Solid State Preamp Reviews

Naim has comprehensively reimagined its Classic Series, which has been around for some 20 years with improvements along the way. Included in the new range of products is the 200 series, comprised of two products: the NAP 250 power amplifier, which I reviewed in the November 2023 issue of Stereophile, and the NSC 222 streaming preamplifier ($8999), which is reviewed here. A third component in the New Classic series, the NPX 300 power supply (also $8999), which is intended to be paired with the NSC 222 and other Naim components, is also considered in this review.

In brief, the NSC 222 is a line preamplifier sporting a precision, microprocessor-controlled, click-free, 100-step discrete-resistor volume stage, a medium-sensitivity moving magnet phono preamplifier, a comprehensive streamer/DAC that can be controlled with the matching Naim app, and a dedicated headphone amplifier. The fully loaded NSC 222 packs quite a punch in terms of facilities and features.

Continuing a Naim tradition, the NSC 222 streamer-preamplifier may be paired with the NPX 300 auxiliary power supply; for the seriously committed enthusiast, a second NPX 300 may be added to the system, providing the option of entirely separating the digital and analog domains. When one or more NPX 300 is installed, the mains-powered supplies inside the NSC 222 are disabled, removing interactions between the local transformer and the digital and analog components inside the NSC 222, including those resulting from radiated electromagnetic fields and core vibrations. Utilization of the external supply allows full electrical separation of the analog and digital sections within the unit. Two separate, high-performance, ring-locking umbilical cables link the auxiliary supply to the two internal sections of the streamer-controller.

This modular design approach allows the user to start with the basic component—the NSC 222—then advance to higher performance levels in logical steps without incurring redundancy.

The physical appearance of these components is classic Naim, with modest changes. The fascia is all black, with heavy sections of satin aluminum alloy flanking a heavy block of polished acrylic. On the far left is the large, illuminated volume knob/encoder, supporting a volume control that suppresses contact noise for smooth, silent operation and delivers a 100dB numeric range in 1dB steps up to 58 and smaller steps thereafter, via a precision discrete resistor ladder circuit, derived from the design from the flagship Naim Statement. To the right of the volume control is a standard 6.35mm (¼") headphone socket and a Type-A USB socket for connecting an external storage USB stick. Next to that is the acrylic middle section with its Naim logo, now backlit in white instead of green. To the right of that is the display window, with large numerals for setting the volume, readable from yards away; it can also display album art when digital music is playing.

On the far right is a vertical line of four multifunction push buttons, to power up or to select an input or operating mode; these functions are duplicated on the supplied remote control. Repeated button presses, either on the remote or those front-panel buttons, allow access to further inputs and modes including vinyl playback. This layered menu design can take a little getting used to; I needed a day or so's practice to operate it with reasonable facility.

The black-acrylic remote control essentially replicates the 222's front panel controls. It is a good size, operates well, and is radio-linked to avoid line-of-sight issues. Display brightness is user-controllable.

The Naim app, for Android or iPad, can be downloaded easily from the web to the user's chosen control device. App features include UPnP library browsing, with album art support, search, and playback controls. In addition to all the digital controls, the app lets you set the 222's input—if, for example, you wanted to play a vinyl record. Other app features include multiroom support (including "party mode"), grouped volume control, discovery of Naim streaming products on the network, and USB/iPod browsing with on-screen volume and playback control. System automation helps synchronize volume control and input selection on compatible Naim Audio devices. I used the app to play music from files stored on a local hard drive and in my Qobuz account, both via Roon—via a separate Roon server, of course.

The back panel of the NSC 222 is densely populated. On the far left is a fused IEC connector—13A European style in my case, since I'm based in the UK. Next to that is the RJ45 (network) connector, then a second USB Type-A connector for attaching external storage. Then come two "remote" sockets for system (On/Off ) synchronization followed by a port for service/diagnostics. Several S/PDIF digital inputs occupy the row below, on BNC, RCA, and dual TosLinks. Farther right are the analog inputs: dual, gold-plated RCA plus ground, supporting the moving magnet phono section, and a single pair of line-level analog inputs on RCA. There is also an 8-pin DIN socket, which can be used as an analog input from supported (Naim) devices; Naim recommends this input for highest sound quality. This connection can also supply power for compatible external phono stages such as the one found in the Naim Solstice turntable. Below the analog inputs are umbilical connectors for connecting up to two external power supplies, including the NPX 300. When no external supply is connected, these connectors must be terminated with the included plugs. Whether or not an NPX 300 is employed, the analog and digital sections of the 222 are galvanically separated.

Far right is the analog output section, with RCA and XLR connectors, the latter pseudo-balanced. By default, only the XLR outputs are active; Naim recommends XLR for connection to the NAP 250 amplifier. There is also a chassis grounding switch, allowing the user to decide which audio-system ground is primary. In some setups, the effect of this switch is mild, but it can make a significant contribution to that subtle sense of musical communication possible with high-quality replay. Power supply artefacts in the noisefloor may be reduced to a minimum when this option is appropriately invoked.

The headphone output is by no means an afterthought. It incorporates a custom, downsized, discrete-circuit Naim power amplifier, which can deliver up to 1.5Wpc into 16 ohms via the usual ¼" (6.35mm) stereo socket; that's enough power to drive a pair of high-sensitivity loudspeakers, ample for any headphone I'm aware of.

In terms of digital playback, the NSC 222 is versatile, supporting USB-connected sources (via front and back sockets), optical and coaxial S/PDIF, and of course network streaming via a designated local network, or linked wirelessly via Wi-Fi. NSC 222 facilities feature Google Cast, Airplay 2, Bluetooth aptX, Spotify Connect, Tidal Connect, and not least, Qobuz. Digital audio format processing handles WAV, MP3, and FLAC, with sample rates as needed up to 384kHz/32 bit, and DSD to DSD128; see the specifications for a complete list of supported formats. (MQA is absent, but these files will play in nonenhanced mode.) My Roon Core Nucleus also supplied much material from my extensive music files, supplemented by live streaming from Qobuz.

As an example of Naim's well-thought-out design, the NSC 222 supports four power modes: standby, network standby, network standby with extra power, and fully on. Network standby allows the 222 to be turned on with the Naim app. Network standby with extra power keeps the 222 fully powered up but with the display and logo turned off.

Technology
Some designers pursue the very latest DAC technologies and DAC-chip implementations, chasing after more bits and higher oversampling rates as if these alone would guarantee a performance margin over nominally lesser implementations. Naim has chosen a well-established DAC, the PCM1791A. As implemented, this Burr-Brown chip operates in its optimal external digital filter mode; a powerful SHARC DSP computes the many filter and shaping functions aiming to maximize sound quality, including high-order integer oversampling followed by pre-filtering at 705.6kHz or 768kHz, according to the required sample rate. Asynchronous sources such as S/PDIF are buffered in a generous memory and reclocked to minimize the jitter that may arise from the digital transport and the S/PDIF interface.

The analog output from the DAC chip is low-pass filtered by discrete-transistor, class-A, active filters employing a topology designed for the task and employing custom-made, low-loss polystyrene capacitors. This type of capacitor is used for all relevant filtering duties, here and elsewhere in the 200 series. Naim says these capacitors are the most transparent. To reduce microphony, these vibration-sensitive components have pre-crimped lead-out wires and are mounted vertically. These capacitors are also thermally sensitive and require hand soldering.

After the low-pass filter is a line stage buffer, a powerful discrete transistor circuit designed to drive long cables, active filters for loudspeaker systems, or multiple power amplifiers as may be required for biamping. Naim specifies nominal figures for frequency response and distortion. RIAA equalization is at a tight tolerance of ±0.1dB out to 20kHz, with a touch of rumble filtering—a sensible –3dB at 10Hz. The –3dB range is 3Hz–40kHz for analog signals. For digital, the –3dB upper limit is a mite lower, at 27kHz, to help filter unwanted ultrasonic processing noise, which could otherwise impair the fidelity of the NSC 222 output stage and the power amplifier that follows by initiating low-level intermodulation distortion.

The Naim NPX 300 auxiliary power supply
As previously mentioned, the NSC 222's performance may be upgraded by adding the NPX 300 power supply, built in matching casework. When this external supply is installed, the internal power supply is disengaged, silencing the internal mains transformer, lowering the noise and vibration floor. Once all those attending my listening sessions had become familiar with what was possible from the baseline, unadorned NSC 222, we unlocked the blanking plugs from the power supply input terminals and connected the hawser-like umbilical cables leading to the NPX 300 external power supply. Powered up again, we left for a tea break to allow the 222 to settle in. Though not previously connected up, the NPX 300 had already been running in for a couple of weeks at this stage.