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Reviewer: Srajan Ebaen
Financial Interests: click here
Source: 1TB AIFF-loaded iMAc, Weiss DAC2 connected via Firewire
Preamp: Esoteric C03, ModWright DM36.5
Power amplifier: ModWright KWA-100, FirstWatt J2, F5, M2, Trafomatic Audio Kaivalya monos
Speakers: ASI Tango R, Voxativ Ampeggio [on review]
Cables: Complete loom of ASI Liveline
Stands: ASI HeartSong - 2 x 3-tier stands, 2 x amp stands
Powerline conditioning: 1 x Walker Audio Velocitor S, 1 x Furutech RTP-6
Sundry accessories: Furutech RD-2 CD demagnetizer; Nanotech Nespa Pro; extensive use of Acoustic System Resonators, noise filters and phase inverters, Advanced Acoustics Orbis Wall & Corner units
Room size: The sound platform is 3 x 4.5m with a 2-story slanted ceiling above; four steps below continue into an 8m long combined open kitchen, dining room and office, an area which widens to 5.2m with a 2.8m ceiling; the sound platform space is open to a 2nd story landing and, via spiral stair case, to a 3rd-floor studio; concrete floor, concrete and brick walls from a converted barn with no parallel walls nor perfect right angles; short-wall setup with speaker backs facing the 8-meter expanse and 2nd-story landing.
Review component retail: €9.350 incl. 20% VAT [the PL-L factoring on subsequent pages is €8.670, the CDC €15.500, the CDP €13.500]

Iconic as are few other audio brands, Nagra is both cursed with and blessed by tradition. What makes a Nagra a Nagra is defined by commandments from the past. Stepping outside the past would undermine the company's heritage and alienate us from its carefully groomed identity. But time moves on. New consumers relate to the golden past not as glorious—they weren't around then—but as passé. Another dual-edged sword is relatively unlimited resources. The Nagra Audio subsidiary is ensconced in the 2.000+ strong conglomerate of the Kudelski Group which is publicly traded on the Swiss stock market. Nagra Audio can pursue insular visions driven by their engineers' flights of fancy rather than any actual market demands. It can thus afford to be glacially slow, idiosyncratic and routinely even - well, outright stubborn*.

On the same ledger's sunny side then are products not merely engineered to a 'T' and which go the distance over many decades of ownership. Despite stout stickers, these products are actually priced to retail well below what current trends in manufacturing profit margins and R&D investment return strategies would have to demand to be considered viable. Again that's because the Kudelski Group can afford to. Nagra Audio is less about profitability and being reasonable. It's more about its engineering team's track record of designing and building iconic products nobody else could - or would**. The new push/pull 300B integrated or power amplifier with solid-state drivers and a transformer stack so top-heavy it must ship disassembled is one such beast. American dealers might view today's MSA stereo amplifier at 60wpc and a mere 10kg with exclusively balanced inputs and SMPS equally incredulous. Aren't the most successful expensive amps in the colonies big, heavy, endlessly powerful and running off traditional power supplies with soda-can capacitors and 2000VA transformers?


* As do all manufacturers, Nagra must buy many parts from outside vendors. With failures, standard MO is to have the vendors exchange their defective parts. With Nagra, not necessarily. During lengthy R&D cycles, their engineers will often insist on fixing parts-related issues themselves. Occasionally it means actually re-engineering an original part. This consumes time and resources other companies would refuse to allocate. It's one reason why time at Nagra flows slower than elsewhere. It also explains why Nagra equipment is exceptionally long-lived. The concept of inbuilt obsolescence is alien to the Swiss.
** For a rather more in-depth view at the Nagra phenomenon, read my 2009 factory tour.

Now add vexingly counter-intuitive remote controls and sideways connector bays. They suggest that to own a Nagra requires not only real money but being properly humiliated by certain idiocies before the applicant is deemed fit for acceptance in the exclusive club. Alas once you actually lay eyes on one of their machines in the flesh, all such musings become...well, eradicated in a blinding flash of white-hot lust. As such and at the end of their far from straightforward path, the folks at Nagra know exactly what they're up to. Basterds!

To get properly introduced to today's object of desire, the company shall do the honors. Here goes: The Nagra MSA casing is faithful to the distinctive look and aesthetic standards of the brand. The front face is equipped with the traditional iconic Nagra elements - the elegant modulometer and large rotating selector. The size of the Nagra MSA is consistent in width and depth (275 x 230 mm without connectors) with the compactness of the PL-L, PL-P and VPS preamplifiers and the Nagra CD players family. The MSA is a stereo amplifier with 60 watts RMS output power per channel into 8Ω. The two channels can be parallel-bridged to reach a double mono output power of 120 watts RMS into 4Ω.

As hinted at by the generous heat sink mounted on the top of the unit—a beautifully machined single block of aluminium —the Nagra MSA amplifier achieves amazingly robust performances. A traditional endeavour at Nagra, the MSA relies on original solutions such as the specifically designed PFC-driven power supply and power output stages. These are based on a double-current transfer driver stage and a pair of Mosfet transistors per channel in a common source push-pull configuration with the output on the drains. This arrangement allows comfortable operation under any situation with no instability even when running in parallel-bridged mode with very low impedances loads. Above all, it guarantees transparency and neutrality that only authentic Nagra electronics can.

From the Nagra mission statement for the MSA:
A Nagra device stands out by virtue of its rigor and truthfulness. It always operates as close as possible to the original sound source. To achieve this, Nagra is always on the lookout for solutions that are both rational and highly efficient while constantly developing new ideas and innovative designs. Some essential components are impossible to find on the market. If they cannot stand up to Nagra quality requirements, they are made in-house. Selection of electrical or mechanical components is without regard for compromise and often to military specifications because one single weak link can jeopardize the quality of the whole product. We value high-precision mechanics, workmanship and perfect finishing to ensure robustness and reliability. The pleasure of owning a Nagra not only springs from the knowledge that it hosts some of the finest electronics available but also has to do with the very concrete understanding—visual and tactile—that every hand involved in the process of putting it together was caring and highly qualified. Many Nagra devices built during the last sixty years are still working perfectly and bring to their owners the same joy as they did on the very first day. At Nagra, the notion of planned obsolescence has never prevailed.

Development objectives - a judicious approach to power: The Nagra MSA stereo amplifier is the result of a two-fold development objective: to devise an electronic design capable of gracefully dealing with the vast majority of speaker systems on the market including those known to be difficult to drive; and to fit it into a harmonious casing expressing the traditional design lineage of previous Nagra equipment. The MSA delivers 60wpc RMS power at 8 ohms. The two channels can be parallel-bridged to reach 120 watt RMS at 4 ohms in mono mode with twice the output current capacity. Nagra engineers consider such a power range perfectly adequate to meet the requirements of most today’s speakers, which, although much more efficient than in the past (sensitivities nowadays easily reach 92 to 95dB), in reality reach their physical and acoustic limits way before the 60-watt boundary.

By tackling power issues in a rational way, Nagra has been able to avoid unnecessary complexity in its amplifier circuits. That's always a good course to take when seeking maximum transparency in sound transmission. In electronics, if you want more power you have to pay a price. In particular output stages must host multiple transistors which causes unavoidable difficulties in terms of component matching, stability, energy supply, heat emission and premature aging.

Stable performance in all situations: Speakers are more and more efficient in terms of output. However, they remain complex loads to control, often with very irregular impedance curves. Amplifiers must then deal with sudden impedance variations of great magnitude especially in the lower frequency ranges to challenge the stability of the circuits. To guarantee unwavering handling of sound signal under all circumstances, the power supply must be able to instantly react to an abrupt increase of current demand while maintaining perfectly stable voltage levels. To this effect, Nagra engineers have developed an advanced solution consisting of a power supply that incorporates an active power correction system known as PFC – Power Factor Correction. The MSA project development also focused on a judicious balancing of the different stages: power supply, input driving and power circuits. At Nagra, the engineering success of an amplifier is measured by the overall balance of the circuits within it. More than the criterion of sheer power itself, it is what determines an outstanding behavior and excellent sonic performance.

A description of the electronics: A new piece of Nagra equipment is rarely designed from scratch. The developments undertaken for generations of previous achievements often represent priceless pillars upon which new evolutions and the latest improvements are based. The Nagra MSA can thus be considered as an evolution of the MPA amplifiers and more recently the PSA and PMA pyramidal amplifiers. The global topology of the circuits is mostly the same, with some in-depth improvements affecting several specific aspects. The circuits for example were completely redrafted. New parts were included where they could bring better performance.

The MSA includes a mother board fixed to the bottom of the large heat sink, as well as six secondary circuits: the input, control, power filtering, drivers, PFC power factor correction (one board per channel) and the output socketry circuits. All circuits have gold-plated print on epoxy resin boards and are the result of advanced developments aimed at improving the ground planes as well as fine-tuning the component layout to prevent ground loops and interference radiation. For the same reasons, the number of wired connections is reduced to the strict minimum. Supply and power transistors that must be cooled are mounted upside-down on the mother board, allowing them to be directly fixed to the heat sink. The mains transformer is located above the mother board on a thick metal plate that acts as both a support and electronic shielding.

Supply circuits: With a PFC-driven power supply, the electrical current is always in phase with the voltage in a perfect sinusoidal curve without interference peaks or distortion. From the network’s perspective, this type of power supply is seen as pure resistance and it avoids polluting it. In a way it behaves nearly decoupled from the network. Another obvious advantage is the cleanness of the current propagated downstream to other circuits. By precisely superimposing current and voltage, the PFC power supply generates little losses. It guarantees a very efficient energy transfer and doesn’t collapse when the load increases. It is therefore capable of reacting extremely rapidly to stress situations—even paroxysmal ones—as is required by power output stages in a power amplifier.

The Nagra MSA PFC power supply is built in ways that fundamentally distinguish it from more conventional switch-mode power supplies. In particular, it has no flyback transformer and no snubber circuit, which can lead to hot spots on the printed circuit board. Instead it is fitted with a sizeable 200VA toroidal transformer that reduces the voltage level to suit the power stage (±35V) from which all other voltages are derived. This transformer runs at the power grid’s frequency and avoids generating any residual HF noise. The filtering section of the power supply taking up a good portion of the mother board also was very carefully devised. The quality of the final result depends significantly on the calculations' accuracy, on the nature and choice of the parts as well as their size. For example, multiple polypropylene capacitors and generously dimensioned self-inductance coils and two sturdy 84'000µF electrolytic capacitors feature in the power supply output stage.