Krell KBL preamplifier Page 3
Dynamically, the KBL has more impact than the No.26, but the leaner harmonic presentation can make the midbass and lower midrange seem a bit lightweight. However, this is actually more realistic. It's very easy to be seduced by bigger-than-life midbass richness, but it just ain't that way in live performance. Too many audiophiles confuse electronically generated low frequencies from Fender bass and synthesizers with the lighter, more transparent characteristics of the lower strings in the symphony orchestra. Really deep, impactful bass, however, such as that produced by 32' and 64' organ pipes, symphonic bass drum, and various electronic musical instruments, is reproduced with much more weight and pitch through the KBL than through any preamp I've heard. In spite of this, the No.26 does provide a more appealing spacious, warm cushion of sound at lower volume levels, where the KBL tends to become unnaturally lean.
If you listen at realistically high playback levels, the Krell will deliver a more accurate rendition of dynamic contrasts and musical textures. If, however, the volume is restricted by system limitations or domestic considerations, the Krell may disappoint. The manufacturer claims that the KBL will provide better sonics in the high gain (9dB vs 3dB) position. I conditionally agree with their suggestion, although in this configuration, the high-output Theta Pro can sound a bit too bright and forward on aggressively recorded pop material. The amazing thing, however, is that the KBL's input never seems to overload, even with the high-output Theta.
System matching is another consideration that must be dealt with when shopping for any preamp. It should come as no surprise that the Krell and Levinson preamps work best with their respective power amps. While the KBL performs musical magic with the KSA-250 and KMA-300, it just doesn't do very well with the Levinson No.23 or 23.5. The latter are not happy marriages, creating sonic results characterized by a narrow, truncated soundstage and lack of detail. No matter what interconnects were tried, single-ended or balanced, the overall sound remained the same. This was a most curious situation, since I've heard the KBL sound absolutely fabulous with Jeff Rowland, Classé, and Jadis amplifiers, as well as my own Adcom GFA-555.
I haven't yet had the opportunity to audition the KBL in dual-mono configuration; perhaps this will solve the Krell/Levinson interface problems. The opposite combination (Levinson preamp into Krell amps) sounds quite a bit better, but the remarkable transparency of the Krell amplifiers distractingly illuminates the No.26's dynamic shortcomings and overly ripe midbass. There was also a noticeable increase in noise and hum with the No.26/KSA-250, or KMA-300, somewhat (though not completely) alleviated by floating the ground on the Krell amps.
Although the KBL's output impedance is very low (a claimed 0.5 ohms!), which theoretically should lessen the sonic effects of different cables, it was definitely happier with specific interconnects. Magnan VI, Straight Wire Maestro, and especially those spectacular Purist Audio Design Maximus (aka "water wire"), appear to produce the best results. Even though the Maximus seems to take forever to break in (so far, 150 hours and still improving), it is spacious, dynamic, harmonically neutral, and above all transparent. This stuff may be hideously expensive, but it is worth the astronomical price. (In this case, you really do get what you pay for.) The Magnan VI is no slouch either, providing a more involving forward perspective but giving up significant soundstage dimensionality and dynamic weight to the Maximus. It should also be noted that the KBL sounds much better in balanced vs single-ended operation. Transient impact, dynamic range (particularly at the top end), soundstage dimensionality, and (surprisingly) harmonic integrity all benefit from balanced operation between preamp and power amp.
And now, the musical truth
Not everyone is looking for the real thing. If you subscribe to the "boom & sizzle" philosophy of musical reproduction, or find the natural harmonic structures and dimensionality of live music boring, the Krell KBL will probably not be your cup of tea. But, as I stated earlier, this preamp will indeed let you know exactly what went on during the recording session, all the warts, pimples, and beauty. In this respect it's similar to the B&W Matrix 800 speaker: garbage in, garbage out. No added flavorings or artificial ingredients.