Tube Power Amp Reviews

Hookup is straightforward, with a single-ended RCA jack input and two pairs of hefty, custom-made, nicely machined speaker terminals (though it appears that only one tap is available from the output transformer). Flip the on/off switch and a red front-panel LED signals warm-up. Within a few minutes of turn-on, the unit reaches operating temperature and the LED changes color from red to green. The amp's sound begins to "develop" after about an hour's warm-up. There's also a three-position input-sensitivity knob that one should not turn with power on. How nice it would have been to have been told that in advance! When I switched sensitivity with the power on, the woofers got sucked in with a "pop" that had me thinking "meltdown." Fortunately no damage occurred.

What Sound!!!
Given what I'd heard at CES, I was not at all surprised by what I heard in my system: the VT8000 MK's overall sonic performance was remarkable by any standard—tube, transistor, whatever.

With just its two output devices, the amplifier appeared to deliver prodigious amounts of ultra-clean, voluptuous-sounding power. True to its hybrid heritage, the sound was neither "solid-state" nor "tubey." That could mean the worst of both worlds: bright and edgy highs, sterile mids, and wimpy, rubbery bass. Instead, the VT8000 combined the midrange richness, purity, and warmth of good tube design with the bass dynamics, extension, and control of the better solid-state amplifiers—and all of this with just two vacuum-tube output devices per channel!

A big "wow" popped out of my mouth the first time I heard these amps performing in my system. For one thing, I realized immediately that I'd never heard the Virgos render a kickdrum as convincingly as they did driven by the VT8000s. It was interesting switching between the Ayre V-1, the Mark Levinson No.335, and the VT8000s. On Alice In Chains' Unplugged—on CD or imported vinyl—the Levinson's kickdrum sound was iron-fisted and rhythmically taut, but somewhat dry and "skin-shy." The Ayre's delivery, while richer and somewhat more involving, with better "skin sense," fell short in rhythmic drive and control. The VT8000's rendering was real, with incredible authority and "slam." You could carve that kickdrum with a knife, so palpable and solid was the picture.

The VT8000's most enduring and important virtue was this incredible solidity, which extended all the way up the frequency band. Everything—from that kickdrum to voices, strings, and percussion—had an equally persuasive solidity, and not at the price of "thickness" or stodginess. Cymbals chimed and shimmered, but also had compelling body and realistic transient attack. Strings had a sweet, silky-smooth quality, but the bodies of the instruments never took a back seat. The sonic picture possessed a meaty, undeniable physicality that was more lifelike than anything I'd heard in my system. This two-output-device amp was a powerhouse!

Luscious mids; highs that were sweet yet extended, airy, and transparent; deep, powerful bass—the VT8000's top-to-bottom frequency balance was as invisibly smooth and extended as I've heard from any amplifier, tube or solid-state—and so musically involving! Though not an all-tube design, the VT8000 gave up nothing in terms of tonal richness to either the VTL MB-450 or the Conrad-Johnson Premier 12.

Nothing in the sound hinted at the solid-state input and driver stages. In fact, the VT8000 combined the big, warm, spacious sound of the 450 with the C-J's "fast," organized picture—minus a bit of the C-J's alluring upper-midrange "glow." The VT8000 is the most neutral amplifier I've had in my system. I couldn't pin a tonal flavor on it.

That's one reason it seemed to catch the timbral and textural essence of every kind of instrument with greater authority than I've ever heard at home. I played the extraordinarily fine-sounding Clarinet Summit LP (India Navigation IN 1062) for a manufacturer who plays the instrument. (That will give it away for some readers.) His reaction told me that he knew the recording, and that the system was "getting" the instrument remarkably right.

The VT8000 produced everything I loved about the original Cary CAD-805 I had in-house for a long-term audition—that ultra purity, delicacy, and harmonic richness—and added what the original 805 couldn't do: the kind of deep, tight bass that does pop and rock without apologies. Perhaps the KR monoblocks fell a bit short when compared with the midrange purity, palpability, and transparency confreed on the Cary by its 300B driver/211 output combo, but with the VT8000 you give up very little in the middle and get so much more at the extremes. And in terms of "slam" and power reserves, there's no comparison.

Classic Records' 45rpm LPs offer spectacular dynamics. I pushed the VT8000 on the Reiner/CSO recording of Mussorgsky's Pictures at an Exhibition, and they didn't run out of steam on the steepest peaks at convincing orchestral volumes. When I moved to my new, larger room, I used the Pictures 45 to repeat the full-court press on the amp. There was plenty of power in reserve; the VT8000 seemed to swing enough current to scale the most challenging orchestral crescendos without strain. These amps will throw you back in your seat every time.

During the many months I had the VT8000s in my system, driving the Audio Physic Virgos and later the Sonus Faber Amati Homages at high volumes, the single pair of tubes never sounded as though they were clipping—not on Led Zeppelin, not on the Ramones. (Rhino's new Ramones anthology is a "must have.")

BIG Soundstage, 3-D Imaging
What particularly struck most listeners who heard the VT8000s at CES was the size of their soundstage, despite the small room size. That proved true in my small room as well. The amps delivered a VTL 450–sized soundstage—appropriately wide, tall, and deep, with outstanding focus to the outer edges, and images commensurate with the stage size. The picture was big, and just as remarkably "there" as it had been in that shoebox of a room at CES.

On Piano in the Background (Columbia CS 8346), a spectacular-sounding Duke Ellington LP multi-miked in the old cavernous 30th Street studio, each cluster of instruments was clearly discernible and separated in space. The reed section—way behind the left speaker in the corner—was impressively well focused, with each instrument well delineated physically, as well as tonally and texturally.

The VT 8000'S delivery of neutral musical truth and purity was unmatched in my listening experience. My ears just wanted to sink into the music, and that's what I did, hour after hour, as long as the amps were in my system. I never felt they were warming things over or getting etchy, yet they sounded sweet and rich and "fast" at both the bottom and top of the dynamic scale. And they didn't change character when I changed level—they sounded equally good played loud or soft. An all-around major-league balancing act.

I heard much less loudspeaker and much more music through the VT8000s than through any other amplifier I've ever had in my system. They were equally impressive with the Virgos and with the Amati Homages—both sounded their best driven by the VT8000s, and the Amati/VT8000 combo was so seductive, so rich, so detailed and physically present, it was sick! Given that the combo costs almost $50k, it damn well oughta sound good!

Negatives?
I suppose some listeners—especially those who listen exclusively to acoustic music—will still prefer an all-tube design, perhaps single-ended. The VT8000 might not equal the midrange delicacy and purity of some single-ended tube amps, and "romantic" they're not, though they do sound rich throughout the audio band, and are as free of sonic nasties as any amp I've heard: no grain, glare, etchiness, edge, "ripeness," compression, midbass "lumpiness," etc.

Dr. Kron warned me of a problem for some potential users. The VT8000 has one unique characteristic that makes it impossible to use in a bi-amped system: the vacuum transducer supposedly creates a minute delay, which means if you split the signal and run the bass to a subwoofer, it will be noticeably ahead of the VT8000s. [This I find questionable.—Ed.] This will not be a problem running a speaker full-range, or when using the Audio Physic Rhea subwoofer, which derives its signal from the amplifier's output taps (ie, the signal is already delayed). I used no subwoofer for the review, of course, but the VT8000's bass response was so powerful and solid, I often thought the Rhea was active when it wasn't.

Another negative is the price: $25,000 is a hideous amount to pay for a pair of amplifiers, and as much as there's more there there sonically, physically the VT8000s seem overpriced. If a heatsink module containing a replacement pair of tubes costs $1000, or even were it to cost $2000, where's the other $12,000? Especially since the VT6000, a very similar design with approximately two-thirds the output, sells for an affordable (!?) $9200/pair. It's a free market, after all, and Dr. Kron is convinced he's got something unique and better than anything else, and that $25,000 is a price the market presumably will bear. For those for whom money isn't a major consideration, I'm confident Dr. Kron will be proven correct. Once you hear these amplifiers, you'll want them.

Baggage Claims
Here's something anyone thinking about buying these amps must consider: It's one thing to buy a vacuum-tube amplifier from a small company when the tubes are available from a variety of manufacturers. But Dr. Kron's "vacuum transducers" are available only from his own Prague-based firm, KR Enterprise. If, God forbid, the company went under and a tube failed, then what? You'd have a $25,000 pair of boat anchors.

This is not to suggest I have any evidence that the company isn't financially healthy or well funded. In fact, when I visited KR Enterprise in the summer of 1999, the factory was humming—and in Dr. Kron and his wife, it seemed to be in dedicated, competent, if decidedly eccentric hands.

Those with the resources to spend $25,000 on a pair of amplifiers, should probably buy a few more pairs of replacement output modules, just in case.

The other issue for American customers is the lack of a formal distributor. The Krons tell me that KR Enterprise has established long-term stable relationships with distributors around the world, but they've had a few problems in America. As a result, KR is now working directly with a small number of American dealers.

Conclusion
It will be interesting to read how these unusual brutes actually measure, but I'd be very surprised to find that the VT8000 MK monoblock doesn't perform well overall. Whatever the numbers show, the actual performance of these amplifiers suggests that the claimed specs are correct. That a pair of vacuum-tube devices can actually deliver that kind of power, and so cleanly and effortlessly, is amazing.

During my many months of listening to the VT8000s, no matter what I threw at them, they sailed along and delivered the most convincing, captivating musical performance I have ever heard in my system—or in anyone else's, for that matter. Tonally, dynamically, spatially, harmonically, rhythmically—whatever criterion you want to apply—the VT8000s' overall performance set new standards for the reproduction of music in my system. I have enough faith in the company to buy the product. Meanwhile, if you can afford the VT8000s and have an opportunity to hear them, do. You'll be impressed.

Editor's Note: Given the disparity between the auditioning comments and the VT8000's measured performance, Stereophile must withhold an unconditional recommendation for this amplifier until we have tried a sample that conforms to its specification.