Krell KSA-250 power amplifier Page 2

During one particularly heated listening session, we had a vividly divided camp as to which amplifier best represented the musical performance. Bob Kraft, bass trombonist, and Ken Harbison, percussionist, both felt that while the KSA-250 was more "dynamically impressive," it didn't have enough "meat on the bone," and lacked the immediacy and warmth of the ML No.23. Their priorities, and desired perspective, leaned more to "I want to hear it from the stage." They both felt that while the Krell had more impact, along with broader, higher, and deeper soundstaging, its leaner harmonic character and more distant perspective produced a less involving experience than the 23.

Al Merz, another NSO percussionist, and I felt differently. While we both loved the sound of the No.23—it represented more of what we heard while on stage—the KSA-250 gave a much more honest picture of what music sounds like from the audience. As I mentioned a long time ago in another amplifier review (Rowland Model 7, Vol.11 No.7), the further away from the stage one gets, the leaner and more transparent the sound. In purely sonic terms, one could say that the No.23 has more lower midrange and midbass energy per unit of sound than did the KSA-250. After hearing the new Krell every day for the past several weeks, it has become apparent to me that this amplifier is indeed more honest, though possibly less satisfying for the listener who wants to be in the middle of it all.

I strongly recommend operating the KSA-250 in balanced mode, if at all possible. Listening tests in both single-ended and balanced configurations using double sets of identical interconnects (Madrigal HPC and Straight Wire Maestro) indicate that soundstaging and dynamics are significantly improved in balanced configuration. Even though signal/noise ratio is only improved by 6dB in balanced mode, the far greater dynamic extensions on either end of the scale indicate that there are many more benefits to balanced operation than simply a lower noise floor. I have had similar experiences with amplifiers from Mark Levinson, Rowland, and Burmester, which lead me to believe that, in general, one should try to utilize balanced operation, if given the option.

Dan D'Agostino made it perfectly clear that the KSA-250 needs only 15 minutes to reach full operating potential. It just ain't so. There is a definite "brown," thick, nasal coloration during the first 30 minutes after power-up, which totally disappears after a minimum of 45 minutes to an hour. By that time, the sound opens up, all colorations disappear, and the amplifier comes to life. In fact, best results appear to come after two to three hours of playing time. I'm not suggesting that you leave this amplifier on all the time (unless you need a space heater), but any serious listening should not be done with less than 1½ to 2 hours' warmup.

The term "awesome" is definitely overused nowadays. But I can't think of another way to describe the KSA-250's sound: a huge soundstage, far exceeding the lateral and vertical speaker boundaries, with a breathtakingly natural sense of depth. So clear, so open, so transparent, so powerful, yet so refined. The sense of reserve power is immediately obvious to the listener, but not in the same way one would normally associate with such an enormous amount of stored energy. This amplifier does the best job, so far, of reproducing the realistic size and dynamics of a live symphony orchestra in my listening room. Yes, the No.23 is excellent, but until you've heard the KSA-250, you haven't heard real dynamics. A perfect example is the beginning of Eliahu Inbal's performance of Mahler's Symphony 5 (Denon CD CO-1088). The visceral weight coming out of the 800 monitors at that first orchestral climax was closer to the real thing than I ever thought possible. Compared to this, the No.23 came off sounding like a peashooter.

Dynamics are just part of the story. Musical transparency is just as important, although it is something usually only found in the finest tube amplifiers and a few solid-state designs. In this area, the Krell and Levinson No.20.5 are surprisingly similar, even though they are class-A designs from different manufacturers. They are both very transparent, allowing the listener to follow each musical line, even within the most complex passages. The principal difference, in this case, is the amount of power and spectral balance. The Levinson is a bit sweeter and more transparent than the Krell, but can't handle full orchestral tuttis without some sonic congestion.

Two good examples here would be Arnold Bax's Symphony 3 (Bryden Thomson/LPO, Chandos CD 8454) and Handel's Water Music (Nicholas McGegan/Philharmonia Baroque Orchestra, Harmonia Mundi CD 907010). Both the KSA-250 and No.20.5 do an excellent job of unraveling the complex woodwind passage in the beginning of the Bax, but when the orchestration becomes more heavy and thick, the Levinson becomes congested, while the Krell retains its clarity and overall musical integrity. On the other hand, the tables are turned with the Water Music, which sounds much more convincing with the No.20.5, mainly because it can delineate the leading edges of all instrumental attacks more clearly than the Krell (as can also the No.23). Which amp is better? Do you prefer chocolate or vanilla? For baroque, chamber music, solo piano, and solo voice, I'll take the Levinson 20.5. But pull out the big orchestral guns, like Mahler and Shostakovich, organ music, full chorus, or just about any pop, from rock to big band, and I'll go for the Krell KSA-250. In other words, the Krell is the more versatile of the two, giving up a little musical delicacy to its more expensive competition.

Another area in which the KSA-250 excels is the accurate recreation of acoustic envelopes surrounding instruments and voices. Up until this amp came along, the only way to get this right was with tubes. Even then, they often can't adequately deal with spatial information at the frequency extremes. The No.20.5 gets it 90% correct, but can't quite resolve that last bit of resonant information surrounding instruments and voices. The No.23 does a little better, but only at the front of the soundstage. The KSA-250 gets it absolutely right, allowing the listener to hear how the instrument or voice interacts with the surrounding space, anywhere in the soundstage, just as in live music. For example, in the fourth selection of Antiphone Blues (Arne Domnerus, saxophone; Gustaf Sjokvist, organ; Proprius CD 7744), the acoustical environment of the recording creates standing waves with the saxophone that are clearly audible with the Krell but almost nonexistent with the Levinson No.23 and 20.5 amplifiers. With the Krell, you not only hear the saxophone in space, but the "ring" of the church acoustic as well. This recreation of ambient information draws the listener into the recording acoustic, not in a forward sense, but almost as if in a surround-sound environment. If you like to be inside the ambient soundfield, rather than outside looking in, the KSA-250 may be for you.

Which brings us back to the question of perspective and soundstaging. Many musicians, including myself, take a rather dim view of the unnatural, bigger-than-life soundstage record producers like to create, often at the expense of our artistic efforts. This is not to say that live music sounds as flat as a pancake. It doesn't. There are those few wonderful recordings in which "more real than life" soundstaging is effective. We all know that tubes are considered the best at this, giving the listener lots of depth and space. But overly exaggerated depth in amplifier design is as much a sin as midrange glare, and has no place in accurate musical reproduction. This is where the KSA-250 weaves its magic—a soundstage so real one can reach out and touch the performers; palpable realism that beats the tube guys at their own game, without creating a false sense of depth. The KSA-250 is better than the Levinson 20.5, which gives good frontal soundstage but becomes somewhat indistinct and truncated toward the rear. The 250 doesn't just offer dimensionality, but clear focus of each individual voice in the choir or orchestra, as it is heard in the concert hall.

Sonic honesty
Some amplifiers tolerate a certain number of sins upstream without becoming upset. Not the KSA-250. It scrutinizes everything, good and bad. It didn't like the upper-midrange glare with the Madrigal HPC interconnect, nor the nasality of the plastic fiber-optic digital cables I tried with the Esoteric and Krell Digital products. Small differences (good and bad) I heard with cables, digital drives, and preamps with my reference No.23 amplifier were greatly magnified by the KSA-250, often to the point of distraction. In this respect, the Krell is very similar to the very honest and transparent B&W 801 Matrix and 800 Matrix Monitors; with garbage in, you get garbage out.

The KSA-250 is not perfect. It is harmonically bettered by the Jadis tube electronics, and does not resolve leading edges of instrumental and vocal attacks as well as the Mark Levinson No.23. It produces a constant low-level hum through the speakers, which could probably drive some people nuts. It runs extremely hot, and sucks juice out of the wall like a sponge. So what? Audiophiles are supposed to suffer a little, aren't they?

The Krell KSA-250 is a truly extraordinary piece of audio equipment. It is ruthlessly revealing of everything upstream and is, in this respect, the finest reference amplifier currently available. It will drive virtually any load, and is the first amplifier this listener has heard that successfully combines ultimate musical finesse with sheer dynamic brawn without sacrificing much along the way. While the KSA-250 does not quite measure up to the finest tube electronics in the area of harmonic accuracy, and falls somewhat short of the best solid-state in the ability to resolve vocal and instrumental attacks, it wins the prize in overall musical and sonic honesty. But if you're thinking about buying one of these, be darn sure that your front-end electronics are the very best, or else you may be disappointed.

If you're in the market for a great amplifier (or even if you're not), you owe it to yourself to audition the KSA-250. It doesn't get much better than this, folks, so find the checkbook, put off painting the house until next year, and get to your local Krell dealer. Now, how am I going to explain to my wife that we need to buy a new amplifier...?—Lewis Lipnick

Krell Industries
45 Connair Road
Orange, CT 06477-0533
(203) 799-9954