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Valve Amplification Company Signature IIa Preamplifier

Valve Amplification Company Signature IIa Preamplifier

I don’t know if Nicolaus Copernicus was eating oxtail soup, looking at an apple falling from a tree, or cleaning his astrolabe when he thought up his theory of the revolution of celestial spheres, set down in his book De revolutionibus orbium coelestium in 1543. But his superior insight, partly derived from mathematical expertise, changed everything, putting the sun at the center of the universe and not the earth, as most of the governing clergy insisted was the case at the time, and became the defining epiphany of the scientific revolution that followed. After Copernicus, clergy could no longer so readily dismiss a Galileo or a Giordano Bruno by saying, Are you gonna b’lieve me or your own eyes? Scientists came to believe in their own eyes— observation before theory the new motto. Likewise, I’m not sure if Alfred Wegener, a German climatologist and arctic explorer, was peeling an orange in 1915 when he thought—Hey! The coastlines of Africa and South America fit together! He may have just been working on a jigsaw puzzle, but, somehow, he came up with the idea of continental drift—that the earth’s landmasses were once one big supercontinent that then broke apart and moved away from one another, giving rise to the oceans and, some eons and eons later, a new revolutionary paradigm in geology. What is certain, though, is that, every once in a while, we get a shift in the way we think of organizing things, be it astronomy, geology, or fried green tomatoes. Stuff we start noticing just doesn’t make sense using the old way of looking, so we have to change the lenses through which we’ve been seeing as through a glass darkly, clean things up, and come up with fresh new approaches.

Kevin Hayes, President of Valve Amplification Company (VAC), has taken fresh approaches to preamp design at least three times since the inception of his company in 1990. I spoke to him recently and the discussion told me much about the “revolutions” in VAC preamps over the past twenty years. Rather than sitting back, practicing science of the caretaker variety and simply refining his existing circuits, Hayes has spent most of his R&D time “interrogating the gross flow of electrons,” identifying where the electronic turbulences are in each given circuit. He wants to see not only what might be improved by parts substitutions, but what entirely different approaches, new topologies, completely different flows of those electrons might bring. For example, in 1998, when VAC issued the aptly named Standard preamp, it altered the VAC lineup, shaking the sun and stars, replacing the original 1991 CPA-1 preamp, and staying in production until 2007—nearly ten years. But, the advent of the Renaissance Signature Mk I pre in 1999 marked a sonic breakthrough for VAC that introduced a new circuit topology—an extremely high-gain, three-stage line section with direct-coupled interstage and transformer-coupled inputs and outputs—and the reliable Standard was eclipsed (if not yet discontinued). Then, very quickly in 2000, Hayes released the Signature Mk II with major changes to 11dB gain and a fully differential circuit with transformer coupling at the inputs. It established yet another major shift in preamp design for VAC and stayed in production another ten years until the recent release of the Signature IIa.

Introduced in 2011, the Signature IIa ($15,500, linestage; $19,500, with phono) represents the first new iteration of VAC’s flagship, transformer-coupled preamp in over a decade. It sports a small boatload of improvements over the prior Signature II. New are the volume control, key passive parts, variable phono loading, and the character of the chassis (better damping, new “energy termination” solutions). Also new is the option to roll tubes in the linestage.

That linestage has 12dB of gain, a frequency response claimed to be flat over the audio band, and an output impedance of 96 ohms. It comes stock with two 12AU7 twin triodes and two E88CC tubes (designed to be swappable). From input to output, the Signature IIa contains no coupling capacitors in order to protect the purity and detail of the hand-wired, direct-coupled triode tubes. There’s no loop negative feedback either, as Hayes wanted the output interface to be completely stable and free from dynamic interactions with an external load. The preamp does not invert phase.

As for the fully differential circuit, because the preamp achieves this through transformer coupling, there are fully balanced inputs and outputs. It also means the Signature IIa should sound the same with either RCA or XLR hookups. And, significantly, the transformer isolates the Signature IIa’s sources from the amplifier it is driving.

The optional, built-in phonostage (my review unit came phono-equipped) is zero-feedback, capable of both mm and mc operation with variable loading. Moving-coil loads are 470, 300, 250, 200, 150, and 100 ohms, while moving-magnet loads are 100x those. The mm phono is fitted with six 12AX7 triodes and is capable of 44dB gain. In mc mode, two wide-bandwidth transformers (sourced from Lundahl) get switched into the circuit, adding 20dB of gain passively.

I’ve been on a preamp quest for a while now, and, in my limited experience, what I’ve found is, features and superior technology aside, tubed preamps are basically designed to create weight and drive or else to have finesse and sophistication. If you look at their spec sheets, you’ll see gain levels that cluster either around 12dB or 20dB and this, generally, tells you what the preamp emphasizes. A gain around the lower figure would lead you to expect finesse über alles. Gain nearer the higher figure suggests tone and drive as foremost. VAC has made preamps in both categories (the Signature I even exceeded the “big on drive” category with a gain of 35dB!) and, given its 12dB gain spec, one might assume the Signature IIa to fall on the finesse side of the fence. And, at first, I thought so too, as, paired with my reference deHavilland KE50A mono amps (40Wpc), it did seem the Signature IIa had all the sophistication of my deHavilland Mercury 3 linestage—lovely with a gentle hand on orchestral music, able to resolve evanescent details and create a subtle, organic flow. But it also somehow sounded “light” to my ear, missing body on strings and sometimes voices, and so I ventured onward, pairing the VAC preamp with power amps that had more output and quickly discovered its strength, tonal weight, speed, serious authority, and ability to throw a big soundstage. The Signature IIa seemed to split the difference between my ad hoc tribes of preamps—or did it just combine the best traits of both?

Physically, the Signature IIa is one of the loveliest mechanical things I’ve ever seen. Though my review unit came in black (silver also available), that hardly begins to describe the illusion of depth in the glossy 10mm-thick faceplates of both the control and power units, glittering with gold metallic flakes embedded just under the layered lacquer finish. What’s more, both have as centerpiece an inset, backlit LED logo with the VAC trademark—an encircled lightning bolt beside capital letters spelling out “VAC.” Running underneath the logos are lines of understated gold script silkscreened on, identifying each. The bling-factor on the control unit is pretty high too, as there are two large, rakishly beveled, hand-sized gold knobs marked Volume and Selector, and four smaller outlying ones marked Monitor and Mute on the left, Cinema (for bypass) and Power on the right. Build-quality is superb and each aluminum chassis is finished with an even, flat-black powdercoat.

Around back, the preamp absolutely bristles with connectors. These are premium Cardas rhodium types that can stand up to a lot of cable swapping. There are four sets of main outputs, two RCA and two XLR; five line inputs, two with both RCA and XLR jacks; a set of RCA Cine inputs; a tape loop; a control knob for phono loading (if phono is fitted); and a set of mc phono inputs on RCA jacks (converts to a sixth line input if phono is not fitted); a selector knob for mm/mc; and a set of mm phono inputs (RCA). Below these connectors are switches for SE/BAL selection and for adjusting brightness or dimming of the logo. Because the Sig IIa has four sets of main outputs, you can readily bi-amp, either single-ended or balanced.

With the VAC Signature IIa, I used four different amps, two sets of speakers, and both balanced and RCA interconnects. For sources, I used analog, CD, and an iMac with a USB DAC. After an initial run-in period of scarcely 50 hours, the preamp distinguished itself in multiple and (I’d previously thought) contradictory areas—finesse, tonal weight, and drive. This preamp created musical momentum in ways that were both powerful and subtle. Add to this, the Signature IIa also demonstrated fine spectral balance and superb dynamic and timbral contrasts. In its performance, it transcended both gross categories of preamp I’d presumed existed. As I mentioned already, though it did not match perfectly with my moderate-power deHavilland KE50A tubed monos, the Signature IIa sounded great with three other amps—a VAC Phi-200 (100Wpc), Herron M1 solid-state monoblocks (150Wpc), and a VAC PA-100/100 (100Wpc). Compared to my reference combo of deHavilland KE50A tube monoblocks and Lamm LL2.1 linestage, the Signature IIa with Herron or VAC amps consistently sounded more polished, with better imaging and a wider and taller soundstage, reaching up to a yard on either side of the speakers and almost as high above them. Believe it or not, the Signature IIa sounded pretty much the same run balanced with Cardas Clear balanced interconnects or run single-ended with Siltech 330i or Cardas Clear unbalanced. As for speakers, both my reference Von Schweikert VR5 HSEs and a review pair of Von Schweikert VR-44s that arrived late in the review period worked terrifically well, with the powered subwoofers of the VR-44s providing more bass presence, detail, and slam. The remote operated smoothly during the entire review period.

Near the end of the review period, with the stock sound of the Signature IIa firmly in my ears, I started rolling linestage tubes. On Hayes’s recommendation, I first tried a pair of Philips E88CC SQ tubes manufactured in Heerlen, Holland. A toggle switch near the right tube socket sets the circuit for one of two types (8416 and 12DJ8; or 6DJ8/ECC88, 6922/E88CC), but since the Philips used the same setting as the stock tubes, I didn’t have to flip it. In fact, all the tubes I tried—pairs of Amperex 7308 PQ, Amperex 6922 PQ, Amperex Bugle Boy 6DJ8, Mullard E88CC, and Mullard E188CC (a 7308)—used the same switch setting. To my ear, the Philips and Mullard E188CC tubes sounded smoother, more liquid, sweeter on top, had more weight, and gave more detailed and longer decays than the stock tubes. The Amperex 6922 and 7308 tubes were more resolving than either, perhaps more balanced through the frequencies, and had superb top-end finesse and air—great for voices. The Bugle Boy 6DJ8s were also airy, but spacious, harmonically rich, and sensuous, especially on orchestral strings. Finally, the Mullard E88CC sounded even more spacious and warm—on the verge of “euphonic,” and, to my ears, mostly pleasing. But these weren’t game-changing differences to me, and I was nearly as content listening to the stock Chinese E88CCs.

Matched with a VAC Phi-200 stereo amp, the Signature IIa consistently produced a clean, punchy, and speedy sound that was never hard-edged. On most orchestral pieces, notably Alfred Brendel’s CD of Mozart’s Piano Concerto No. 12 in A Major, K414 [Philips], strings were sprightly and airy but authoritative when called for. There was an inner liquidity to piano notes. Attack transients were exceedingly fast, just on the pleasing side of sharp, and I experienced no fatigue. Interior shadings—the notes as they developed—were completely natural, evolved in time, and breathy with life. On Brazilian Dreams [Manchester Craftsmen’s Guild] by Paquito d’Rivera with the New York Voices—a CD I’ve used as a demo at shows—I heard, on tune after tune, an amazing clarity, precision, and punchiness without any etch or analytic quality to the male and female voices, brass, and d’Rivera’s agile alto clarinet. I heard more detail and my listening seemed more alert and lit up.

Even with amplified music, the Signature IIa, consistently demonstrated an ample sensuousness as well as excellence with timing, detail, and finesse. Austin’s been the town for live rock for a good couple of decades now and Jimmy Lafave has been one of its local heroes. His live CD Austin Skyline [Bohemia Beat Records] is a treasure. When I spun his cover of 60s hit “Walk Away Renee,” LaFave’s electric rhythm guitar and Larry Wilson’s lead both produced ripe, ringing tones with tasteful plucking and light sustains. Reacting to LaFave’s rough-edged and plaintive veteran wailer’s voice, tinged with smokey shadings, Wilson bent out a clear and bluesy solo, full of aching lamentation. His fills made for open, airy, and privileged interplay with LaFave’s deft frailing and strumming, producing a seamless, sparkling electric tapestry. I noted the drumming had march-like, doublethunks from the kickdrum and that the electric bass was subtle, unobtrusive, and tight. And the organ stayed in the background, too, gently comping and undergirding the whole sonic field until the final choruses, when it emerged and claimed the tune as a dirge. Each of the band’s light crescendos came with a gently rising momentum, making for a succession of sonic swells that captured the ambience and clarity of this live club date.

When I hooked the solid-state Herron M1 monoblocks with their 220k ohm input impedance to the Signature IIa, they were absolutely no sweat to drive. The system sound became warmer, more “tubelike” actually, with more emphasis on the smooth midrange, lovely scaling, and an even more organic flow to the music. Turning to analog, for example, I dug out my stereo LP of Yevgeny Mravinsky conducting the Leningrad Philharmonic Orchestra performing Tchaikovsky’s Symphony No. 6 in B Minor, commonly known as “Pathétique” [DG]. I used a ZYX Airy 3 cartridge (0.24mV) and clicked through the resistive loading options of the mc phono, adjusting the convenient dial on the left of the back panel for ragged violins and tinges of grey in the treble, trying to find the most clear, sensuous, and dynamic sound. On this and other LPs, I seemed to set the load either at 150 ohms or 200 ohms. On Adagio-Allegro non troppo, the first movement, there were gorgeously dark and delicate shadings from the violins at first and big, dark notes from the bass viols. I got a big soundstage, the scaling was impressive, and where came the movement of the theme from the second to first violins, it was a sweet and gentle thing that gave a real sense of spaciousness in the orchestra. Languorous passages with solo oboe fell away to a septet of woodwinds, then pianissimo brass fanfares. Later, there were sudden bursts of orchestral energy, quick turns of pace, and occasional splashes of brass turning to crescendo. The tonal richness of cellos and basses contrasted with the gentler shadings of violins and the piercing sweetness of a clarinet. The abundance of complex orchestral gestures and motifs, the alternately grave and dashing movements of the theme, all showed Tchaikovsky’s orchestral painting at its most tragic and complex, attesting to the Signature IIa phonostage’s sophistication with dynamic range and multiplicities of timbre, showing its breadth of power to communicate Tchaikovsky’s rich flows of momentum and tides of psychological expressivity in orchestration.

The phono also performed with wonderful tonal weight, detail, and timing via its mm inputs with my Ortofon GM Mono Mk II SPU cartridge (3.0mV). Dave Brubeck’s “Blue Rondo à la Turk” from the immortal Time Out LP [Columbia] spun with speedy, sparkling highs from Brubeck’s piano. There was a propulsive momentum with drums, bass, and piano tripling in unison on the famous theme. Paul Desmond’s alto sounded cool and sweet with small dynamic explosions. When Joe Morello hit the fan of his ride cymbal repeatedly, punctuating the rhythm, the sound shimmered out in time with the beat. But when he hit the cap, the cymbal rang like a damped cowbell. The Signature IIa with the Herron monoblocks created a sound that had real living presence to it.

Finally, I paired the Signature IIa with my VAC PA-100/100 stereo amp (based on the 1947 Williamson circuit). This sound was always rich and resolving, particularly suited to voices and strings. Returning to digital playback, I selected a piece of Baroque sacred music that never fails to move me. Its 13th century text is a sorrowful hymn to Mary set by Giovanni Battista Pergolesi in 1736. I’ve numerous recordings of it, but I chose Stabat Mater: A Tribute to Pergolesi [DG], a recent CD I ripped to Apple Lossless on my iMac’s hard drive running Leopard 10.6.8 and played back via iTunes (10.5.3) and a JoLida Glass Tube DAC. With Anna Netrebko (soprano) and Marianna Pizzolato (contralto) singing with the Orchestra dell’Accademia Nazionale di Santa Cecilio directed by Antonio Pappano, the title tracks opened with a beautiful duet, Stabat Mater delorosa, interweaving vocal parts but offering distinct timbres between singers. Pizzolato’s contralto was at first smoother, more liquid, sometimes with a slight stylistic thickness in her throat. She sang with rapid tremolos and brilliantly suspended topnotes that spun out over a conjunct bassline. Netrebko’s soprano sounded thinner, but much more agile, and, partly because of the close-miking, partly due to the Signature IIa’s resolving abilities, I heard very subtle shadings of grief and passion in her voice as she addressed herself directly to Mary mourning the death of Jesus. I found this level of detail extremely touching and appropriate to the somber dignity of the music. And the Baroque violins, played without modern vibrato to sweeten the sound of the bow crossing the strings, nonetheless sounded rich, lush, and detailed.

Through the rest of the eleven movements, both singers had numerous shifts of vocal intensity—moderate volumes rising to full-out song, then whispering, and full-out again with passionate topnotes held a good long while, attesting to the system’s power. And when they sang together, there wasn’t just a layering of their voices, but a thrilling intensity too, as they reached dramatically, with precisely differing timbres and vocal registers, for volume and harmony together. The system with the Signature IIa preamp sang along, never ragged or harsh in the difficult sustained topnotes and dynamic peaks, always producing a clear and emotionally compelling sound sensitive to all the glorious subtleties of this superb vocal performance.

Kevin Hayes has really outdone himself with the VAC Signature IIa preamp. A statement piece at a luxury price, it plays music with extraordinary finesse and drive, accurate timbres, spaciousness in the soundstage, swift attacks and aching decays, and an even spectral balance. Of all the preamps that have been in my system, it is the one that most wisely balances the ofttimes contradictory qualities of superior drive and great finesse. Completely versatile, it can be voiced by rolling tubes to suit just about any ear, has numerous inputs for a multitude of sources, can be fitted with an outstanding phonostage, and be run balanced or single-ended. It performed splendidly with three of my power amplifiers, both tubed and solid-state. Besides all this, it looks flat fantastic, a fancy piece of audio bling perched atop its own power pedestal.

If you’re in the market for a reference-level preamp, I heartily endorse auditioning the Signature IIa from VAC. It will take you a long time to exhaust its possibilities—it did me—and you may never find the end of them. That is, not until Kevin Hayes next cleans his astrolabe or peels an orange.


Number and type of inputs: Three unbalanced on RC A jacks, two balanced/unbalanced (selectable) on RC A/XLR jacks, one moving-magnet and one moving-coil phono input (with optional phono module); if no phono module, one additional line-input on RC A; one tape monitor, one unbalanced theater-bypass input
Number and type of outputs: Two RC A, two XLR, one RC A tape
Tube complement: Two 12AU7 and two 6DJ8 (linestage); six 12AX7 (phono)
Input impedance: 100k ohms
Output impedance: 96 ohms
Phono gain: 44dB (moving magnet), 64dB (moving coil)
Phono loading options: 470, 300, 250, 200, 150, and 100 ohms (mc); 47k, 30k, 25k, 15k, and 10k ohms (mm)
Audio chassis dimensions: 18″ x 5.5″ x 14.5″ (plus knobs and connectors)
Power supply dimensions: 18″ x 3.9″ x 14.5″ (plus connectors)
Weight: 20 lbs. (audio chassis); 23 lbs. (power supply)
Price: $15,500 as linestage, $19,500 with phono input

Valve Amplification Company
1911 N. East Avenue
Sarasota, FL 34234
(941) 952-9695

Associated Equipment

Analog sources: TW-Acustic Raven Two turntable, TWAcustic Raven 10.5 tonearm with ZYX Airy 3 cartridge (0.24mV), Ortofon RS-309D tonearm with Ortofon 90th Anniversary SPU (0.3mV) and Ortofon GM Mono Mk II (3.0mV)
Digital sources: Cary 303/300 CD player, Apple iMac with JoLida Glass Tube DAC
Preamplifiers: Lamm LL2.1 and deHavilland Mercury 3 line stages, VAC Renaissance III preamp (with phono), Herron VTPH-2 phono stage, EAR MC4 step up
Power amplifiers: VAC Phi-200, VAC PA-100/100, Herron M1 monoblocks, deHavilland KE50A monoblocks
Speakers: Von Schweikert Audio VR5 HSE, Von Schweikert Audio VR-44 (for review)
Speaker cables: Siltech 330L, 330L jumpers
Interconnects: Siltech 330i, Cardas Clear, Auditorium 23, DH Labs Revelation; Cardas Clear
USB cables: Wireworld Silver Starlight, Cardas Clear
Power cords: Siltech Ruby Hill II, Siltech SPX -800, Cardas Golden Reference, Harmonix XDC Studio Master
Power conditioner: Siltech Octopus Signature 8
Accessories: Box Furniture S5S five-shelf rack in sapele, HRS damping plates, edenSound FatBoy dampers, Winds VTF gauge

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