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Reviewer: Ken Micallef
Digital Source: McIntosh MCD 201 CD/SACD player, Oracle CD 1500 [in for review]
Analog Source: Kuzma Stabi/Stogi turntable/arm combo, Denon DL-103 cartridge, Auditorium 23 Denon step-up transformer [on loan]
Preamp: Shindo Allegro
Amp: Art Audio Diavolo [in for review], Art Audio Symphony II [in for review]
Speakers: DeVore Fidelity Super 8s
Cables: Auditorium A23 speaker cables, Crystal Cable Micro Speak interconnects
Stands: Salamander rack, 2" Mapleshade platforms (8" x 15" x 2"), Blue Circle custom amp stand
Powerline conditioning: JPS Labs Kaptovator, Shunyata Black Mamba and Anaconda Vx Powersnakes, Hydra 4 [on loan]
Accessories: Mapleshade Surefoot and Heavyfoot brass points and IsoBlocks; (8) RPG ProFoam damping panels/ceiling treatment, Mapleshade Ionoclast for static cling
Room size: 24' x 12', short-wall setup
Review component retail price: $7,000

Classic Cars and Mark Twain
What does the term classic mean to you? "A classic book", states that bastion of everyman input, Wikipedia, "is one written in ancient Greece or ancient Rome. The word classic can also be applied to literature and other art that is widely considered a model of its form."

That's pretty declarative already. Wikipedia then goes on to say that "almost any older car in fine condition becomes a classic" -- even my '79 Ford Pinto? -- and that certain movies, books and, of course, music, can acquire classic status. There is even a Korean movie, The Classic that "tells the parallel stories of a mother and daughter who fall in love". Spanish painter and sculptor José Victoriano González-Pérez hit the nail when he said "The way to become a classic is by not resembling the classics in any way," but I somehow prefer Mark Twain's
thoughts on the matter: "[A classic is] something that everybody wants to have read and nobody wants to read."

Hundreds of deep listeners (down with audiophile, up with deep listener and, of course, up with people) have confirmed the Art Audio Diavolo to be a modern classic with the electronic jangle of their credit card and cold hard cash purchases. Indeed, the Diavolo does so many things well and in such a clear, novel and dare I say ageless fashion, that it remains the best selling amp of the Art Audio line behind head man Joe Fratus' own PX-25.
Knowns and unknowns
Brought to market in 1995 after considerable research into the possibilities of the then largely unused KR Audio VV32B valve, the Diavolo is not your father's -- or even Harvey 'Gizmo' Rosenberg's -- SET. The Diavolo is a 13wpc SET that can drive almost any reasonable speaker; that delivers room-filling sound with mightily extended bass; that possesses a sweetly illuminated midrange, decent treble elucidation and smoothness; and that just basically boogies as well as any solid state amp - yet without the commensurately bleached stranglehold on harmonic finesse found in most sand engines.

A very heavy, very beautiful polished stainless steel amplifier, the Diavolo, like all amps from Art Audio, sounds much louder and powerful than its respective wattage ratings would imply. Flea-watt amps usually turn me off even if they sound wonderfully sweet, detailed and über present. I have been a slow convert to the SET clan especially when paired to most Lowther-endowed speaker designs - but I surely have come around in my thinking. I still don't get hot and bothered over the sound of a gorgeous SET midrange that can't seem to find its bass trousers. Yet I can better appreciate its glories than in years past when I thought my BAT VK 75 was the path to deep listening perfection (can you say Titanic and iceberg?). Art Audio makes SET designs that a he-man could love. I'm talking amps with tightly defined bass, a well developed soundstage and solid frequency extension throughout the range.

Like other Art Audio amps, the Diavolo employs output transformers built of a "novel split core type not normally associated with single-ended designs and custom-designed by Art Audio to give a wider bandwidth than most generally available transformers". That may be Art Audio's website spin but it is easily verifiable by listening. The Diavolo fills my room with sound as perhaps no other amp I have reviewed. Like many other contemporary tube amps, the Diavolo is a zero feedback, pure Class A triode stereo design and features circuit boards (multi-layered 2 oz. copper trace) rather than point-to-point wiring. Art Audio uses low ESR/ESL Aerovox capacitors in the power supply, along with smaller value Rubycon and Philips caps. German-made Wima metalized polypropylene caps are used in the signal path. The Diavolo employs a choke regulated, CV-378/GZ-37 tube-rectified power supply supported by ceramic tube sockets with silver plated pins that offer a very tight fit. It is finished in a polished (non-magnetic) stainless steel chassis with gold-plated (or chromed) transformer caps. The Diavolo comes stock optimized for a 6-ohm output impedance but can be internally set from two to eight ohms at the factory. It weighs 60 pounds and measures 18.25" W x 13.75" D (incl. heat sinks & terminals) x 10" H. Tube compliment is one pair each of 6DJ8 and 12BH7 driver tubes, two CV 378s (choke-regulated) and two KR VV32B power tubes. (This tube is no longer in production though Art Audio has bought up a sizeable stock. Currently, the amp is shipped with either KR Audio 300BXLS or 842VHD tubes, the tubes under review here, though 32Bs are still available by special request.)

Diablo Diavolo!
A SET amp that offers both a palatable, detailed midrange for nirvana seekers and a serious booty blast for real-world listening? A beauty of an amp that connects the micro and macro dots, dynamic shifts, subtleties and such that turn HiFi into music? Fugheddabaudid. Stunatz!

The Diavolo handled everything put to it with the same generous depth of soul and detailed intellectual reach. I have not heard the much vaunted PX-25 but I have heard the Art Audio Symphony II. While the Diavolo does not offer the same level of treble purity and upper midrange glory/transparency as the 300B-endowed Symphony, it exceeds it in terms of sheer bass performance and low end girth. Again, the Diavolo competes with most SS designs for room-filling bounty. Its level of traction -- in delivering clearly defined bass notes, be they electric bass guitar, bass drums or depth-charge worthy drum-and-bass fare -- puts this amp in a proud league of its own. Nothing less than you would expect from a classic.

The Diavolo is not quite as transparent nor in possession of the finely textured soundstage as its Symphony II sibling or certain rather more expensive SETs. The Diavolo is all about the essence of the listening experience. On first blush, its upper treble sounds a little forward as though it couldn't quite find its groove. And the Diavolo midrange is not as svelte as more expensive SET designs I have heard. Where this amp excels is in the total experience department. Once you have tunes cranking and your ears warmed up, the Diavolo is dynomite. Its character is forgiving and full-bodied with every style of music, from the electronic requiems of Massive Attack to the shouting big band stomps of Dave Holland to the sensuous jazz-pop of Erin Bode, all portrayed in an effortless
and completely holistic manner. You won't miss anything with the Diavolo. Instead, you'll be reaching to hear your favorite recordings cast in a hearty SET glow.

842 vs 300BXLS
I listened to three recordings first with the 842 power tubes, then the KR 300BXLS.

A recording I often use to judge macro and micro dynamic contrasts is the Dave Holland Big Band's What Goes Around [ECM]. A Grammy-winning CD, What Goes Around is a modern big band performance that features some of the finest Jazz musicians working. The Diavolo presented a full-scale rendering of the disc with all its soaring solos,
coiling bass lines and fiery drumming intact. Acoustic bass was exceptionally deep and detailed, possessing a deep growl. Excellent resolution and dynamics were offset by an occasionally strident treble and a clustering of instruments in climaxes that may have been partially due to the recording itself. While the upper treble was not the smoothest I have ever heard, a full, present but not overly sweet midrange provided a very involving listen.

On the opposite end of the things, Danish vocalist Susi Hyldegaard's Blush [Justin Time] is an extremely intimate recording of deep-toned, practically submerged upright bass, subtle electronics and Susi's remarkable voice, the latter a cross between Erkyah Badu, Björk and a post-shock-treatment Ella Fitzgerald. The Diavolo made the most of Blush's upfront, seriously palatable sonics and window-shaking bass notes. Alas, the instruments and vocals seemed to clutter at the front of the stage, a constant with the Diavolo. It doesn't do depth or imaging as well but its room-filling aptitude helps to overcome that particular weakness.

Sea Hawk seems cut from the John Williams cloth, a swashbuckling, ultra-dynamic orchestral performance that is part classical, part soundtrack, part 1812 fireworks. The curtains rise and the titles rush at you from the screen: Pulse pounding! Drama! Romance! Tympanis ring, strings swoop, brass roars and the Diavolo was having a house party with me invited. It proved its dynamic mettle here from a whisper to a scream in 40 seconds flat.

Dropping the 300BXLS power tubes into the mix completely changed the Diavolo's basic character. As though revealing a layer of previously obscured brilliant light, the 300B XLS tubes brought out the Diavolo's upper treble agility but not at the expense of its walloping low end. This gossamer quality improved soundstage, imaging and transparency. Cymbals had more shimmer, bass grew a tad tighter and overall the music became more glistening, sweet and perhaps even more dynamic. Tonality benefited the most and the entire presentation became more alive.

Ditto for the Hyldegaard CD. Through the 300BXLS, her voice became even more intimate and most notably, longer decay trails appeared in the mix. Energy, detail
and focus improved. The Holland disc confirmed the basic traits of the 300B XLS in the Diavolo but here the bass somehow sounded less meaty, most likely as the result of the tubes' upward shift in tonality. Still, soundstage and resolution seemed to improve.

The devil in the details
No doubt about it, the Diavolo is not the most neutral amp in the world. It certainly errs on the romantic side of absolute neutrality. It juiced up discs that were already warm to begin with and made voices and acoustic instruments particularly fruity at times. But the Diavolo is not colored in an overly lush, bass-flabby way, nor is it all saccharine and rolled off. The Diavolo is more about midrange beauty, buoyancy and, particularly with the 300BXLS, treble elucidation than about syrupy and cellulite. And we are talking serious power. Some might think its treble forward but none could deny the Diavolo's exceptional dynamics, high resolution and room-filling gusto. For 7K, the Diavolo is the kind of tube amp that a macho man could feel comfortable and stretch out with, whether rocking out with the classics, jamming with some alien electronica or zapping his solars clean with some swinging jazz bop. The Diavolo, to give new meaning to Mark Twain, is truly a classic that not everyone may have heard yet but should hear.
Manufacturer's website