CAT JL2 Signature Mk 2

It's no secret that the Internet has risen in prominence in the minds of consumers over the last decade, and traditional retailers in just about every market segment have taken it on the chin during that time. While some audiophiles celebrate lower prices due to online selling of audio gear, serious listeners now have fewer opportunities to audition gear for themselves because so many dealers have gone under. Audiophiles now rely on what other people have to say about a speaker or CD player that's particularly appealing, and this has created a situation where words have become especially suggestive.

Say "stereo amplifier," "single-ended triode" and "300B" to an audiophile, and he'll immediately form a mental construct of the sound such a component would have and even the speakers with which it would be used. Switch to "mono amplifier," "push-pull" and "KT88" and another picture begins to take form. "Low-output moving-coil cartridge" is evocative enough on its own to conjure an idea of the sound it will produce, while "digital-to-analog converter" needs a qualifier, such as "tube output stage" or simply "1985," to create an impression.

Using 6550s to produce a claimed 100 watts, the Convergent Audio Technology JL2 Mk 2 stereo amp conveys the notion of a medium-power amp that will drive more speakers than its SET counterparts, but won't be up to the task of powering tough loads or filling a large room. Its triode circuit implies a warm, fluffy midrange with obvious reduction of top-end sparkle and low-end grunt. Its "sweet" and "forgiving" midrange-centric presentation, will "heighten involvement" and "bring listeners closer to the music." On paper, it's a "solid," "conventional" design, if rather "blasé."

But a little investigation blasts these quaint assumptions to pieces and proves that the JL2 Signature Mk 2 ismuch more than it appears to be.

Details, details

While it's a common practice to compare audio electronics to sports cars, the massive JL2 Signature Mk 2 ($16,995 USD) is made of stronger stuff. It's a Hummer in amplifier form, its rectangular chassis accented with gleaming chrome, like the shiny bumpers and grilles you see people adding to their tanks-on-wheels. Thus, the JL2 Signature Mk 2 is big and heavy 18 1/2"W x 27"L x 10 1/2"H and 145 pounds and the antithesis of the paperback-book-sized switching amps that are multiplying these days like mosquitoes after a summer rain.

Like that of the SL1 Ultimate Mk 2, the chassis of the JL2 Signature Mk 2 is made from heavy-gauge steel, not aluminum, and the inside surfaces are covered with Ken Stevens' special "resistive damping compound" to control resonance. Running down the center is a pair of potted output transformers, which were designed by Ken Stevens. To say they were over-spec'd would be an understatement they weigh 27 pounds each and could be used in amplifiers that output much more power than the JL2 Signature Mk 2. Even the tube complement is over-spec'd. When was the last time a stereo amp used 16 6550C output tubes to deliver a mere 100 watts per channel? The six driver tubes are common: one 12AX7, one 12AU7 and one 6922 per channel. CAT supplies Winged C output tubes with the JL2 Signature Mk 2. Ken settled on these after much experimentation because they sounded good and were reliable -- in that order.

In the amp's ventilated rear section are power-supply capacitors and an isolation transformer. As with his preamp, Ken warns against using any power conditioners with the JL2 Signature Mk 2. The isolation transformer, which he designed, makes such extra components superfluous. You plug CAT equipment right into the wall.

The line-level inputs RCAs only and speaker binding posts are located at the side of the amp in order to shorten the signal path for each channel. If your cables are stretching now, they likely won't reach with the JL2 Signature Mk 2 in your system. The power switch is around back. Throwing it for the first time created such a draw that a couple of CD players cycled off and on, and then a breaker tripped. Cycling the breaker manually a few times fixed that, but the CD players continued to burp whenever the CAT amp was turned on. I've reviewed some powerful amps, but none has strained my house's wiring like the JL2 Signature Mk 2. Still, the amp performed without issue during its stay.

Oh, my aching back

The JL2 Signature Mk 2 comes double packed in two extra-thick cardboard boxes, which make the fact that it's delivered by a freight company, not Fedex or UPS, all the more understandable. Lifting the amp out of those boxes is a two-person job that I stupidly did myself. It's an awkward heave, mostly because it's difficult to determine how to balance the amp once you have it off the ground. Don't overanalyze it; brute strength is the only thing that will get the job done.

I used the JL2 Signature Mk 2 with CAT SL1 Ultimate Mk 2 and Audio Research Reference 3 preamps, and the Aurum Acoustics Integris CDP CD player/preamp. Sources included an Audio Research Reference CD7 CD player, an Ayre Acoustics C-5xe universal player, and Zanden Audio's Model 5000 Signature DAC and 2000 Premium transport. Speakers were Wilson Audio WATT/Puppy 8s and MAXX 2s, and Verity Audio Lohengrin IIs. I had an abundance of amps on hand for comparison, including Lamm ML2.1 SET and M1.2 Reference hybrid monoblocks, Atma-Sphere MA-2 Mk III OTL monoblocks, an Audio Research Reference 110 stereo tube amp, and a Conrad-Johnson Premier 350 stereo solid-state amp. The preamps, Audio Research CD7 and Ayre C-5xe rested on the nanoparticle shelves of a Silent Running Audio Craz 4 Reference rack, with the Lamm and Atma-Sphere amps on Silent Running Ohio Class XL Plus2 platforms. The Zanden separates sounded best on a pair of Harmonic Resolution Systems granite-and-aluminum bases.

Interconnects and speaker cables alternated among Shunyata Research Antares Helix and Orion Helix, Crystal Cable Ultra, and the wonderful Acapella High La Musika that I'll be writing about soon. Power cords were Shunyata Research Anaconda Helix and Python Helix in both Vx and Alpha variations, with Essential Sound Products The Essence Reference for the CAT preamp and amp. The JL2 Signature Mk 2 ships with a stout Virtual Dynamics power cord, which I used for a short time, but I greatly preferred the ESP cord for its cleaner, more vibrant presentation. I adhered to Ken Stevens' directions and plugged his preamp and amp directly into the wall. A Shunyata Hydra Model-8 or V-Ray scrubbed clean the power to the other products. I set the JL2 Signature Mk 2 on the floor with two slabs of Corian underneath. It's never a good idea to put a power amp directly on top of carpet, which can impede the flow of air through the chassis.

Before doing any listening, I had to set the tubes' bias and push-pull balance an easy task because of the top-mounted controls and LCD meter. CAT recommends adjusting new tubes for two weeks after they are installed and then never again. The reason for this is spelled out in the manual: "The bias will go slowly down as the tubes get older and are used," and "older tubes sound better at a lower bias current." It's hard to leave that nifty meter and those knobs alone, but consider it an order after the first two weeks. The tubes of each channel are adjusted as a group, but you can use the meter to check the individual reading for each tube and thereby pinpoint any that go bad.

"That preamp guy's" amplifier

In my earlier review of the CAT SL1 Ultimate Mk 2 preamp, I discussed how Convergent Audio Technology came into being basically on the strength of the SL1 preamp, which was Ken Stevens' first commercial product and CAT's only product for more than a decade. Ken Stevens built his company on the SL1, and his reputation as an audio engineer is intimately tied to his preamp. Even today, with various mono and stereo amplifiers under his belt, he is still known primarily for the SL1. At this year's CES, after I talked with Ken for a few minutes in the hallway outside his demo room, two guys passed by. One referred to him as "that preamp guy."

There are worse things in life than being known for the work you do, especially when what you do is design and manufacture amplifiers like the JL2 Signature Mk 2. Call it a triode amp with guts, or an easy-going muscle amp, so expertly does it mate beauty, finesse and refinement with raw power. Its triode disposition is obvious from its round, sweet midrange, but the CAT amp belies its 100Wpc rated power output, controlling speakers, including those with big woofers, with ease and never showing signs of strain as the music gets louder. It's an amplifier with all of triode's strengths and none of its failings, and it obliterates some of the rules by which tube amplifiers are traditionally auditioned and judged.

The JL2 Signature Mk 2's drive is most obvious right where you think it would be in the bass, which extends past the point where other tube amps, even other solid-state amps, peter out.
This is not over-damped bass that throbs like a bad headache, but rather low frequencies with an organic kind of weight and bloom that propel the music at its intrinsic pace. There is ample midbass punch and low-bass growl for even the most rowdy hard rock, like AC/DC's Back in Black [Epic EK 80207], which has been nicely remastered, and then a light touch that can differentiate the upright bass and kick drum on "Jump," from the Bill Charlap Trio's Somewhere: The Songs of Leonard Bernstein [Blue Note 94807]. For me, great bass isn't that which reaches the lowest notes with the greatest pounding force. Instead, great bass simply conveys all the power of the music without being conspicuous, putting a natural kind of flow above pyrotechnic flash. Solid-state amps often get the power right, while tubes forego the attention-grabbing pomp. The CAT amp does it all in a way that sets a standard for low-frequency realism.

From my experience, 6550 output tubes can sound vivid, but sometimes this overreaches into glare and hardness. Here again the JL2 Signature Mk 2 defies expectations. The entire treble range has a fine, filigreed character that conveys the unique textural makeup of guitar and the complex harmonics of piano like the best OTL amps I've heard. This gives the CAT amp a distinct kind of sonic sophistication that never turns ugly. Its transparency is manifest and not showy like so many of the things it does so well.

Diana Krall became an audiophile darling and then an audiophile cliché because her voice sounds so darned good on so many audio systems. The CAT amp driving the Wilson MAXX 2s practically conjured her out of thin air from the DualDisc version of Girl in the Other Room [Verve B0003758-82], while with the Verity Lohengrin IIs, the sense of space surrounding her was more evident, but her voice was a bit less dusky. Which one of these presentations was the right one? Your guess is as good as mine. But in both cases, the JL2 Signature Mk 2 handed the bits'n'bobs off to the speaker, which reconstructed them into a musical presentation. This amp will show up a good many speakers, so complete is its performance.

The JL2 Signature Mk 2's lone deviation from perceived neutrality is one that many audiophiles prize: a juicy midrange that doesn't sound drenched with color or overly plump. Here, those 6550Cs sound more like EL34s, maybe even a touch like 300Bs, imparting a sweet fullness to voices that I can't imagine too many audiophiles will moan about. It's a strength to my ears, but I acknowledge that various other amps don't display it, and also lack the endearing presence that it brings.

If you haven't heard Seu Jorge's collection of David Bowie covers, The Life Aquatic Studio Sessions featuring Seu Jorge [Hollywood Records 2061-62576-2], you have missed a demonstration-quality CD flush with memorable music. Jorge sings in Portuguese, which puts an interesting twist on Bowie's songs. The different language becomes an additional instrument, conveying new facets of these recognizable songs. The presence gained with the CAT amp was thrilling, especially with "Changes," which is more closely miked than the other songs on the album. The JL2 Signature Mk 2 cast Jorge's voice in aural granite. It was centered, filling the space between the speakers and projecting forward of the speaker plane. It was big and redolent, a palpable replica that evoked images of a front-row seat in a small venue. Jorge is no disembodied ghost; the CAT amp won't have it any other way.

A discussion of ghosts is the perfect segue to a discussion of this amp's most elusive characteristic: the almost unexplainable confidence it instilled as I listened to music with it. I had the sense that the JL2 Signature Mk 2 conveyed each recording in the way it was meant to be heard with all its subtlety and power, aggression and elegance. As with a Hummer powerful and sure-footed I came to rely on the JL2 Signature Mk 2, and it delivered without fail.

All-tube showdown

Along with the JL2 Signature Mk 2, two tube amplifiers I've written about this year are stiff competition for amplifiers at any price. The Audio Research Reference 110 ($9995) is a hybrid stereo amp that uses JFETs in the input stage and matched pairs of 6550C output tubes to produce around 110Wpc, 107 watts at 1% distortion to be exact. The Atma-Sphere MA-2 Mk III ($32,800 per pair) is an output-transformerless monoblock specified to deliver 220 watts at 8 ohms. The load of the partnering speaker is more critical with this amp, although its ample tube complement and power output makes speaker mismatches less likely than with the less-powerful Atma-Sphere OTL amps.

Because the CAT JL2 Signature Mk 2 has only single-ended inputs and the ARC Reference 110 accepts only a balanced signal, I couldn't use the single-ended-only CAT SL1 Ultimate Mk 2 for comparing the two amps. While I have two preamps that worked with both amps and the Atma-Sphere monoblocks, which accept single-ended input but sound best balanced, I used the Aurum Acoustics Integris CDP most often. It's sonically neutral and very quiet, and its volume control is adjustable in 0.5dB increments, making it very easy to match the loudness of all the amplifiers.

In my review, I wrote that "The Reference 110's tonal color, expert inner detailing and expansive soundstaging are things often reserved for the very best single-ended amplifiers, but its 110Wpc output makes it able to drive real-world speakers." This all applies to the JL2 Signature Mk 2, which adds greater rhythmic drive the ability to accentuate the music's momentum, often laid down by drums and bass and seemingly even greater power. While the Reference 110 and JL2 Signature Mk 2 output roughly the same amount of power, the CAT amp sounds more powerful. It doesn't do this by making that power sound conspicuous, which is what solid-state bruisers can do, but rather it seems to have a deeper reserve from which to draw. I know -- this last point makes little sense given the identical power output of the two amps, but it's the best way to describe the added authority of the JL2 Signature Mk 2. Ken Stevens chalks it up to the generous number of output tubes he uses, along with his overbuilt output transformers, brawny power supply, and use of triode mode.

While the ARC and CAT amps sound similar in some obvious ways, the Atma-Sphere monoblocks are utterly different amplifiers. Their OTL circuit leads to a direct, see-through midrange that will surprise even experienced listeners. Yet, even here, the CAT amp holds its own, presenting the heart of the music with no obvious lack of transparency. However, there is greater body a more physical sense to each note. Yes, two rather different midrange presentations can't both be transparent, so which one truly is that of the leaner-sounding Atma-Sphere amps, or the fullness of the CAT amp? The Atma-Sphere midrange certainly sounds less adorned, but the density of the CAT midrange is what I hear from live music. You win either way, I guess.

As with the Audio Research amp, the Atma-Sphere mono amps don't sound as authoritative as the CAT JL2 Signature Mk 2, and they are supposed to deliver double the amount of power. File that under "Hmmm." Obviously, there's more to sounding powerful than sheer power output itself. In the bass, the CAT amp is also superior, though the MA-2 Mk IIIs are certainly not weaklings, providing commendable low-frequency energy and detail. But the CAT amp delivers more weight and a more realistic portrayal of bass dynamics, which is nearly impossible to detect if your speakers can't reproduce it. The MAXX 2s can, and the CAT amp made it plain.

In the end, your budget may play the biggest role when it comes to choosing among these three amps -- the gap between $9995 and $32,800 is a canyon to be sure. But in the middle sits the JL2 Signature Mk 2, and in important ways it is the best amp of the three.

Where that leaves us

At this point it's obvious that I love the CAT JL2 Signature Mk 2, and I think you will too no matter what amp you are using right now. It revises what we audiophiles should think when we read about a "tube amplifier" that offers "mid-level power" and runs in "triode." The JL2 Signature's bass energy and drive are by far the best I've heard from a tube amp, and its realistic low-frequency weight and bloom are things you just don't hear from solid-state amps. The highs of the CAT amp are delicate and as detailed as your source will allow, and the midrange has the kind of presence that is audiophile gold. But it's the combination of all these things that makes the JL2 Signature Mk 2 an amp to love. It seems improbable that they would all be together in one amplifier, but there they are.

Ken Stevens may be known for his SL1 preamp, but his JL2 amp is an even more significant product, and that's saying a lot. I put the JL2 Signature Mk 2 with the Wilson Audio Alexandria X-2 and MAXX 2 speakers in a group of the finest audio components I've reviewed. "Don't buy another amp until you've heard this one" became an audio-reviewing cliché sometime during the Pleistocene epoch, but it's the wisdom of the ages when applied to this amp.

Review Summary

Sound "Call it a triode amp with guts, or an easy-going muscle amp, so expertly does it mate beauty, finesse and refinement with raw power." "There is ample midbass punch and low-bass growl for even the most rowdy hard rock" and "the entire treble range has a fine, filigreed character that conveys the unique textural makeup of guitar and the complex harmonics of piano like the best OTL amps."

"The JL2 Signature Mk 2's lone deviation from perceived neutrality is one that many audiophiles prize: a juicy midrange that doesn't sound drenched with color or overly plump."

Features "A little investigation proves that the JL2 Signature Mk 2 is much more than it appears to be." "When was the last time a stereo amp used 16 6550C output tubes to deliver a mere 100 watts per channel? The six driver tubes are common: one 12AX7, one 12AU7 and one 6922 per channel." The output transformers "weigh 27 pounds each and could be used in amplifiers that output much more power than the JL2 Signature Mk 2."

Use "CAT recommends adjusting new tubes for two weeks after they are installed and then never again. The reason for this is spelled out in the manual: 'The bias will go slowly down as the tubes get older and are used,' and 'older tubes sound better at a lower bias current.'"

Value "In the end, your budget may play the biggest role when it comes to choosing among these three amps -- the gap between $9995 and $32,800 is a canyon to be sure. But in the middle sits the JL2 Signature Mk 2, and in important ways it is the best amp of the three."

Article written by Marc Mickelson

Source Soundstage online Magazine