Krell Evolution Preamp and Amplifier

Equipment report
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Solid-state power amplifiers
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Krell Evolution
Krell Evolution Preamp and Amplifier

There is a level of excellence at which conventional words about quality and cost-effectiveness become meaningless. Like the very best cars, watches, and wines, and every other assault on the consumer state of the art that you can actually buy, price ceases to be an object. You choose because it is a personal passion—if not an obsession—and because you are lucky enough to be one of the handful of people who really can afford the very best.

The Krell Evolution preamp and amplifier are cases in point. If all you wanted was very good, or even excellent amplification, you could buy a Krell 400Xi integrated amplifier at a tiny fraction of the price. The Krell Evolution Two monaural preamp costs $40,000 for a stereo pair, and the Evolution One 450-watt monaural amplifier costs $50,000 a pair. At their prices, you reach a point of diminishing returns in dollars-for-sound-quality that borders on madness.

It is, however, a fine madness. In fact, it is glorious excess! The Krell Evolution series is some of the finest audio equipment ever made—as it virtually must be at the price. It is almost faultless in terms of performance, appearance, and the sheer joy of listening.

In saying this, I am not trying to imply that the Krell Evolution preamp and amplifier will suit everyone’s taste. Anyone who is truly familiar with the high end knows that the real issue is not whether all preamplifiers and amplifiers sound alike, or even which sounds “best.” It is rather how different their nuances can be, and how important it is to find the precise mix that suits your ear and taste.

We talk a lot about musical accuracy and absolutes in The Absolute Sound. We place an almost ritual emphasis on listening to live music as a standard. The truth is, however, that no two reviewers share the same taste or define absolutes the same way. We all do share a common joy in music, but no one who reads the magazine with any frequency can believe we share the same musical taste.

Moreover, as someone who travels to some twenty to thirty countries a year, I have heard live music sound so different in so many places, and the sonic nuances of a given performance shift so much in character as I move through the performance area, that I am not about to designate one mix of sound characteristics as a standard. Anyone who believes that there is one such standard for the sound of live music has led an amazing sheltered and musically narrow life. Even if the illusion of electronic reproduction could be perfect—and it can’t— the issue of which musical reality a given audiophile prefers would still be a matter of personal experience and taste.

In short, if you have heard the sound of Krell electronics before, and have preferred the sound from a different type of electronics, or the sound character and “voicing” of a different designer or manufacturer, listening to the Krell Evolution series may not change your mind. I would, however, still look on the review that follows as little more than a petty appetizer—the audio equivalent of an amuse bouche—and make a real effort to listen to this set of Krell gear.

This does not mean that the Krell Evolution Two preamplifier and Krell Evolution One amplifier are some kind of radical sonic breakthrough; the Krell Evolution series lives up to its name. I have always found Krell to produce some of the most musically realistic electronics available, and I have heard Krell equipment evolve since the first Krell amplifier was put on the market. With only one or two exceptions, each new design has been a step forward on a continuing journey.

The best aspects of the original Krell sound-character and “voicing” have always been preserved, but the original virtues of deep-bass power and rich natural timbre have been steadily enhanced, while air, life, microdynamics, soundstage depth and detail, and the upper octaves have improved to contenders for the state-of-the-art. The Krell Evolution Two and Krell Evolution One do push the envelope significantly further than any previous advances in the Krell line, but they still are evolutions not revolutions. As HP pointed out long ago in the early issues of TAS, the high end is about nuance not absolutes. This is even truer today. If it isn’t at least very goodand very reliable over time, a product is at most worth about a three-sentence dismissal. Any manufacturer who can’t meet those tests should be driven out of business. The standards of the rest of the industry are simply too high.

At the very top, however, nuances get harder and harder to describe without ending with a long chain of superlatives, nitpicking the product for reasons based on the reviewer’s personal taste, or simply trying to force an artificial degree of balance and “objectivity” into the review. Words are not sounds, and the issue is sounds and not words. Moreover, the problem of separating the nuances of the electronics from factors like source material, front end, speakers, and room also get to be more difficult.

I used the Evolution One and Two with a wide range of DVD and CD players, a range of cartridges and head amps, and in two listening rooms. I used it with the new Krell LAT-1000 speaker, the TAD-1, the Thiel CS7.2, and briefly with a pair of Quad ESL 989s. I used a variety of cables, including Discovery, Kimber, Wireworld, and Transparent Audio.

The fact is that all the speakers and other active components I used were more colored than the Krells, as were my listening rooms. This gear is good enough to tell you much more about the production problems and values in source material than about its own limits. I could prattle on about how well it did with various individual recordings, but it all adds up to the same message: The Krells caught out the source material; the source material did not catch out the Krells.

But let’s give words a try. The preamp and amp match each other exactly in sound character, and the result is as intensely musical as the source material and the rest of the system permits. With the best material it provides something approaching the level of detail you actually get in a live performance in a great hall. The kind of detail that never calls attention to itself unless you really listen, but adds a sense of dimension, life, and air that is impossible without it.

Equally important, this detail comes without any exaggeration of the upper octaves, “etching” and hardening of the musical material, or acoustic games that emphasize apparent detail at the expense of slightly reducing the dynamic energy and life of the lower midrange and upper bass. The Evolution preamp and amplifier are not tweaked or “voiced” for detail freaks, they are designed for music.

As is the case with many of today’s best high-powered amplifiers, the Krell Evolution One provides an amazing amount of musical life and detail. If your speakers can really use power effectively, and without distorting, the Krell gives you realistic dynamics from the softest possible passages to the loudest.

Microdynamics and macrodynamics are truly excellent, with as much air and natural sweep as the recording allows. There is no hint of polite compression or of a loss of power at any listening volume I can stand, and performance at enjoyable listening levels is effortless. This mix of timbre, detail, and dynamics is sometimes called tubelike. Solid-staters tout it as “Class A” sound. In practice, it is extremely rare in either the best tube amps or Class A designs. I didn’t have a convenient assortment of the world’s best tube and Class A gear to compare the Krell Evolution to in some kind of acoustic shootout, but the Evolutions were superb, and if acoustic memory serves me well, even the best tube and transistor gear I’ve auditioned over the last two years did not reach this standard. I’m not a great fan of mentioning how equipment interacts with individual recordings; the end result is too random and case-specific. I review as much on performance with mediocre and bad recordings as good ones—the best performances far too often are not of audiophile quality and the music with the best audiophile quality is often boringto- irritating.

It may be worth noting, however, that the nuances of the consistently natural recording techniques used on the Chesky label did come through as clearly as I have yet heard them. So did the quality of Telarc’s most recent work on SACD. (Try the Kunzel and Cincinnati Pops Orchestra recording of Hanson’s music and the Järvi and Cincinnati Symphony playing Dvorak and Martinu. Not my favorite music, but excellent recordings per se.) The Evolution series is also, however, mercilessly revealing of the many problems in most SACD players. (I found the McIntosh MVP861 to be distinctly freer of the dynamic constraints and subliminal “noise” than the Sony SACD and other low-to-midpriced players I have heard, but I have scarcely performed a survey of the latest competitors for the state-of-the-art.)

The Krells also did an exceptional job with slightly bright and hard, but otherwise excellent recordings, such as the L’Archibudelli & Smithsonian Chamber Players recording of the Mendelssohn Octet for Strings [Sony Vivarte]. The instruments actually sounded like the eight Stradivarius instruments they really are. Given the almost uniform close-miking and/or brightness of most recordings, this is a true blessing. It is even a greater blessing on more natural, simple jazz and chamber music of the kind that can actually sound realistic in a home listening environment.


If you are into very complex and dynamic musical material, this equipment is equally impressive. This is true even with musical “worst cases.” The Evolution series does as much as any electronics can to make Wagner’s exciting moments excuse those interminable dull half hours between them. It sorted out the climaxes on my recordings of Saint-Saëns Symphony No. 3 better than any competing electronics to date. (The climax tends to sound like a series of semi collisions on a busy freeway, even when played live in a large church.) It also made as much sense out of Mahler’s Eighth as this particular ego trip full of overblown music permits. The quality of the Ozawa/Boston Symphony Orchestra recording on Philips was particularly striking. Bass performance is one hell of a trip, although it may be a bit controversial. I’ve heard several other designers criticize “Krell bass” in the past. Some argue that the deep bass is somehow tweaked or exaggerated a bit. Dan D’Agostino notes, “I’ve always believed in designing the most neutral amplifiers possible. To that end, I believe that to accurately reproduce the lowest bass frequencies requires large amounts of power. The Evolution One is the ultimate realization of this design philosophy. In the dynamic contest between the speaker and the amplifier, large amounts of power also allow the amplifier to ultimately control the loudspeaker, not only to make it ‘go’ to produce the sounds, but also to make it start and stop quickly…[It] is not ‘Krell bass’ per se, but rather the flawless execution of a fundamental design principle. The listeners hear exactly what is on the recording.”

Whether any outside criticism is ultimately an exercise in righteousness or jealousy I leave to the reader. Speaking for myself, I have no doubt that the Evolution One and Two have some of the most detailed, quick, and powerful deep bass I have ever heard. What I hear is exceptionally musically natural—not exaggerated in any way— and the Evolution One does the best job of driving my reference TAD-1s and Thiel CS7.2s to get every last bit of deep bass from organ, drum, and electronic instruments that I have yet heard. If the deep bass is really there, the Evolutions will make you feel it, both viscerally and aesthetically.

As for soundstage, I can see some audiophiles complaining about soundstage width for the same reason they feel the Krells do not provide enough upper-octave energy and detail. Wide soundstages have become almost a fetish in some high-end circles—all music must be recorded in the musician’s armpit and listened to in Row A. The end result, however, is both over-bright and two-dimensional. It smacks more of hearing damaged by too many loud concerts and listening sessions to sonic spectaculars at room-blasting levels. It simply isn’t music.

Like the best Conrad-Johnson gear, the Krell Evolution series puts the third dimension back in music by providing exceptional depth. It also provides exceptional reproduction of hall sounds and musical mechanics—bowing sounds, score rustling, etc.—when these are on the recording (great for live and natural recordings). This effect is enhanced by the imaging qualities of both the Evolution One and Two. They can’t fix the oftenstrange musical images that emerge even in good recordings, but when the imaging is natural and detailed, the Evolution Series components preserve the size, the place, the stability, and the layers of imaging. The result is a more open soundstage, better reproduction of life and air, and a greater ability to lose yourself in the music.

As for compatibility, I should note that the combination of the Evolution One and Two and the new Krell LAT- 1000 (review forthcoming) produced an impressive synergy with a slightly warm, mid-hall mix of timbre and soundstage characteristics that suited a very wide range of material. The Evolution One also did exceptionally well in driving my TAD-1s and Thiel CS7.2s with a wide range of speaker cables, getting the best in terms of power, control, and definition out of each speaker. I did not encounter any problems in terms of interconnects when I used a variety of balanced and single-ended cables instead of CAST cables. The Evolution One and Two were very revealing of the strengths and weaknesses of all my reference “wires,” although I should note that Kimber Select cables performed exceptionally well with both pieces of electronics. If I have any caveat about compatibility, it is that I would not use the Evolution One and Two with a warm, dull speaker with rolled-off highs. Quite frankly, I can’t think of any good electronics I’d use with such a speaker or why anyone would conceive of using state-of-the-art electronics with some idiosyncratic candidate for the audio rubbish heap.