Krell Solo 575 monoblock power amplifier Page 2

Also immediately obvious was less air on top than with the darTZeels, and a narrower soundstage that concentrated more of the orchestra between the speakers instead of spreading it out past their outer side panels. I'm not sure how this is possible with monoblocks; perhaps it had something to do with the Krells' somewhat less generous top-end extension.

The overall sound was definitely drier than the darTZeels, but this was still at the very beginning of my listening. I decided to stop analyzing and instead just listen for pleasure—the way I used to before this became a job—to find out if my auditory pleasure zones would, over time, connect with the sound of my system as driven by the Krells: something that did not happen with the Bricasti Design M28 monoblocks ($30,000/pair).

I pulled out some of the many thousands of LPs I have that have never been played. One was a still-sealed copy of Music of Lodovico Giustini, Volume I, Performed on the 1720 Cristofori Pianoforte at the Metropolitan Museum of Art by Mieczyslaw Horszowski (LP, Titanic Ti-78, footnote 1). Obscure? Yes! But here's a "harpsichord with hammers" that has no pedals and thus no pedal-actuated sustain. This perfectly quiet pressing (after an ultrasonic cleaning) of a wonderfully dry yet tactile recording, made in the museum's André Mertens Galleries for Musical Instruments, brought the performance to life in my room—and from Horszowski's perspective.

The Solo 575s and the SAT tonearm were made for that instrument's rich, powerful lower register and its paucity of sustain, which were reproduced with unflinching control and solidity. The sonic integrity seemed well maintained up and down the keyboard, and was free of electronica.

Next up were Mozart's four horn concertos, with Lowell Greer playing a valveless natural horn (made in 1987, after an 1818 original made by Raoux, in Paris), and Nicholas McGegan leading the Philharmonia Baroque Orchestra, recorded in the chapel of San Francisco's Lone Mountain College (LP, Harmonia Mundi USA HMU-7012). The recording engineer was Wilson Audio Specialties' Peter McGrath, who was then still recording in the analog domain. (He now makes digital recordings in high-resolution surround sound.) Mastering was by the late, great Doug Sax at the Mastering Lab. I didn't know either man was involved before I removed the shrink-wrap. That's part of the fun of collecting records.

Through the Krells, Greer's horn had a warm, vivid, pleasingly soft sound, its image suspended between the speakers in a soundstage of moderate depth. The other horns, woodwinds, and strings were also nicely rendered, producing an enveloping and satisfying listening experience.

I then compared an original pressing of Neil Young's On the Beach (LP, Reprise R 2180) with the reissue included in the boxed set of Young's Official Release Series Discs 5–8 (4 LPs, Reprise 535704)—initially not to test the Krells, but as part of a review of the Young set. Chris Bellman had cut the new LPs from the analog master tapes (which I saw, stacked behind the board, during a visit last year to Bernie Grundman Mastering). I focused on one of Young's most elegant melodies: "See the Sky About to Rain." It opens with a tremoloed Wurlitzer electric piano laying out the chords, followed by a pedal steel guitar in the right channel, and a thick-sounding drum kit centered behind Young's voice.

Both versions sounded better than I'd ever heard them—but that was because I hadn't heard this album in many years, during which time my system has greatly improved. What I learned was that the original pressing's richer sound came at the great expense of image precision, focus, and clarity. The reissue put all of the instruments and voices in far more precise focus, though the warmth of Young's voice in the original was now somewhat harsher. The bottom end had greater punch and precision. Though I found the reissue better focused overall, especially the drums, I could make a case for either pressing—and both demonstrated that the Solo 575 didn't produce the velvety transients and textures I expect from class-A. With both pressings, the cymbals sounded neither romantic nor soft. In fact, they were a bit crunchier than I'd expected.

Class-A with an *?
During the time when I stopped analyzing the Solo 575s and simply enjoyed the musical ride, I was always, with familiar recordings, well aware of the augmented bass wallop: The effect was always pleasurable, and produced exhilarating rhythm'n'pace. Otherwise, I was able to let go of the darTZeels' more familiar sound and fully accept that of the Krells—though I was also well aware that the Krells' sound was less refined overall. What I expect from class-A amplification—textural richness, suppleness, delicacy of attack, generous sustain, and far-as-the-ear-can-hear decays—never materialized. But the far more expensive darTZeels (151,000 Swiss francs/pair, equivalent to $157,000/pair at the time of writing) produced all of those in greater abundance.

Instead, the Solo 575s' overall attack was speedier, with less generous sustain and somewhat steeper/faster decay than through the darTZeel amps. However, those qualities better matched the Krells' punchier low-frequency personality. The Solo 575s breathed as a tightly sprung whole, producing a coherent sound from top to bottom.

I felt that, at higher SPLs, the Krells were adding a splash of hash and/or brightness, which somewhat offset the strong pluses of their tighter grip and rhythmic tautness. This was most audible with pop and rock recordings and vocals, and less so with recordings of unamplified instruments. But this characteristic wasn't to the point of being distracting or objectionable. It was audible only occasionally, and then gone. At the same time, when a recording contained very high frequencies, or a mix with a high-frequency EQ lift, those frequencies were reproduced with an unexpectedly sweet and silky quality.

The last record I played before returning to the darTZeels was an AAA reissue of Sam Rivers's Contrasts, recorded in December 1979 (LP, ECM 1162). Rivers plays soprano and tenor sax and flute, George Lewis plays a monstrous, sometimes blatty trombone, Dave Holland is on bass, and Thurman Barker plays drums and mellifluous marimba. Mention free jazz to many—even some Frank Zappa fans—and they freak out. They're hung up. Why anyone who enjoys Zappa's good-humored, nonstructured meanderings wouldn't dig Contrasts escapes me. In "Circles," Lewis blats away in the left channel, Rivers blows on soprano and Barker drums in the center, and Holland bows in the left channel. It's closely miked and pleasingly raucous. At high SPLs, the entire record produces delirious chaos.

Contrasts brought forth all of the Solo 575's strengths: punchy, woofer-gripping lows, whether from plucked or bowed bass or growling trombone; pleasingly sizzly but not overly hashy cymbal strokes; and smooth, almost silky upper highs from Rivers's flute. The sound was brash yet involving, the images large and pleasingly confrontational. The stage was somewhat narrow and not especially deep.

Swapping in the darTZeel NHB-458s and playing the heavily panned drum solo in "Zip," also from Contrasts, put the differences between the two amps in sharp focus. The darTZeels produced less bottom-end grip but more nuance. Cymbals had more sizzle and less crunch, and there was more air around Rivers's flute. The soundstage was wider and deeper, and aural images on it were more compact and better focused, though edge definition was less severe. The overall sound of the far more expensive darTZeels was more refined, in terms of both transient performance and dynamic gradations.

In short, the class-A/B darTZeels simply sounded more like class-A amps than did the Krells. Listening to the Krells, I missed what the darTZeels did best; listening to the darTZeels, I missed what the Krells did best.

Playing a long set of tunes stored in the Meridian Sooloos—all from CDs ripped at full 16-bit/44.1kHz resolution—verified the positives and negatives revealed by this comparison, though they were always complementary in ways that made me want to keep both sets of monoblocks on hand, one pair each for different types of music.

For instance, in "There'll Be Some Changes Made," from Chet Atkins and Mark Knopfler's Neck and Neck (now 25 years old . . . how can that be?), via the Krells the taut bass line more effectively tapped my toes and carried forward the tune. The darTZeels' sound was more supple, expressing greater stage depth and, especially, width, and the guitars were better separated from the reverb. The same was true with the CD-resolution file of Chuck Berry's "Rock & Roll Music": the Krells exacerbated the glare of the reverb, but startlingly clarified the piano and, especially, some of the percussive accents buried by the more-than-six-times-the-price darTZeels.

Equivocating Conclusion
In the past few years, apart from my reports in "Analog Corner," I've reviewed mostly power amplifiers. Every one of them has sounded different from all the rest, and I could happily live with some, but not others. The Bricasti M28 monoblocks, for instance, which measured as well as the Krell Solo 575s, according to JA, didn't tickle my auditory pleasure centers as much, despite the Krells' somewhat coarser overall sound.

The Solo 575 monoblocks were in my system for well over a month, and during that time I enjoyed how they drove the Wilson Alexandria XLFs, especially on the bottom. But more important—because the sound was whole from top to bottom—I found no fault with any single aspect of Krells' sound until I swapped them out for the far more expensive darTZeel NHB-458s.

The Solo 575s' taut bottom end produced always-entertaining rhythmic drive and pleasing musical flow. Their punchy but nonaggressive top end was likewise fast, and the surprisingly silky ultratop, which appeared when least expected and was always very welcome, added to the endless excitement and strong listening involvement these amps produced in me.

When I returned to the darTZeels, my system's sound was texturally more subtle overall, and in some ways more polite. Transients were more nuanced, the soundstage widened and deepened, and, particularly with classical music, I found the results more appealing—but I also happily listened to a great deal of classical music through the Krells.

If you listen mostly to classical and jazz, I recommend that you give the Solo 575s a listen—but proceed with caution. And if you listen mostly or exclusively to rock, and your speakers have good bottom-end extension, and—especially—if they thrive on lots of power and can deliver wide dynamic swings, you need to hear the Solo 575s. Just don't expect the usual buttery class-A sound: However well Krell's iBias circuit works to increase efficiency and thus decrease heat, it melts away some of that butter. Which is what left me wondering if iBias results in true class-A operation—or class-A*.

Footnote 1: In spite of its description as a pianoforte, the instrument on this recording is actually the earliest surviving instrument made by Bartolomeo Cristofori—a gravicembolo col piano e forte (harpsichord with soft and loud).—Richard Lehnert
Krell Industries, LLC
45 Connair Road
Orange, CT 06477-3650
(203) 799-9954

dave03hd's picture

You keep on bringing up your dartzeels in this interview, comparing it with the Krells. Thats like comparing a Volkswagen to a Porche, come on now! Not even a fair comparison. Personaly I think the Datzeels are overpriced because you have to handle them with such kid gloves or they will break down.

georgehifi's picture

Seeing this more and more, manufacturers under quoting the 8 ohm wattage to make the 4ohm look closer to doubling.
Krell's specified
575W at 8ohm
900W at 4ohm

Stereophile tested
625W at 8ohm
910 at 4ohm

A KSA-250 from 1991 gave
325W at 8 ohms
635W at 4 ohms
1000W at 2 ohms
Now this is almost doing the doubling act.

Cheers George

Ghagherr Withernickers's picture

Sir, and this is the reason I stay with FBP-450MCX mono blocks.

So far, seems to be all the power I'll ever need, and has already sent Watt Puppies to an early grave. (I like to listen loud), and regularly trips the LED overload warnings on my Vandersteens.

I could be tempted to go Halcro monoblocks next, though its a significant step up in price. So I'll mull over that.

I think first I might try the Yamaha NS-5000's. Love that midrange dome, materials, and 12" drivers tops it off for me.