Krell KSA-250 power amplifier More Comparisons

John Atkinson compared the KSA-250 with the Mark Levinson No.23.5 in September 1991 (Vol.14 No.9):

My second comparison of the Mark Levinson No.23.5 was performed with the obvious head-to-head competitor for the $5900 No.23.5, the $5900 Krell KSA-250. While each ranks among the finest solid-state amplifiers I have used, they still differed significantly in their sonic characters, meaning that a system set up optimally for one would need some adjustment to get the best from the other.

In a nutshell, the Krell was less upfront in its midrange balance than the Levinson, sounding slightly "slower" and less vivid overall. It was also softer in both the upper bass and extreme highs, and presented a deeper soundstage. The Steinway piano on Stereophile's Intermezzo album was distinctly set more forward in the soundstage via the No.23.5 when compared with the KSA-250, with slightly less of a sense of the surrounding space. Microphone hiss was also a little more obtrusive in the top octave as presented by the Levinson. The Krell didn't quite achieve the dynamic contrast offered by the Levinson, however, nor was the piano's left-hand register quite as well defined. It would be a hard call deciding which amplifier was a better match for the Wilson WATTs and Puppies, the Krell offering a better balance overall but losing out to the Mark Levinson from the upper bass on down.—John Atkinson

Thomas J. Norton compared the KSA-250 with the Bryston 7B in December 1993 (Vol.16 No.12):

With analog program material (the above observations were made with Compact Disc as a source) the picture changed rather significantly. Much of the Bryston 7B's excess warmth dried up. This was a rather surprising observation, inasmuch as analog is often credited with being warmer-sounding than digital. My experience with a Clavis cartridge—a close relative to the more expensive Parnassus in the present system—does indicate, however, that this family of cartridges tilts more to the lean and tight than to the rich and full. As I am still scoping out the sound of the analog front-end used here, it's a bit early to totally pin down its inherent sound, but in fairness I cannot ignore the fact that the 7Bs definitely sounded lighter on their feet with this particular analog front-end.

I used the digital front-end for the remainder of the evaluation because I am more familiar with its performance. The C.E.C./Levinson is a first-rate combination, but the C.E.C. transport is also slightly rich rather than analytical. A brief trial of the setup with the yet-to-be-reviewed California Audio Labs Delta transport did indicate a slightly cooler sound with the latter, though with a slight but noticeable sacrifice to that three-dimensional, grainless midrange heard with the C.E.C.

To settle the matter—if not once and for all, then at least to my present satisfaction—I pulled out our Krell KSA-250 for a side-by-side comparison with the Bryston 7Bs. This particular Krell model was discontinued earlier this year, but it's a Class A (and class-A) amp with which I have had a great deal of experience. The listening room took on a toastier ambience with the KSA cooking on all burners (the Brystons, unlike the Krell, run relatively cool), but I proceeded with the comparison regardless. Somebody had to do it, and all that.

I began with unbalanced inputs to both amplifiers, and the Brystons still in the parallel mode. With the Krell, the sound tightened noticeably. It was not quite as sweet-sounding overall as the Brystons, but was in no way lean'n'mean, either. The Krell's bottom end was tighter and more detailed, its potency a bit less obvious than that of the Brystons, but certainly not seriously lacking in that respect. "Man in the Oven" on the Krell definitely had a more defined, transparent quality, with a less warm but better focused acoustic bass. The extra warmth of the Brystons added a welcome warmth to the vocal, however, pulling it slightly more forward and imparting immediacy. The Bryston did display a touch of occasional brightness in the low treble here. This hadn't been evident when I auditioned it alone, but it was audible next to the more laid-back Krell. This was quite minor, however.

On the strikingly recorded "Under the Boardwalk" from Rickie Lee Jones's Girl at Her Volcano (WEA International WPCP-3710)—which is an early RLJ album that's not, to my knowledge, generally available on CD in this country—the Bryston brought a good sense of space and openness with its characteristically clean top end. The vocals were solidly set in space, both in width and depth. The sound was very dynamic and slightly forward, which suits this music perfectly. The bottom end here had solidity and drive. Only a slight hardness was noted at the conclusion.

Surprisingly—based on my experience with the two amplifiers to that point—the Krell only finished a strong second here, with the lead-in voices less spacious and differentiated, the highs a bit drier and less clean. The bottom end on the Krell, as before, remained tighter and leaner than that of the Brystons. This tended to open up the overall sound somewhat, but the bigger bottom end of the 7B was put to good use on this recording. Both amplifiers turned in first-rate performances here, but the Brystons took the checkered flag.

Overall, however, the balance of strengths on the WATTs/Puppies slightly favored the Krell, particularly with its more tightly controlled—if not always as big or impressive—bass. But the strengths of the Brystons continued to impress, and they presented a strong challenge to the more expensive Krell.

To gain an additional perspective on the 7Bs' performance, I also auditioned them driving a pair of Acarian Alón IVs. The Alóns, still in their break-in stage, were less neutral through the midband and a bit more potent in the deep bass than the Wilson WATTs/Puppies. They also had a less finely rendered (though still very good) soundstage, and, I felt, a smoother though no less detailed top end. The Alóns are considerably less pricey than the Wilsons, though hardly cheap, and are more likely to be found at home in a system with the comparably priced Brystons.

My observations on the 7Bs through the Alóns were little different. The Brystons remained in the parallel mode. Their top-end response was still clean and detailed, yet at the same time silky and sweet. That bloom to the midrange remained. Imaging was excellent, though the Alóns were, as I noted above, a bit less holographic than the Wilsons, particularly in defining front-to-back-depth. The Brystons' slight lack of top-end air and more obvious low-end softness remained.

My notes comparing the Bryston 7Bs (still in parallel) with the Krell KSA-250, this time on the Alón IVs, also look like near copies of my earlier notes with the WATTs/Puppies. The Krell continued to have the less rich, more open sound. On the Rickie Lee Jones "On the Boardwalk" cut, the Krell came out ahead. At the very beginning of the piece, there is a hard-to-identify sound in the far background. On the Krell, it was more sharply defined, and while I still could not make out exactly what it was, it sounded like a young child saying something that prompts a chuckle from one of the musicians. With the Brystons it was still audible, but less clearly focused. The Krell also gave a more immediate sense of the recording space.

Listening to both the Krell and the Brystons with a balanced connection, I initially thought that the Brystons, if anything, were now a bit softer and looser—not a plus. But further listening indicated that the sound was essentially similar to that with the unbalanced link, consistent with my ongoing observations about balanced vs unbalanced connections when used for short runs in home audio. In another environment, perhaps, balanced operation might make more of a difference.—Thomas J. Norton

Thomas J. Norton compared the KSA-250 with the Krell KSA-300S in October 1994 (Vol.17 No.10):

I could tell something special was happening in my system, but the KSA-300S must be compared with its peers to really tell the whole story. Fortunately, a late-production KSA-250—Krell's predecessor to the KSA-300S as their top-of-the-line stereo power amplifier—was available. Indeed, the KSA-250 is the amplifier I've used most frequently over the past several months—I know its sound pretty well. Though out of production, the 250 remains a formidable performer, and, given the current state of amplifier design, I would not expect any new amplifier to better it by a dramatic margin. But though it held its own against the new KSA-300S in a closely matched comparison (at equalized levels), the new amplifier was the winner in all respects save one. The 300S is richer and more full-bodied through mid- to upper bass, less laid-back and more timbrally right. The older amp is leaner and less palpably real—even slightly threadbare—in comparison.

Initially, however, the KSA-250's leaner sound gave an impression of a bit more openness and spaciousness; a leaner tonal quality will often produce this effect. (This is one reason why producing a good, big loudspeaker with extended bass and a clean, open top is such a delicate balancing act; the same is true, though generally to a far lesser degree, of electronics.) On vocals, the 300S's fuller sound clearly won out; the performers simply sounded more human, more touchable, less electronic. Voices on the 250 were breathier, more sibilant, less fleshed-out. A slight fizziness in the top of the 250's audible range simply was not a factor with the 300S. The latter was simply at ease with everything—a powerful presence, yet at the same time subtle, refined, and self-effacing.

Again, Rickie Lee Jones's "On the Boardwalk" clearly displayed the differences between the two amplifiers. As the music began, quietly and slowly, the 250 initially appeared airier and more open. As it progressed, the 300S's smoother, more grain-free sound took over, the 250 now seeming a bit lean and etched in comparison. The 300S had more punch and weight, especially through the midbass, and a more fluid, coherent sound overall. Both amplifiers impressed equally in the deep bass. The 250's relative leanness gave it a more superficially open quality, but at the cost of richness and a fully developed sense of weight and drive. The KSA-250 is still a very fine unit. But it has more than met its match in the 300S.—Thomas J. Norton

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