CuttingTHE Edge Electronically reprinted from December 2007 MASTERPIECE! Audio Research 610T Monoblock Power Jonathan Valin

t is a little sobering to look back to 1973 and the first pieces of Audio Research gear II heard—the SP-3 preamp and D75 amp powering Magneplanar I-Us in a stereo demo that, for me, has never been bettered or forgotten— and then to consider how consistently and naturally all the subsequent ARC gear I’ve heard, and I’ve heard a lot, has been voiced. From the start, ARC components had a sound that was uniquely, indelibly, addictively “right.” ARC’s designer and founder William Zane Johnson called this sound “high definition,” a trademark that still appears on the faceplate of each and every ARC component. And even in 1973 his creations were astonishingly high in definition; indeed, their standard-setting resolution, lifelike size, bloom, and airy brightness, and exceptionally low levels of tube-like coloration were a large part of what set them apart from the darker, thicker, blatantly euphonic sound of the tube preamps and amps that preceded them. Not that everyone preferred high definition tube sound. There were those, then, and are those, now, who thought and think that tubes should invariably make music sweet, round, and rosy, that prettifying sources is the ’s job in life—the very thing that sets it apart from the crisp, clean, “neutral” presentation of the . Johnson never bought into this model. Indeed, it was the superior accuracy and neutrality of transistor electronics—which in the late 60s and early 70s were even more in the ascendant than they are today—that inspired him to outdo solid-state at its own game. His tube products were expressly designed not to artificially prettify recordings; instead, they were intended to be as faithful and transparent to sources as electronics can be made to be. When it comes to 12AX7- based preamps and 6550-based power amps, the very concept of transparency was really born with Audio Research.

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The inspiration for these ruminations is in the front of the chassis and the amp’s complement, the solid-state rectification the 610T monoblock power amplifier— nifty vacuum-fluorescent display, which and regulation of the power supply, the latest in ARC’s long, storied line of reads out bias measurements for each tube the increased energy storage, or some high-powered tube and the (as well as A.C. line-voltage levels, power concatenation of all three (plus circuit subject of this review. Replacing the output, and total hours of tube usage).1 tweaks and changes I don’t know about), celebrated Ref 600 MkIII (much beloved ARC says that power-supply energy- the 610T’s sounds less like “classic” by our EIC, Robert Harley) and capable storage has been increased substantially ARC than any Audio Research amp I’ve of better than 600 watts into any load this in the 610T to an astonishing 1000 joules, previously owned or auditioned. side of a short circuit, it is the culmination with substantial impact on sound quality Though ARC amps have always been of William Zane Johnson’s almost forty (for which, see below). In a hybridizing closer to neutral in balance than other years of experience in amplifier design and move that Johnson has made successfully tube and most solid-state amps, they constitutes both a continuation of and a before in other products, ouput stage have been neutral with a distinctive significant advance beyond the virtues of power-supply rectification and regulation twist. Seemingly biased slightly toward the previous ARC superamps. is solid-state, while input gain stage upper midrange and lower treble, they The changes in the 610T begin with regulation is both tube and solid-state. have tended to sound attractively bright, the way it looks. Designed and built As usual with ARC, the 610T’s ultra- bloomy, present, airy, and clear. (If you on a vertical rather than a horizontal wide-bandwidth output are think of the tonal balance of a great two- chassis, it is a tall, rectangular, 170-pound custom-made, with separate 4, 8, and 16- way —without a two-way’s brushed-aluminum tower, which mounts ohm output taps.2 Be aware that the 610T’s roll-off in the bass—you’ll get the idea.) its input and output tubes in the open input is balanced only, so you’re going to As I said in my review of the wonderful on its top plate, without a surrounding need a preamp with balanced outputs. Focal-JMlab Electra 1007Be mini-monitor cage. (In the dark all those lit-up 6550s You’re also going to need dedicated 20- [Issue 176], I’ve always liked the little bit glow like rows of candles on a tube- or 30-amp lines to feed a pair of 610Ts, of added transient zip, low-level dynamic/ lover’s birthday cake.) Concealed within each of which can draw as much as 2300 harmonic resolution, and lifelike air and the massive tower is a ground floor that watts from your wall outlets (1700 at rated brightness of the traditional ARC balance, houses output and power transformers, output). because, to my ear it sounded more like real and a second story for power-storage-and- Usually in ARC reviews I spend some instruments in a lively hall. Nonetheless, regulation components. The tower design time discussing how much closer Johnson that extra energy in the upper mids could allows the 610T to rely on convection has managed to inch his tubes toward solid- make certain instruments—like flutes or rather than built-in fans (with built-in fan state territory, without giving up his claim piccolos or upper-octave strings—sound a noise) to cool its complement of twenty- on the tube’s own patch of sonic ground, touch brighter than life. With the 610T this three tubes. That said, don’t count on and I will do so again here. But bear in mind has changed. convection to cool the 610T overly much. that, while the 610T is greatly improved in The new amp seemingly “re-biases” tonal On a hot afternoon, the forty-six tubes in neutrality, frequency extension, imaging, balance to dead-center neutral, significantly a pair of these amps can raise the ambient resolution, transient speed, power delivery, extending this neutrality downward and temperature of your listening room by a and transparency to sources, it is the upward without sacrificing the traditional good 15–20 degrees in next to no time, way these new improvements seamlessly ARC virtues of lifelike air and bloom in making warm-weather listening necessarily integrate with old strengths—like air, the upper octaves or, for that matter, in a challenge (and necessarily brief). bloom, and soundstaging—that makes this the midrange or bass. (Think of the 610T’s Although the 610T, like virtually every amp so special. Indeed, it is the synergy of bass-to-treble balance as now being more Johnson power amp, uses 6550C old and new that makes the 610T the current like that of a great three-way loudspeaker, output tubes—sixteen of them in sets of standard in high-powered tube amplification. rather than a great two-way.) For ARC fans, eight matched pairs—in a fully balanced, Let’s begin with tonal balance, as it is the difference will be unmistakable and, at push-pull, Class AB circuit, it also uses likely to be the first difference from past first, a little disorienting, in part because (for the first time) two 6550Cs as driver ARC amps that experienced listeners will of the many other sonic differences than tubes—each controlling one bank of eight notice. Whether it is the revised tube accompany it. output tubes operated in unison. Twin First, the hint of soft white grain 1 ARC projects tube life at around 2000 hours. 6N1P and a 6H30 follower make up BTW, you would be well advised to turn the that generally accompanied the upper- the input gain stage. The combination of 610T’s display off whenever you listen to midrange/lower-treble emphasis of ARC the 6550 drivers and 6N1Ps/6H30 inputs music, as its current draw slightly darkens the amps (a coloration I strongly associate amp’s sound. has allowed for a welcome simplification 2 Some experimentation with the output with ARC electronics, in general) has been of power-tube biasing; instead of having taps is probably a good idea. I’ve found, for virtually eliminated. While recent ARC instance, that the MAGICO Mini, a nominal to adjust the 16 output tubes individually 4-ohm loudspeaker, sounded its best via the amps and preamps have already reduced (as you did with the Ref 600 and previous 610Ts’ 8-ohm taps rather than its 4-ohm ones. this coloration considerably, the 610T Contrarily, the 4-ohm Magenpan MMG and ARC amps), in the 610T you need only bias MG12 (reviewed in this issue) sounded better banishes it almost completely. the first two output tubes via set screws with the 4-ohm taps. Second, image focus has changed for

December 2007 The Absolute Sound The Cutting Edge

the better. Compared to a Class A or and the right source) do this conjuring trick Specs solid-state amplifier, a pentode amp tends with select voices and musical instruments. to make voices and instruments sound It won’t do this consistently, of course— & Pricing big and rather loosely focused. (To use most of the time you’ll have to settle for Type: Monoblock tube power amplifier the analogy to speakers again, a superb approximation of the real thing Output power: 600 watts continuous at in Class AB image like Magneplanars rather than a facsimile—but the fact that it 16 ohms from 20Hz–20kHz (approximate rather than like dynamic speakers.) As with can do it at all is amazing. actual power available at “” 630 ARC’s traditional tonal balance, I generally Fourth, transient attack has also watts [1kHz]) THD: Typically 0.5% at 600W at 1kHz; preferred these larger images to the razor- received a new jolt of speed, particularly below .05% at 1W at 1kHz cut miniatures of solid-state. Nonetheless, in the midband. When I reported on Power bandwidth: 15Hz–150kHz a happy medium needs to be struck, and how realistically the Kuzma and Walker Input sensitivity: 4.2V RMS the 610T strikes it. Though still life-sized, turntables (with Air Tight PC-1 cartridge) Input impedance: 200k Ohm (balanced) Tube complement: Eight matched pairs voices and instruments now have, dare I reproduced the thunderous initial G minor of 6550C; one 6550C regulator; one 6H30 say it, higher definition. On a well-recorded chord of Andrej Gavrillov’s piano and the regulator; two 6550C driver; two 6NIP LP, like the Skalkottas Sonatina No. 3 for answering shrieks, plucks, and groans of input; one 6H30 follower Dimensions: 13.5" x 23" x 20.8" Violin and Piano [EMI], the 610Ts make Gidon Kremer’s violin that begin Schnittke’s Weight: 170 lbs. each, net (495 lbs. per instruments that can be scaled to life size in witty dialogue between tonality and atonality, pair, shipping) an average listening room, such as Niklos Quasi una sonata [EMI], I was also reporting Price: $39,990 per pair Patrikidou’s violin, sound neither too big on the 610T. Though a great solid-state Audio Research Corporation nor too small, neither too loosely focused amp like the MBL 9011 or the GamuT DI 3900 Annapolis Lane North nor too tightly focused, but just right. Ditto 150 still holds a transient-speed edge on Plymouth, Minnesota 55447 for voices, like Joan Baez’s sweet joyful the 610T, this is one very fast tube amp that (763) 577-9700 audioresearch.com soprano on “Gospel Ship” [Joan Baez in can hold its own on everything from string Concert, Part 1, Cisco/Vanguard]. I’ve always pizzicatos to that lightning timp strike near JV’s Reference System thought that lifelike image size was a greatly the close of The Firebird. Moreover, the 610T : MAGICO Mini II, MBL 101 undersold virtue, as it not only tends to maintains the tube’s superiority on stopping E, Ascendo M-S MkII, Focal-JMlab Electra 1007Be, Sound Lab M1, Magneplanar make performers and instruments more transients, reproducing decay and ambience MMGMG12/1.6/3.6/20.1 realistically present but also makes them as realistically as any amp I’ve heard. Linestage preamps: Audio Research sound less “hi-fi,” by drawing less attention Fifth, there is the unusually lifelike way Reference 3, Audio Space Reference 2, MBL 6010D. Lamm Industries L1 to the speakers. The 610T is the most that the 610T delivers power. It is a bromide Phonostage preamps: Audio Research PH- lifelike imager I’ve yet heard from ARC (or to say that a tube amplifier clips “softly,” 7, Lamm Industries LP-2 Deluxe anyone else). rounding off transient peaks when it runs Power amplifiers: Audio Space Reference Third, maybe as a result of its improved short on steam rather than shearing them One, MBL 9008, Lamm ML-2, Gamut DI 150 Analog source: Walker Audio Proscenium imaging (and the overall lowering of off the way a solid-state amp does (with Black Diamond record player colorations), the 610T is also the most finely subsequent audible ). However, Phono cartridges: Air Tight PC-1, detailed ARC amplifier I’ve heard, which is it is one thing to clip softly; it is another Clearaudio Goldfinger v2 actually something of a surprise, since the not to clip at all. We are talking here about Digital source: ARC Reference CD7 Cable and interconnect: Tara Labs “Zero” first thing that generally gets traded off a monoblock amplifier that is capable of interconnect, Tara Labs “Omega” speaker against very high power in an amp is low- 630 watts of pentode power into any load. cable, Tara Labs “The One” power cords, level resolution. Not here. With a speaker Unless you’ve heard a tube amp that is this Synergistic Research Absolute Reference speakers cables and interconnects capable of truly exceptional resolution seemingly unrestricted in power, you may Accessories: Shakti Hallographs; Walker and near-lifesized imaging—like the two- have trouble understanding how smooth Prologue Reference equipment stand; way MAGICO Mini II or the one-way and unstrained—how non-hi-fi—the 610T Walker Prologue amp stands; Richard Omega Max Hemp—the 610T can make sounds. Gone is not only any clipping Gray Power Company 600S/Pole Pig line/power conditioner; Cable Elevators an instrument like a clarinet not only sound distortion but the very sense of a dynamic Plus; Walker Valid Points and Resonance like a clarinet, but look like one, too. The ceiling hanging above the music. I think the Control discs; Winds Arm Load meter; sonic cues that clue you in to the size, shape, best way to conceptualize this, at least for Clearaudio Matrix record cleaner; HiFi- Tuning silver/gold fuses material composition, and mechanical those of you who know your recordings, workings of an instrument are so plentiful is to think of an album in which dynamic here that it is almost as if a life-sized, large- limiting has been deliberately applied— format photograph of the instrument is such as an old RCA Dynagroove—and being projected between your speakers. I’m then think of an album in which no limiting talking a “fool-you” facsimile of the real has been used—like a Sheffield direct-to- thing such as you generally only get with disc. The 610T consistently sounds like sound effects, like doorbells on DVDs. Here the Sheffield, and makes most other amps is an amp that can (given the right speaker sound like the Dynagroove.

The Absolute Sound December 2007 The Cutting Edge

Getting rid of any of the usual chokes or CD it is playing, and in reducing its own on power delivery has a wonderful signature reduces our sense of listening to liberating effect on music of every kind. and through an electromechanical chain It is not that music will play “louder” with of hardware. I’ve always felt that the first the ARC 610T, although it will; it is the obligation of any piece of stereo equipment way it gets loud that is so uncannily lifelike. is to disappear as a sound source. The 610T Take a tenor voice, such as Mario does this to an extent I’ve never before Lanza’s on “Il lamento di Federico” from experienced with an amplifier. For the most Cilea’s L’Arlesiana (Mario Lanza Live in part, it simply lets you forget you’re listening London [RCA]) for example. Part of the to a hi-fi. reason why a tenor voice is no snap for Oh, there are still a few areas where the an amplifier to reproduce (and why it can 610T reminds you that it’s there. For one, cut through dense instrumental textures instrumental action better than any it is consistently a little forward sounding, and seemingly soar ahead of and above amplifier I’ve yet heard (and, in so doing, starting its imaging nearer to the plane an entire orchestra) is the tremendous makes instrumental dynamics more lifelike of the speakers, rather than deep behind amount of acoustical power it has in the than any other amplifier I’ve yet heard). them. For another, as good as the 610T 2–3kHz range (the “formant” range for Finally, soundstaging, always an ARC is in the treble, you cannot listen to it in higher-pitched male singing voices), for strength, is here taken to a new level. On a comparison to a great solid-state amp like, which see the chart to the right, reprinted great orchestral recording like Lutoslawski say, the GamuT DI 150, and honestly say from the late John Eargle’s superb text conducting the Nationales Symphonie- that it has all of the top-octave speed, focus, Music, Sound, and Technology (Van Nostrand Orchester des Polnishcen Rundfunks in a and detail that make something like the Reinhold, 1995]. bracing performance of his own Concerto piano on the truly superb Decca Headline A powerful tenor can reach astonishing for Orchestra [EMI]—one of the truly great recording Mr. John Cage’s Prepared Piano so dynamic peaks on fortissimos. Indeed, pieces of music of the second half of the uncannily like a virtual choir of cymbals, this Lanza recording has undone many twentieth century—the 610T fills the back bells, and drums. Through the 610T, all an amplifier at CES and in my home. At third of my room with a virtual orchestra, these sounds will be somewhat more lifelike levels, during the searing climax wall-to-wall, wall-to-floor, floor-to-ceiling. relaxed, more gemütlich. (Paradoxically, this of the Cilea aria, most amps simply hit Even on smaller-scale music, like Joan Baez isn’t as true of the low bass, where the the wall—making Lanza’s gorgeous and the Greenbriar Boys singing “Banks of ARC will reproduce ostinatos like the deep voice sound progressively rougher, the Ohio” [Joan Baez, Vol. 2, Vanguard], the cello and doublebass pizzicatos at the start shriller, flatter, “beamier,” as he nears the 610T will fill the space between speakers and of the Passacaglia of the aforementioned crescendo’s peak, before shattering at the boundaries with near-life-sized images of Lutoslawski Concerto for Orchestra with peak itself as if from mike overload. Joanie, her backup singers, their instruments, precise pitch definition and astonishingly Rather than roughening and flattening and the ambience of the recording venue. realistic air and speed.) Lanza’s voice during the crescendo of (There are reasons why manufacturers of The Audio Research 610T is the best this aria and then clipping at its climax, big speakers, like Dave Wilson, often prefer high-powered tube amp I’ve heard in thirty- the Audio Research 610T has the power the 610T—they will drive any speaker and five-plus years of listening. It is, to date at reserves and the natural delivery to project fill any space, no matter how small or large, least, the greatest achievement of William Lanza’s voice as he himself was projecting with music.) Z. Johnson, whose long, legendary career it, making it sound bigger rather than I started off by saying that it wasn’t the as the chief designer and moving force beamier, fuller rather than flatter, stronger individual virtues of the 610T but their behind the Audio Research Corporation rather than shriller, more forward rather synergy that makes the amp so special, is spangled with great achievements. For than more recessed as he builds to the because what all of these things add up to— those with the kind of money and space crescendo and then to simply sail through the improvements in neutrality, coloration, and ancillaries that the 610T demands, I the peaks without any loss of composure or imaging, resolution, transient response, cannot recommend it highly enough. For impact. I’ve called this ability to realistically power delivery, action, and staging—are a the rest of us, it is something to dream reproduce the way imaging changes with huge improvement in transparency to the about. If ever I’ve heard an amplifier changes in dynamics “action” or bloom, source. By this I mean that the 610T imposes worthy of being called “reference,” the and the 610T simply handles vocal and less of its own signature on whatever LP 610T is it. TAS

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