Krell KBL preamplifier
By Lewis Lipnick   •   August, 1991 About three weeks ago, while perusing the gear in a local audio retail establishment, I overheard a salesman, who could well have been selling used cars, giving a classic spiel to an obviously confused customer. "You see, sir, all preamplifiers basically sound alike, especially with line-level inputs. The only differences are in the number of features." He went on to tell his prey that spending big bucks for high-end products such as Krell or Mark Levinson (neither of which he sold) would be a big mistake. I choked back my automatic response of a certain bovine term, but thought it better to continue my fly-on-the-wall masquerade.

Unfortunately, this perception of "all line-level preamps basically sound alike" is not uncommon, and is further exacerbated by one particular mass-market audio magazine's claim that high-end audio products do nothing more than cost more money. Even I used to believe this crap, since my sole literary audio input originated from the same publication. I was quite happy in my ignorant bliss until the fateful day I set foot in that first high-end audio salon. Product names I'd never heard of before—Quad, IMF, Linn Sondek, et al—greeted my ears and eyes. But it was a preamplifier, an Audio Research SP-3, that really changed my life. It was so much better than my McIntosh C-26: clearer, more open, spacious, and a soundstage (a term I'd never heard prior to that day) that went on forever. That one product shed a whole new light for me on the importance of a good preamp.

Of course, in those pre-digital days, the phono preamp section was of utmost importance (as it still is for many audiophiles), but even the line-level stage of that SP-3 (which eventually became an SP-3A-1) offered a much more musical presentation of my open-reel tapes. With the advent of the CD, the design of high-level stages has become more critical, and has spawned a whole new industry dedicated to the "line-level preamp." The logical question to ask concerns the validity of passive line stages, which many believe to be superior to any active design. I don't agree that the passive route is the way to go, mainly because I haven't yet heard any passive device convincingly reproduce the dynamics present in live music.

So where does that leave me and the Krell KBL? An interesting question, principally because I haven't particularly liked any Krell preamplifier to date, and have been quite pleased with the Mark Levinson No.26 that I bought about two years ago. The KBL is undoubtedly the finest preamp ever to come from Krell. It's priced in the same league as the No.26 ($4500 for the Krell vs $4850/$5450 for the Levinson unbalanced/balanced), is a "line-level only" component which can be combined with a matching phono stage (Krell KPA vs Levinson No.25), and offers balanced operation (as does the No.26 with its optional input card). It can also be mated with another KBL for dual-mono operation.

Except for a few dissimilar features offered by each manufacturer (KBL has two balanced inputs, while the Levinson incorporates useful stereo/mono switching capabilities), and a cost differential of $950, these two units can be considered direct competitors within the high-end audio marketplace.

Technical highlights
As with everything else Krell's Dan D'Agostino designs, the KBL is a visual and technical tour de force. The external power supply is fully discrete, double-regulated, and uses two 50VA-potted, board-mounted transformers. The circuitry is DC-coupled (as in all Krell components), and operates in pure class-A. Fully complementary, discrete circuitry for both positive and negative portions of the waveform are utilized, and the line-stage rails are fed by individual tracking regulators to maintain low rail-voltage offsets. According to the manufacturer, each output section of the KBL is actually a small class-A power amplifier capable of swinging 65V peak-peak.

There are six inputs on the rear panel, two of which can be used for balanced or single-ended operation via XLR inputs. Two buffered tape loops are available, as well as two sets of outputs (one with XLR for balanced/single-ended use, one for single-ended only via female RCA jacks). The front panel is a study in simplicity and elegance. Four circular knobs—input selector, tape monitor selector, symmetry (balance) control, and volume—are positioned in pairs on either end, with two push switches and dedicated LEDs to indicate status (selectable gain 3dB or 9dB, and absolute polarity reversal). The Krell logo and a blue power LED are placed in the center.

When two KBLs are configured for dual-mono operation, the 11-detent balance control adjusts for differences in level between the non-inverted and inverted outputs from the two separate units. Two LEDs located on either side of the balance control are activated in dual-mono operation (which can be accomplished by the consumer via internal switches), and will only light when channel imbalances occur. There is no AC power switch, since the KBL is designed to be left on indefinitely. Both internal and external fit and finish are gorgeous (as is typical of Krell products), and internal access is easily accomplished by removing six countersunk hex bolts on the top cover. All in all, a very attractive, extremely well-built piece of machinery.