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Finally there is unwelcome radiation getting into the system. This comes from all around. Our wirelessly connected world is an excellent free source that keeps on giving yet our own audio gear happily contributes high frequencies too which are picked up by adjacent gear and find their way into the signal path. As we experienced in our last few houses, utility power in each and every one was different. They overlapped only in not being of the quality we wanted. To get the best sound we went through much power-related trial & error. Most important was to always start out without any filters, regenerators or what-nots to make the sound as good as possible. That result should tick off each audiophile box of background blackness, staging, imaging, frequency response and most of all tonality. Only after such an initial process where fighting ground loops might be the main battle, additional tweaks and accessories may enter the scene.

It appears to us that passive filtering is far more effective than its active counterparts including power regeneration. Passive filters can include devices which do not physically connect to the grid at all. We obtained very positive if expensive results from the Lessloss Blackbody, a passive noise absorber which really cleaned up the sound. Just as positive were the results with the cheaper Shakti Stones. What these examples have in common is their use of crystals. Crystals are extraordinary materials. Their extremely ordered atomic building blocks give them very special features. Crystals do occur naturally but can be grown and thus selected for specific purposes. Modern life would be very different without crystals. Their semiconducting properties led to transistors and are thus found in nearly anything electric.

Crystals also have a resonance property which clocks for example make use of. A piece of piezoelectric material—a material which under pressure accumulates an electric charge that can be used to drive something—has very visible use in an electronic cigarette lighter. Your thumb depresses a lever which applies pressure to a piece of piezoelectric material. This builds up a charge which is quickly discharged to form a spark that ignites the simultaneously released butane gas.

In many crystals this piezoelectric effect also works the other way around. An electric field of a certain frequency will excite a crystal to resonance or oscillation which transfers electrical energy into heat to effectively absorb its electrical field. This is the very capacity exploited by many crystal-based filters. And there is yet another effect where crystals can be helpful in filtering. This is the triboelectric effect. We all have encountered this when we ran a comb through hair to generate static electricity. This is due to the triboelectric effect and accompanying frictional properties of the materials in combination with conditions like air humidity. Materials that exhibit this triboelectric effect are sorted into an order whose rule states that the further two materials are apart within that order, the easier a charge is generated.

Now imagine an audio cable of a copper lead within a sheath. The sheath and copper wire are prone to the triboelectric effect once there is friction between the two. Sending a signal through that copper wire will make it resonate no matter how minute. You now can imagine how the choice of dielectric materials and more specifically their place within the triboelectric order influences the amount of static build-up. When this static electricity is absorbed by a crystal, it no longer does any harm.

Why this detour into crystals and their effects? The subject of today's review is the PranaWire Linebacker, a passive power line filter. PranaWire is part of the Lotus Group operated by California’s Joseph Cohen. We met Joe for the first time some time ago and since then witnessed without fail how he managed time and again to get systems under show conditions to stand out in very positive ways. Besides knowing his technical stuff, Joe clearly is not afraid to experiment, to try different things and think out of the box.

His Linebacker is completely passive, i.e. without any electronics in or around the device. It consists of an aluminum cylinder of around 152 x 76 x 50 millimeters. At one end sits a male IEC, the other sprouts a 50cm length of Pranawire Satori terminated with an Oyaide F1 female IEC. The Satori is a member of Pranawire’s Realization cable range. It is built up of 7 gauge (3.66mm) 6N OCC silver-plated copper. So far so good. Until we mention the additional layers surrounding the conductors. Here Joe added a layer of crystalline material—he won’t disclose details of course—which not only gives the cable its bulk but also bestows upon it noise-absorbing qualities. Next to the cable’s crystalline coat the aluminum enclosure also is filled with such material albeit different from the conductor layer to provide additional noise absorption whilst shielding the male plug. The Linebacker is thus effectively a standard short Satori cable with a spare filter clamped to one end. It should be no surprise that the already high-quality Oyaide F1 with its palladium and platinum coatings over beryllium copper alloy is further damped by Pranawire to attenuate mechanical resonances. Joe explained that the final production version of the Linebacker differs slightly from our review sample by filling out the rear opening of the Oyaide F1 in a cosmetically tighter fashion.