Krell Full Power Balanced 600 power amplifier:
Page 3 The FPB 600 was factory-fresh, as was the FPB 300 I reviewed for Hi-Fi News & Record Review in December 1996. That model sounded quite unremarkable when auditioned at first plug-in; while the acceleration in quality was impressive as the early tens of minutes went by, it was a week before a close approach to its final performance plateau had been achieved.

Forewarned by that experience, I broke the '600 in on a diet of stereo music for a week. Thereafter, matters were fairly stable. The FPB 600 can, of course, be left in standby for longer periods of inactivity, and switched off altogether for a vacation, but for regular use I tended never to switch it off, being generally unwilling to sit out the 15-minute climb in sound quality from "standby" to fully warm.

If you really want to hear what an FPB 600 can do, make sure that the demonstration unit has been broken-in before you begin listening. A fellow listener questioned the need for this procedure: "Does it mean that an amplifier design is flawed?" I opined that it was very likely that all audio electronics show some improvement when run-in, but that this is simply less obvious with poorer-sounding product of inferior transparency.

Power—and then some!
Zero to 60 in 4.2 seconds! So kick down the volume pedal at last! The resulting impact was colossal, unexpected, unprecedented, totally in control, easy, hugely loud yet unfatiguing, exciting, involving, thunderous, and effortless. Here was the audio equivalent of a Porsche or a Ferrari—no excuses, no practical limits. In musical terms, the '600 suggested an impact comparable to that of such high-performance automobiles—and for a whole lot less money!

And while a Porsche or a Ferrari will demand to be exercised—to be stretched, revs soaring—this amplifier was also happy to glide along like a Lexus when fed undemanding, low-level program. It could do both. Mighty impressive.

My preferred speakers have never sounded more themselves than in the company of the FPB 600. I learned to highly value that innate truthfulness during the review period. That particular quality of the FPB 600, and its overall performance level, made comparisons with SE tube designs largely redundant—even when the Krell's volume was contained within the power compass of the smaller amplifiers. Even though the best SE tube designs sound sharper and meaner than the FPB 600 (due in part to loudspeaker interactions), with an expression of microdynamics that the Krell didn't quite capture, no SE can deliver the top-to-bottom tonal balance and neutrality of this solid-state design.

In the bass the FPB 600 was simply awesome, interacting powerfully with the Wilson X-1/Grand SLAMMs to deliver previously unheard bass extension, while superb articulation and slam were both evident. Powerful bass notes stopped and started with amazing control, percussive bass was very realistically "present," and complex bass lines were played tunefully and with very fine rhythm. The FPB 600 felt as if it could bodily pick up those X-1 juggernauts and run with them. With such a display of raw power, this amplifier seemed equally adept at conveying fine texture and tonal color on acoustic string bass. The title track of Airto Moreira's Killer Bees (B&W BW041), for example, sounded awesome, a huge soundstage building to superbly developed dynamics and great jazz rhythms.

Solo grand piano verged on the revelatory. Somehow John Atkinson's full intention as recording engineer seemed to be mightily expressed by the Krell/Wilson combination. Truly dynamic, wholly realistic sound levels and quality were attained on his excellent recording of Robert Silverman playing piano works by Liszt (Sonata, Stereophile STPH008-2). I have never heard a Steinway Grand reproduced with such palpable reality as this. Powered by the '600, the smaller Wilson WITTs didn't do such a bad job either on this recording.

Without fail, every time I returned to the '600 I heard an unmistakable sense of grip, a close embrace of speaker and amplifier, always in step. Its sound was beautifully poised and superbly founded, its source deep, even immovable—unshakeable. With the larger loudspeakers, the effect was comparable with moving my system from a room with a suspended timber floor to one with 2' of reinforced concrete under the speakers.

I rate the FPB 600 as the "fastest" of the big superamps in terms of rhythm and timing. When downscaled into a small, "fast" UK audio system, the big Krell remained graceful and capable, while classy amplifiers—albeit of more limited bandwidth and power, such as the Naim NAP250—still had the edge in terms of absolute pace and timing. However, even here the gap has now been narrowed. Only the most critical rhythm fans will find the Krell wanting.