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At the last Milan show we met with IsoTek’s Keith Martin. We had some tea and lunch and as a result of various conversations were eventually sent a surprise package with some of his latest products. Next to IsoTek Keith also runs Blue Horizon. The former focuses on power products, the latter on more general audio accessories. In our package we found—among other things we will report on separately—a so-called Mains Noise Analyser under the Blue Horizon brand. A clear aluminum casing of 17 x 10 x 7cm has a black semi-translucent fascia with a 3 x 2.5cm window for an LCD display. The only connection to the outside world is a C2 shotgun connector. Use is as simple as blinking an eye. Plug the provided mains cable into a wall or other outlet. Then read the number displayed on the small screen and listen to the noise emitting from the small single driver firing out the back of the device.
The display goes from 000 to 999. From 000 to 200 green lines above and below the digits indicate the noise level from good to fair. 200 to 400 gets yellow lines for just acceptable noise levels. Above this level the lines get red for poor to horrible AC line noise. The speaker adds an additional and unexpected indicator of mains quality. We encountered slow ticks, low-frequency brown noise, loud white noise and—hold on to your berets—radio reception of various Christian stations! Hey, we did say this subject bordered on the religious.
Those familiar with the Audio Prism Noise Sniffer will spot a resemblance to the Noise Analyser though the Blue Horizon adds the numerical output which makes the judging and comparing process a bit easier. It does however lack the volume attenuation possible with the Noise Sniffer.
Keith Martin explains: "In general the Noise Analyser analyses all frequencies found on the mains, then filters out the main 50Hz sine. All other frequencies detected are displayed in parts per 1000 as a proportion of the mains and amplified for audible output. Using this promillage, a reading of 500 is thus proportional to 50% unwanted frequencies. The Analyser is not a spectrum analyzer. By comparison it is far more simple. It does however put into context the ever growing problem with our power lines around our homes. There we have two types of mains noise. Common mode is usually referred to as RFI and differential mode is created when components draw power."
With our new loaner toy the first thing we did was of course run around our house and plug its power cord into any available outlet. The outcome was a real shocker. We’d measured some of these outlets earlier with a simple Fluke meter and found that voltage was quite stable but had some DC riding along. This DC or zero offset will cause some transformers to vibrate and to emit direct noise; and cause additional noise from microphonic components like certain tubes. Hence we have a PS Audio Humbuster on hand to filter out that DC component whenever necessary. With the visual and aural output from the new analyzer things now looked pretty nasty.
Actual reading from Avantgarde Acoustic Duo subwoofers mentioned later
We found an average reading of 615 on the wall outlets plus many radio stations. These radio stations were mostly Christian sorts of (m)utterings. That wasn't surprising. We live in the Dutch Bible Belt after all. An Internet search showed that they all occupy the AM band. Whether these radio stations are of the pirate variety we don’t know—yet—but we counted at least 5 different station which at times interfered with each other. Bottom line? The power in our house was far from free from unwanted artifacts and our installed power-line wiring inside the walls must act as an effective antenna.
