Krell KSA-100S power amplifier:
Page 2 Further sonic improvements were brought about through use of the Purist Audio Designs System Enhancer CD and the Gryphon Exorcist. I experimented with the various speaker cables I had on hand, and found the Dunlavy D-8 to provide the best overall match. Both the Purist Colossus II and TARA RSC interconnects worked well in the system, the Purist cable sounding a bit more mellow.

The CAT SL-1 Signature preamp was Stereophile's 1993 "Product of the Year," and I had no reason to believe that combining it with the KSA-100S would be in any way problematic, but I wanted to check out how the KSA-100S would fare with its Krell-mate—the KRC. This also allowed me to compare the KSA-100S with the Bryston 7Bs at matched levels (the CAT's volume control has discrete steps that are too big for level-matching), and to evaluate the KSA-100S's unbalanced vs balanced mode of operation (the CAT is unbalanced).

The KRC turned out to be a superb preamp—every bit as good as Tom Norton said in his review, though I still prefer the CAT. Comparing the balanced vs unbalanced connection to the KSA-100S through identical lengths of TARA RSC Master, I found that the balanced connection was indeed superior, having a noticeably lower noise floor. Most of the listening involving the KRC was done through the balanced connection.

Sound
As I've already said (you didn't skip "Listening Preliminaries," did you?), my initial impression was that the KSA-100S had a rather soft sound by solid-state standards—not dull, not rolled-off, just a bit on the soft side of what I take to be neutral. This impression diminished with continued listening and changes in associated components, but it never quite went away. Compared to the Bryston 7Bs, the Krell KSA-100S had somewhat smoother, more delicate highs, but the Brystons evinced sharper focus and had more snap.

This was apparent on "Festival Day in Seville"—track 3 on Reference Recordings' HDCD sampler. Listening through the KSA-100S, everything seemed to be in its place, with good depth and with transients having clarity without edginess; but when I changed to the Bryston 7Bs, the sonic picture was further cleaned up—as if a haze that I hadn't previously noticed had been wiped away. The bass drum on track 1 (the first movement of Nelhybel's Trittico) seemed very deep and firm through the Krell, but was deeper and firmer through the Brystons.

Mark Levinson's (the man's) recording of Bach's Sch&3252;bler Chorales (Cello Acoustic Recordings, Vol. I) was less forward through the Krell, but this was not an advantage on this recording; the Brystons reproduced the organ's sonority with more authority, and the ambience of the recording site was more present. With this recording, I also found the sound to be subjectively louder through the Brystons, even with the levels matched and the Brystons' output set a hair lower. (Neither amp was anywhere near its maximum output; the KSA-100S had only the lowest-level bias indicators lit.) The Krell's dynamics were again bettered by the Bryston monoblocks. The many percussive sounds of the All Star Percussion Ensemble (Golden String GS CD 005) had lots of clarity and detail through the Krell; but the Brystons, while sounding just a bit on the brash side here, had more get-up-and-go.

Switching back and forth between the two amps, using the CAT SL-1 Signature or the KRC, with levels precisely matched, I had the persistent feeling that the Krell KSA-100S, while not deficient or lacking in any obvious respect, was edged out by the Bryston 7Bs in communicating the excitement of music that's high in rhythm and dynamics (footnote 2).

The KSA-100S came more into its own in its depiction of midrange timbre, especially voices. These tended to sound a bit too forward via the Brystons, especially with recordings that are already on the rough (read, digital-sounding) side. The otherwise fine studio recording of Candide (Deutsche Grammophon 429 734-2) gets somewhat fierce in the climaxes; the choral tutti (as on disc 1, track 8) were definitely easier to listen to through the Krell than through the Brystons. Voices—eg, Jerry Hadley's "It Must Be So" in Candide—tended to have a more "rounded" quality, somewhat reminiscent of tube amps—although not, I hasten to say, to the degree that would fully satisfy hardened tubeophiles. Neither amp scores particularly high on the "forgivingness" scale, but I'd put the Krell ahead of the Brystons. The Dunlavy SC-IVs have a tonal neutrality that's unequaled in my experience, and with speakers (and other components) that are further toward the bright side (footnote 3), the Krell's relative softness/forgivingness is likely to be more of an asset.

KSA-100S vs KSA-300S
When I finished listening to the KSA-100S in the context of my own system, I shipped the unit to Santa Fe for measurements. A couple weeks later I was off to Santa Fe myself, to participate in the latest set of loudspeaker listening tests, reported on last month (Vol.17 No.8). After the loudspeaker listening tests were concluded (and, for me, not a moment too soon), I spent a day in Tom Norton's listening room, comparing the KSA-100S with the previously reviewed '300S. The system consisted of an Accuphase DP-65 CD player, Krell KRC, and a pair of Energy Veritas v2.8 speakers, with TARA Labs RSC Master and Monster M-1500 interconnects and tri-wire Monster M-1.5 speaker cables. The power amps, both of which had been on for several days, were operated in the balanced configuration.

One of my reservations about the KSA-100S had been about what I felt to be its somewhat restrained sense of dynamics; this was an aspect of its performance that I particularly wanted to compare with the '300S. As the Energy Veritas v2.8 has reasonably high sensitivity (about 86dB) and does not present a difficult load, it was a good speaker to use in this comparison. I wanted to make sure that the KSA-100S would not be working near its power limit, so the highest level I used lit only the third set of LEDs, which measured about 93dB (Radio Shack meter, C-weighted) at the listening position. All critical comparisons were done with levels matched.

In casual listening, the amps evinced an obvious family resemblance, being easy on the ears and having little of solid state's typical edginess. However, in matched-level comparisons, the differences that emerged were not trivial. The KSA-300S was simply more dynamic, with a more rhythmic quality, but with none of the added roughness that often characterizes high-powered amps. The first track of Mickey Hart's Planet Drum (Rykodisc RCD-10206) came across with much more weight and authority; I had greater difficulty keeping my toes from tapping.

Bass fundamentals were firmer and apparently deeper. The opening of Turandot (London 414 274-2) was similarly more exciting through the KSA-300S, voices having more body and being more sharply focused in the soundstage. (Remember: each amp was set to operate at the same level, well within its power limits.) The All-Star Percussion Ensemble's version of the Scherzo from Beethoven's Symphony 9 seemed quicker, and instruments within the soundfield were more clearly defined. The greater precision of depth and imaging was also apparent while listening to "Make Our Garden Grow," track 8 on Testament (Reference RR-49CD, footnote 4). Many people believe that, as long as they're not driven into clipping, lower-powered amps tend to sound better than higher-powered ones. That may be so in some amplifier lines, but I didn't find it to be the case with these two Krells.

Conclusion
The KSA-100S, built with legendary Krell attention to construction quality and able to drive difficult loads, is undoubtedly a highly competent amplifier. Its sonic personality is slightly on the soft, forgiving side, which usefully minimized the hardness of many digital recordings. If past experience with Krell products is anything to go by, the KSA-100S is likely to be highly reliable, and will maintain a higher-than-usual proportion of its resale value if (when?) its owner decides to move further upmarket.

I would have liked to have been able to conclude this review by advising would-be KSA-300S owners to save $4000 by purchasing the KSA-100S and still get essentially the same sound. Unfortunately, I can't. Although I could be quite content listening to a system featuring the KSA-100S, I found that, in specific comparisons, the KSA-100S was decisively bettered by its senior sibling. With each amp operating well within its power envelope, the '300S offered a more dynamic, more rhythmically involving sound, with greater clarity and better bass definition. If you want the sound that TJN praised so highly in his review of the KSA-300S, you just have to shell out the big bucks.

However, there is—as Yoda said—another. In extensive matched-level comparisons, I found that the Bryston 7B monoblocks plumbed the nether regions with greater ability, and offered a generally more dynamic, exciting sound than the KSA-100S, albeit at the cost of an occasional touch of brashness. I wasn't able to directly compare the KSA-300S to the Bryston 7Bs, but I'd go for the KSA-300S if I had a very generous amplifier budget. With a somewhat less generous amplifier budget—say, about $5000—the choice is less clear-cut.

The Brystons are well-built (if not to Krell standards), cost about 20% less than the '100S ($4390 vs $5500), and, in the series mode, offer substantially more power. Given my tastes and the components currently in my system, I'd choose the Bryston 7Bs. But the Krell KSA-100S remains a worthy contender, especially for systems that are on the borderline of being too bright.

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Footnote 2: I noted this slight lack of dynamic drive in my own auditioning of the KSA-100S, performed before I read RD's report. I felt it primarily to be a function of the amplifier's having a rather lightweight bass register, something I found surprising in view of the reputation of earlier Krell amplifiers for visceral low frequencies.—John Atkinson

Footnote 3: Maybe Obi-wan Kenobe should have said to Luke Skywalker, "Beware the bright side."

Footnote 4: The recording quality is first-rate, but the Turtle Creek Chorale's performance of one of the most moving songs Bernstein has written illustrates everything I hate about choral arrangements of Show music.