Krell Evolution 707 AV Preamp Reviewed

Published On: April 6, 2009
Last Updated on: October 31, 2020
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Krell Evolution 707 AV Preamp Reviewed

When you want the best and have the funds to pay for it, there are few AV preamps to consider. The Krell Evo 707, the Meridian 861v6, the Theta Casablanca and the Mark Levinson 502. See Ken Taraszka, MD's full review of the Krell Evo 707 here to see if it is the right one for your top of the line theater.

Krell Evolution 707 AV Preamp Reviewed

By Author: Dr. Ken Taraszka

Ken Taraszka M.D. is an anesthesiologist by trade based in Tampa Bay, Florida. Ken is also a professional audiophile and home theater writer specializing in AV preamps and all facets of the audiophile market. In the past, Ken has been a staff writer and editor at He has also at times been a frequent contributor at


In the world of high-end audio, few brand names come with as much fanfare as Krell. The entire life of this company has been dedicated to making the highest-end products on the market and pushing the envelope further and further forward with each new release. The Evolution 707 AV preamp is their new reference AV preamp, offering 8.4 channels of audio output, Krell proprietary video scaling and processing and four-to-one HDMI switching with the ability to decode all the new codecs of Blu-ray and HD DVD, as well as absolute top of the line analog performance. The Krell Evolution 707 is designed to be the hub of the finest music and home theater systems on the planet. While its $30,000 price tag will keep it as only a dream item for many of us, for the Warren Buffetts of the world, this piece strives to be the absolute cream of the crop in the AV preamp world, while all its modern technology should keep it current for years to come.

Additional Resources
• Read more reviews of AV preamps from's staff.
• Find an AV receiver to pair with the Evolution 707.

The massive size and weight immediately call attention to the Evolution 707, while its simplicity of design and features enable it to perform better. The Evolution 707 is 17 inches wide, 10 inches tall, 22 inches deep and weighs 49 pounds, so you'll either need some help to safely position it into your rack or to let your dealer do the install and save your back.

Review Update - Room Correction and More
Krell has recently added the Automatic Room Equalization System (ARES) to the Evo 707 AV preamp. Utilizing the included high quality microphone that has come with every Evo 707 AV preamp since the first release, and a firmware and dual DSP hardware update (which is included free from Krell) owners of this reference level piece can now enjoy the benefits of auto room setup and equalization to correct for room and speaker placement issues. The new ARES system from Krell measures speaker position, phase and distance and determines ideal subwoofer crossover points as well as correcting for inherent performance of the speaker system and room surface issues.

One of the super cool features of Krell's room EQ is its memory, allowing users to have up to three different EQ settings, based around different speaker placement or uses. You can have a single setting for dedicated two channel listening, one for home theater and another for multi-channel audio or what ever you desire. You could even set up three different listening positions for home theater should you sit in very disparate positions or any combination of the above to suit your needs.

Krell's EQ system also allows for lots of flexibility for each of its three memory positions. You can have the system EQ the entire frequency range, or from only 63 to 250 Hz, maximizing the low-end correction where all or most of the room problems occur. No matter how you decide to use the ARES you have two additional options for each memory setting for Movie or Music curves in addition to the flat curve the base system provides. Any of these additional curves can be added of subtracted without re-running the setup.

The addition of the new room correction software doesn't affect the manual EQ options the Krell Evo 707 has had since it first came out, and doesn't affect the memory of up to four manual EQ settings. What the ARES does do is apply individual EQ curves to each of the Evo 707's 8.4 channels allowing you to maximize even the most complex systems and environments. The addition of the 32-bit dual DSP boards (free from Krell to all Evo 707 owners) allows this massive undertaking and further pushes the Krell Evo 707 to the forefront of the AV preamp world propelling the already top of the heap Krell Evo 707 AV preamp to an even higher level. This unit has been the absolute benchmark from which all other AV preamps have been judged by me and for good reason. The new room EQ pushes it even further forward and should convince even the non believer that this is truly the best AV preamp ever made.

Twelve output channels allow for dual center speakers and four subwoofers with a variety of implementations for each of them, with the options based on the number of subs used. If you have only a single subwoofer, it is defaulted to LFE and to supplement the small speakers. Once you add more, options for stereo subs, LFE, Small and more come into play. Output channels offer balanced, single-ended and Krell's proprietary CAST• outputs that allow enhanced performance when using this with other Krell gear. Audio inputs include a balanced analog input and seven sets of single-ended stereo inputs, a 7.1 analog input, two stereo CAST• inputs, four optical and coaxial digital inputs and one out each, as well as both tape and VCR loop ins and outs.

Video connectivity consists of four composite and S-Video and three component video inputs, with one each for the main and secondary zones, four HDMI inputs and one HDMI output. Krell's onscreen display is available on all video output and the video section can scale analog inputs to 1080p/60Hz. All video is transcoded up to HDMI but, as always, HDMI is not transcoded to analog. The Evolution 707 offers a second zone video output via component with accompanying analog stereo outputs, but the unit will not decode digital inputs for the second zone so a second stereo analog connection might be necessary, depending on your sources. The Evolution 707 does not offer room correction.

The remote is exactly what you'd expect from a top of the line Krell component, as it is machined from a solid block of aluminum. It is simple in its layout and is functional (despite lacking backlighting) but let's face it: if you are dropping this kind of cash on an AV preamp, you aren't using the included remote even if it is nicely built. Control of the Evolution 707 is handled by the four 12-volt trigger outputs, one input, an RS-232 port for syncing with third-party controllers, an RC-5 in and two Krell Link connectors for controlling other Krell gear in your system.

The digital processing circuitry of the Evolution 707 runs in dual precision mode, with a word length of 64 bits to maximize performance. The preamp mode allows both stereo and multi-channel analog inputs to bypass all digital circuitry while separate power supplies for both analog and digital sections ensure the best performance, and are made with custom low-noise transformers and regulators. The Evolution 707 uses a standard 15-amp IEC connector for power and has a hard power switch on the rear of the unit and a standby activated by the remote or front power button.

The Hookup
I have had many of the top AV preamps made today, but the Evolution 707 physically dwarfs them all. This preamp is nothing short of huge and packs the significant weight you would expect from a beefcake component like the Evolution 707. Safely unpacking the preamp requires two people; I unpacked it myself without incident, but I wouldn't recommend it. I had to restructure my AV rack, as fitting this monster in requires 13 inches, as Krell recommends three inches of breathing room above it. I was glad I did, because this unit runs hot, even when in standby mode.

The build quality of the Krell Evolution 707 AV preamp is beyond reproach. My unit came in a beautiful brushed aluminum finish. with red and blue lights and a blue-ish purple display. The variations of finish with shiny arched plates in the middle and the large brushed aluminum face with small and evenly dispersed buttons for functions spread across it, the display to the top left of the front and that massive machined volume knob in the middle make this a piece of gear that will inspire lust in any man. All the surfaces are finished to perfection. Not only does it look great, it feels amazingly solid. The centrally-placed volume knob is massive and feels incredibly smooth. It looks so good that you'll want to get up to use it rather than the remote. The buttons offer excellent tactile feedback when depressed, and lighting to confirm the action. Source buttons have two lights above them, so you can tell which is playing in which zone.

Connecting the Evolution 707 to my system was simple, thanks to HDMI. I connected my PS3, a Denon DVD2500BTCI Blu-ray transport, Toshiba HD-XA2 HD DVD player and cable box to the four HDMI ins and ran the single out to my Sony 70-inch XBR HDTV. I also ran the component video output of my cable box to the component ins to test the scaling of the Evolution 707. My Teac Esoteric DV-50s was connected via both stereo balanced and single-ended multi-channel connections and my Apple Airport Express was hooked up with an optical digital feed. All channels were run with Transparent Reference balanced interconnects and speaker wires, initially through a Mark Levinson ML 433 three-channel amp, then later to Krell's Evolution 403 three-channel monster amplifier to power a variety of speakers used for this review, specifically the Escalante Fremonts, Definite Technology Mythos STs and Canton Vento systems. I ran AC power to the unit through my PurePower 700 power regenerator, which helped keep the preamp powered up with stable, regenerated electricity. The physical connectors on the preamp were superb. I personally hate the HDMI connector in general, not the one-cable HD audio-video functionality it brings us, but the actual connector itself. Often HDMI connections are loose or tough to engage and they can wiggle out from minimal force while you're adjusting other wires in a system, but thankfully, this is not so with the Krell Evolution 707. The HDMI connections were easy to engage and locked in solidly, staying firmly in place. All connectors were first-rate on this piece, over-built from the hefty gold single-ended connectors to the robust balanced ins and outs.

The back panel was laid out very well, allowing easy access to all connections. The HDMI ports were closer together than I'd have liked, but I was able to fit even large cables to them without an issue. This was especially important to me in this review, since despite owning some of the largest AV racks made and having them four inches from the rear wall, this preamp went almost to the back of my rack and sometimes I had to locate the connection by feel. I was happy that once I made the connections I could forget about them.

Once all the connections were made, I fired up the rig and went through the menu, which is pretty simple and basic. Pick your source, assign its input and assign how to reproduce the signal from that source. You set your maximum display resolution, then enter speaker size and distance, set the levels and you are good to go. A very nice microphone and cable come with the Evolution 707 for auto speaker set-up, but this feature is awaiting software revisions, so I did this manually. Being an early release unit, mine also did not support the new codecs in bitstream, so I had to pass LPCM for these in this review. I initially had some strange and inconsistent results with the Evolution 707 locking onto certain digital signals, but a call to Krell tech support got me the newest software and resolved these issues. I let the Krell burn in for a week before sitting down to do any critical listening.

I first swapped in just the AV preamp into my system, as I like to make one change at a time. I was immediately impressed by the improvement in bass control, so when I first sat down to do some listening, I went for bass. I chose The Sheffield Drum & Track Disc (Sheffield Lab). The attack and follow-through on the drums and cymbals were simply amazing. When the bass drum kicked on the opening jam "Amuseum," it was the best I have ever heard. Having grown up with and around drummers, I am used to hearing live drums. The Krell Evolution 707 made for the most lifelike drums I ever heard from my stereo. Later, when I mated it with the Evolution 403 amplifier, it was even better. Not only could this combo do the powerful bits, it presented a totally silent background, so the dynamics were insane. You could literally go from 100-plus dB peaks to dead silence, making the resumption of playing that much more incredible. Cymbals had just that perfect shimmer to them without glare or edge.

I went back a few decades to Jimi Hendrix's Axis: Bold as Love (Experience Hendrix) and prepared to blow out any potential cobwebs in my system. I have been a huge Hendrix fan for thirty years now and this is one of my favorite albums from the master, so I was set to see how the Krell Evolution 707 did with this classic. From the start of "EXP" and the swirling effects to the deep bass lines in "Wait Until Tomorrow" and "If 6 Was 9," I was constantly amazed at how well the Evolution 707 did with bass. Not only did it give me amazing bass definition, it had a rich midrange and detailed but not harsh or edgy highs with tons of air, making even this dated recording sound phenomenal. Krell is known for having the best bass performance with an audiophile amp, but this preamp was pulling off the same feat, much to my amazement.

I cued up Ray Charles' Genius Loves Company (Monster Music), and from the smooth and subtle nature of Norah Jones' voice on "Here We Go Again" to the luscious depth of the stand-up bass on "Fever" to the a cappella version of "Unchain My Heart," all the vocals were clearly discernable. I couldn't have asked for more. Everything was accurately placed and clearly distinguishable, with huge amounts of air around the instruments giving them each their own place in the massive soundstage.

A favorite SACD of mine is Elton John's Goodbye Yellow Brick Road (Island). The keyboards that open "Funeral for a Friend" not only had air and space, but also depth and weight. The surround effects were well-balanced. Vocals were clear and crisp without being biting and the dynamics were unbelievable. The ability of the Krell Evolution 707 to go from absolute silence to massive sonic output is astounding. The subtle nature of the title track was wonderfully handled, drawing you into the music making you forget about the world around you.

Moving onto movies, I cued up the Blu-ray version of Wanted (Universal Studios Home Video). The uncompressed DTS HD Master Audio track was incredible. The surround effects and sound space were not only wide but also deep and tall, while even the subtlest details came through clearly. Gunshots rang out across the room, with the sounds perfectly following the image. Though the movie is utterly implausible and frankly dumb, the effects offered by it made for great amusement and kept me rapt throughout an otherwise lame film. Explosions could be played at realistic levels, but sounded as deep and complex at civil ones. If I wasn't reviewing this gear, I would have stopped the film and moved on, but it sounded so good, I finished the film before ejecting it. Trust me, with a pile of gear needing my editorial attention in the middle of the holiday season, this is no small compliment.

I cued up the new Batman movie The Dark Knight (Warner Home Video) and was fortunate enough to have both a Blu-ray and a standard DVD for comparison. I started off with the standard-definition DVD. The Krell Evolution did a great job portraying a large soundstage and powerful explosions, but after awhile, I switched to the Blu-ray version with its uncompressed Dolby TrueHD soundtrack and I was just floored. The uncompressed audio made the standard-definition DVD audio soundtrack, which had until now sounded very good, seem outright thin and lacking in depth. Explosions were deeper and fuller and the soundstage much wider and more open. Voices were not only clearer but also truer, and subtle details became completely evident. I switched back briefly to the standard-definition DVD and found I had missed things that were utterly apparent on the Dolby TrueHD soundtrack. I have heard these new uncompressed audio tracks before, but never on my reference rig, and they are just that much better there than in smaller systems. If you have not yet heard what these new uncompressed audio codecs can do for home theater, you are sorely missing out. The Krell Evolution 707 reproduces them better than anything I have heard to date.

I ran my Scientific Atlanta high-definition DVR by component video and HDMI to test the scaling of the Evolution 707. Like the audio sections of this preamp, the video scaling was exceptional. I know my Sony TV doesn't have the greatest internal video scaling, but I was amazed how much better the Krell's scaled output was from 480i sources than when fed directly to my TV over HDMI. Images had better edge detail and smoothness, even with fast motion. The scaling was excellent. Though not as good as with a native 1080p source, such as Blu-ray or HD DVD, it was clearly better than when handled by my TV's internal processor. If I needed another HDMI input, I would be perfectly happy to let the Evolution 707 handle my cable feed from component and let the Krell scale the lower resolutions up rather than giving the job to my Sony XBR. While using the scaler, I watched many shows, from Boston Legal to House and others that have 5.1 audio tracks. The reproduction from the Evolution 707 was impressive. Compressed audio of cable channels can be weak, but the Krell portrayed them with openness and space, making everything from background music to voices that much clearer. At this price point, you should expect to find a component that is great at everything, including bringing legacy formats to HD standards. The Krell Evolution 707 AV preamp can pull off this feat without breaking a sweat.

Low Points
Those looking for each and every one of the latest technologies and features won't appreciate the Krell Evolution 707 for what it truly is. It doesn't have XM or Sirius satellite radio inputs, nor does it have direct iPod interfacing, for that matter. The second zone is limited to stereo analog audio and component video, and there is no way (like a USB input) to directly connect it to your PC or Mac for use as a music server, but this is not what the Evolution 707 is really about. It is a statement component designed for the absolute best sound from all current and existing formats. Those interested in adding these features can do so via other components, like a satellite radio tuner or a Krell KID iPod doc, but at an additional cost above the asking price of $30,000.

The Krell Evolution 707 is the biggest physical AV preamp I am aware of and will require a large and solid shelf to support its massive size and weight. The display is functional, yet you cannot rename your inputs and the panel can't be dimmed. I really want the scaler to handle HDMI inputs as well, and the issue with the unit accepting DTS HD Master Audio and Dolby TrueHD via bitstream needs to be resolved, but all these gripes are trivial once you hear the sound of the unit. Krell reports than in Janaury 2009 there will be a gree software upgrade to the 707 that will allow HD audio formats to flow into the 707 via HDMI.

When striving for the best of the best, you take no prisoners and accept some compromises in features. Just like the Ferrari FXX, which lacks things like powered windows and air conditioning, the Krell Evolution 707 skips on many of the modern bells and whistles, like iPod interfacing or an Ethernet port for connecting to your computer music library. Instead, it maximizes everything else, making it perform better than any other unit available. Offering exceptional analog and movie performance, with decoding of the new uncompressed codecs (though only via LPCM in my early production model) and an exceptional video scaler for analog sources, this piece is designed for the customer who wants the absolute best in an AV and music system. Diehard audiophiles used to running a two-channel preamp with home theater pass-through can get rid of that other preamp and know they've got the best of both worlds in one box. This is without a doubt the best-sounding AV, two-channel and multi-channel preamp ever made.

My father always told me, "You get what you pay for." In the case of the Krell Evolution 707, he was without question correct. The Krell Evolution 707 simply is the best AV preamp I have ever heard to date in my home, at any trade show or anywhere else, for that matter. The Evolution 707 reveals bass extension and definition and keeps the mids and highs detailed and accurate, but never lets them become edgy, while providing plenty of separation and air around the components of music or movies. The background is as quiet as I have ever heard, making the dynamics and transients even more amazing. This piece is designed to satisfy the most demanding audiophiles in the world who want both home theater and audio from one system, and to those people, I say go listen to it, but bring your checkbook, because you won't want to leave the store without one.

  • Anonymous
    2021-06-21 14:12:19

    I enjoyed reading your review of this fine piece of uber high end equipment. Not being a man of any count financially, I kind of hope I never hear one in use. If I did, I might have to decide to sell a kidney or testicle in hopes of gaining the funds necessary to be able to come home from a hard days work and experience audio / video nirvana.

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