Audio Research 610T Monoblock Power Amplifier

Masterpiece!

Usually in ARC reviews I spend some time discussing how much closer Johnson has managed to inch his tubes toward solidstate territory, without giving up his claim on the tube’s own patch of sonic ground, and I will do so again here. But bear in mind that, while the 610T is greatly improved in neutrality, frequency extension, imaging, resolution, transient speed, power delivery, and transparency to sources, it is the way these new improvements seamlessly integrate with old strengths—like air, bloom, and soundstaging—that makes this amp so special. Indeed, it is the synergy of old and new that makes the 610T the current standard in high-powered tube amplification.

Let’s begin with tonal balance, as it is likely to be the first difference from past ARC amps that experienced listeners will notice. Whether it is the revised tube complement, the solid-state rectification and regulation of the power supply, the increased energy storage, or some concatenation of all three (plus circuit tweaks and changes I don’t know about), the 610T’s sounds less like “classic” ARC than any Audio Research amp I’ve previously owned or auditioned.

Though ARC amps have always been closer to neutral in balance than other tube and most solid-state amps, they have been neutral with a distinctive twist. Seemingly biased slightly toward the upper midrange and lower treble, they have tended to sound attractively bright, bloomy, present, airy, and clear. (If you think of the tonal balance of a great twoway loudspeaker—without a two-way’s roll-off in the bass—you’ll get the idea.) As I said in my review of the wonderful Focal-JMlab Electra 1007Be mini-monitor [Issue 176], I’ve always liked the little bit of added transient zip, low-level dynamic/ harmonic resolution, and lifelike air and brightness of the traditional ARC balance, because, to my ear it sounded more like real instruments in a lively hall. Nonetheless, that extra energy in the upper mids could make certain instruments—like flutes or piccolos or upper-octave strings—sound a touch brighter than life. With the 610T this has changed.

The new amp seemingly “re-biases” tonal balance to dead-center neutral, significantly extending this neutrality downward and upward without sacrificing the traditional ARC virtues of lifelike air and bloom in the upper octaves or, for that matter, in the midrange or bass. (Think of the 610T’s bass-to-treble balance as now being more like that of a great three-way loudspeaker, rather than a great two-way.) For ARC fans, the difference will be unmistakable and, at first, a little disorienting, in part because of the many other sonic differences than accompany it.

First, the hint of soft white grain that generally accompanied the uppermidrange/ lower-treble emphasis of ARC amps (a coloration I strongly associate with ARC electronics, in general) has been virtually eliminated. While recent ARC amps and preamps have already reduced this coloration considerably, the 610T banishes it almost completely.

Second, image focus has changed for the better. Compared to a Class A triode or solid-state amplifier, a pentode amp tends to make voices and instruments sound big and rather loosely focused. (To use the analogy to speakers again, pentodes in Class AB image like Magneplanars rather than like dynamic speakers.) As with ARC’s traditional tonal balance, I generally preferred these larger images to the razorcut miniatures of solid-state. Nonetheless, a happy medium needs to be struck, and the 610T strikes it. Though still life-sized, voices and instruments now have, dare I say it, higher definition. On a well-recorded LP, like the Skalkottas Sonatina No. 3 for Violin and Piano [EMI], the 610Ts make instruments that can be scaled to life size in an average listening room, such as Niklos Patrikidou’s violin, sound neither too big nor too small, neither too loosely focused nor too tightly focused, but just right. Ditto for voices, like Joan Baez’s sweet joyful soprano on “Gospel Ship” [Joan Baez in Concert, Part 1, Cisco/Vanguard]. I’ve always thought that lifelike image size was a greatly undersold virtue, as it not only tends to make performers and instruments more realistically present but also makes them sound less “hi-fi,” by drawing less attention to the speakers. The 610T is the most lifelike imager I’ve yet heard from ARC (or anyone else).

Third, maybe as a result of its improved imaging (and the overall lowering of colorations), the 610T is also the most finely detailed ARC amplifier I’ve heard, which is actually something of a surprise, since the first thing that generally gets traded off against very high power in an amp is lowlevel resolution. Not here. With a speaker capable of truly exceptional resolution and near-lifesized imaging—like the twoway MAGICO Mini II or the one-way Omega Max Hemp—the 610T can make an instrument like a clarinet not only sound like a clarinet, but look like one, too. The sonic cues that clue you in to the size, shape, material composition, and mechanical workings of an instrument are so plentiful here that it is almost as if a life-sized, largeformat photograph of the instrument is being projected between your speakers. I’m talking a “fool-you” facsimile of the real thing such as you generally only get with sound effects, like doorbells on DVDs. Here is an amp that can (given the right speaker and the right source) do this conjuring trick with select voices and musical instruments.