Naim Supernait integrated amplifier
By Art Dudley   •   January, 2008 "We've tried making it more powerful. When I was away on holiday, some of our people cooked up a more powerful version and presented it to me on my return. It sounded awful."

That was Naim Audio's founder, the late Julian Vereker, MBE, talking to Sam Tellig about the 15Wpc Naim Nait 2 integrated amplifier, as reported in the April 1990 Stereophile (Vol.13 No.4). His words were the first thing this ever-cynical reviewer thought of upon learning that, some seven years after Vereker's death, the company he left behind had been rattling those same pots and pans.

Then again, after 23 years of writing about domestic audio, I've come to where I can tell when a company is promoting a product simply because they must, and when there's some sense that the thing they're offering is special. And it's obvious: Everyone at Naim thinks that the new Supernait integrated amplifier is really special.

So my hopes of pre-judging a new audio amplifier were once again dashed: I would have to get my hands on a Supernait, read the owner's manual, install it, and use it to play music. Most of which seemed like a pleasant idea, once I stopped to think about it.

Description
A considerable increase in power is not the 80Wpc Supernait's only calling card: It also contains a 24-bit D/A converter, addressable through any of five S/PDIF inputs: two RCA coaxial jacks, two TosLink optical jacks, and one front-mounted 3.5mm "mini-TosLink" jack, the latter for use with portable media players, which also accepts analog signals. That's a remarkable thing, made all the more remarkable by the fact that Julian Vereker also scorned the idea of having D/A converters and their datastream sources physically separate from one another. It's getting so a fella can't even leave the planet for a few years without other people coming in and stirring the pot.

The Supernait's digital input section begins with a Crystal CS8416 receiver chip, which identifies the incoming datastream as 44.1, 48, 88.2, 96, or 192kHz. Conversion is handled by a stereo 24-bit/192kHz D/A chip from Burr-Brown. As the owner's manual states, the Supernait's digital circuitry is designed to recognize stereo PCM datastreams only; its digital output will be muted in the face of DSD, DTS, or other such data. Absent a recognizable digital input signal of any sort at any of the five inputs, the S/PDIF board powers down altogether, in an effort to maintain the purity of an alternative (analog) signal.

The Supernait's analog inputs outnumber their digital counterparts: There are six in all, most of them addressed by both RCA jacks and Naim's traditional DIN sockets. (Where both exist for a given input selection, the two types of jack are wired in parallel with one another.) The DIN input socket reserved for Aux 2 also contains a 24V DC output, to power one of the company's outboard phono preamplifiers. (Typically, that would be the Naim Stageline, although I imagine the company's Prefix, specific to the Linn LP12 turntable, would work as well.)

Unlike other recent integrated amps, the Supernait incorporates a fully active line-level preamp, said to be derived from class-A circuitry developed for the company's flagship NAC-552 ($28,100 including companion power supply). Volume and balance are controlled with very-high-quality potentiometers—I heard not the slightest trace of degradation when adjusting the latter to the left or right of center—which are motorized for use with Naim's standard remote handset. I was very happy that the serenely attractive Supernait lacks a digital display; instead, it has a single tiny LED each for the volume and balance knobs, and equally subtle illumination for the soft-touch selector switches. (I can also live without knowing which digital sampling frequency is in use at any given time, though not everyone may share that indifference.) Sadly, unlike the NAC-552, the Supernait has no mono switch.

The output section of the Supernait's power amplifier, derived largely from Naim's NAP200 amp ($3100), is biased to operate in quasi-complementary class-B. That's very much a Naim tradition, albeit one that Julian Vereker suggested wasn't a strict requirement for good performance, but merely an architecture within which he was comfortable working. (Vereker also thought it possible to make an excellent-sounding tube amp, but disliked working with such high voltages.) According to some Naim insiders, the quality of their power transformers—designed in-house and sourced from the same company for most of Naim's existence—is among the keys to their amplifiers' musical success. One staffer told me that Naim has actually looked into the idea of using switch-mode power supplies in some products, going so far as to build a couple units of the company's classic NAP250 using such a thing—but the noise levels were always unacceptably high compared with the more traditional approach.

Setup
A pioneer in recognizing the need for good power-supply design, Naim Audio has also distinguished itself with an original approach to power-supply implementation. Almost from day one, Naim has made sure that all of their low-level circuitry is kept as far as possible from the power-supply circuitry that feeds it, and that all amplification circuits use a central point within that remote power supply as a common reference for zero voltage potential: a system-wide star ground, if you will. That philosophy has given way to a commercial line in which remote power supplies are available for many of their products—as standard items or, just as often, as upgrades representing various levels of cost and refinement.