Krell KAV-400xi integrated amplifier
As it turned out, no. True, the KAV-300i wasn't designed to drive Apogee's 1-ohm Scintillas the way Krell's massive separates could, but Krell had designed an integrated that would test the proposition that a properly designed single-box component could rival or surpass the performance of more costly separates. It had just been so long since anyone had attempted such a feat that most audiophiles had never even imagined it possible.
Today, high-performance integrateds are, if not thick on the ground, common enough that no eyebrow is raised at the prospect. Krell obviously took this as a new challenge, and went back to the drawing board. The KAV-400xi outputs 200Wpc to the 300i's 150Wpc, and takes its cue cosmetically from Krell's sleek Showcase line, which uses stout corner posts and milled aluminum panels to create a bombproof chassis. It also sports a continuous-spin digital volume control, balanced circuit topology, and a slick little membrane credit-card remote—and, at $2500, costs just $150 more than the almost-10-year-old 300i.
It has always been a truism that Krell is serious about build quality; now we know they're serious about that value thing, too.
Truth! stark naked truth, is the word
That post-and-panel aluminum architecture isn't just window dressing—Krell wants the chassis to be rigid and nonmagnetic. And big: The amplifier's 17" depth enables the KAV-400xi to house its massive power supply at a distance from its audio circuit boards, which are stacked adjacent to the rear panel's inputs and outputs. The power supply itself, located in the front half of the chassis, consists of an 800VA toroidal transformer, a 55,000µF capacitive reservoir, and discrete regulators for the preamp and power-amp sections.
Krell says the KAV-400xi's gain stages are derived from the same ultra-high-bandwidth, low-noise, current-mode technology that the company developed for its KCT class-A series preamp. The output stage uses six parallel-linked high-speed bipolar transistors for each channel's positive and negative legs (because it's a balanced design, that totals 24). This clever system trades on the rapid response of low-rated output devices without eschewing the brute force of their global output. And it works—the 400xi is specified as delivering 200Wpc into 8 ohms and 400Wpc into 4 ohms.
The audio circuits are symmetrical and differentially balanced. In keeping with Krell tradition, the circuit is class-A up to the output stage, and the output is DC-coupled to the speakers. The audio circuit board is flanked by two substantial internal heatsinks, and the amp's top and bottom plates are liberally vented to enable heat dissipation. My KAV-400xi got somewhat warmer than body temperature, but never so hot as to discourage catnaps on the part of a tired but relentlessly exploratory kitten.
Volume control is effected by a resistive-ladder network, and the source switches are linked by relays to the rear panel's inputs. There's a single balanced source input (pin 2 hot) and three single-ended inputs, including the tape monitor. There's a preamp output, and speaker connection is by way of WBT binding posts—one of which the no-longer-napping kitten managed to snap off with a flying tackle when I precariously balanced the amplifier on its faceplate to change speaker cables. Even broken, however, it grasped the spade lug securely. There are also 12V input and output triggers, an RC-5 remote control input, and an IEC socket.
The faceplate is sleek to the point of stealth. There's a tiny power/standby pushbutton, a small round IR receptor, and six tiny pushbutton switches (B1, S1, S2, S3, Tape, Mute), each with a tiny LED indicator directly above it. A small fluorescent display window and a round-capped rotary volume control complete the facilities.
There is no balance control—but the KAV-400xi uses a balanced resistor ladder for volume control, so of course the amp's balance can be adjusted. That's where its credit-card remote comes in. I'm probably just stupid, but I had the dickens of a time figuring out the remote. It's a universal model that also works with other Krell components, and it has a pair of source switches at the top, labeled CD and Pre. It wasn't immediately obvious to me that I had to press Pre before every command or the 400xi wouldn't accept it. I suspect that wired remote input on the rear panel is the giveaway—Krell assumes its customers will be using a system remote or home automation system such as those made by Crestron.
If you've a yen for incorporating your two-channel system into a multichannel home-theater setup, the KAV-400xi's assignable Theater Throughput mode toggles the designated input into and out of unity gain.
I am as true as truth's simplicity
The KAV-400xi doesn't require any real setup. Just connect the inputs, speaker cables, and AC cable, and turn it on. It sounded pretty good straight off, seemed to blossom a bit after about 10 minutes, and that was that. I didn't notice much improvement with additional burn-in.
The Krell DVD Standard DVD player is fully balanced, so I used the B1 input on the amp and plugged the Musical Fidelity Nu-Vista 3D CD player into S1. I couldn't detect a noticeable difference between balanced and single-ended operation, but the 400xi is balanced from input to output; if your most critical source offers balanced outs, there's no downside to using it, and some theoretical advantages. So why not?
The KAV-400xi is hefty at 36 lbs, but not brutally massive the way Krell's biggest components are, which means you don't have to hire an architect to design a shelf that will hold it. It bounced along contentedly on Solid-Tech's elastic-banded Feet of Silence (no, I didn't make that name up), which are not designed for massive loads. You do want to give the 400xi a lot of breathing room, however.
The amp appears to be fairly easygoing when it comes to speaker loads, too. I challenged it with Krell's own $8000/pair Resolution 2s, a 4-ohm load with a claimed sensitivity of 89dB. Ignore the specs, however; I found the Rez 2s to be speakers that really wanted to be spanked by their amplifier—they sounded best when dominated by a big brute.
The 400xi was well up to task, demonstrating that it's not just the sons of Krypton who hide their powers behind mild-mannered exteriors. Yes, the Krell was super—both of 'em, actually. However, I felt that auditioning an amplifier solely with a loudspeaker born in the same stable was a tad too cozy, so I wired up a pair of PSB's $4999/pair Platinum T6 Towers: 4-ohm speakers that don't seem substantially more sensitive at 90dB, but that subjectively seemed to require less boot. The T6 is the next model down from the $6999/pair Platinum T8, which John Atkinson reviewed in November 2003. The KAV-400xi was in complete control of both sets of loudspeakers, producing balanced sound from bottom to top.
I enjoyed the sound of the KAV-300i when it was released, but that was eight years ago, and since then, solid-state design has come a long way—at least, the best of it has. The KAV-400xi retained the 300i's best qualities-control and unpixelated timbre—while improving on it across the board, especially at the frequency extremes. The older integrated's bottom end, which I admired in its day, seems overemphatic compared to the 400xi's deep, taut, natural bass.
I hadn't expected this. I once joked to JA that the only newsworthy review of a Krell amplifier would be one that could scream "Krell designs component with no bass response!" The company has certainly not done that this time out, but neither does the 400xi have big bass sound. Its low end just sounds accurate.
Did I say "just"? That's not simply rare, it's a daring move for a company known for its big bass. I suspect that a certain number of consumers might misinterpret the accuracy of the 400xi's bass response for something else: excessive leanness. More on this anon, as one of my erstwhile editors was fond of saying.