Krell Evolution 900 Monaural Power Amplifier 
Home Theater Power Amplifiers Mono Amplifiers
Written by Jerry Del Colliano   
Friday, 01 June 2007

I have owned various Krell amplifiers in my reference systems over the years, each providing hours upon hours of listening joy. Recently, Krell has released a new top-of-the-line lineup of gear under the Evolution moniker that speaks to those for a need for the best of the best and a willingness to pay for it. The review system under evaluation is comprised of a $10,000 Krell Evolution 505 SACD player with 24-bit 192 DACs, a $15,000 Krell Evolution 202 two-chassis stereo preamp and the monstrous Krell Evolution 900 monaural amplifiers at $20,000 each, or $40,000 for the stereo pair as reviewed. My review samples are done in Krell’s signature silver finish, which is breathtakingly beautiful out of the rack and poised on a simple table as it is installed in my reference system.

To start, it is important to note that the Krell Evolution 900 power amps are nothing short of huge. With a travel schedule that has me out of the country more than in the States over the past two months, I hired Simply Home Entertainment to come out and set up my Krell Evolution system in a way that simply and neatly bypasses my reference installed home theater. The SACD player was installed above the two-chassis preamp on a modern-looking table to the right of my seating position, which came out more elegant than expected. The amps were placed by two strong men beside my Wilson WATT Puppy Version 7 loudspeakers. Connections were made one of two ways during the review. The first was with Krell’s proprietary CAST system. Alternatively, the system was wired with Transparent Reference XL interconnects. The Krell Cast system is a unique system that allows for one voltage gain stage throughout the audio chain. In the world of absolute audio, less is always more, and I found the CAST system to be a very unique solution that I recommend any careful listener to audition. I also used Transparent Reference XL cables for the speaker connections. At this level, each gradation of high-end cable is easily audible, even to the untrained ear.

Starting with the power amps and without getting too geeky, these Krell mono blocks have a lot of goodies under the hood. Most notable are the massive 6000 VA power supplies, which surely make up quite a bit of the weight of each beefy amplifier. Krell’s CAST system boards also add to the unique design of the amps, allowing your entire Krell audio system to act as one in terms of the way they are connected. There are microprocessors that monitor the inner workings of the amp in order to protect your investment when you may have had one too many sips of Macallan 30 during a loud, late-night listening session. Krell’s Current Mode speaks to the overall design of the amp, which allows the component to operate in the current domain rather than the voltage domain, unlike most other high-end amps. Krell’s Active Cascode Topology reduces distortion by doubling or tripling the amount of active devices used in a gain stage, resulting in the Evolution’s very clean and fast sound.

The preamp is a dual chassis model like the Krell Evolution 2 and the Mark Levinson No. 32 which, among many benefits, allows the designer to keep the potentially noisy power supply away from the sensitive electronics in the controller unit. The $15,000 202 also operates in Krell’s CAST system and is a fully balanced design. The volume control is ultra-sexy, with a truly great feel. The volume “pot,” if you will, is computer-controlled by a 16-bit balanced resistor ladder, creating smooth volume transitions and resulting in no audible noise from the volume control.

The Krell 505 SACD/CD player is a $10,000 dedicated audio machine that uses some of the finest digital to analog conversion money can buy. The player is, not surprisingly, wired for a CAST connection and is built like a tank. The metalwork is so tightly machined that the player feels more watch-like than a high-end SACD/CD player. In fact, when a disc spools up, you can barely hear it with your ear to the side of the player. Strangely, a player at this price point cannot play a DVD-Audio disc but it can play CD, SACD, MP3 CDs and many other discs.

Starting with CD, I spun up “Gypsy Eyes” from Jimi Hendrix’s Electric Ladyland (Universal MCA). I was ill-prepared for how impactful the Krell Evolution system sounded. The bass, a topic I will touch a lot more on later, was lower than I thought I could physically get from my Wilson WATT Puppy Version 7s. What struck me was how warm and three-dimensional Hendrix’s vocals sounded. The Krell Evolution 900s were able to reproduce that warm, Neumann-mic vocal sound from an older recording as if it had been remastered to a higher-resolution disc (which it has not been, shamefully). The walking bass line of “Rainy Day, Still Dreaming” resonates so strongly in my new room that I couldn’t believe the sensation. Rock-solid, round and tight only start to describe the low end of the Krell Evolution system. With the volume at impressively loud levels, the Hammond organ sounded as detailed in the mix as Hendrix’s wha-wha’ed-out Strat, which is mixed way more up in the overall sound picture.

I judge audio components more on their ability to make real music sound incredible than how good an audiophile recording can sound with the newest, most incredible recording techniques. This is mainly because, as a proud non-audiophile, I would never consider investing in something like a pair of $40,000 amplifiers unless they can make my spine tingle on the best musical performances ever to grace some master tapes. This brings me to The Beatles Rubber Soul (Parliphone – EMI). The hard-panned sound of this strikingly good 1965 recording speaks to the real reason why you realistically could start even thinking about justifying the incredible expense of a pair of Krell Evolution amps. On “Norwegian Wood,” the pairing of George Harrison’s guitar melody and the sitar sound beamed forward into the room, lighting it up with sound as you might expect to hear from live instruments rather than from stereo gear. On “Drive My Car,” Ringo’s cow bell had incredible pop to it, yet the piano sound in the back of the mix was a little congested. Harrison’s guitar solo beamed in front of the soundstage from the right speaker. The overall sound is so compelling that it makes you start hunting through your piles of CDs for more Beatles records, which is exactly what I did.

The transition from Rubber Soul to Magical Mystery Tour was an easy one to make in terms of heading to my racks of CDs, but left me sitting in my listening room thinking about how prolific the best artists were in the late 1960s. To creatively develop from writing and performing nifty pop songs in 1965 to Sgt. Pepper’s and then Magical Mystery Tour in just two to two-and-one-half years is truly incredible by today’s standards. On Magical Mystery Tour, you still hear remnants of the hard-panned stereo sound from the earlier records; the production and recording techniques are so much more advanced. The introduction to “Strawberry Fields Forever” sounds so incredible you might just play it 10 times before you accept that you are listening to a mere CD. The horn melody sounds a bit compressed, which is more of a set-up than anything you are about to hear. The vocals jump into three-dimensionality with the volume up in a way that I have never been able to get in my system. This is the kind of musical experience that would make a kid throw his iPod into the East River and start dreaming up every possible way for him to buy his first Krell amp. I don’t think of Beatles records as a place to demo bass performance, but on “Baby You’re a Rich Man,” you simply can’t believe how deep the tight low end can go on this vintage track, because if baby, you are a rich man, too – you might just drag these amps home. I promise it feels absolutely fantastic to be “one of the beautiful people in the world,” if even only for a few months in my case, while I evaluated this system.

Moving into more modern recordings, I reached for a record that, as a teenager, I used to take with me to SoundEx, my local high-end Mecca in Philadelphia. Don’t look for it today – they are long out of business after trying it a “build it and they will come” showroom that included 26 properly-treated listening rooms and every high-end component known to man, including an awful lot of Krell. This is where I got my first-ever listen to Krell and I was hooked right then and there at 14 years old. However, it took me easily 15 more years before I could actually call a Krell amp mine. “Synchronicity 1” from The Police’s stellar Synchronicity album not only provides an audio demo that stands the test of time, it speaks to the lost art of a band that took pride in being not just excellent songwriters but also in playing their asses off. Stuart Copeland is quite possibly the single best rock drummer in the history of rock music (click here to go to our forum to post your hate mail regarding slighting Neil Peart and John Bonham) and this track shows exactly why. The breakneck pace of this incredible song puts it on the short list with Rush’s “YYZ” for sheer progressive rock showmanship. The sound of Copeland’s snare jumps at you through a cacophony of sound that blends together into one hell of a song. With the Krell Evolution 900 amps in my system, you can feel the drums even in a complicated mix like this. “Synchronicity 2” is a more popular track than its predecessor in terms of 1980s rock radio airplay and, in terms of enjoying these Krell amps, the driving Sting bassline had me reaching for the volume to push the limits of what I could stand, as if I simply couldn’t get enough of the low-end impact. “Wrapped Around Your Finger” also had very good low end. However, the vocals didn’t have the pop that I was able to hear on other tracks, even from earlier recordings. The snare fills and cymbal trickery are still enough to keep you on the edge of your favorite easy chair and, as the song crescendos into the chorus, the entire track holds together like it’s constructed with super glue. The sound never gets shrill, cold or disjointed. With the Krell Evolution 900 amps in the loop, you have a rock-solid foundation for literally any speakers you choose to own.

Speaking to the audio excellence of the Krell SACD player as a front end to the Evolution system is its ability to make seemingly lackluster SACD material sound specifically good. One of the best examples of this phenomenon is Michael Jackson’s Thriller, which I thought (from past reviews on SACD) was one of the worst-sounding examples ever of a great record on a high-resolution disc format. With the Evolution 202 stereo preamp, Evolution 900 amps and Krell 505 SACD player in my system, I have changed my stance on 1982’s Thriller on re-released SACD. On my personal favorite track “P.Y.T,” the Quincy Jones production elements literally fill the room, almost as if it is mixed in 5.1, when played through the Krell Evolution system. The very subtle drum fills (play the track on your system and listen for them if you never noticed) are so tight that you get to experience a tremendous musical foundation on one very solid pop song. The Steve Lukather guitar chops are understated, yet very nifty upon close scrutiny. After a few times through an old favorite like Thriller, it’s easy to equate listening to Thriller on a Krell Evolution system to the reactive experience of wolfing down the sound like a Double Western Bacon Cheeseburger from Carl’s Jr. The bass has an addictive element and the highs are silky smooth, without the limits you get from tubes. Yet, as you spend more and more time with the Krell Evolution system, you get past the flashiness of the power and realize that the fine details are so well represented that you might as well be sitting down with Thomas Keller at French Laundry. Audio elements blend in unexpected but beautiful ways.

Moving to more complicated mixes, “Café Reggio” from Isaac Hayes’ Academy Award-winning motion picture soundtrack for Shaft (Stax – SACD) provides for wonderfully rich guitar tones that have the liveliness of tubes with the seemingly unlimited energy of a powerhouse solid state system. Forget all of the “Krell sounds cold” clichés. If you haven’t heard Krell Evolution, you don’t know how faithfully Dan D’Agostino’s designs can reproduce music. The string accompaniment is lush and deep-sounding, while the horns have a bit of bite to them, exactly as they should, both flavors flourishing at the same time in ways few audio systems can reproduce.

For all Krell salespeople who have the pleasure of having an Evolution system in their listening rooms, be sure to keep a copy of Keb’ Mo’s Just Like You (Epic) on SACD within reach to play the role of super-closer Trevor Hoffman with a three-run lead heading into in the ninth inning of an important game. “Dangerous Mood” shows how a high-resolution audio format like SACD, when paired with an all-out music playback system like the Krell Evolution system, can shake you to your soul by reproducing music in ways that you might not have believed were possible before you sat down in the hot seat. On a pure DSD recording (why weren’t they all when Sony was trying to make this format fly?), everything you lay your ears on is pure candy: extremely tight and low bass, rich organ sound and nearly three-dimensional vocals. Once again, the highs are vibrant but in no way harsh, with the bass the best I have ever heard in my system. Upon listening to “Dangerous Mood,” you will likely be in so dangerous a mood yourself that it could inspire you to actually invest in such a dramatic music playback system.

The Downside
Sonically, the most jaded recording and mastering engineers would be hard-pressed to pick fault with the electronics. Krell critics will need to reevaluate their opinion of Krell based on the extended highs and even better bass that one can hear on the Evolution system. Yet there are issues that need to be considered when investing in a system at this level. First of all is heat. The Evolution 900 amplifiers pump heat into your room, the likes of which I haven’t felt from an amplifier since the days of the Cello Performance II Class A mono blocks. I had my AC unit set on 69 when it wasn’t even 69 outside in order to keep my room comfortable during my many hours with the Krell Evolution system. Size is another consideration if you, like me, rack-mount your equipment. I am not sure a typical Middle Atlantic rack will accommodate the depth or the weight of the amplifiers. Perhaps they are meant to be installed on the floor, parked on some slabs of granite, but as a recovering audiophile, I do what I can to rack-mount my gear in order to have the best of both worlds.

The Evolution 202 stereo preamp is also hard to pick fault with. As a two-chassis device, it competes favorably with the best from Mark Levinson and Halcro and, as a system, provides impressive musical performance. With that said, the remote truly stinks. Built of aluminum, it is heavy, not backlit and hard to use. To suggest that an audiophile client will be using a Crestron system is a bit presumptuous. The buttons are all about the same size. Volume should be larger and should be more responsive. The knob on the front of the preamp is great, but the remote stinks.

The Krell Evolution 505 SACD player is a very capable front end and a valued part of the overall audio system. Its remote is just as bad as the Evolution 202, with the front faceplate taking the “one button fits all” approach too far. In a dimmed room, it’s nearly impossible to make the player do what you want. Switching from 5.1 SACD to stereo is a complicated but not impossible feat for the player. There should be one button that accomplishes this important task. The last dig on the player is a frustrating one, and that is at $10,000, there is no excuse for the 505 not to play every DVD-Audio title - not just the ones without digital rights management coding. When $500 players on the market can play every disc on the market, it's hard to understand why a $10,000 unit can't perform the same feat.

In terms of accurate and exciting musical reproduction, I don’t think you can do any better than the Krell Evolution system in today’s marketplace. $65,000 is a lot of money to invest if you are judging the performance of the system merely from this review. Before you pass judgment on the system, take a listen with my warning – the sound is addictive. You might find yourself rolling into your local high-end audio dealer at 1 PM to find the salesman looking to actually go home at 7 PM, and you’ll be wondering where the time went as well as the remainder of your home equity line of credit.

Dan D’Agostino and Krell have outdone themselves with this Evolution audio system. It is the most exciting package of electronics I have auditioned in my system. The Evolution system was able to get bass from my Wilson WATT Puppy Version 7 loudspeakers that I thought you needed a subwoofer to hear. The highs are spectacular and the ability to resolve detail is second to none. Forget the Patek Philippe for now. Cancel your order for the Gulfstream G150 – you might just need a Krell Evolution audio system first.
Manufacturer Krell
Model Evolution 900 Monaural Power Amplifier

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