Krell KSA-100S power amplifier John Atkinson Compares

John Atkinson compared the KSA-100S with the KSA-50S in August 1995 (Vol.18 No.8):

When I auditioned the Krell KSA-100S before publishing Bob Deutsch's review last September, I found, as did RD, that the '100S had a slight lack of dynamic drive. I felt this 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 Krell amplifiers for powerful low frequencies.

Listening again to the KSA-100S after an interval of several months, I was struck by the same signature. The extreme lows were not as visceral as I was expecting—particularly when compared with the much-more-expensive Levinson No.20.6es. In addition, while the '100S's upper bass bloomed satisfyingly, this was perhaps too much in absolute terms. The bass guitar on "She Just Wants to Dance," from Keb' Mo's superb eponymous debut album (Okeh/Epic EK 57863), sounded rather indistinct, even considering that the B&W Silver Signatures are themselves rather ripe in this region. The synth bass line on Us3's "It's Like That," with its intriguing harmonic turn at the top of the riff, sounded a little behind the beat, too boomy, with the '100S driving the Silver Signatures.

Through its balanced inputs, the Krell KSA-50S was 0.21dB less sensitive than the '100S. I therefore matched levels by always increasing the Levinson preamp's output by 0.2dB when the '50 was driving the B&Ws. In a direct comparison with the '100S, the '50S actually sounded sweeter in the midrange. The smaller Krell, for example, made Barbara Hendricks' voice sound more delicate, less forceful, as she navigated the tricky ornaments and graces in the solo soprano part in the "Et incarnatus est," from Mozart's unfinished C-Minor Mass (Peter Schreier, Dresden Staatskapelle, Philips 426 273-2). The bigger amp, however, had more of a sense of ambient bloom around the orchestra—perhaps due to its more expansive upper-bass balance.

The '50S did have a better sense of pace, however. The "fat potato" synth line in the Us3 track mentioned earlier boogied a bit better via the more lean-sounding '50S. However, the persistent hi-hat cymbal riff on this track sounded more like real cymbals via the more expensive amplifier. Other than in the areas noted, these two amplifiers are very close in their overall presentations.—John Atkinson

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