One glance at Niro Nakamichi's NIRO range, and you know you are in the presence of something special. One glimpse, and I just couldn't wait to try out one of these over-engineered oddballs. I mean, the first analogy to pop into my head upon seeing the NIRO 1000 Integrated Engine was that it looked like a high-tech Ninja/Transformer robot peacock, what the Japanese would make if origami moved from paper to metal. (The separate pre-amp and power amp are just as outr .)
It's the 'peacock-ness', the fan-tail heat-sink array that renders the NIRO so distinctive, but the heat sinks are not mere styling conceits. This pair of extrusions embodies what NIRO is all about. So how can heat-sinks be the key to a design? However much I adore Pathos' Logos heat-sinks, which spell out the company's name, they only address, after all, wholly aesthetic concerns; Pathos could have used any old heat-sinks, but - being Italian - they preferred to make them look good. The NIRO's, on the other hand, are genuinely part of the circuitry.
To get to the 'root' of NIRO, you should know the parent company's name: Mechanical Research Corporation. Just as every brand creates its identity by having a special area of concern - Wilson-Benesch, for example, specialises in carbon fibre usage - NIRO devotes much of its attention to magnetic forces and 'unwanted currents'. Because current-carrying parts generate magnetic fields and forces, and all signal-carrying components can be caused to vibrate because of those forces, Nakamichi firmly believes that due - no, make that excessive care should be applied to those areas throughout the circuitry.
According to Nakamichi, 'In an environment inundated with electromagnetic fields, such motion induces unwanted current in response. [such forces] cause distortions that degrade the quality of the audio signal. Physical fields lie at the root of these phenomena, and combating them requires electromechanical engineering of a very high calibre.' Hence, the word 'mechanical' in the company's name.
So, you're still wondering, how do heat sinks affect sound quality? Ordinarily, heat-sinks are finned, rectangular structures with the sole task of dissipating heat. But if the nearest heat-sink fin is distanced from the active device, the heat then has to pass through the amp's structure. In NIRO's 1000 Power Engine, each heat-sink is a sub-assembly containing a push-pull output transistor pair, mounted immediately adjacent to one another to ensure thermal parity. Nakamichi explains, 'Using a dedicated subassembly for each transistor pair promotes uniform, efficient dissipation across all the fins with no "hot spots".'
Nakamichi mounted the heat-sinks with specially-designed supports that prevent the transmission of vibration. These mounts use a custom-made, conductive, non-magnetic gold-plated alloy, while the heat sink fins vary in length. Thus, any resonance from external sources, including excitation due to a speaker's high sound pressure levels, will be 'diffused' over a range of frequencies. Moreover, the heat sinks are fitted with a 3mm-thick resonance-damping bar, the structure also ensuring uniform heat distribution, a reduction in the time required to reach stable operating temperatures, and the prevention of external vibrations from interfering with the audio circuitry.
This concern for the electrical/mechanical relationship goes much further, Nakamichi applying it to the 1000 series models' entire component layout, including the power supplies. The design keeps all high-power wiring short and even prevents the transformer's primary and secondary wiring from physically crossing over each other. Nakamichi notes that, 'These goals simply cannot be achieved with traditional chassis layouts, which are conceived in two-dimensional space. The NIRO 1000 three-dimensional implementation is ideal and significantly reduces "noise pollution" generated by the power supply.'
To dissipate vibrations from the power transformers and chokes, they're mounted via custom-engineered springs, each with characteristics specifically matched to the weight of the supported component. Thus, the unwanted energy is converted into heat. Nakamichi feels that the gain even for this seemingly minor detail is 'an astonishing difference in sound quality.'
It goes on and on, detail after detail, in the best 'Japanese obsessive' manner: The transformers and chokes use 'inverted mounting' because in this manner they are fitted at the most mechanically stable part of their casings, and therefore cannot worsen unwanted vibration. Moreover, because the transformer and choke wires exit through what would normally be the bottom cover, even shorter wiring paths between these parts and the rest of the power supply can be realised. Even the AC input connector block is 'trick': it's spring-loaded, with an appropriate stabilizing pressure, to dissipate vibrations that might be transmitted via the power cord into the amplifier chassis, while a 1mm air gap between the connector block and the chassis 'ensures complete isolation from high-frequency interference.' (I swear I didn't make up this feature!)
Inside, the PCBs employ free-floating mounts made of special insulating dampers to isolate them from mechanical and electrical interference. The input stage board is located near the top of the chassis, to position it as far away as possible from the power supply and servo circuitry, while the line input connector is located at the top of the chassis immediately above the board. To keep inter-stage wiring as short as possible, the power stage board is located immediately beneath the input stage. To guarantee that mains-borne nasties are kept at bay, power is supplied to the input stage through a shielded channel