will induce a current flow in an adjacent conductor. Lay a power cord next to a pair of interconnects and you'll induce 60Hz noise in the shields of your signal-carrying cables—and perhaps in the signal conductors themselves, if their shields prove inadequate. Digital datalinks (transport to processor) also radiate high-frequency fields in the MHz range that can induce polluting noise in nearby interconnects and power cords.
The sonic effects are subtle but pernicious. To me they always sounds like a scrim of grain, glare, and distortion riding the signal. Nothing freaks me out more. What to do? First, get them power cords away from interconnects and speaker cables! If they must cross, keep them at 90 degree angles to each other, and separated by at least an inch of space. Two inches is even better, as a magnetic field's strength decreases with the square of the distance—current-inducing magnetic fields are four times stronger at one inch than at two.
If you're using an audio rack, try to gather and flow interconnects down one side and power cords down the other. It's not always easy, as both captive cords and IEC receptacles can be located practically anywhere along the rear panel. Try keeping them in place with large, loosely fastened plastic tie-wraps. Cinching the cables tightly against the rack or stand is not such a good idea, however. First, like everything else in the playback chain, wires are microphonic, and you don't want them vibrating any more than they have to. Don't believe it? Move your phono cable around while the gain is turned up. Or hook up a speaker with zip cord and whack the wire with a hammer. The thumps and bumps emanating from the speaker might surprise you.
The second consideration is based on a concept I recently heard about from that tireless wire maniac, Roger Skoff of XLO. Magnetic fields, he explained to This Rather Started Journalist, "Actually traverse the entire universe with infinite extension!"
"Yes, magnetic fields don't die out, they just keep on getting weaker and weaker the farther out you go. It's like the idea of continually halving the distance between you and me, Jonathan. You'll never actually reach me!"
I breathed a sigh of relief.