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.
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.
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.
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.