AFTER NEARLY A DECADE of existence, the sweet sound of commercially produced low-power, singleended vacuum tube power amplifier offered by such manufacturers as Art Audio should by now be quite familiar to the audiophile world. Popular in Asia and elsewhere for decades, single-ended topology power amplifiers now find homes in North America as well. With the resurgence of horn loudspeakers, these amplifiers are especially appealing. The Super Jota, reviewed here, has already gained a good deal of fame in specialty audio circles. Indeed, the six-watt Art Audio PX-25 amp I examined in TAV Vol. 7, No. 4 proved to be a marvel in its own right, confirming its engaging performance when paired with sufficiently efficient loudspeakers. Some aficionados may consider the PX-25 to be a “specialty amp” when compared to the more powerful 20-watt stereo Super Jota, which sports the latest Czech 300 BXLS power triodes.

Background
The Jota’s original configuration (which is still available today) features the Czech KR brand 20-watt VV32B output tube which offers energetic and true-to-life performance. The merits of this tube in this application established the brand as a legend among followers for conveying musical purity. It is also a power amplifier that mates well with less efficient loudspeakers where lower powered triodes are not typically applied with success. Using pure Class-A, zero feedback, and a stiff, well-regulated power supply, one would swear she’s putting out many times her rating of 20 watts per channel.

I first heard a prototype Jota, sporting fresh KR 300 BXLS triodes (and putting out as much as 20 watts), last year at an Audio Society meeting in Atlanta. The crowd and I were impressed by the sterling performance of this stereo amplifier. Immediately thereafter, with the support of TAV’s Editor Pitts, we began the gentle push for a review sample early in the production life cycle. Having appreciated the amplifier’s performance first hand as it drove a pair of Avantgarde Trio speakers at the time, I knew that something really special was going on here.

So now, I’ve had the Super Jota nestled in my listening room and attracting crowds of her own for the last few months. She’s a mighty pretty girl too, sashaying in her polished stainless-steel “chassis” with gold accents and sexy blue indicator lights. Yep, she’s a looker, with sound to match. Most every listener, male and female alike who visited my listening room, exclaimed “Wow, what a beautiful piece of work.”

Switching to the 300 BXLS-based Jota from the earlier version required only modest circuit component modification and refinement (which I will summarize later on). This more costly version features the remarkable power triode sourced from the house of Riccardo Kron located in Prague, the Czech Republic, which is today better known as KR Audio Electronics. Art Audio Chief Joe Fratus indicates he worked closely with Kron over several months to refine the 300 BXLS up to its current performance and durability standards. This work was intent on better suiting the Jota’s proven circuit topology and extracting the most from it.

The Sound
Of all the amplifiers I’ve had in my listening room for review over the years, few attracted as much attention as did this Jota 300 BXLS. Its reputation had spread by word of mouth, or should I say by “ear” among my area audiophile community. Folks were coming up with most any excuse to drop by and bring their favorite recordings. “Laymen” visitors, unfamiliar with the resurgence of vacuum tubes in audio, were completely taken aback by this amplifier, by its beauty and its performance. As I mentioned earlier, the original VV32B triode version can hold its own in any reasonable situation. However, this version of the famed 300B triode series processes music in its own special way, one that is often hard to describe in conventional terms. Like a fine wine, it’s in the character. You’ll know it when you hear it and taste the glorious midrange, upper register harmonic structures and expansive soundstage which emanates from this amp. Using this more powerful tube (near three times the power of the standard seven-watt 300B), it will actually provide convincing bass, bass that can actually be felt. This is what sets the Super Jota apart from other similar amps and can mesmerize the listener. In my opinion, if you apply this modest power amplifier to a reasonably efficient loudspeaker, say one that puts out 88 dB SPL or greater with a one-watt input, and if you keep the volume below frontrow, hard rock levels, in a room of reasonable dimensions, one not over damped, the Super Jota should be able to convey the full dynamic range of the source material without heartache. In other words, we’re not talking about rattling the neighbor’s windows here.

Techno-babble and specs aside, there is something special with how this Jota “synergizes” with a phono source. With CD or reel-to-reel tape, the unit is magnificent enough, but with a phono cartridge providing the music, she is especially at home, exhibiting just the right mix of analog sweetness and light, while resolving harmonic textures in their full flower. This amplifier’s ability to resolve detail is simply
astonishing. As you move up the line and introduce her to higher resolution preamps and cables, the more she reveals her extended capabilities.

Quality music listening should be a joyful experience shared with others, not one of just sitting alone stone faced, in your private listening enclave. This amplifier begs you to share the experience with others, and this I did on many occasions, knowing she would deliver the goods. I enjoy a wide variety of music types, from Bach to the Beetles, and a whole lot in between. This Jota amp expressed all these naturally and honestly adding few characteristics of her own.

This amp will make you smile, and passing the surest test of all; does it drive you to pull out of all your old favorite recordings, ones on all types of media, resurrecting some you haven’t played in years? And when you do, does it have you exclaiming, “Wow, I don’t remember this recording sounding so good?” Oh yes, the 300 BXLS Jota made me do this, in spades. On more than one occasion my wife Joan popped into the listening room, curiously inquiring, “What’s all the fuss down here?” In fact, she had to ask if I had given up fishing, my other favorite hobby, just to clear me and my audio-junky friends out of the house for awhile.

This amplifier is known to have mesmerizing effects on listeners. On one occasion I witnessed groups of middle-aged, retro-hippie guests clustering around the gleaming Jota, standing for long periods between the speakers declining to sit down and relax. With lights down low, they drank-in Pink Floyd’s Dark Side LP. Behaving just like a bunch of crazed front-row groupies at a live rock concert. Yes, I was reassured; the amp was getting through, evoking all manner of emotions and flashbacks to younger, faster days and hazier nights. This defines this ART’s ability to handle complex and demanding material at speed, no floppy, flubby, sluggish behavior here boys and girls. She had me spinning my favorite discs aplenty.

Its ability to plumb the depths of deep bass is remarkable for a 20- watt-per-channel amplifier. She works out my Von Schweikert VR- 6s down to 20 Hz with ease. E. Power Biggs low pedal organ notes were conveyed convincingly with little stress or strain. Joe Morello’s drum licks on Take Five were about as sharp as you’ll ever hear ‘em.

Sweet as she is, this Jota won’t pretty-up crummy sounding recordings. Once a sow’s ear, always a sow’s ear, she tells it like it is, without fanfare or coloration. With sources and associated gear that are equally neutral, this amplifier does not have a particular “sound” other than a soothing sweetness, without artifice and without sacrificing detail and speed. If you are following musical lines, dynamic contrasts can be a special pleasure with the Jota, and you’ll find any congestion of complex passages is a rarity with this amplifier.

The Jota also offers some operating flexibility in the form of a frontmounted input level control featuring a precision Alps component. In my experience, this potentiometer did not get in the way of the music at all, and it’s nice to note that the resistive elements are out of the signal path when it’s rotated to full volume. It may be used as a level control when the amplifier is served directly from a line-level source such as a CD player or converter. This Jota operates fine in this mode, yet I’m partial to active preamplifiers, particularly the ones with those handy remotes and with control and switching features. And it seems I get the most sparkling sound in this mode with a quality active preamplifier, in this case my AR Reference 2, MK-II, tube unit. The Jota’s single-ended input RCA terminals are first-rate as are its heavy-duty, knurled loudspeaker terminals; I just wish there were a second pair with standard spacing for ease in bi-wiring with heavy cables. The power cord is detachable so you can apply your choice of after-market types. In this case I used the Kimber Palladian PK-10
Gold, further enhancing the amplifier’s dynamics.

The 300 BXLS amplifier never ceased to amaze me. I found myself immersed in a sweeping soundfield, and in the better recordings the soundstage appeared truly threedimensional, with ample space and air surrounding the performers and their instruments. Amazingly, vintage or historic archive recordings were rendered in a remarkably lifelike fashion, exhibiting a modern presence despite their age. In sum, this amplifier exemplifies the best qualities of the 300B genre, showing its dynamic capabilities to full advantage.

Circuit 300 BXLS Revisions
Now what do you get for your extra bucks in either a new or modified unit? Art Audio Chief Joe Fratus and colleagues have done their homework here and spent over eight months evaluating every component in the signal path to get just the right sonic and performance fit, while paying special attention to maintaining low distortion. As a matter of course, Fratus’ team works closely with their suppliers and manufacturers to assure that performance goals are met. This approach actually produces better product for all parties in the collaboration.

The basic circuit topology of the earlier amplifier has remained unchanged, with the only adjustthe audiophile voice ments needed being ones to the voltage and current settings to accommodate the more powerful, higher current output tube. A new single-ended output transformer was not required, though Hovland capacitors and other topquality components are applied to maintain the Jota’s performance standards. The revised, directly heated 300 BXLS has increased current capacity and uses a re-engineered cathode filament structure named the “Kanthal” by Kron. This attractive large-envelope tube stands 6.5 inches from pins to top, nearly an inch taller than many 300Bs. Joe Fratus says that the 300 BXLS is plug-compatible with the standard Jota amp, which has an output power of around 16 watts. However, to maintain low noise and achieve further benefits from the potential of the revised tube, certain associated component values were revised to adjust circuitoperating voltage to 450 volts and current to 140 milliamps. This raised the new amp’s output to 20 watts, well within the tube’s capabilities with its massive plate. This amplifier still features a zero-feedback, auto-biasing circuit and a power supply featuring solid-state regulation paired with soft-start CV- 378 (GZ 37) tubes. Older Jota amps can be converted to 300 BXLS operation at the factory. The Jota operates in pure Class-A bias, so whether playing music or idling, she runs pretty toasty in comparison to similar powered solid-state amplifiers, or even push-pull tube units.

Conclusion
I guess you can tell by now I’m pretty entranced by this remarkable amplifier. Even with her conservative 20-watt output capability, when paired with a reasonably efficient loudspeaker, plus source electronics and accessories of equal quality, you will be transported to the recording venue. This was true for me with a wide variety of recordings and musical styles. While not inexpensive, she does offer top-tier performance in her class. Experiencing this amplifier over several months is one of the most memorable audio and music appreciation encounters I have ever enjoyed and actually exceeded my expectations. As I stated in the beginning, I knew something really special was going on here, and indeed there is. Named after a Spanish dance, the “Jota,” she does indeed live up to her reputation, filled with life and expression. Throughout the Jota’s residence in my listening room, she performed flawlessly which is most encouraging for an amplifier that some folks may consider an exotic. It you are ready to take the adventure with this type of amplifier, I would put this Jota at the top of my list. While not inexpensive, this amplifier delivers performance at the head of its class. Without aberrations or artifice, she is in fact in a class of her own. Seriously consider taking her for a spin if you’re up to the excitement.