October 2001 Reviewed by Jeff Fritz	Krell Theater Amplifier Standard

Description Model: Theater Amplifier Standard Price: $7500 USD Dimensions: 17.25"W x 9.75"H x 17.25"D Weight: 100 pounds Warranty: Five years parts and labor	Features Krell Current Mode topology Bipolar transistors Surface-mount technology Balanced (XLR) and single-ended (RCA) inputs Bridgeable channels Five-way gold-plated binding posts Aluminum cabinet (Architech) 12VDC trigger

Krell’s power amplifiers have always been the bread-and-butter products of the Orange, CT-based company. Long before they made speakers, surround processors, or CD players, Krell produced extremely rugged, built-like-a-tank, hotter-than-heck amps. The original KAV-500 multichannel amplifier was one of the first high-end power plants for large home theaters, so today, when many companies are producing their first multichannel power amps, Krell is several generations down the road with the introduction of the Theater Amplifier Standard (TAS). So the question is, what has the company learned, and how does this amp differ from past efforts?

First, and most obviously, the external cosmetics are a bold departure from the black and gray of the previous KAV line. Krell's new Architech construction starts with four solid machined-aluminum corner posts, which eliminate any possible chassis vibration. The side panels, which are securely fastened to the corner posts, and the shielded plate over the transformer, add structural rigidity to this solid foundation. There is more to it than this, but the primary point is that it is a significant structural upgrade over the folded-steel chassis of the former KAV products, which was not the most refined from a visual standpoint. The TAS is taller and narrower too, thereby allowing easier placement on a shelf or rack. Other changes reportedly include refinements in Krell’s engineering and manufacturing, which aid serviceability. The TAS benefits from much of the technology originally developed for Krell's top-of-the-line preamplifiers and power amplifiers including Krell Current Mode topology and new surface-mount technology, which allows for maximum efficiency in circuit-board layout.

The amplifier is rated at 200W to all five channels, driven simultaneously into 8 ohms. Krell claims the amplifier will double its power into 4 ohms, and then double again driving 2 ohms. Given that, the amplifier is a powerhouse for the majority of users. Twin 1.4kVA transformers make up the bulk of its 100-pound weight. Krell has always insisted that power supplies be capable of delivering ample reserves, and this unit's rock-solid 2800W power rating embodies that philosophy. Peering inside the amp, I noticed a metal shelf horizontally dividing the chassis, on top of which resided the five amplifier channels. Each channel is a self-contained module, which is a popular configuration when dealing with numerous heatsinks and internal components. Under this shelf are the transformers, which are effectively shielded from the audio circuitry.

The front panel has a large circular power button outlined by a blue light when powered on. The back is cleanly laid out, with five-way binding posts and balanced and unbalanced inputs. I must say I really like the amp's cosmetics. It's sleek and polished -- very cool. Two thumbs up for the new look!

Into the fire

I used the Krell as a workhorse for several speaker systems and in numerous configurations. I had it driving a sub-$3000 Acoustic Research home-theater speaker system as well as an over-$100,000 Wilson Audio super system. This allowed me the opportunity to test the Krell's mettle in diverse applications. The simple, uncluttered layout of the rear panel was a breath of fresh air compared to the cramped quarters on most multichannel amps. I used a variety of banana plugs and spades interchangeably without a hitch. The taller chassis aids in real-world installation. Lots of real estate is good for hook-up purposes. The amp was driven by the Krell Home Theater Standard 2 processor (review to come) via Nordost RCA cables.

Trial by fire

I attempted to establish the Krell’s limitations right away by feeding it to the Wilson X-1 Grand SLAMM Series III/ WATT-Puppy 6/XS subwoofer combination. This is a challenging load due to the numerous drivers and the sheer immensity of the XS. I endeavored to trip up the Krell’s ability to drive the system, with all kinds of hell breaking loose on the screen and in my house, including a big bass signal being fed to the sub. If the TAS were going to cough and hack, it would surely be during this test.

But the Krell never skipped a beat -- it drove the complex arrangement of the Wilson speakers to reference levels and beyond. My house, on the other hand, objected strenuously as items were rattling and falling off the walls (literally) during the train scene in Unbreakable. The only word that truly applies is scary. I was afraid that something was going to break -- hopefully not my wife’s Wedgwood, or I’d be finding a new listening place. I was unable to find the limitations of the Krell amplifier’s power with the Wilsons, although it should be noted that the Wilson speakers are extremely efficient, so this is perhaps not terribly surprising, even though it was quite impressive.

Perhaps a more complex load, or lower-efficiency speakers, would not fare as well. A slew of lower-sensitivity Von Schweikert VR-3.5 speakers made the Krell work harder. The only effect this had, though, was on my preferred volume setting on the processor. I raised it a bit past my normal level setting. Sound quality remained consistent -- the TAS simply allowed the speakers to give whatever they were capable of. In this case, the sonic warfare taking place in Gladiator’s opening scene is always a good test. As the fireballs hit the trees behind the Germanium army, arrows fly, swords ring on one another, and horses thunder past. All of this organized aggression came through without congestion. The sound was effortless and clear, just as it should be.

The sound of a home-theater amplifier is not solely about limitless sonic bombast, unless of course all you watch are action flicks. (Don’t laugh, I have a few friends...but that's another story.) I like to mix it up quite often, so I took out one of our reference DVDs to test the Krell’s ability to handle subtlety and refinement. The Eagles Hell Freezes Over is a great test for vocals, as we have Don Henley, Joe Walsh, Glenn Frye, and Timothy B. Schmitt all giving us their respective take on the matter. The differences in vocal inflection, no matter who was singing lead, were clearly apparent. Also, I could not find any grain or noise in the upper frequencies, which made intelligibility on a par with the best I’ve heard. If you are after a clean, clear midrange on up to crystalline upper treble, the Krell is a champ.

Wait, there’s more! I also noticed increased delineation of instruments and sound effects. The TAS's ability to unravel complex music really separates it from many a muscle-bound brute. It truly possesses increased resolution. I’m not just talking about a veil being lifted, but about giving higher definition to sounds and increased separation to individual instruments. It takes a good recording to get a handle on this quality, but once identified it can be picked out quite easily. American Gramaphone’s Home Theater Demo DVD [AG 2496-7] features Mannheim Steamroller’s "Moonlight at Cove Castle." This track is peppered with castanets mingling with the sultry musical score. The Krell TAS deciphered the complexity of it all and presented a precise rendering. Now if only I had a high-definition monitor to see the same level of detail in the video.

Home-theater enthusiasts looking to upgrade from the best receivers available to really great separate components have a lot to look forward to. Comparing the sound of the Krell TAS to that of the internal amplifiers of the B&K AVR307 is interesting and supports some basic tenets of high-performance audio. First, the B&K is exceptional as a receiver. In fact, it earned a Reviewers' Choice award as one of the best receivers I have heard at any price. It stands to reason, though, that there must be some compromises made when all the processing and control circuitry along with the amplification is crammed into one chassis. Separating the amplifier from the cabinet simply makes sense. In the case of the TAS, it translates to increased realism, power, and sonic impact, all of which simply means more enjoyment to the end user.

Not only was the Krell better at reproducing even the most dynamic movie soundtracks, it was also adept at extracting the last bit of detail and nuance from subtle cues present in music. The B&K, for example, on Fleetwood Mac’s DVD version of The Dance, did not present "Landslide" with all Lindsey Buckingham's delicate guitar work intact. Through the Krell, the sound had more dimension and delicacy. When playing Unbreakable, the Krell revved up faster and communicated the sound of the train through all the speakers with more realism. I know this seems like old news, but it 's surprising just how much you gain when adding an amplifier of this quality to a receiver-based system. Every possible area is improved, making it one of the most dramatic upgrades you could make to an AVR307-based system.

Putting out the fire

The Krell Theater Amplifier Standard is the most expensive home-theater amplifier I have yet tested. In fact, I would suspect many people have not contemplated an amplifier this expensive (yet). I have had a number of extremely fine two-channel amplifiers (many by Krell) come through the system over the years, many more expensive than this one, and that for only two channels. I've become quite used to a high level of power coupled with a refined, resolving sound. The Krell Theater Amplifier Standard possesses these qualities in spades, which is quite an accomplishment, especially considering it has a full five channels of power. Its sound is remarkably clean and precise, to an extent that it would find a welcome home in a picky audiophile's system. It excels in the areas of power delivery, load-driving ability, dynamic range, and neutral, accurate sound. It has all the performance attributes one could conceivably require for a state-of-the-art home theater. When you add these qualities to the attractive styling and extremely rugged construction, not to mention the Krell name backing it, you have the makings of a superior product, and one hell of an amplifier.

Manufacturer contact information:

E-mail: krell@krellonline.com
Website: www.krellonline.com

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