Shunyata Research • Zi-Tron Sigma Power Cords

"They're just power cords." Yeah, right.

by Vance Hiner | August 14, 2015

hey're just power cords. Just power cords. That phrase is a millstone around the neck of anyone who buys or sells power products. Because power cords are a mere six feet of conduit in the massive grid we all sip from, it's difficult for some people to even consider the possibility that these strands of metal have anything to do with the ultimate sound that audiophiles are seeking. In point of fact, electrical-current delivery and management have everything to do with sound reproduction. While veteran audiophiles are quick to point out that the listening room itself may be the most important component of a great audio system, some of those same people overlook this bit of science: when we listen to music in our homes, what we actually hear has as much to do with electrical impulses and current delivery as it does with sound-wave reflection and absorption. The degree to which the electricity used to power our components is free of pollution and delivered instantaneously determines, at least in part, how well the recorded presentation fools us into thinking it might be real.

Nay-sayers argue that the last six feet of wire in an electrical path cannot make a difference. If that were true, then it's odd that audio designers take such great care in getting power management just right within their components. After all, it's all just the same electricity, ain't it? No, these designers struggle with two very real problems: noise in the electrical path and unstable current delivery. Within a very limited amount of space, there's only so much equipment designers can do to address such issues. What some people fail to grasp is that the electricity that courses through an audio system follows a circular path through hot and neutral wires and not a straight line. When audio components are inserted into this circle, they sit between the hot and neutral wires of the power line, not at the end. Everything within that loop can interfere with the delivery of the instantaneous power that audio components need in order to reproduce the most believable sound. If that interference weren't bad enough, each component also introduces its own noise back into the loop, which further affects other components. It's a bit of a mess. So, if a power cord could significantly reduce audible noise in that path without impeding current flow in any way, it certainly would be worth considering.

In spite of all the evidence that electrical-current management affects sound, there are those who are convinced that aftermarket power cords are the work of con artists. They have the double-blind, A/B/X blindfold tests to prove it. But know this: the double-blind fundamentalists say their tests also prove you and I can't tell the difference between various amplifiers, preamplifiers, DACs, and record players. Is that a group you really want to join? Absolutely nothing in this article will convert someone who steadfastly doubts that power management matters into one of the faithful. So, to members of the crusading Flat Earth Society, I say, These aren't the droids you're looking for. To everyone else, If you have discounted previous attempts at power conditioning, it may be time for a second look.

Back in the late 1980s, during the early days of audiophile-grade power cords, the performance results of these products were varied, to say the least. A few were clearly better than stock cords, but many more were poorly designed and actually created as many problems in the sound of the components they were attached to as they fixed. Many cords reduced a system's noise floor, but they could also make components sound sluggish and constricted. The challenge was to reduce noise without impeding current.

Many of these early cords and even some modern iterations have managed to address one of those problems but not so much the other. Caelin Gabriel was a master electrician and audiophile of the time who was particularly frustrated by power products of that era because he said he knew they could be designed to perform much better. Gabriel's understanding of what was possible grew out of his extensive work as a scientist for the US military agency that specialized in sensitive sound-monitoring technology as well as significant private-sector employment in the field of IT network architecture. After building several popular power-conditioner and cable prototypes for fellow hobbyists, he decided to launch Shunyata Research in 1998, a three-person operation located in his garage.

Seventeen years later, the company's products are being used by a number of the world's leading recording studios, recording artists and electronics and speaker manufacturers. Gabriel has also been granted seven separate US patents for technology used in the manufacturing and development of power cords, signal cables and power conditioners. It's worth noting that patenting something in the US is not at all like copyrighting or trademarking it. Patenting is a costly, multi-year process in which applicants must prove to experts in the patent office that the invention is both unique and actually works. No one can earn a patent for putting something ordinary in a fancy package. To be clear: the US Patent and Trademark Office does not merely sell patents to the wealthy, nor does it license "snake oil."

Shunyata's new Zi-Tron Sigma power cords are the culmination of Gabriel's breakthroughs in power-cord and signal-cable performance measurement and innovations in power delivery and distribution. Each Sigma cord is designed to act as an individual power conditioner at the source of noise pollution, the component itself. The Sigma Digital, Analog and HC cords are equipped with filters that address the very different frequencies of noise produced by digital, analog and high-current components. Shunyata claims that the resulting reduction in Component to Component Interference, or CCI, and the level of instantaneous current delivered by the Sigmas cannot be matched by any other existing set of power cords.

In addition to the filters, the Sigma cords are equipped with Shunyata’s newly designed CopperConn connectors, which incorporate a base metal of solid Tellurium copper to significantly improve connectivity over standard metals such as brass or bronze. The connectors are then treated with Shunyata’s patented Alpha Cryogenic Process, as are all metal parts used in the Sigmas. The Sigma Digital and Analog have 8-AWG VTX conductors, while the Sigma HC utilizes a combination of three 10-AWG conductors with a 6-AWG aggregate copper material.

Shunyata’s Gabriel says the Sigmas challenge the status quo because they address what he calls Dynamic Transient Current Delivery (DTCD) while significantly reducing conducted and radiated RFI/EMI. Based upon my experience, Shunyata's Alpha-series cords already do an admirable job of addressing those issues. So, what brings the Sigmas to reference-level performance? Gabriel explains that, "Where they differ is primarily with respect to DTCD. The Sigma cables have a larger-gauge conductor which improves its DTCD performance relative to the Alpha cables. But even more importantly is the geometry of the VTX conductor that is used in the Sigma cable. VTX conductors are made in the shape of virtual tubes. The core of the conductor is completely hollow so that all of the current travels through the circumference of the conductor minimizing skin effects and inductance reactance."

've owned just about every iteration of Shunyata's power-cord line since the Taipan Alpha back in 2005. Much like the best amplifier designers, Caelin Gabriel has been on a continuing quest to improve power delivery while, at the same time, doing no harm. That is, of course, easier said than done. Gabriel's previous power cords could, nonetheless, always be characterized by certain sonic attributes. For example, the old Python Alpha possessed a warm and cozy quality compared to some cables that came later in the line. The legendary King Cobra CX had a sweet top end, very neutral mids and produced prodigious bass. To my ears, the Cobra Zi-Tron cord sounded a bit lean and analytical when compared to the Alpha Analog and Anaconda Zi-Tron cords, its bigger siblings in the Shunyata line. The goal was transparency with every cable, but a signature always found its way into the final product, whether it was as a result of cost limitations or design choices. This is true of every piece of audio equipment I have ever auditioned.

When Shunyata's new Sigma power cords settled in, I was a bit flummoxed. While I can't claim that these devices have no sonic signature, I can say that I struggled to define one. Let me explain. A full loom of Sigma power cords removed so much noise pollution and current impedance from my system that what I noticed most was more of what sounded like an actual musical performance as opposed to a representation of one. I kept forgetting about the cords because I was repeatedly drawn to the recording itself. On many forums and even in some professional reviews, you will see people claim that power-cord performance is "system dependent" because all power cords have a "flavor." The Sigma power cords challenge that orthodoxy.

After spending several months with the Sigmas in my system, I can say that they represent a significant step forward in power management, though I will offer one note of caution: if you are someone who uses a power cord to fix a shortcoming in your system, these cables will disappoint. They do not subtract from or alter the fundamental sonic personality of a system. For example, my PS Audio DirectStream DAC still sounds a bit laid back compared to other converters, but the Sigma Digital power cord enabled me to better appreciate this DAC's subtle, analog-like charms. My Conrad-Johnson Premier 350 amplifier still has its tube-like midrange and famous Teflon transparency, but with the Sigma HC delivering its current, the amplifier sounded like I refreshed those "tubes" and added some extra Teflon capacitors. These cables are not pricey tone controls, but if your goal is to hear your components produce sound that's as much like real music as they're capable of, then the Shunyata Research Sigma power cords may be just the droids you've been looking for.

Shunyata Sigma cords should not be evaluated right out of their suitcases. That's right. Suitcases. Secret-agent-style suitcases. When I was unpacking them, my ever-patient wife dead-panned, "Did the Russians on eBay promise you security codes for those?" The woman kills on open-mic night. Yup, these babies are sure to get a thorough once-over when shipped internationally or at an airport if you happen to look like Jack Brauer. For those who scoff at such bling, I was assured by the folks at Shunyata that the cases have very little to do with the cords' list price. They even said they'd refund the cases' production cost to anyone who didn't want them. You clearly don't need cases for your power cords, but they certainly make secure shipping and authentication easier in the event a person might want to resell them later.

The best way to describe the performance of the Sigma power cords right out of the case is to say that they are initially stunning and then variable for about two to three weeks. Gabriel says that all power cords perform unevenly until the dialectics and metallurgical materials in the cables have "settled." To accelerate this process, he recommends daisy-chaining the cords on a high-current fan for one week (two weeks for the high-current cords), before introducing them to a system. So that is exactly what I did. And sure enough, during the three weeks after adding the cords in stages, I heard various aspects of the music I auditioned become accentuated. This happened with each cord and has been my experience with every other Shunyata power cord I have added to a variety of highly resolving systems. One day, the upper range was prominent; the next day the bass would be very deep but a bit muddy. At no time was the sound bad, but those who are sensitive to even minute changes in their system, as I am, would be disconcerted by the variance in presentation if he did not know what to expect.

Look at it this way: the settling process is aural proof that these cords are doing something very real. Just as those who purchase a component containing Teflon capacitors are told to anticipate some break-in, fussy Sigma owners will want to follow the prescribed burn-in procedure. Or, if you are a Jeff Bridges kind of dude, you can just hook them up and enjoy the trip, man. 'Cause it will be a bit trippy.

began critical listening by hooking up the Sigma HC to my Shunyata Triton power conditioner and then, a little later, I attached the Sigma Analog to my Convergent Audio Technology Renaissance Black Path SL1 preamplifier. Immediately, I noticed that the opening guitar line of Kasey Chamber's Wayward Angel CD [EMI Music Distribution 571398] had far more texture than I remembered. In addition to the twang, I also noticed the buzz and pluck of each note. It reminded me of how brand-new heavier-gauge strings would sound on the 1960s Fender Telecaster I used to borrow from a friend back in my garage-band days: steely, razor sharp and resonant. This is what the Sigmas did repeatedly in my system: they unearthed nuances that, while small, had a greater visceral and emotional weight than one might expect when speaking of them in the abstract.

Unlike some especially revealing equipment I have heard, the Sigmas kept micro details in perfect musical proportion. In other words, the Sigmas brought out nuances without spotlighting them in a way that would detract from the rest of the performance. For example, on Diana Krall's Live in Paris [Verve E651092], there is applause on the opening track that has always sounded ashy and reminded me a bit of white noise. It was an extraneous sound I wanted to get past quickly so that I could begin enjoying the actual performance. With just two of the Sigmas managing the electricity, I could more distinctly hear individual hands clapping. There was flesh against flesh separated by various members of the audience joining and exiting the ovation. Do I need to hear such micro cues? No. But they do help me pretend that I'm actually at the venue.

The Sigmas offered more than detail; they provided such a clear window into the performance that I had an entirely new set of psychoacoustic responses to a recording I had already heard many times. When the strings swelled in unison on Krall's rendition of "I've Got You Under My Skin," I got goosebumps for the very first time. This swell of the orchestra had a "lift" that I normally associate with a live performance. For a brief instant, I was with Krall's band at the Olympia on that autumn night back in 2001. What's the price tag for moments like that? Some folks are willing to pay $3500 for a nice watch that tells them exactly what time it is. I prefer a device that repeatedly transports me through time and space, even if it is just an illusion.

Recently, I discovered Canadian singer Stacey Kent's Dreamer in Concert CD [Blue Note 6809322] thanks to a late-night Pandora listening session. Her quartet's performance at La Cigale in Paris was engineered and produced in a way that puts any number of studio recordings I own to shame. Particularly impressive is how the producers have managed to capture the venue's ambience and the performance's electricity without shortchanging the tone and timbre of each instrument and Kent's voice. As good as this recording is, the Sigma power cords enabled me to hear so deeply into it that I felt as though I were onstage, listening to the monitor feed. For example, I could clearly hear that Jeremy Brown's double-bass lines were being amplified for the audience, just as they would sound at a performance. Without the Sigmas feeding power to my Triton and preamplifier, some of those bass notes sounded, by comparison, a bit blurry, bloated and boomy. With the Sigmas in place, Brown's playing came across as distinctly louder yet also more tuneful.

After the first two Sigmas had fully settled, I connected the Sigma HC to my Conrad-Johnson Premier 350. Immediately, I noticed that quiet instrumental passages could reach startling loudness in the most effortless manner I have ever heard in my system. Jonathan Valin has called this phenomenon jump and the Sigma HC delivered it on nearly every recording I auditioned. For example, on The Wailin' Jennys Firecracker CD [Red House Records 1952], many tracks begin with soft singing or subtle guitar work followed by multiple instruments entering one at a time, followed by an nearly instantaneous burst of sound as the instruments all take off in flight. With the first three Sigmas in place, those moments sounded far more real than they do without the lightning-quick electrical-impulse delivery of these innovative power cords.

To prove the point, when my friend Blackmore came by for a visit before I hooked up any of the Sigmas, we played "Close Your Eyes" from the incomparable Slam Stewart and Major Holley album Shut Yo’ Mouth [Delos 1024] in which a piano line is followed by a repeated kick from a bass drum. After just one Sigma HC was added to the system from the wall to the Shunyata Triton power conditioner, we replayed the track and I noticed Blackmore's head jerk back a bit, as though we'd suddenly hit the gas pedal in a car. In typical Blackmore fashion, he said, "That was different," and shook his head. Jump is a good way to describe this, but snap would also capture some of the effect.

The word grip is normally used in reference to power amplifiers. To me, this describes how firmly a device can convey the force, weight and substance of transients, especially the mid-to-low-level variety, which can be flabby or somewhat murky when played through lesser equipment. The Sigma Analog and HC power cords applied a grip to these sounds that was simply startling. Throughout Jackson Browne's "Too Many Angels" on the Still Alive CD [Elektra 7559615242], there is a running bass-and-conga line that has a delicious texture due to what I assume is the bassist sliding his fingers down the instrument's frets and the conga player running one of his hands on the top of the conga skin as he strikes it with his other. Prior to adding the Sigmas to my system, I could hear that texture, but I was unaware of just how tight and together the two instruments actually are. It's a detail I might notice at a performance but something I rarely do on recordings. Jim Keltner's tom tom fills also punctuate this track, but the Sigmas revealed a "hammer of the gods" quality that further intensified the song's sonic drama.

To borrow from the automotive world, I'd say these cords can go from 0 to 60 in less than two seconds; that's some g-force anyone should notice -- even after listening with cords from Shunyata's more affordable Alpha line. As good as Alphas are, and they are very good, the fact is that size matters when it comes to current delivery. The 6-AWG and 8-AWG amalgamation of cryogenically treated, high-purity copper in the new Sigmas cannot be ignored. The result is a sound that is as big as the gauge. One of my favorite pop recordings of the last decade is Death Cab for Cuties' Plans [Atlantic 7567838342]. Listening to an album whose nooks and crannies I know this well should not result in many surprises. Yet, the Sigma Analog and HC cables in my system produced music I could swear was a solid remaster of the original recording, even more so than the Alpha cords. The bass was tub-thumping good and the highs simply sparkled. I am a big fan of Ben Gibbard's songcraft, but I never paid much mind to how tight, forceful and accomplished the entire band is on this release. The Sigma treatment brought out the bedrock interplay between bassist Nicholas Harner and drummer Jason McGeer in a way that had my head bobbing and feet tapping. I was tempted to do some air-drum work during "Soul Meets Body," but I stopped short just as my wife walked through the living room. When I noticed she was smiling and singing along, too, I knew the effect was not just in my head. Shunyata’s Gabriel says that by improving the speed of current delivery, ". . . the size and scale of the music can be significantly improved with a wider and deeper soundstage and a more open and expansive decay of the notes. There can also be an impression of a fuller, richer quality with greater bass extension and definition." I agree.

After a few weeks of fun with the Sigma Analog and HC cords, I connected the Sigma Digital to my PS Audio DirectStream DAC. Initially, I sensed a dry, ashy quality to all my recordings. I also noticed a sense of restriction, as though big notes were being sucked through a narrow straw. The outstanding bloom and depth of soundstage of this DAC was decidedly diminished and the presentation was somewhat flatter than usual. An hour later, the bass was enormous and boomy. Based upon past experience with Shunyata's line of Zi-Tron power cords, I recognized this immediately as a settling issue. So, I put on Pandora and just enjoyed "tunes" for a few days.

When I returned to critical listening, the world-class DAC was back, but the Sigma and DirectStream combination was, to borrow from the jazz vernacular, "mo betta'." The DirectStream is a very analog-sounding piece of digital equipment. Going from the already impressive Shunyata Alpha Digital cord to the Sigma Digital is a substantial upgrade; it's like moving from a C-Class to an S-Class Mercedes. Both are nice cars, but you'd never get them confused. Like the Alpha Digital, the Sigma acts as a separate power conditioner and, consequently, removes a significant amount of digital noise generated by the DAC itself and isolates the DAC from the rest of the system. I suspect Gabriel's use of a VTX conductor and larger-gauge wire in the Sigma are why detail and dynamics now emerge from the DirectStream in the same dynamic, natural and effortless way they do from some of the best vinyl systems I have heard. With the the Sigma Digital power cord attached, my reference DAC was as close to the the musical bullseye as I have heard from a digital source in my system.

The final Shunyata cord placed in my system was the Sigma Digital to my PS Audio PerfectWave transport and this had an even greater impact than the one I added to the DirectStream DAC. Gabriel acknowledges that a Sigma's performance can vary from component to component. "The differences that can be achieved are dependent upon the individual electronic components that the cables are used with. Some power supplies are more advanced than others." In the case of the DirectStream DAC, its design team has indicated in a variety of forums that more focus and expense were devoted to managing power-supply issues in this flagship product than was practical with the company's much older and less expensive transport.

When I started critical listening to the the additional Sigma Digital cord, three terms came quickly to mind: natural, effortless and three-dimensional. Just as my DirectStream DAC comes closer to an analog presentation than any DAC I have owned, the transport was now singing the same song. I'd never thought of this transport as fatiguing until much of the digital noise and hash it was generating were removed from the system. The relief was palpable. Spinning Stacey Kent's Paris-concert recording again was like returning to the second set of a show after having a stiff drink: everything was more inviting and fun. Was there weightier bass? Deeper soundstage? More detail? Yes, yes and yes. But what really stood out was how much more musical CDs sounded. It's an often-used analogy, but adding the Sigma Digital really did remind me of a good turntable upgrade.

For one of my final critical listening sessions, I started streaming Eric Bibb's Blues People album [Stony Plain CD 321379] on Tidal. The live feel of this primarily acoustic album as well as the close-mic production make it a good selection for assessing transients, instrumental timbre and realism. On the track "Silver Spoon," as Bibb hammered on and off the steel strings during the opening guitar riff, I could easily hear the "clack" of the strings hitting the guitar frets, something you don’t usually hear from a seat in the audience. I have noticed this before, but with the Sigmas in place, I felt like I was sitting right next to Bibb. When the electric-bass lines started and the rest of the band joined in, I was surprised to feel my pulse quicken a bit at the sheer percussive force and clarity. This is what I go to intimate live performances for. I have no means of measuring it, but the effect is about as addictive as anything I've experienced in this hobby. The first time I encountered this profoundly live quality in a piece of gear was when I hooked up my CAT Black Path Edition preamp. I suspect it's the result of what equipment like this removes from the signal path and how such gear manages power. My friend Blackmore says a really great audio component reveals "the blood and guts of music" and will sometimes make you "duck at a cymbal crash or rim shot." That's what my CAT preamplifier does and what the Sigmas do -- in spades.

The asking price for five Sigma power cords is a lot of cash by anyone's measure. In fact, cost was the only downside I would identify. On the other hand, many of Shunyata's closest competitors' flagship power cords are at least twice to three times as expensive. Every customer wants to know whether a product is worth the price and no reviewer can easily answer that question when the product works as advertised. What I can say is that the Sigma power cords are the best I have ever used and that each one's performance exceeded my expectations. They provided more than a mere incremental improvement in my system over the company's previous offerings and the list prices reflect that. While an entire "loom" of the cords will be out of many peoples' reach, even individual cords yielded impressive results. According to my ears, the most dramatic improvement resulted from adding the Sigma HC's to my Triton power conditioner and to my amplifier. The results derived from adding the Sigma Analog to the preamplifier and the Sigma Digital to my transport were about on par with each other. The Sigma Digital's effect on my DAC was slightly less notable.

o one who is being objective would argue that a person should spend this kind of money when the same outlay could purchase more pleasing speakers or significantly better source electronics. That said, I have purchased several multi-thousand-dollar components that did not yield the level of improvement I heard from adding a single Sigma cord to my system. If you already like how your system sounds but want to explore its performance potential, the Sigmas should be at the top of your audition list.

A truly great audio component manages to preserve as much of the truth of the recordings it delivers as possible, even when those recordings contain flaws. It can bring us a step or two closer to the actual master recording and, without obscuring the flaws, show us enough of the music's beauty and magic that we begin to forget those flaws. The very best among these components cause us to fall under the spell of the music, delaying bedtime or rushing home from work for another dose of the good stuff.

The Shunyata Zi-Tron Sigma power-cord system is just such a transformative component. That's right -- component. It's simply inaccurate to use terms like accessory or tweak to describe equipment that unearths so much music from the recordings we love.