Krell K-300i Integrated Amplifier, Sonus Faber Olympica III Loudspeakers, ZenSati Cabling

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 COO, 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. 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.

The second advance, which the company calls XD, is a method for reducing output impedance. The key insight, which Goodman told me was discovered in the course of developing the K-300i integrated amplifier (€7000), 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.

Bogolu Haranath's picture

Another super-integrated under $10k? ......... There is some tough competition in this price range :-) .......

Long-time listener's picture

I don't see any mention of price in this post. But anyway, there is stiff competition in that range. My NAD M32 (US$4000) has tone controls, which this Krell doesn't have; it uses far less energy; and it doesn't have that ugly bulge in the center of the front face. The sound has color, texture, detail, and punch. So Krell will have to do more to impress me.

Bogolu Haranath's picture

True ...... NAD M32 was reviewed by Stereophile and is included in the Class-A listing ......... I was just guessing the price of the Krell integrated :-) .........

Bogolu Haranath's picture

Anthem STR integrated, $4,499 is also this price range, which is included in the Stereophile Class-A ........ Anthem integrated provides room correction capabilities :-) .........

T-NYC's picture

I guess no one at Krell has heard of the 1939 Lincoln Walsh patent for this used in his Brooks amplifiers, or of Nelson Pass' patent for this (carefully worded to specify transistors and thus end-run the Walsh patent) used in his 1975 Threshold 800 and all of his designs since, or of all of the 1970s Japanese amps from JVC, Technics, and others using "Sliding Class-A". More of these if I thought about it for five minutes. Hopefully the editorial staff at Stereophile will, among other things, act as a corrective to marketing-inflation, which ultimately undercuts the credibility of the audio community. If you do so, then perhaps a reminder to Hegel that feedforward was invented in 1928; first commercially exploited by Quad in the 405 amplifier released in 1975, and used today by Benchmark, Devialet, Linn, and others, would also be helpful.

CG's picture

Not that my endorsement matters, but I agree with you.

An awful lot of these new products really might be great performers and might sound excellent, but the marketing claims are bologna. "Quantum" this and "new technology" that. (I suppose when you get down to it, everything is based around quantum mechanics...)

Why can't they just say that they've worked really hard at optimizing the details of a proven type of circuitry and have made good improvements on or found a way around pitfalls of the traditional approaches? Or, even, that they've just made it sound very, very good.

It is all either misleading or insulting, depending on your point of view.

I am NOT commenting on whether any product sounds good, great, lousy, or wretched here. Just that the marketing is, maybe, a bit disingenuous.

One comment: Feedforward was indeed first applied to electronic circuits in the mid 1920's by Harold Black. This was before his work in the use of feedback. (The patent for the use of feedforward was issued in 1928.) However, I'd suggest that ducks used the feedforward technique well before that to point themselves in the right direction to get where they wanted to go across a running stream. Black "just" applied that idea to electronics - a brilliant concept.

T-NYC's picture

A very good point; thank you! A reminder that we discover more than we invent.

Krell Industries's picture

Thank you for your comments regarding past sliding bias schemes, however, I wanted to point out that ours is a proprietary system that is considerably different than other past schemes you mention, and if you would like to get the complete technical info from one much better equipped to provide it than me, my email is

All the best,


T-NYC's picture


Thanks for your offer. I'll send an email. If you have a circuit diagram (best) or a white paper elucidating your innovation I'm happy to review it and if I'm mistaken to openly state this and stand corrected. There are two distinguished PhD physicists now retired but with a history of contributions to audio science and two more such, decidedly not retired but in no way competitors to Krell, whom I will consult when I receive your data. Like me they will be interested and pleased to see an actual innovation in a largely moribund discipline. Continued in email....


Krell Industries's picture

TB, I have forwarded your contact info to David Goodman, our Director of Product Development for the past 32 years, and he will reach out to you via email. All the best, Walter

T-NYC's picture

I promised to post here if I had reason to alter my opinion; I do and I am.

This is an evolution of the eighty-year thread of "sliding class A" designs, however Dave Goodman has really thought about engineering fundamentals and in doing so framed the actual problem quite differently than his predecessors. This enabled him to arrive at an engineering solution that has great elegance and is a clearly tangible improvement on prior art. My hat is off to him for his accomplishment, and I have strong reason to believe this is the final evolution of "sliding class A". Yes, newer devices will be released in time that will enable further circuit improvement, but conceptually this is it.

Also yes, mea culpa, I must exonerate the Krell marketing department. iBias truly is intelligent bias.

A number of comments in this thread involved price. I'm very definitely in the NAD budget group and very grateful that NAD and a few similar firms exist, sourced in China, Taiwan, Thailand and Malaysia, producing affordable, well-engineered products. That said, this integrated amplifier is Krell engineered and Krell build quality and manufactured in the USA. The price is not inexpensive, but for the overall quality level, built in the USA, it is extremely fair.

Thank you, Dave Goodman for our dialogue, and Walter Schofield for making it happen.

Bogolu Haranath's picture

Stereophile has reviewed with measurements, Krell Solo mono-block power amps with I-Bias :-) .........

T-NYC's picture

Yes, they did. They also have reviewed similar designs from Threshold, and multiple Japanese firms, and go back far enough and you'll find Gordon Holt referencing the original -- the Brook amplifier. So your point is?

Bogolu Haranath's picture

I was just mentioning it for information purpose only, if someone is interested in Krell I-Bias :-) .........

audiodoctornj's picture

Mr. T NYC there are always similarities to past circuits and evolutionary designs. The proof is how does the product perform.

I had the pleasure of owning a JVC RS77 a Super Class A sliding Bias design in the 80's first it never even got really warm so Class A it probably was in name only, nor did that piece sound even remotely tube like, it was a decent receiver and that was it.

Fast forward to the Class A Ibias K300i it does get warm, sounds amazing and just draws you into the music in a way that is way more organic and flowing then most solid state designs.

We are thrilled to have a K300i on the floor and it is one of the best sounding integrated amplifiers on our floor and we have a lot of them we have: Naim, Anthem, Micromega, NAD Masters,Synthesis, Coda, to name a few.

To the comments made by the other gentleman, we too have the NAD M32 which is a digital amplifier, it is a lovely piece but it is nowhere near the magic of the more expensive K300i.

The Krell K300i is a joy to use and the sound of its built in dac is extraordinary for such a reasonably priced option $1,000.00

The Krell K300i offers an abundance of Class A power 150watts, can drive anything, comes with a fantastic dac, has a ton of inputs including HDMI, and a great built in streamer, is both MQA and Roon ready, and is compact enough to fit on a real shelf.

Sound wise the K300i is just outstanding.

Dave Lalin, Audio Doctor NJ Krell dealers

Long-time listener's picture

"we too have the NAD M32 which is a digital amplifier, it is a lovely piece but it is nowhere near the magic of the more expensive K300i..."

I can imagine that might be true--and in fact it should be if it's more expensive. The thing is, I may be old fashioned but I've never understood why high-end manufacturers scorn those who wish to use tone controls. (The NAD also has a balance control--does the Krell?) It's true tone controls may introduce a tiny extra bit of distortion--depending on implementation--but the first thing I notice about any recording or any pair of speakers is whether the bass-mids-treble balance is right. Once in a while turning up the bass a notch adds the bass foundation that's really needed on old recordings, or you can adjust the treble to avoid too much brightness. Where's the crime in that? Of course, I could seek out only those few very very perfect recordings, but I prefer to seek out MUSIC and have equipment that is flexible enough to let me enjoy it. So the Krell for me is therefore nowhere near the magic of the M32. I will stick with NAD, or Luxman or Accuphase (if I can afford them), companies that aren't so snooty tooty about these things and let the listener use his own judgment about how to shape the sound. Sorry 'bout that.

Bogolu Haranath's picture

Marantz and McIntosh are also in this under $10k price range .......... McIntosh also provides, an AM/FM tuner and tone controls :-) ..........

Bogolu Haranath's picture

Some of these under $10k integrated amps also provide good quality headphone outputs :-) ........

T-NYC's picture

Dave Lalin,

My comment was not about this unit's perceived sonic merits or lack thereof. It was fully aimed at their marketing dept not their engineering dept. This is not "similarity of circuit"; it is the same fundamental circuit. It happens to be a good design and if the Krell engineers are using it there is reason to believe performance will be good. If the product is good the marketing people do not need to gild the lily with verbal invention.

As for the rest of your comments -- the first great class A solid state amps include the Electro-Research A-75, Stax DA-300, Mark Levinson Ml-2, and Krell KSA-50 among others. None sound "tubey", they were all attempts, quite good ones, at making straight-wires-with-gain. The JVC amp you referenced was class A in sliding mode, just like Threshold amplifiers, and was quite exceptional in its class.

BTW, Harmon Kardon Citation II & V, Futterman H3aOTL, Marantz 8 & 9 did not sound "tubey" either and their designers would have been horrified if they did. You may be new to Stereophile and therefore missed Bob Carver's T-mod episode here, which while widely misunderstood, was intended to show that amplifier sound is the result of transfer function. That is, one could take a perfectly good linear amplifier and screw it up to sound like mediocre tube designs of the 1950s or any other sonic signature within power supply limits.

Tube sound in the Krell if your description is accurate, indicates it is a signal processor, not a straight-wire-with-gain. As Krell has a mixed but overall quite good engineering track record, I hope it is your description that is inaccurate, not the purposeful design of the amplifier.

Naples Audiophile's picture

The under $10k price point for an integrated is crowded. There are a ton of excellent integrated amps to be had. Fir example the Yamaha 2100 and 3000 are amazingly good amp that produce warm detailed sound. I’m not sure that high end mfgs can compete at lower prices

Richard D. George's picture

Sonus faber speakers in recent years are no longer overly warm and laid back.

The Olympica III's are quite good.

Bogolu Haranath's picture

Sonus Faber Olympica III has many favorable reviews posted online ........ There are also several videos including Upscale Audio video presentation :-) .........

audiodoctornj's picture

Mr T you speak like an engineer, not an audiophile reviewer.

All manufacturers aim to produce amplifier designs which are straight wire with gain, however, all amplifiers we have tested do sound different.

We have many different solid state amplifiers in our shop and hooking up the same loudspeakers, cables and source components do produce different sonic results.

An amplifier's sound quality is affected by the amount of feedback, the circuit design, the Class and type of amplifier, and the type of parts.

If you listen to a Parasound vs a Krell vs an Electrcompaniet all three of these solid state amplifiers have a different sound.

An amplifier producing a warmer or brighter sound or a bigger sound stage, or a more flowing sound quality is not about the company trying to deliberately flavor the sound it is a combination of virtues that the engineers are striving for in their design.

A BMW and Mercedes and Audi are all three fantastic cars they all have their own particular feelings, design attributes, and corporate identities.

As per tone controls, yes the M32 is a lovely piece and tone controls are good, many high end companies do not use tone controls because many people don't care for them or they dont use them.

Sound wise the Krell is a much fuller sound then the M32.

Dave Lalin,
Audio Doctor NJ Krell dealers

As per a Mcintosh having an Fm tuner that is lovely the Krell has a digital tuner and most stations today have a digital counterpart so we would take a digital tuner

Bogolu Haranath's picture

Not to dispute your comments ......... McIntosh MAC 7200 ($7,500) provides 200/WPC and headphone output :-) .........

McIntosh also makes MA 9000 integrated amp (without AM/FM tuner) which has 8 band parametric EQ and headphone output ....... 300/WPC, $10,000 :-) ........

T-NYC's picture

A good many manufacturers do strive for formatted sound, not straight wire with gain. The difference in sound is a direct result of difference in transfer function, nothing more; nothing less. Back to the original point -- the Krell engineering team may have done a good job; the Krell marketing team did not and the editorial staff of Steroephile should stop acting as extensions of marketing departments and name bull when they hear it. BTW I knew Rondi & Dan pre-Krell (and Stu Hegeman, Julius Futterman and many more) so you may assume I'm familiar with amplifiers in general and Krell in particular.

Ortofan's picture

... third-harmonic distortion is preferable to second-order.
Let's see if he can convince AD of that proposition's validity.
It can be a sidebar to AD's review of the K-300i.

Bogolu Haranath's picture

3rd harmonic distortion 'draws' people into music, while 2nd harmonic distortion totally 'drowns' people in the music :-) .......

Fred Locks's picture

Who in their right mind would spend that kind of money on an amp without a proper volume knob? This amp looks great but I wouldn't go near it without a proper volume control. It amazes me how bad the ergonomics are on so many pieces of hi-fi equipment. Stereophile should do a survey on this subject.

audiodoctornj's picture

The Krell K300i is $7,000.00 without a digital board, and $8,000.00 with its digital streaming board. The Anthem STR and the NAD M32 are both $4,500.00 integrated amplifiers with Dacs, in the case of the Anthem you would need to add a good digital streamer and digital cable so add $700-$3,000.00 to the price depending on quality of streamer.

The NAD M32 is a Blue Sound Node so it has streaming built in.

We have many intergrated amplifiers on display: We sell the Naim Uniti Nova $7,500.00, the Krell K300i with streaming option for $8,000.00 the NAD M32 at $4,500.00 and the Anthem STR at $4,500.00 plus a few lesser known intergrated amplifiers.

The Krell is clearly in a different level of sound quality than the Anthem and the NAD M32, the Krell has a lusher more musically engaging sound, with a huge soundstage and shows its Class A heritage. The Anthem STR has wonderful room correction but doesn't have the same degree of musical involvement and dense layered soundstge that the Krell has.

We have never been drawn to the sound of Mcintosh which is warm and musical, but doesn't have the superior clarity, coupled with speed and articulation while also sounding warm and musical that the Krell offers.

The closest in terms of price and performance is the wondeful Naim Uniti Nova which has a few advantages and a few disadvantages vs the Krell, the Krell has more power and can drive speakers without losing steam, sonically the Naim is a bit more rhythemic the Krell a bit clearer with a slightly wider soundstage.

The take away is the Krell K300i is a fantastic integrated amplifier that shows its heritage and is acutally a much more involving product sonically then previous Krell products, the digital board is a superb performer for a $1,000.00 add in that the K300i is a Roon endpoint, MQA compatible, has Tidal and Oubuzz, sounds amazing, and is both managable in terms of size, weight and heat generation makes this one of our favorite itegrated amplfiers.

As per Volume knob the push buttons work great, the remote works great and the app works great so not having a big volume knob is really not an issue.

Dave Lalin, Audio Doctor NJ

Long-time listener's picture

"The Krell is clearly in a different level of sound quality than the Anthem and the NAD M32, the Krell has a lusher more musically engaging sound..."

I'll take your word for that--not trying to argue that point with you. Quite a number of years ago I had a Krell DAC that convinced me of their ability to make quality equipment. But I've blown through too much money just trying to put together even a relatively modest system to think about spending another $8000 unless stock prices decide to double sometime soon. Many speakers, etc., have come and gone. I've achieved (temporary) musical happiness in a "desktop" system by pairing the NAD M32 with a pair of Buchardt Audio S300 MKIIs. Their sound is extremely weighty and full-bodied for a bookshelf speaker and balances the relative lightness of the NAD wonderfully. I've also switched from Audioquest copper cables to Neotech cables (manufactured in Taiwan) that use UP-OCC copper; UP-OCC is magic stuff and despite what Audioquest says about their "perfect-surface copper" sounding better than anything else, I disagree.

Someday maybe I can own a fine Krell amplifier.

Bogolu Haranath's picture

For approx. the same price as NAD M32 or Anthem STR, one could consider the new B&W Formation Duo wireless speakers ......... No need for amps, pre-amps, source components or cables ........ Just power cord connections :-) ..........

Long-time listener's picture

... then the sound becomes 100 percent "take it or leave it." I'd much rather have separates and be able to switch various parts in and out as I choose, and as better products become available, so that I can achieve the kind of sound that -I- want.

Bogolu Haranath's picture

One of the advantages Krell K-300i and the newer Krell XD amps have is, very low output impedance ....... So, the Krells have the proverbial 'iron fist' control of the loudspeaker drivers (transducers) ....... The 'damping factor' of the Krells, is in the hundreds, by a factor of 10s compared to most of the amps ...... The other amplifiers that I know of, that have similar very low output impedance are Linn Klimax Solo mono-blocks, Hafler Transnova 9500 and Aragon 8008, which were reviewed and measured by Stereophile :-) ........

Bogolu Haranath's picture

BTW ...... Naim Uniti Nova does not have as high a 'damping factor' as the new Krells ........ Stereophile reviewed and measured that Naim component :-) ........