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|Pick your world view
Our bi-amp Cabbie asks a very pertinent question. What role does an active preamp really play in a 21st-century digital system outside of input switching and volume control? Clearly not gain. Most modern digital sources drive most modern amps to full output directly. Nor resolution enhancements. Or do you find the argument persuasive that -- lots of -- additional analog circuitry could increase resolution? Not. Common sense suggests that the best any active circuitry could hope for in that regard is utter transparency. Let's thus tally up our compelling reasons for adding an active preamp to a standard 2V-out CD player and 0.5V input sensitivity amplifier. Redundant gain. And resolution that's at best equal to -- but more likely, subtly diminished over -- no preamp at all. Bitter blimey. That certainly couldn't be all of it. Could it?
Surely not if the Cabernet - um, weighed in on the matter. While its massive gain per se is certainly redundant in the vast majority of applications, it's necessary for signal conditioning. Think of it as distilling for alcoholic potency. The multiplication factor of high gain (times x) becomes our aural distillery. It potentizes the signal. Regardless of how small a glass you eventually pour right off the tap -- in our context, regardless of how far you attenuate the signal at the preamp's output -- the distillation has already occurred. A minuscule serving will have the same potency and taste as a large one. Even if you squandered 95% of your goblet's fill by pouring it on the floor (wine tasters spit it back in the glass, audiophiles reduce the volume), you'll have enjoyed an undiluted taste. In which case the massive gain wasn't redundant at all. Rather, it turns out to have been an elemental facilitator of an alchemical process.
What audible qualities does one accrue from this signal conditioning process? With the Cabernet, color and dynamics to begin with. Both appear to be a function of how well the input driver stage of the following amp is - well, being driven. Naturally, any flotsam noise in our preamp's bowels is amplified along with the signal. Noise components become a percentile ingredient of our brew. That is independent of eventual serving size as well. Especially with valve-powered high-gain preamps then whose main signal attenuation occurs behind the final gain stages, elimination of operational noise is one of the biggest circuit design and implementation hurdles. That's why hi-gain valve preamps are rare. Quiet thermionic operators are far easier to execute with very low gain. If the Cabernet's case evidence is anything to go by, there's clearly an awful lot to be said for its deft hi-gain angle. Here is Mick Maloney's explanation for certain design decisions:
|"Good active preamps always sound better -- we suspect but aren't positive -- because of impedance matching. A passive must drive an amplifier without muscles. There's no grunt to pass on the signal as uncolored and accurate as it was received. So a passive loses information. The standard ratio for impedance matching used to be that the driver (source) impedance was 1/10th of the driven component's (load). Hence a 10Kohm input Z amp needs a 1Kohm output Z preamp. Passives just barely manage this. Many simply don't. The output of our 101D is around 200 ohms. The impedance ratio with a SS amp of around 10K input impedance is 50, with a typical tube amp about 500.
"But we go a bit further. We put another tube (half of the 6SN7) in front of the 101D. This gives high gain and completely frees up the 101D. The load it now sees is a mere breeze. That's very important. Get the various circuit parts completely free of strain and effort. The sound then becomes free and 'bouncy' as you wrote. Likewise for the power supply. Those 5881 tubes are shunt regulators. This isolates the preamp from power supply variations. The ultra-low impedance regulators supply a constant voltage to the preamp with one hand tied behind their backs.
|"The other issue preamp designers have to contend with is sensitivity. High gain preamps do sound best in our opinion but they prefer low input sensitivity power amps (1V or higher for full output). That's rarely the case these days. Everyone wants their power amps to work with passives or source-direct. Such power amps have high gain typically achieved with high-gain driver stages. That really renders them integrated amps - without volume controls. These power amps with quasi preamps in their front ends amplify the connected preamp's output to the point where noise floor becomes audible and hum and hiss become problems.
"It's a really difficult job to get direct-heated tubes like the 101D quiet without yet another preamp to amplify the noise floor again (which is always present with every tube device). Supratek power amps keep this in mind and simply turn the gain of the preamp into current to drive the speakers. The resultant lack of complexity of extra driver stages also makes our push/pull amps very transparent. They sound like SE amps -- nice and pure -- but have real power to drive real speakers. And when I build custom SE amps, one driver stage is sufficient (or sometimes two low-gain driver stages). When it comes to power amps, less is more.
"So Supratek uses preamps to get the magic and power amps to keep it. I like high efficiency speakers myself. I have a 100+dB fully active system with a valve crossover/pre and 3 amps including SE monoblocks. It sounds very good. Since I've gone the Dual pre route of late, I'm achieving results that are just as good if not better in some respects - with a set of home-built electrostatics for testing amplifier drive. That's something I would not have thought possible just a year ago; our Dual preamp with our 100-watt KT88 PP amp and a SS amp on the bass. Because the amplification is so free, the stats reflect this. Because of their demanding load behavior, usually stats demand complex and consequently veiled amps that hamper their very fine resolution. Our method really brings out the best from them. In the end, it's all about making everything free and easy, a heaven where everyone is happy and untroubled and everything is thus beautiful. Scientists call that impedance matching."
|The special merit of the Cabernet Dual resides in not only introducing this liberated breath or flow to the music but to not sacrifice hard-hitting attacks in turn. This must be qualified by my particular speakers not inserting a crossover until about 40Hz. The 101D-covered spectrum of the crossover-less front array extends beyond 35Hz. That means the power band of bass and midbass is still driven from the direct-heated triodes. Ideally, you'd want speakers whose woofer artillery covered at least the two bottom octaves. That would take full advantage of the 6SN7 bass circuit. On the phenomenal semi-symphonic Sur album by Spanish pianist Dorantes [EMI 7243 538417 2 0], the Flamenco-styled chordal piano percussion on "A ritmo de berza" perhaps wasn't quite as hard-hitting as over the Wyetech preamp. Yet the subliminal rubato factor in the lyrical passages -- what I earlier called the inner movement --|
|was superior. And it didn't undermine the pungent sharpness of metallic harmonics when the pianist really leans into the upper-register keys to suggest guitar attacks. Very pronounced too -- and connected to the buoyancy -- was the endless ringing out of piano strings underneath a suspended damper pedal. Such elongated decays are an area where the slightly soft-sounding Zanden absolutely excels to set new marks for digital. The Cabernet truly dug into this aspect and laid it bare in all its glory.
In fact, the low-gain Zanden's slightly polite mien when compared to the more explosive Esoteric machines seemed to particularly benefit from the Cab's dynamic expander action. (To revisit the earlier simile, low alcohol content goes in one end and comes out the other alchemically transformed and far more potent). Perhaps there's no music genre better at conveying rhythmic looseness than swing. It's all a'shimmy and a'bop. Pretenders and the real McCoy are easily distinguished. While the notes may be identical, one rhythm sticks, the other dances. I'm a big fan of French Gypsy guitar. One of the undisputed masters of the present-day scene is Romane. He's a true dare devil of swing. On Romane & The Frederic Manoukian Orchestra [Iris Music/Harmonia Mundi 3001 851/HMCD 87] he pulls off what had kept eluding Django Reinhardt despite mighty efforts - to record guitar-led Manouche Jazz with a premium big band.
|This is a landmark recording. Colorful arrangements would make A. Khatchaturian proud but are of course culled from Nino Rota, Duke Ellington and Gil Evans precedents. A lineup of premium soloists each take turns at heated solos. In many ways, letting this CD run through from first to last track epitomized the pertinent Cabernet quality in a driven rather than lyrical context: rhythmic elan that was fabulously loose yet never sloppy. German wunderkind Joscho Stephan is arguably the superior guitar technician. Yet he doesn't swing as easily. He lacks Romane's rhythmic freedom. The Wyetech Jade's timing isn't as dry as Joscho's - but it's not as supernaturally between-the-cracks and out-there as Romane's (or Stochelo Rosenberg's whose three collaborations with Romane rank among the very best of modern Gypsy Jazz.)|
I'm deliberately letting actual musicians stand in to make audiophile points. We're dealing after all with qualities that belong to the artistic realm. They only make sense when approached from there. Test bench jocks would completely miss this fine print. It's further relevant to distinguish Cab Swing from the nearly mindless hard bop that, in times past, seemed the particular providence of the Naim aesthetic. I'm not talking about so-called PRaT. This is a more subtle and organic quality. It's completely non-metronomic. It's fluid rather than mechanical, intuitive rather than mathematical, easeful rather than muscular. It may seem odd to credit a preamp with introducing a higher rhythmic freedom. And perhaps that's not exactly what it is. Alas, it is a far more relevant pointer than casually calling it the tube magic. What is that, exactly? Aren't there so many different kinds - of tubes and classes and circuits?
By now, something should be abundantly clear. The Supratek Cabernet Dual indeed belongs into that rarefied group of components that have reviewers and owners alike go poetic to define what makes them unique and special. Shampoo commercials? French vs. Teutonic swing? Buoyancy vs. PRaT? Such outré descriptions leave objectivists reeling and exasperated. How does one linguistically capture the human elements though that make certain components transcend their mechanical souls, that render the music less mechanically defined and more artistically relevant? Like pornography, you know it when you hear it. But could you define it in a court of law if your life depended on it?
Enough then of poetically rendered soft facts. Back on the terra firma of hard facts. The gain structure of the Cabernet is so elephantine that even with the 101D circuit set to minimum gain, I couldn't open the master volume beyond 8:30 with the massive Butler Audio Monads and 101dB Zu towers. By comparison, the Wyetech Jade in that context approached 10:00 o'clock for equivalent levels. Using more gain on the Cabernet produced increasing amounts of power supply noise. In the most reduced gain setting and with the master volume at standard listening levels, the Supratek preamp even in this imbalanced power scenario proved dead quiet. Quite the compliment to engineering excellence Down Under chez Mick's and Kevin's. Naturally, no sane audiophile would ever combine a high-gain preamp and high-power amp on my speakers for a normal-sized room. To be more conservative in the straight jacket department, enter my customary 2wpc Yamamoto. It has never yet run out of steam even with a passive preamp. I thus wasn't quite sure how high I could set the 101D circuit's gain before I'd run into amplified noise.
A mere step down from the unloaded transformer feed ended up with the Monad's master volume setting - and zero noise. There wasn't any noise in the max-gain feed either on actual listening volumes but useful range became nearly too narrow. (Though unapologetically micro-power stock, the fierce little Yamamoto mini is a rather high-gain device itself). Being inherently leaner, more lit up and microdynamically more agile than the Monads, the boot-up-the-arse dynamic pressure of the Supratek now made for a kind of robustness and impact which a lousy 2 watts simply shouldn't be capable of. This only lent further credence to the signal conditioning action proposed earlier. It is the real raison d'être for modern active preamps.
The Supratek/Yamamoto duo catered to my more-adrenaline-than-mass proclivities like a private masseur who works your muscles to perfection. The Australian preamp only further accelerated the Yamamoto's reflexes. It most assuredly did not slow 'em down. Simultaneously, it added overall weight and fleshed out the dynamic envelope of transients. This shifted the Yamamoto's innately lit-up balance just a few feet into warmer 300B land without any fuzzies. Tone got weightier without any lack of articulation. I would also have to call the design brief's optimization of the 6SN7 bass circuit a smashing success. Just remember that the EQ'd nature of my speakers below 40Hz makes hard pronouncements less absolute than with a lesser level of compensation. Another upshot of enhanced weightiness and greater dynamics was scale. Things didn't grow bigger laterally or in depth. Rather, the inherently phantom nature of invisible sonic images acquired a few more degrees of virtual visibility. This was addressed not to the eye but the feeling dimension for emotional intensity rather than spatial scale.
The shiny pendant of the (audio) chain?
Some experienced 'philes have called the preamp the most critical part of the system. Needless to say, take out any active part and you'll have no sound. From that perspective, all components are of equal importance. But I can understand their point via the following reasoning. Liberated from the conversion challenges of the amp/speaker interface -- converting electrical into mechanical energy which entails very pragmatic challenges and practical constraints -- an active preamp isn't strictly necessary. A simple passive pot will do the basic job. Switching isn't essential either. Swapping a few leads by hand works (and many of us only use a single source to begin with).
A superior and expensive linestage thus needs to justify its existence far less on practical grounds than any amp (can it drive the speakers without distortion is its foremost concern) or any source component for that matter (which is simply indispensable). A preamp becomes far more of an artistic rather than essential proposition. What can it contribute beyond mere convenience features? Asking these questions might explain why particularly preamp designers feel called upon to push beyond textbook mechanics. It's perhaps here where an electronics designer can imprint his personal vision of 'musicality' the most.
He doesn't have to control speakers. He doesn't have to retrieve data off a disc without errors. His job is more interpretative. He's not only at liberty to ask what needs to be sonically enhanced to render the final outcome emotionally most convincing. He lacks real purpose if he doesn't. You could say then that with a preamp, the human dimension becomes of paramount concern. If so, the purchase of a preamp becomes the least spec-driven electronic purchase in a two-channel HiFi system. Because interpretative freedom is greatest here, it's also where a designer's personal vision and yours need to overlap the most to be relevant. Perhaps. This wraps up my attempt to rationalize the "preamp is most important" argument. Something about it does make a strange kind of sense. It's not most important per se but it could very well be the most influential electronic decision to determine the overall feel or vibe of your system's sound.
Be that as it may, it's beyond argument that this preamp has a very pronounced effect on the musical gestalt. Its greatest achievement seems to be that it's got both feet firmly on the ground. It conforms to science and art. On the science side, it does what a superior active preamp should - condition the signal for more current drive, make it more robust and fleshed out to optimize the workings of the amplifier. Do all of that without compromising resolution or noise floors. On the artistic side, it adds the ephemerals, the intangibles. Some artsy preamps lose their grip on science. They become too euphonic and unpredictable. They season indiscriminately. They're like a pianist who turns Bach into Mozart. How to introduce just the right amount of flair while keeping the score honest to the composer? Playing all the right notes is merely the first step. It does not bring the notes to life. Birthing a score to life requires a great interpreter. If he's also possessed of flawless technique, even better. If he can interpret anything and everything and remain true to such varied composers' styles, he's the one in a thousand.
That's the Cabernet's league. Naturally, it's also a wildly flexible machine. Sussing out the various permutations of settings on the sound will take time. Ideally, I'd have more conventional bi-ampable speakers whose bass systems cover a broader bandwidth than my Definitions. That will do proper justice to the Cab's 'Dual' designation. I'll simply have to wait for the appropriate speakers to show up. In the meantime, the Cabernet Dual represents my first encounter with the exalted class of preamps I've always only read about - the great Audio Notes, Kondos, Lamms and Shindos. Even without having sampled any of those, the greatness of the Supratek is self-authenticating. As a linestage, it's also the very best from this Australian stable which, in essence, has specialized in this product category though custom amps were offered and two new production amps are waiting on the launch pad. [A Cypriot audiophile owned the big Kondo and still possesses serial # 0000 of the darTZeel preamp. He quite prefers his Supratek Cabernet Dual.]
As a lover of single-ended triode amps, my audiophile journey has veered towards passive preamps. I had an Art Audio PX-25 with integral GoldPoint attenuator. At the time, I concluded that to do better would require a preamp of at least $3,000 - and it likely would be a setback in terms of transparency and speed. When the Music First Audio Passive Magnetic with S&B attenuation transformers appeared for review, I bought the sample. It's sonically invisible, adds a very subtle texture of silkiness and improves low-level listening. My Yamamoto amp is so open and fast that I wasn't really keen on fattening it up or slowing it down. Nor did the Yamamoto seem in need of any surgical enhancements. All I wanted was functionality (volume control) and the utmost in transparency.
Rather unexpectedly, the Supratek Cabernet Dual opens up new dimensions of tone color, impact and suavé factor without booking any setbacks against the passive. It thus makes a very compelling -- and dare I say addictive -- argument for the active preamp concept, even in a context where source unity gain never exceeds desired playback levels. Where it is unique in my experience thus far -- never mind its bi-amp nature -- is in the level of elegance introduced which I've attempted to hint at above. This is a very immaterial thing. On a physical scale, it'd weigh less than the proverbial Egyptian feather of the Pharaoh's Ka. In the material sense, the Wyetech Jade in fact is every bit as heavy-weight. It's only in the listening that the gap between the two appears to release what audiophiles, in general, refer to as a higher potency of magic. To the extent offered here, I'm admittedly on virgin ground. Hence no ultimate statements, no perfectly conclusive conclusions.
I've talked about the concept of alchemy. It suggests an answer to the vexing question of how apparent redundancy -- the very existence of this product category -- could do this. I'm convinced that it's a matter of signal conditioning. Like powerline conditioning that works (not all really does), active preamps of the Supratek's caliber are far from superfluous. In fact, I'm beginning to accede that they might be central to our pursuits. They could be instrumental in pushing a system firmly from the mechanical into the organic realm of operation. If you know Mariza's Transparente album, you know exactly what I'm talking about. It's all about the breath beyond physical lung action. It envelops everything, all of the accompanying instruments, in particular Mário Pacheco's weeping Portuguese guitar. Forget notated scores. They tell what notes to play. They don't begin to suggest how to suspend them as living things in temporal space; how to make them dance. Transparente then becomes a poster child for the Cabernet. And the album title is equally fitting. If this kind of review talk rings your bells, the Supratek Cabernet Dual is your kind of device. It's a terrifically inspired piece of the advanced audio design arts. Black arts - for white magic...
For additional ruminations on this very unusual preamp, read my further thoughts in a subsequent feature here.
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