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Reviewer: Srajan Ebaen
Source: Zanden Audio Model 2000P/5000S
Preamp/Integrated: ModWright SWL 9.0SE; AudioZone PRE-T1 [on review]; Music First Audio [on review]
Amp: 2 x Audiosector Patek SE run one channel each, the other shorted out; Canary Audio CA-308 [on review]; Fi 421A [on review]; Yamamoto A-08S [on review]
Speakers: Zu Cable Definition Mk 1.5; Gallo Reference 3; Ars Aures Sensorial [on review]
Cables: Zanden Audio proprietary I²S cable, Stealth Audio Indra (x2), Zu Cable Ibis, Zu Cable Birth on Definitions; Crystal Cable Reference power cords; ZCable Hurricane power cords on both conditioners
Stands: 1 x Grand Prix Audio Monaco four-tier
Powerline conditioning: 2 x Walker Audio Velocitor S
Sundry accessories: GPA Formula Carbon/Kevlar shelf for transport; GPA Apex footers underneath stand, DAC and amp; Walker Audio SST on all connections; Walker Audio Vivid CD cleaner; Furutech RD-2 CD demagnetizer; WorldPower cryo'd Hubbell wall sockets
Room size: 30' w x 18' d x 10' h [sloping ceiling] in long-wall setup in one half, with open adjoining living room for a total of ca.1000 squ.ft floor plan
Review Component Retail: $2,400/1m RCA/BNC; $3,200/1m AES/EBU

Serguei Timachev of Stealth Audio Cables deserves laurels for going perhaps farther than any other small specialty cable maker by considering the whole picture including those pesky connectors. His discovery of the infamous spool of amorphous alloy that would become the secret ingredient of his special edition Indra was both a blessing and a curse. A blessing because it led to what many believe to be the finest analog interconnect made; a curse because Timachev is condemned to a one-time, quickly dwindling supply of unobtainium. But even in that curse hides another blessing - a fierce personal drive to get very similar results via some other -- circuitous -- route. The Indra conductor's Achilles heel is that it does not lend itself to digital or speaker-level applications. Needless to say, the highly favorable reviews on the Indra compelled our Russian inventor to revisit his best efforts of all non-Indra categories to narrow the gap. For his analog interconnects, current Indra runner-ups are his MetaCarbon (a metallized Carbon caber) and below that, the NanoFiber (pure Carbon). Both cables eliminate metal-based crystal boundaries for hi-tech fibers instead of amorphous metal alloys. The Meta reintroduces just a skoch of metal for better high-frequency extension.

For his previous top-line $600 Varidig digital interconnect, the Indra-chasing answer is the new Sextet. The name is descriptive. Think six gently twisted Varidigs around a common core. This paralleled, deep-immersion cryo'd contraption is terminated either RCA or BNC in Serguei's proprietary Carbon/Titanium/Teflon/silver connectors. A fully balanced version with a proprietary connector exists as well. Digital cables in this day'n'age of USB and FireWire are a strange anachronism. Call them a left-over from the separate everything days of HighEnd audio. CD players split in twain for transports and outboard DACs. They later split into even more parts when anti-jitter boxes and upsamplers became the rage. They separated once again when expensive outboard reclockers à la dCS and Esoteric appeared. The latter days of USB-connected hard-drive servers are still in the future for this type of cable. Hence straggling anachronism.

Being such an anachronism myself -- 2-channel, tubes, digital separates rather than CPU based -- my Zanden components nevertheless add a new wrinkle. An internal reclocker is accessed via a 6-lead, modem plug terminated I²S cable built by Zanden. RCA, BNC or AES/EBU connections cannot take advantage of the 5000 Signature DAC's reclocker. They are thus all -- by both definition and listening -- relegated to 2nd place no matter the quality of the digital interconnect.


I²S and all other standard cable formats can be connected in parallel between Zanden's transport and DAC. Simply selecting a different input on the converter makes the superiority of the external reclock connection obvious. However, standard digital cables are still the - ahem, standard MO to connect digital transports and external DACs. Hence products like today's Sextet. Because its designer is a veritable treasure trove of opinion and experience, we'll open the review with him Talking Tech.


"Incorporated in 1999, Stealth Audio Cables is still a young company. Fortunately for the customers, we simply have no other way to survive and make our way in the overcrowded world of today's high-end cables but make our products speak for themselves. Every particular aspect in our cable designs is there because it makes sense. Being the chief designer, I am able and willing to explain why things are there and why they're done a certain way. The choice of conductive and dielectric materials, connectors and structural core materials is a very careful process in which I try to leave positively nothing unconsidered. As I progress in my understanding of how things work and thus progress in my design ability, I rely more and more on custom parts and material, some commissioned, some made in my little laboratory and prototype shop. The standard, off-the-shelf materials simply no longer do what needs doing at the cutting edge.
The conn job

My customers and dealers often ask. What do you do differently compared to other cable companies? I could easily talk for hours about this. Much of what we currently do is implemented, mentioned or considered by nobody else. A particular list of these things as they pertain to my Varidig Sextet follows. The Varidig Sextet is, in fact, six Varidig cables in one cable, wrapped around a braided Kevlar core and terminated with a very good RCA connector custom-designed for digital applications. Each of the six Varidig cables employs a pure solid silver signal wire and a quad-layer, variable pitch Litz return.


This concepts mimics running several DAC chips in parallel, which is incorporated in numerous statement converters. This is sometimes referred to as stacked DACs. In digital, this concept offers better low-level resolution and better resonance control. This results in a better approximation of the musical signal and less pre- and post ringing (which, according to some sources, is the main reason for digital's different sound compared to analog.) The Sextet is a digital cable with no analogs in the cable world - pun intended.


Unique and unusual aspects of this cable:
  • Variable (length-specific) geometry - to the best of our knowledge, nobody else does this for digital cables.
  • Multiple paralleled cables - nobody runs several identical cables in parallel .
  • Porous Teflon (which is better than solid Teflon) - perhaps not an exclusive item but still rare.
  • Kevlar cable core. Kevlar is stronger than steel but I am not aware of any other cable to use it as a cable core.
  • Nobody uses machined Titanium for connector shells. Titanium is strong, light-weight, non-magnetic, extremely corrosion resistant but expensive (and difficult to work with).
  • In my custom RCA connectors, the dielectric is Teflon and contacts are solid silver. I use less metal than even the very good Eichmann or WBT Nextgen variants.
  • Nobody uses anything like my machined Teflon cones adjacent to the RCA connectors to give a cable the required geometry to stabilize the impedance while the cable approaches the termination point.
  • We now also have our own XLR connectors (Teflon dielectric, very light hollow solid silver contacts, Kevlar supports, locking ability, Titanium shells). Even the best and most popular connector manufacturers like Cardas and WBT do not make their own XLR connectors. It's too difficult and expensive. Furutech and Xhadow do offer XLRs but ours are objectively better.
  • The cable is flexible and very user friendly but virtually unbreakable due to its Kevlar center core. I actually thought about giving a strange little demonstration at one of the shows: tow a car using the Indra or Sextet as tow line, then demonstrate that the cables will still work after such abuse.
  • Nobody uses Litz for digital cable returns. This creates a more "transparent" ground path and works to higher frequencies to reduce the effect of RF and EMI interference on the ground return.
  • Nobody uses variable wrapping pitch in cable geometries to control resonances. This is like using multiple ports in a ported loudspeaker box. The main high "Q" resonance is broken down into several smaller ones of lower Q for far more linear overall performance.
  • Because the cables are made by hand, we can fine-tune both their electrical and mechanical damping separately (details below).
  • An assembled RCA-terminated Varidig Sextet is very light weight (under 2 oz. including the connectors).


My standard Varidig is a good cable and usually well accepted by the listeners. But occasionally, owners complained of sterility, probably the only complaint I ever had on the Varidig. The Varidig core concept is one of overall impedance linearity and smooth impedance matching between the cable itself and its terminations. This concept isn't my own but well known in microwave electronics whose engineers work with ultrasonic bands. Even circuit board traces often use variable thickness for the same impedance matching purposes.


So the Varidig is different from any other digital cable on the market because its porous Teflon dielectric is thicker in the middle of the cable than at its ends. This specialized dielectric geometry greatly reduces the sudden impedance mismatches at the critical points, i.e. between the inherently low-impedance RCA connectors and the cable itself. This allows us to achieve a true 75-ohm impedance over the entire length to greatly reduce signal reflections.


The dielectric is porous and contains air bubbles. This reduces its dielectric constant from 2.0 - 2.2 (typical for solid PTFE Teflon) to approximately 1.4 - 1.6. In general, the lower the dielectric constant of a dielectric used, the lower the energy storage in cables. This transforms into perceived speed, both analog and digital. Like all advanced Stealth cables, the Varidig Sextet is made of extremely thin wire and constructed entirely by hand. The impedance matching geometry can only be made by hand and is thus not available in bulk-spooled unterminated form. It cannot be machine-made, cheaply reproduced or copied overseas.


By the way, the name Varidig comes from variable digital. In my opinion, it's a good name. The only name I like better doesn't belong to me - Bitmaster digital cable by Empirical Audio. On to the differences in digital cables. While still audible, they are usually not as pronounced as in the analog interconnects. That's mostly because a decent DAC can lock to a digital signal being transmitted via just about any two wires and still sound halfway decent. And yes, a good digital cable will sound better.


Digital signal is transmitted via a digital transmission line where the output impedance (of a transmitting device), the digital interconnect cable impedance and the receiver (DAC) impedance should be the same: 75 ohms (or 110 ohms in AES/EBU balanced digital). This is characteristic, not electrical impedance and directly related to cable geometry and dimensions. It can be calculated using several parameters of a cable but all we need to know to understand the Varidig concept is that for the given center conductor gauge of a coaxial configuration and given dielectric, a thicker cable will have a higher characteristic impedance than a thinner one.


The vast majority of digital audio cables used for S/PDIF are coaxial and made from machine-made bulk. The interesting thing about characteristic impedance is that while it's defined as the impedance of a cable of infinite length, a short piece of the same cable will have the same characteristic impedance if this cable is constant in diameter along its length. The Stealth Varidig digital cable is different. Its thickness (diameter) is not constant and varies along its length. Why is it done that way?


It will be clear very soon. As stated already, standard digital cables exhibit 75 ohms of characteristic impedance terminated with connectors at both ends. These connectors are seldom BNC-type bayonet and predominantly RCA types. While BNCs do exist in a true 75-ohm format, RCAs do not. The only very close approximation is the WBT Nextgen but its dielectric is not Teflon but some molded plastic. These connectors break far too easily but otherwise are an excellent design. Common RCAs have a much lower characteristic impedance, usually somewhere in the 30 - 40-ohm range. Ditto for chassis-mount female RCAs.


When these 30 or 40-ohm connectors are attached to a 75-ohm cable, it creates an impedance mismatch at both termination points. According to digital signal transmission theory (and practice), we have two things happening: our signal is either partially absorbed or reflected at these impedance mismatch points. What portion of the signal is reflected or absorbed is difficult to tell. Less than all, more than nothing - some for certain.


What does this mean? Some of our precious source data is lost. However, some people like the results. They confuse loss of information with extra warmth but on a high definition screen, it's easy to see it for what it is - signal degradation. For an audiophile with ears, lost data ain't good. Reflected data is even worse. When the signal is partially reflected back from the connector, it travels backwards along the cable only to bounce back at the other end until it eventually transforms as heat. The artifacts of that ricocheting portion interfere with the main signal and distort the presentation. This also explains why digital cables of the same construction and material sound differently at different lengths. The Varidig suffers no impedance mismatch barriers because of its unique construction.


In additional to impedance matching, the Varidig cable has considerably less pronounced internal cables resonance than usual. Less ringing equates to more subjective clarity in sound. When we place an audio system in a room, we prefer non-parallel walls to reduce standing waves. Additionally, we treat with acoustic devices for optimum damping, neither too much or too little.


We are doing the same thing inside the Varidig. In addition to its superior dielectric properties, porous Teflon is soft and can be made more or less dense to fine-tune its mechanical damping factor. With our Varidig, no length-dependant sonic differences are on record which means that it sounds the same at all reasonable lengths. This is based on the statistics we have accumulated by carefully examining the feedback from our customers.


However, S/PDIF and AES/EBU cables sound different despite using the same design concept. The reasons, in my opinion, include the following:

  • Connectors noticeably affect the sound quality in all cables but digital in this regard is even more critical than analog. S/PDIF and AES/EBU cables employ different connectors and are partially responsible for the sonic differences.
  • In both DACs and transports, S/PDIF and AES/EBU chips are different and these chips have different sonic signatures. In some pieces, the chips are identical but the AES/EBU signal goes through a built-in impedance matching transformer - a new sonic variable.
  • There is no way to predict whether S/PDIF or AES/EBU will sound superior. The only way is to compare both pathways in any given system.

Actual listening. Beyond a certain point of competence, digital cables indeed make smaller and smaller differences. Alas, those shrinking violets can bloom louder and bigger again as the overall resolving power of a system increases. If you believe that high-efficiency speakers are a mandatory ingredient for high resolution (100dB and up), perhaps those without them needn't be too worried about the nth degree of improvement by way of digital interconnects? Be that as it may, the remaining cable differences revolve around subtle timing issues. Think camera lens focus and the difference between lock and a quarter click off. Timing issues affect clarity, micro detail and transients/decays. They do not affect tone color or frequency response amplitude. That's not to say poorly designed digital ICs couldn't be tone controls. But focusing on competent digital cable designs, the final arbiter will be the amount of remaining jitter and signal scatter.


How much of that is audible? I call it natural resolution. Fake resolution relies on treble emphasis and transient hype. While incisive, this type of resolution is fatiguing and thereby unnatural. Real articulation as a result of time coherence is easy. Precision now sounds sweet rather than edgy, trailing edges elongate, transients are crisp and energetic without being sharp and annoying. Less efforting attention is required to make out what's playing on even the most microscopic of levels, i.e. the ambient life in the shadows. This act of gazing -- or listening in our case -- sees and hears things as just so. It's inclusive. It's free of strain and deliberation. That's why in the end, it's hard to make out and impossible to quantify. You see, our brain is extremely capable of filling in blanks, especially when those blanks shrink to slivers ever easier to bridge. The ultimate difference between no blank and one blank isn't final resolution at all. It's the relaxation of effort.


That's bloody tough to comment upon seriously. Rather than weigh objective items -- hard data -- we instead attempt to watch the mechanisms of perception. The listener becomes the focus. It's not about what she hears but how she hears it. Psycho stuff in short. How reliable is this type of approach in the first place? It actually takes a while for our ear/brain mechanism to figure out that it no longer needs to interpolate. Quick A/Bs won't do at all. Whatever first tips off our mechanism to slow down or stop is impossible to predict. In fact, it's something we realize only well after the fact. Only when we return to the prior state which conditioned us to work for a listen do we notice the difference. There's more blurring now. It doesn't automatically get corrected and resolved by our brain just yet. It will soon again, once we revert back to the old mode of more effort before we again stop noticing it. So this is tricky. It's very personal terrain.


Accordingly, all I'm prepared to say about the Stealth Sextet is that like the Indra, it supports peak resolution while inducing a very relaxed, effortless psychological state. You notice things without even trying, whenever your attention is spontaneously attracted to a specific detail in a song you know well. That's it. With the Indra, I believe there's actually a difference in the sound. With the Sextet and when compared to other top notch digital cables, there's simply obvious clarity. It's as though someone had stopped all the ripples of even subliminal blurring. That's a tiny thing in the objective realm. It's far more significant in the subjective realm where the state of the listener is concerned. It's very different from the usual what's-it-sound-like list. Cynics will call it a cop-out. Other might consider it a conceptual opt-in. Think about the basic issue proposed: listener comfort especially in the context of a truly hi-rez rig. What's that mean to you? In the end, long-term audio satisfaction and enthusiastic system use depend on this factor more than any other. Does listening to your tweaked-to-death rig stress you out in any way, shape or form? Or does it rejuvenate, energize and relax you?


In my book, the Varidig Sextet belongs into the latter class of devices. It doesn't so much sound better. Rather, it moves a digital system into a more analog-feeling direction. Compared to patently inferior cables, higher resolution of course also sounds better. But once timing-induced shakes and blurs become small enough to be mentally overlooked or interpolated away, the quantitative final result is more or less identical. How you get there now becomes the reward and question. Here's the thing. A cheap USB cable connecting a hard-drive to a DAC could outperform the world's most elaborate S/PDIF interface (if our hard-drive was equipped with the requisite connector). It's likely that this is where things are eventually headed. For now, the Sony/Philips Digital InterFace aka S/PDIF is our collective audiophile burden to carry. If you're a two-box gal or guy, that means a digital interconnect. If you're a critical listener with a really good system, you'll need a really good digital interconnect. That's where a cable like the Sextet comes in. As for me? It's back to my I²S connection. It outperforms even the best es-pee-diff. Perhaps next time the industry invents a connection format for audio, they can give us something better than the truly funky RCA standard?


But for now, 2005 and as CD listeners, that's what we're stuck with. If Timachev's claims are factual, his Sextet is the first-ever true (end-to-end) 75-ohm RCA-terminated digital interconnect on the market. Based on its performance, it should probably be thought of as the digital Indra. It makes music seem more natural and at ease...
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