Many audiophiles have an over-simplified - and negative - view of single ended triode amps. But it's time for them to start listening. Whether it's playing back big bands or string quartets, the Art Audio Jota bumps up against stereotypes: There's no over-ripe midrange, mushy bass, roll-off at the frequency extremes. In fact, with the exception of the overall smoothness and the inherent organic quality of the sound, I would never have guessed this amplifier was an SET.
The Jota is a pure class A, 20-watts-per-channel, transformer coupled, single ended tube amplifier designed around the KR Enterprises VV 32B output triode tube. The output tubes are mounted on a special isolation plate assembled with vibration dampers to isolate them from chassis vibration. The sockets themselves are ceramic with silver-plated pins. The dual mono design also features an automatic biasing circuit.
The amp is named for a type of folk dance from Aragon, Spain, that consists of hoppy steps in 3/4 time. The image of a folk dance is apropos, here, for the Jota will get your feet tapping in no time. Musical? Yes. But not in the double-speak definition of this word you may have heard before - "musicality" as an excuse for shortcomings in detail retrieval, dynamics, and performance at the frequency extremes. Indeed, the Jota excels in these and other areas. I was hard-pressed to find any manifest deficiencies. And its temperament does not require the talents of a live-in mechanic.
Its physical appearance is striking: gleaming, polished, nonmagnetic stainless steel and black transformers with gold-plated caps to match the Art Audio badge. The blue-crystal power status lights are recessed on front of the unit and have an almost neon light effect that complements the rest of design.
In performance, it's dynamic, to say the least. Whether fleshing out the mids, scaling the highs, or plumbing the depths, the Jota's ability to convey dynamic gradients surprised me. I had expected the midrange to be somewhat lush, but it was not. And the rest of the frequency spectrum offered more than I imagined possible. Indeed, my push-pull reference needs to be seriously goosed to get a comparable sense of presence. Sadly, when played in back-to-back comparisons, and loudly enough to bring the life back into the presentation, that reference amp still sounds relatively hard and mechanical.
Low-level resolution was unsurpassed, in my experience. The amp can crank out serious volume and still come across as sounding effortless. So unused to the unusually smooth sound was I that during my first week with the unit, I often found myself cranking up the volume in an attempt to get that edgier push-pull sound to which I was accustomed. The Jota refused to deliver, until forced to clip. Even then, the clipping was gently' and the amp always recovered quickly.
On the Shadowlands sound track {Angel CDQ 55093}, the Choir of Magdalen College made delicate, yet fully energized entrances. Articulation was precise, yet full and well rounded, and triangle strikes that were difficult to distinguish on other amps rang out clearly.
In the intro to "Brother," from Bill Frisell's Nashville {Nonesuch 79415-2}, Frisell slides his finger up the string of his guitar, and I heard it move two frets farther, and sustain longer, than ever before. The entire album (which can get somewhat raucous while remaining musical) was much more liquid than I recall from many previous listenings. It also offered a better view into the details generated by the harmonics of many stringed instruments, layered across the soundscape. Subtle murmurs, bites, growls, twangs, and snaps all came into aural focus.
The soundstage offers excellent depth and vertical aspects. Width was most appropriate, but the coherence between it and the depth this amp reveals was most interesting. Overall, soundspace created was quite different from anything I was familiar with. The sense of immediacy, with loads of hall and studio ambience, seemed, at first, incongruent. It's hard to describe - it's certainly not the usual "I heard things I have never heard before." Here, I am talking about a different realm, where immediacy, depth of field, and energy within the room conspire to create an entirely different experience of the event unfolding. Then, it clicked. The stage is full, with appropriately sized and spaced performers. This sounded right .
The frequency extremes were the biggest surprises. Pristine, yet delicate and extended highs. The high Japanese bells in "Sagrada Familia " from Robert Rich's Gaudi {HS 11028-2} were easier than ever before to identify. And on the other end, Mary Black's No Frontiers {Gift Horse D2- 77308} took my Dunlavys to a new level of nuance and depth. The bass guitar's foundation at the bottom and the buzz at the top were palpable. The Jota also extracted more than a bit of warmth, fullness, and weight from the bottom end of these speakers. Since the Dunlavys are more analytical (overall) and leaner in the bottom (particularly) than, say, the Cabasse Catalanes, these are good things; they benefited from the solidity and depth of the bass offered by this amp by offering a few more Hertz and even better articulation than usual. Considering that they already excelled in the latter, I was impressed by the improvement.
On Weinberger's Polka and Fugue {RR-58CD} and other orchestral works, bass drums sounded whacked (as they should), timpani revealed the nuances of their limited range, cellos murmured and bloomed, and the lower register of the piano was clear and well weighted. Loud and complex passages unraveled admirably.
More than once was I startled by the attack of instruments and vocals on Dead Can Dance's Into the Labyrinth { 4AD 9 45384-2}. Both male and female voices are pure - well-rounded, liquid and, at the same time, exceptionally detailed. Cymbals and gongs lingered longer before they disappeared into black space. I often caught myself tapping along to the tunes, which tells me it reproduces transient information very well. "WBAI," on Oregon's Ecotopia { ECM 83 3120-1 }, practically snapped my neck with blindingly fast, fluent drums.
On "Loisaida," from Joe Jackson's Body and Soul { A&M SP5000 }, horns were delivered with presence, that is, more than just bite, and with a depth of body that went beyond the visible. The bass came in sooner than I was used to and the weight of the drums allowed me to hear them deeper into the mix, with the walls of the hall supporting them. The piano was crystalline, but not sterile - its percussive nature was exceptionally conveyed; as the keys moved, hammers and hammers struck strings. "Heart of Ice" fades in with a bass drum, which, although far in the back of the stage, simply won't relent. With the Jota, it stayed recessed, but never released its grip on the fore of the mix. The dynamics portrayed by the Jota on this song were compelling, going from a subtle piano solo, building in horns ( that could easily be mistaken for oboes, so delicate is the entry) to a building crescendo, complete with a mantra-like, simple lyric, to a wall of sound that is nothing less than arresting. The Jota delivered, again.
In short, the Jota took my system to a new level of musical realism (and enjoyment). I have sufficient symptoms of sleep deprivation to prove it. I wanted to review it because my curiosity about the single-ended sound was roused, but I didn't have the proper speakers for the some of the flea-powered gear that dominates that market. It has been said that the lower-powered triode amps, mated with appropriate speakers, are capable of even more nuance and emotional engagement. I'd like to try them for myself, though if it gets better than the Jota, you'll find me in a puddle of tears. If, at this moment, I had to pick one amp to spend the rest of my life with, the choice would be an easy one.
STEPHAN HARRELL
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MANUFACTURER INFORMATION
Art Audio USA
34 Briarwood Road, Cranston, Rhode Island 02920
Phone: (401) 826-8286; fax: (401) 826-3903
catsarta@worldnet.att.net
Price: $7,995
SPECS
Output power: 20 watts per channel, class A
Input sensitivity: 400mV for full rated output
Input impedance: 180 k/ohms
Output impedance: 1.1 ohms
Frequency response: 20 Hz to 20 kHz -0.5dB (full rated output)
Tube Compliment: two KR VV32B output tubes; two Mullard CV 378 (GZ 37) rectifier tubes; two 6922/ 6DJ8 gain stage; two 12 BH7 additional gain and cathode follower NOS tubes are an available option for driver stages
ASSOCIATED EQUIPMENT
VPI HW-19 Jr./PT-6 pick-up arm/AT OC-9 cartridge; CAL Delta Transport driving CAL
Alpha DAC (with 24bit/96k upgrade and GE 5751 tubes) via Illuminati D-60;
Nakamichi RX-202 deck; Audible Illusions M3A preamp (MC phono board) w/ Edichron 7DJ8 tubes, C-J Premier 11a; Dunlavy SC-III speakers; Cabasse Catalane 500 speakers; REL Strata II sub; Tice Elite Power Conditioner; Argent Room Lens; Tara Labs RSC Reference Gen 2 interconnects; Tara Labs RSC Prime 500 cables; Belden 17504 power cords; Rosinante Dark Matter equipment stands; Bright Star air mass; Townsend Seismic sink; Sound Organisation amp stand; Mana Soundframe; VPI 16.5 record cleaner
MANUFACTURER'S RESPONSE ...This review is based on the standard version of the amplifier, but Art Audio has recently introduced a higher powered version based on the KR 52BX output tube. This version of the Jota is capable of 40 percent more current delivery and a higher damping factor to accommodate the customer who owns a speaker system that needs greater control (larger woofers in dynamic speakers). We can also install, by special order, output transformers that accommodate impedance loads down to 2 ohms, with no loss in maximum output power. These special order, hand-wound output transformers are for customers who already own speakers with difficult impedance curves or for someone who wants to pair the Jota with an efficient electrostatic or ribbon-type speaker system. Finally, for further flexibility, either version is available in a monoblock configuration.
JOE FRATUS
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SCOT MARKWELL COMMENTS
I concur with Harrell's findings on this amplifier. The Jota truly is an excellent example of a properly executed SET. If anything, I believe that he has understated what the unit does well. I listened to it for a couple of weeks on the Horning Alkibiades Signature Golds, a friendly impedance match (6-8 ohm load) and an easy drive, at 99 dB/watt. I confess that I was almost irritated that the Jota sounded as good as it did, in that it put to shame almost every other SET amp I had on hand for my survey, with the exception of Wyetech Labs Topaz 572, a superb stereo unit from Canada, which costs almost $4,000 more than the Jota and offers 23, rather than 20 watts per channel. The Topaz has deeper, better articulated, and more powerful bass, and a more linear output throughout the full frequency range, but could not match the midrange creaminess of the Jota on massed orchestral strings - amazing to hear and unmatched in all my experience with SETs. For example, I played the Britten Four Sea Interludes [Previn; EMI SLS 5266], and never have I heard this selection's beautifully recorded massed violins better reproduced. The comparably priced Vaic 52 ST integrated amp has more dynamic impact when pushed, but could not reach as deep into the bass nor render such an extraordinary string tone. Both the Wyetech and the Vaic have more of a solid-state type of midrange signature (fine solid-state, to be sure), which indicated to me more of a true, honest "accuracy," in a technical sense, but the Jota was simply ravishing, despite sounding as if it were looking just a bit through rose-colored glasses. OK, this is not quite reality, but it is a quality I could live with and cherish, especially since this exquisite string reproduction seemed to hardly color any other part of the spectrum - and I listen to an awful lot of orchestral strings. Play string quartets or a sonata, and the amp sounds clean, lustrous, and grain-free. But those massed groups - man, what a treat! Its bass reproduction is also almost top-flight for an SET. I thought, however, that when pushed, it showed some signs of distress in the reproduction of powerful low-bass transients more readily than in any other portion of the frequency spectrum. But kept within its (admittedly high) limits, it held together well. This is not the best amp for those whose tastes run to loud, driving rock or hip-hop bass compositions, but for most orchestral, pop, and jazz, it is well suited to the task at hand.
I also was pleased at the low level of distortion, especially at higher listening levels and on high-frequency percussion transients; as Harrell intimates, the Jota was capable of lightning attack and delicate, sweet decay, without blurring or ringing. And its ability to produce a credible soundstage, whether of a studio for pop music, a live rock venue, or differing orchestral halls, was first-rate. My reference solid-state Plinius SA-250 can create a more majestic, properly scaled spatial perspective, but it can't match the sheer beauty of the Jota's midband reproduction.
In sum, I was extremely impressed with this amplifier. On a properly matched speaker system, this is an SET that can play all types of music with aplomb. The key here is "properly matched" speakers. When I first heard the Jota, I was attempting to drive a set of Burmester B97 speakers in HP's Room 1, which would seem an ideal situation, given the Burmesters' 97 db/watt sensitivity. But the speakers' cruel impedance dip to 2 ohms in the low bass made the amplifier bottom out and sound weak and spineless.
But this is not what this kind of amplifier is designed to do. If you stick with a 6 to 8 ohm load (or even slightly higher), use a full-range, low-coloration speaker with first-class midrange and high-frequency capabilities, stay above 91-92 dB/watt sensitivity, and do not try to play at 110 dB levels, you will be hard-pressed to find a better amplifier.