Krell has long been the best known and on the whole the most credible full line producer at the high end. The company now includes loudspeakers and SACD players as part of its portfolio, and a universal player is on the roadmap to accompany the pre and power amps and CD players that make up the core of the Krell range, alongside the home theatre processors and multi-channel amps that have been added in the last few years. DVD-Audio is on the roadmap as part of universal player project currently in development. With its obvious rival, Mark Levinson, apparently having hit the buffers, only Classé from Canada looks as though it will be able to stand up to the well oiled Krell machine.
Krell amplifiers went through a fallow mid-life period some years ago, but has recovered spectacularly with the powerful and capable FPB range, which is aimed directly at the cost no object audiophile end of the market. But Krell is also interested in more moderate price points, and for some time has produced reasonably priced integrated amplifiers, of which the KAV400xi is the latest, and let's make no bones about it, the greatest.
The KAV400xi is the replacement for the KAV300, but an unusually glamorous one. It is built into a slim line and undeniably elegant version of the Showcase type housing, with the now familiar fabricated aluminum flat panels for each surface, joined together by half-rounded solid machined end caps with a polished finish, not just on the front, where such details are most obvious, but on all four corners. The front panel is equipped with a row of small buttons for source selection and mute, and a continuous turn digitally controlled resistive ladder encoded volume control and a small display to show the current operating status. The back panel is fitted with inputs sockets for the four single ended line inputs, which includes one tape circuit with a monitor facility, and a pair of XLR sockets for a single balanced mode input. Preamp level outputs are available to drive an external power amp. Speaker connections are to stout WBT terminals. Everything about the KAV-400xi screams 'quality'.
This is a thoroughly contemporary design, which fully reflects Krell's usual priorities, starting with the non-magnetic enclosure. Open the lid and you'll see that the internal view is dominated by a massive 800VA toroidal transformer. It drives 55,000mF of reservoir capacity with separate regulators for the low and high-level circuits. The power amplifier demonstrates once again Krell's customary distain for impedance loading variations with in output that behaves in a textbook way, doubling in output when the load impedance is halved. It is rated at 200 Watts/channel into 8 Ohms, and 400 Watts into 4 Ohms.
The amplifier gain stages make use of an ultra-wide bandwidth, low noise current mode circuit topology that Krell has championed of late. A similar theme is reflected further upstream in the output stage, which is built around a six high speed parallel connected relatively small value output bipolars for each of the positive and negative going phases of each channel - a total of 24 output transistors. All circuits are symmetrical and balanced, and fully Class A up to the driver stage, and the amplifier is DC coupled to the load. The main circuit board is populated with surface mount components, and input sources are selected by relay.
If you happen to have Krell CD or SACD player, you'll have a good use for the balanced input, not least because balanced operation with Krell is not window dressing, but an integral part of the Krell ethos, and in contrast to some other balanced designs, backed by fully balanced internal circuitry. The back panel is also home to 12V trigger in and outputs, and a remote control input that can be used with an external repeater. The final element in the user interface is the remote control: a tiny, slim line system handset, powered by a long life lithium battery, and fitted with domed membrane switches. It repeats the front panel facilities and adds balance adjust, plus controls for CD players and tuner (see below). It's a sexy enough design in keeping with the amplifier as a whole, but not particularly tactile. Similar criticisms could be made of the front panel controls which are very tiny, but there is a more substantive criticism which is that the volume control steps are very coarse, which is particularly noticeable at the bottom of the volume control range, and which can make it hard to find exactly the right volume settings in some circumstances. Krell please note.
Special features include a so called Theatre Throughput mode, which is a volume/balance control bypass facility intended for use with an external preamp/processor when which can then control the level of all channels in synchronization, without needing two level controls in circuit, and without danger of upsetting the balance between main speakers and the others. The Theatre Throughput mode works with a nominated input, and is an elegant way of combining a high quality stereo system into a multichannel home theatre system without throwing the baby out with the bathwater.
The baby Krell is a little different in one other respect too, in that an add in PC board will be available to add FM tuner facilities to the basic amp, turning the basic 400xi into a compact, high power stereo receiver.
How It Sounds
Let us start with what the Krell KAV400xi is not. This is emphatically not a classic Krell high-end amplifier in a shoebox. But then it is no ordinary amplifier either. In particular it is nothing like the integrated amplifiers produced by mainstream producers, but with more power perhaps and a better finish. It is still something special, something altogether more exacting than the run of the mill, and its music making ability is not compromised by any perceived necessity to sound comfortable with less than ideal matching loudspeakers and source components. In particular, it is not an especially forgiving amplifier, and it is designed to make the best of what it is used with, even if this means turning a spotlight on their inadequacies.
Turning to what the Krell is, we are talking about a refined and extremely detailed amplifier, with a slight tendency to leanness. It doesn't have the body and warmth of some competing designs, solid state or (in particular) tube based, but its easy transparency and clean balance makes it a refreshing alternative to much of the opposition. It is neither more obviously right or wrong. It simply casts music in a slightly different light. But this is also an extremely powerful amplifier, palpably more so than most integrated amplifiers into a wide range of loudspeakers.
One of the best qualities of the Krell is its consistency. Not only did it brings the same qualities to the party with a wide range of partnering equipment, it was up for almost any challenge, its performance stretching to match the capabilities of the rest of the system. It was hard to find a system that the Krell didn't suit. Loudspeakers like the Focal.JMlab Mezzo Utopia (to be reviewed in Enjoy the Music.com™ in the not too distant future) which react poorly to amplifiers deficient in resolving ability, worked better than I had expected with the Krell, though there was clearly more to be had from these speakers which was found with true high end designs from Hovland and elsewhere. Nevertheless, the Krell's even handed way of performing at different volume levels, and its propulsive, on-the-ball timing make a big difference. Perhaps most of all, it is the lack of an obvious aural signature - there's little of the slight hardness and opacity that afflicts many otherwise good solid-state amplifiers.
Krells generally are bred to deliver fast, accurate and tuneful bass, and the KAV-400xi is no exception. I can think of some well known solid state amplifiers which tack the Krell's drive and tunefulness, and which sound rather slow and soggy by comparison, but which have a reputation for a natural sonority and sense of architecture that perhaps eludes the Krell. To an extent it is a matter of taste and also what happens to work best with the rest of your system. But I tend to lean towards the Krell way of doing business. The entry level Krell seems to be to me more pliable, more responsive to the differences between one recording and the next than most, it is easy to hear through, and it doesn't impose an obvious 'voice' on the music. It is also particularly strong with transient based material, and what is music if it isn't a sequence of spaced out transients? Classical piano sounded physical and solid, and plucked strong instruments reproduced with a clarity of line and an almost tangible sense of presence, but strings have sheen and polish, and there is a sense of getting to grips with the structure of complex material that is both unusual and gratifying. But the KAV-400xi doesn't have the almost train like physical inevitability of the big Krell FPB series amplifiers, and it doesn't quite have the same ethereal air and absolute precision of their best components either.
Frequency Response: 20Hz to 20kHz
Signal To Noise Ratio: 99dB (A weighted)
THD: 1kHz <0.04%, 20kHz <0.25%
Input Sensitivity: 0.644Vrms
Input impedance: 47k Ohms
Output Impedance: 0.17 Ohms
Inputs And Outputs: 1 pair balanced (XLR), 3 pairs single ended (RCA), all with Theater Throughput, tape in/out single ended, pair pre-amplifier output sockets, single ended. Loudspeakers 4mm binding posts
Other Sockets: 1 RC-5 in/out, RC-5 remote control in
Net Weight: 14.1kg.
Finishes: Black or silver
Accessories: 4 spikes and cups included