VAC Phi 200 KT88 tube stereo/mono power amp 2x100w stereo / 200w mono

Recent Western literary theory makes a distinction between the author of a book and its writer. The author is the ephemeral entity conjured as the consciousness within a given work -- a novel, say -- while its writer is the actual person who wrote it. The essential difference is that the writer has a life outside the scope of the book -- s/he eats, sleeps, messes around, plays with stereos, etc. The author resides only in the work itself, spectrally, a being conjured by the words of the text -- limited in existence, only a voice or a presence behind the words. There might be a parallel to this in hi-fi: an audio component not only has its "writer" -- the designer who goes on living life, designing other components, showing up at Consumer Electronics Shows, racing balloons in Kansas, shredding the break on the Inside Reef at Makaha -- but also its "author," the virtual voice within the machine. 

 

In this sense, the "writer" of the Valve Amplification Company is Kevin Hayes, president and chief designer of fine audio electronics since VAC's inception. I have met Hayes, exchanged jokes with him at audio shows, and spoken at length with him on the phone. He is definitely a personage. And yet, each VAC component has also its "author," a specific character conjured in the sound of the individual piece of gear itself, a kind of spirit in the sound. If we apply this philosophic notion of split entities to audio, it runs counter to the traditional audiophile view that identifies a particular "house sound" throughout a given line of electronics, insisting that all components produced by a company share, by design, a common character. 

 

My own thinking about VAC electronics had ascribed to them a shared house sound, a constancy of voice (or single authorial presence) that was warm, somewhat sumptuous, and emphasized sensuousness over precision. But to my ears, the Phi 200 stereo amplifier ($9990 USD) is something quite distinct from this. It breaks with my own prior assumptions about any "house" sound VAC gear might be said to possess. 

 

The description of the Phi line of amps on VAC's website boldly compares their sound with that normally associated with solid-state: "The Phi amplifiers produce the areas of beauty typically associated with good vacuum tube designs, but also go well beyond this, producing bass impact, speed, and dynamics that have converted many adherents of solid-state design." And, a bit further down the page: "You will hear the punch and control normally associated with solid-state amplifiers. . . ." 

 

I heartily agree. Kevin Hayes has created something startling in the Phi 200, his latest tubed amplifier. The authorial voice that emerges from it produces a quality of precision -- in imaging, microdetail, microdynamics, transient speed, treble extension, and bass grip, all within a generous soundstage -- that many think is possible only with solid-state designs. This ain't your Daddy's Oldsmobile, people. 

 

 

The Phi 200 is a 100Wpc power amplifier with speaker taps for loads of 1-2, 2-4, and 4-8 ohms. Its tube complement consists of four KT88s and four 6SN7s. Though it can be easily converted for use as a 200W monoblock via a mode switch on the rear panel, I never used it that way. Fully balanced in its circuitry, the Phi 200 has both XLR and RCA input modes, and its gains are a claimed 36dB single-ended or 30dB balanced. The input and driver stages are the class-A, direct-coupled, low-mu triode circuits originally developed for VAC's Phi 300 amp (150Wpc). The bandwidth claims are impressive: 13Hz-70kHz power bandwidth and a frequency response of 4Hz-75kHz. 

 

The Phi 200 is large -- 17.8"W x 8.75"H x 17.8"D -- and weighs 90 pounds. Most of its weight is in the rear, where the massive, custom-wound transformers are mounted. The nonmagnetic chassis is 2.4mm thick and comes in an impressive black powdercoat. The 9mm-thick faceplate comes in black lacquer with gold flecks, or silver lacquer with the chassis in contrasting black powdercoat. The VAC logo, on a handsome piece of recessed glass on the front panel, is backlit in blue when the amp is switched on. All in all, the look is clean, post-utilitarian, and very attractive.

 

 

The Phi 200, introduced at the 2008 Rocky Mountain Audio Fest, was developed from the Phi 300 stereo amplifier (now the Phi 300.1a in current iteration), which Kevin Hayes had created in 2006. "It brings the Phi technology to a price point accessible to more people," he told me by phone. 

 

When I asked what the Phi technology is, precisely, Hayes explained that it’s a new front-end and driver-circuit topology he'd developed from the high-mu paraphase circuit employed in his first amps, the PA-45 and PA-90 monoblocks from 1990. Paraphase refers to the type of phase inverter used in the front-end with single-ended signals, and differs from the Williamson front-end circuit used in VAC's PA-80/80 and PA-100/100 stereo amps from later in the '90s. Whereas the Williamson front-end circuit used a "cathodyne" phase splitter that is capacitively coupled to the driver, and the paraphase circuit in the earliest VAC amps used high-mu triodes, also capacitively coupled to the driver stage, the new Phi paraphase circuit uses low-mu triodes at the input and driver stages and eliminates the capacitors for direct coupling to the drivers. In balanced mode, there are no coupling capacitors in the input and driver stages, and, even in single-ended mode, the input circuit has only a "half-capacitive" stage -- still fairly direct, compared to earlier VAC designs. 

 

What this means for the listener, Hayes said, is that Phi amps are much faster than VAC's first paraphase mono amps and Williamson-derived stereo amps, and hopefully produce more vividness and energy without giving up anything in terms of liquidity, nuance, and soundstaging. 

 

What Hayes didn't expect was an improvement in bass performance. "Some hear a distinct increase of bass control and articulation," he said. But what was most interesting was that the new Phi circuits didn't change the basic match between the output stage and the speakers, where many have assumed tube amps lose their grip on the bass. "It is assumed that the damping factor has to be high," Hayes explained, "but the new circuit in the Phi 300 (and subsequent 300.1 and 300.1a) and Phi 200 didn't change the damping factor one bit." 

 

Hmmmm, I thought. O brave new world that has such amps in't! 

 

 

The Phi 200 arrived in a large (24.5" x 12.75" x 13"), sturdy cardboard box, nested top and bottom in thick, fitted blocks of urethane foam. Inside were eight boxed vacuum tubes -- four Shuguang KT88-SCs and four Shuguang 6SN7s -- each tested by VAC and carefully labeled for a corresponding socket position on the amp's top deck (even the center pins of the power tubes are so marked). In a nice touch, the amp's faceplate was covered in a soft polishing cloth held in place by a cat's cradle of rubber bands. There were also a stock power cord (which I did not use), a yellow ochre plastic bias tool (marked Vishay Spectrol), and an 8.5" x 11", 15-page owner's manual that meticulously describes setup, tube position, and operation. The warranty is two years, parts and labor, excluding tubes. 

 

I seated the tubes in their sockets, carefully matching each to its designated position on the chassis, then hooked up the cables. The Phi 200's connectors are mounted on the top of the chassis at the rear, along a narrow shelf behind the power and output transformers. This proved very convenient for attaching the spades of my speaker wires and RCA and XLR interconnects (I alternated my use of the latter). 

 

Biasing the tubes was a cinch -- the bias lights are in a row behind the output tubes, and each glows red or orange or green, depending on the setting. With the amp on and no music playing, you insert the blade of the bias tool (or a very thin-bladed, flathead screwdriver) in the numbered hole in the chassis that corresponds to a particular tube, fit it into the slot in the head of the bias screw inside that hole, and turn the screw. The bias light will go from red through orange; when it has just turned green, the setting is correct. The procedure was familiar to me; it's pretty much been the bias routine for VAC amps for over 15 years. 

 

Switching from balanced to single-ended operation is similarly easy. Each channel has a set switch just to the side of each input tube. The forward setting is labeled Singled Ended, the rear setting Balanced. Just make sure both channels are set correctly and you're good to go. The VAC Phi 200 is turned on and off with a switch on the right of the faceplate -- much more convenient than amps with power switches on the back! Finally, the Phi 200 does not invert absolute phase. 

 

Throughout the review period I used various combinations of cables, including a couple of very reputable, high-end brands, and both XLR and RCA interconnects, before settling on my reference Verbatim speaker cables, Verbatim RCA interconnects, and Cardas Golden Reference AC cord. I also tried two different preamplifiers: a deHavilland Mercury 3 and a VAC Renaissance 3. The Phi 200 sounded best run single-ended via its 4-8-ohm taps (my Von Schweikert VR5 HSE speakers are rated at 91dB and 6 ohms). It performed very well with both preamps, though most of my listening was done with the VAC Renaissance 3. With the stock and various NOS input and driver tubes I tried, in both balanced and single-ended modes, the amp operated smoothly and without a hitch throughout the review period. Break-in did seem to take a while, likely due to the transformers needing serious run-in before they settled. I ran the amp for over 200 hours before taking any listening notes. 

 

 

 

The imaging, speed, and soundstaging were spectacular with "Smooth," from Carlos Santana's Supernatural (CD, Arista 07822-19080-2). Instruments extended far into the room, my speakers disappeared, and the band was spread horizontally across a wide soundstage as Rob Thomas's electronically manipulated and sometimes deliberately artificially dry voice dodged annoyingly here and there in the soundfield. Other than that studio trick, the sound was clear and extremely liquid, the Phi 200 providing the best soundstage I've ever heard in my smallish (12'W x 16'L x 8.5'H) listening room. The sound was also extraordinarily clean, with each instrument in its own defined airspace. These aren't things I usually crave in my listening, but I had to take notice of every excellence provided by the Phi 200: clear, sometimes crystalline timbres in the highs, tremendous drive and detail, and lots of timbral separation among instruments. "Like solid-state," my notes say, "but with more liquidity, more sensuousness note to note" -- and yet no tubey warmth, confirming almost completely the claims made on VAC's webpage. 

 

From Eric Clapton's famous Unplugged (CD, Reprise 45024-2) I got consistently tight bass, great pitch definition, and a supremely clean sound. My notes: "Clarity, clarity, clarity." From my usual electronics I heard greatly improved transient snap, microdynamics, and drive. Voices and instruments were more sharply defined, and small details I hadn't heard before, such as the squeak of fingers on wound guitar strings, popped in and out of the mix. Female backing vocals, the buzz of Clapton's bottle slide on the steel-wound strings, and the soft whump of a washtub bass -- all bubbled sweetly into the soundfield. 

 

Conventionally, you'd think that a sound as detailed as I'm writing about would have produced an overall impression of an "analytical," even a clinical sound, but that was far from the case -- what resulted was an even stronger connection to the music. I must have listened to "Tears in Heaven" over a hundred times through various systems over the years, but hearing it with the Phi 200, all the nuances -- Clapton's marvelously percussive nylon-stringed guitar intertwining as intricately as bougainvillea on a bamboo lattice with Andy Fairweather Low's tasteful accompaniment on his own nylon-stringed guitar, Chuck Leavell's mournful synthesizer, Nathan East's tasteful and at times melodic plucking of the bass, the subtle background singing of Katie Kissoon and Tessa Niles, the regret-tinged timbre of Clapton's lead vocal -- came together in what seemed a performance as close to "live" as I've ever heard. This noble dirge of a song, its humble prayer, and its tragic story affected me as never before. It was emotional. 

 

But in those first few weeks I also struggled to sort the character of the Phi 200 from what turned out to be high-frequency distortion picked up somewhere and amplified by the system. The highs in classical music and female voices seemed peakish, even edgy at times, and violins and soprano voices were often oddly ragged. I heard a top-end tizz -- a very fine hash -- that translated into a kind of grit in the treble range. Trying a few different cabling combinations revealed the problem to be one of airborne vibration. My right speaker is right next to my audio rack, and the tops of the CD player and preamp naturally pick up a lot of airborne energy. This normally isn't a problem with my reference monoblock amps, the tubed deHavilland KE50As, or other amps, but the Phi 200 moved so much more air, proved so dynamic and fulsome in top-end extension, that it energized my listening room to the point that I heard problems. 

 

At first, I placed a few ziplock bags filled with rice -- my do-it-myself damping pillows -- atop the preamp. This did the trick, however inelegantly. Later, via Audiogon, I discovered some handsome dampers of solid brass made by edenSound. These chamfered discs, called FatBoys ($39 each), are 3" in diameter and about 1" tall, with Elastomer on the contact end to protect your gear, and completely calmed the excess energy on the preamp chassis. I continued to use the bags of rice on my CD player, and eventually tucked them inside some black cotton Tibetan shoulder purses ($7 each) I found at my local singing-bowl store. I liked that they were decorated with the mandala of the I Ching. 

 

Those problems solved, the Phi 200 provided such tremendous clarity that it made me curious about period instruments and the rapid vocal ornamentations in music from the Italian Baroque, particularly the compositions of Vivaldi. I wanted to pit the amp's speed against its clarity, its ability to keep up with virtuosic performances on multiple instruments, their harmonies and distinct timbres, and hear if it could reproduce these without losing significant detail and thus becoming more impressionistic than precise. 

 

I played several different Vivaldi recordings in my collection -- Fabio Biondi and Europa Galante, the Venice Baroque Orchestra with Giuliano Carmignola, Rachel Podger's La Stravaganza, and several of the operas -- but in the end focused on soprano Sandrine Piau's In Furore: Laudite Pueri e Concerti Sacri, with the Accademia Bizantina directed by Ottavio Donatone (CD, Naïve OP 30416), particularly Vivaldi's motet In furore iustissimae irae for soprano, two violins, and viola e basso. The Phi 200 proved superb with period strings, rendering a fast, clean sound without glare, etch, or that notorious sourness that many complain such instruments have when played without vibrato. The amp captured all the vivaciousness and warp speed of play of the baroque ensemble. Especially satisfying were the overtones and harmonics of the instruments being woven together in an involving musical tapestry. I was able to consider the complexities of tone not only of each instrument, but also the superadded richness of tonalities and drive that emerged from each thematic run of the ensemble's playing. And Piau's singing in the closing Alleluia was a combination of percussive, pulsating trilling and gorgeously rapid roulades. As a test of the amp's agility, speed, and timbral accuracy, Vivaldi and a virtuosic soprano presented no problem. 

 

But for all the pleasures of the Phi 200's speed and accuracy, I wondered about midrange sweetness, and a kind of tonal richness I call saturation, along with the tonal complexity I'd already heard -- the plumminess of a single note, and gravitas vs. vivacity. For this, I listened to J.S. Bach's Suites for Solo Cello in a new digital recording by Jean-Guihen Queyras (CD, Harmonia Mundi 901970.71), and here the contribution of the VAC Phi 200 to my system's sound made for a revelatory and pleasurable experience. In Allemande, the second movement of Suite 4, Queyras's cello sounded rich, resonant, resolute, and made for soaring melodic lines. The sound was big, sonorous, and room-filling, sometimes jumping out of the speakers in a startling way, but pleasing in all its warmth and musicality. The supreme clarity of the sound captured how precise and articulate Queyras's fingering is, how sensuously in time with his bowing. I could hear the cello's body, its depth of resonance and generous warmth, particularly when it picked up the vibrations of the lower strings to resonate in the wood, each note full of microtones and natural-sounding harmonics. Queyras's patient, even playing was never rushed, never ornate with flourishes, but lovingly pensive -- like musical thoughts, completely sensical and yet emotional as well. I could hear his short intakes of breath in rhythm with the beginnings of extended sequences of bowing. The long decay of the cello's resonance was also completely audible, even after Queyras had stopped bowing -- a precious piece of performance detail heard in live concerts but often missing from recordings. It was the best I've ever heard this recording sound. Several nights running, I listened to these two CDs many times through, deep into the early-morning hours, for the sheer enjoyment of their plush yet supremely articulate midrange capably rendered by the Phi 200. 

 

Not to ignore the VAC amp's reproduction of vinyl recordings, I listened to lots of LPs -- jazz, piano, blues, and symphonic music. These analog recordings exhibited a character in keeping with what the Phi 200 revealed of digital recordings. I played a reissue of Holst's The Planets, with Zubin Mehta conducting the Los Angeles Philharmonic (180gm LP, Decca/Speakers Corner SXL 6529). The first movement, Mars, the Bringer of War, presented a fine and articulate timbral palette. Exquisitely rendered were the tonal contrasts between the solo trumpet and horn fanfares, and between the violin section and the piccolo and flutes. Treble extension was very fine and sophisticated, but when the drumstrokes, trombones, tubas, and bass viols are all played at the climax of a crescendo, I missed some of the bottom-end slam and fullness of my reference deHavilland KE50A monoblocks. Yet with the Phi 200, each drumstroke and bass note seemed more contained in the midbass, each sound tighter, more taut and controlled, with perhaps better pitch definition, if a shade lesser in sheer impact. Again, the VAC amp had an easy time precisely distinguishing among the varied timbres of violins, horns, oboes, flutes, and piccolo. There were gorgeous contrasts of the timpani with glockenspiel, flute, harp, bassoon in Mercury, and lots of the varied tonal colors of strings, horns, and woodwinds in Jupiter. I could easily tell the trombones from the French horns. 

 

I compared the VAC Phi 200 with three different power amplifiers: my venerable VAC PA-80/80 (80Wpc; discontinued), my reference deHavilland KE50A tube monoblocks 40W;  and a pair of Herron Audio M1 solid-state monoblocks (150W, . In each case, with the same recordings, the Phi 200 proved superior in resolution, inner detail, imaging, soundstaging, speed, and pace, rhythm, and timing (PRaT). Its top-end and midrange definition, articulation, and dynamics were amazing. The VAC PA-80/80 has a much softer sound, a warmer and more prominent midrange. The deHavilland KE50As are bloomier, giving the notes more body and longer decay, and have a fuller bottom end. But the deHavillands are more Impressionist in approach, more enveloping and perhaps more dramatic; the Phi 200 was more precise. Finally, the solid-state Herron M1s somehow sounded more tube-like than the Phi 200 -- mellower, softer in attack, closer in character to the deHavillands than the Phi 200. All in all, compared to the amps in my collection, the Phi 200 seemed a new beast altogether -- unbeatable in soundstaging and inner detail, wondrous with imaging, speedy in attack, blessed with superb top-end clarity and sparkle and a gorgeous midrange, and exerting a powerful grip on the music's timing and the midbass. 

 

 

 

. . . Garrett Hongo