Krell K-300i Integrated Amplifier, Sonus Faber Olympica III Loudspeakers @ Munich High-End 2019

Krell had a big display at Munich High End show and seems to be on the brink—or maybe in the midst—of a major new-product and marketing surge.

Walter Schofield, the company's CEO, told me that in addition to a few new products recently introduced, many more are just on the horizon. The new products—and the new marketing push—are based on two recent technical advances.

1) The first, iBias, which was introduced by Krell in 2014, is a sliding-bias scheme that ensures there's always a positive bias for both phases of the waveform. Sliding bias is like class-A in that a bias voltage is always maintained, eliminating crossover distortion, but instead of a large, constant bias as in class-A, the bias voltage tracks the signal, staying as small as it can be while assuring that it's bigger than the signal. In contrast to most (or all? I don't know) other sliding-bias approaches, iBias uses the amplifier's output —not its input—as its reference, so it accounts for the interaction between the amplifier and the loudspeaker.

Longtime Krell designer David Goodman told me that the resulting distortion is almost entirely of the third-harmonic variety; he insisted that third-harmonic distortion is preferable to second-order—which provides some indication of the sound Krell is aiming for.

2) The second advance, which the company calls XD, is a method for reducing output impedance. (The K-300i's output impedance is <0.035 ohms across the audio band.) The key insight, which Goodman told me was discovered in the course of developing the K-300i, is that "lowering the output impedance below traditional norms" results in "substantial sonic improvements."

Krell's technology surge comes with a renewed marketing effort aimed at altering the brand's image. On the substance side there's a renewed emphasis on product reliability and customer support: The K-300i brochure notes the company's commitment to "ultimate reliability" and "white glove service," and the 300i comes with a minimum 5-year warranty. On the image side, there's a focus on nature and humanity. That brochure offsets images and descriptions of the product and its sound with nature photos and an endorsement of the Nature Conservancy.

The energy savings facilitated by iBias fits this environmental image—but many audiophiles will likely be more influenced by the practical advantages of the technology than the planet-saving ones. The K-300i can deliver 150W into 8 ohms and double that into 4 ohms, according to published specifications. A pure class-A amplifier capable of that much power would be big and heavy and dump a lot of heat into the listening room. The K-300i is a normal-sized component—a typical 17 1/4" wide and 18" deep and a few inches tall—and it weights a modest 52lb. It burns just 46W at idle; a 150W class-A amplifier would consume more than ten times that much power and put more than ten times as much heat into the room. 

Is the K-300i's sound consistent with the company's new more approachable image? Is it, as the brochure suggests, "clean, powerful, natural sound in all its subtleties, colors, and gradations"? It's impossible to judge based on a short listen in an unfamiliar room and system with unfamiliar tunes, but here's my first impression. The sound with the K-300i driving the Sonus Faber Olympica III Loudspeakers was exceptionally fast and clean—more clear mountain stream than, what, furry animal babies? I don't know these loudspeakers, but I've found the Sonus Faber house sound to favor warmth and ease over speed and ultimate resolution. Driven by the K-300i, the Olympicas didn't lack for warmth—nor were they the least bit bright or etched. But there was no dearth of articulation, from the bass on up. So, yes, waterfalls and Alpine pools, bracing, cool, clear water—those aren't bad sensory analogies. As for the subtleties, colors, and gradations, judgment on that will need to await a longer, more focused listen.

A streaming DAC module is available for, I think, an extra $1K; the DAC supports Roon, Tidal, Qobuz, Spotify, and MQA. The K-300i's warranty is 5 years from the purchase date, or six years from the time it was sent out from the factory, whichever is longer. 

Not far out on the horizon is the K-300p--an MM/MC phono stage with versatile loading options, which was on static display at the show. Price TBD....
.........Jim Austin  - Stereophile