Naim ND 555 and PS 555 DR

Music servers and computer audio
Naim Audio ND 555/PS 555 DR

The streaming board was all-new, Naim’s six-layer NP800 streaming section being co-designed by, and exclusive to the company. It’s controlled by the player’s ClockMaster circuitry, which is located near the DACs when in UPnP (network playback) or streaming mode, to reduce jitter. In addition, the streaming board is mounted in its own Faraday Cage, physically isolated from the rest of the player, while the DACs themselves – selected Burr Brown PCM1704U-K resistor-ladder designs chosen purely for their sound – each sit in their own miniature Faraday Cages.

It says we bypass the DACs internal digital filter and use the SHARC. This is accurate for most of our players (e.g. NDX2 with the PCM1792A DAC). However the PCM1704 is a pure mono R2R DAC with no built in digital filter. Burr Brown say use it with their external digital filter chip the DF1704. We obviously do not use the DF1704 and use we the SHARC with our own integer oversampling algorithm converting to either 705.6kHz or 768kHz (depending upon incoming sample rate). 

It’s all about accuracy and resistance to interference: the digital signal flows from the inputs to the DACs using I2S, with its separate clock signal, over Low Voltage Differential Signalling, used for its high accuracy and very low radiated field, while a 40-bit SHARC DSP processor is used for jitter-busting (or actually jitter-removing) buffering, and oversampling. When it comes to digital filtering, instead of using Burr Brown’s DF1704 filter chip – the obvious partner for the pure mono R2R DAC design, which has no built-in digital filter – Naim uses the SHARC along with its own integer oversampling algorithm converting to either 705.6kHz or 768kHz (depending upon incoming sample rate). 

All this is about as far as you can get from the ‘off the shelf’ streaming solutions found in lesser players. In addition, the ND 555 uses 13 of Naim’s Discrete Regulators – as seen in many of its other ‘DR’-suffixed products – to noiseless clean DC power. Separate regulators are used for the DACs, the clocks and the output stages, and the sections of the player are physically separated right back to the two large multipin Burndy power supply sockets on the rear panel.

And that’s where the idea of the twin power supplies comes in. As standard, with a single 555 PS connected to both Burndy sockets, the 555 PS receives several separate 22V supplies for the analogue section and a mixture of 15V, 12V and 10V supplies for the digital circuitry. Switching over to two 555 PS supplies effectively separates the two sections of the ND 555 all the way back to the mains plugs, and means one is only supplying the analogue section, and the other the digital. 

Given that, when using a single 555PS, the only ‘point of contact’ between the two sections would be in the transformer of the power supply, doubling up may seem overkill. However, when discussing the clearly audible effect of using two power supplies with the NDS, the suggestion was that as well as increasing this separation, the strategy reduces the load on each power supply, which might have the effect of bringing about a noise reduction.

But there’s a difference with the ND 555’s design. The impression gleaned at the time of the launch of the new network players back in March 2018 was that the extensive use of the DR technology in the ND 555 might mean the dual power supply strategy would have less of an effect than it did with the NDS. Not that the company wouldn’t suggest trying it, of course – business, after all, is business…

Having run an ND 555 almost since the first review samples escaped into the wild over two years back, I was pretty sure of a couple of things: one was that both the player and its power supply were more than adequately run in, both having been used daily and kept powered up 24/7, and the 555 PS having been ‘inherited’ from my old NDS. The other? Well, through a variety of amplification and speakers to have passed through my hands during their tenure, there was never any sense of wanting more, of anything being missing – not only is the Naim a superb front-end for reviewing, but it’s also a delight to listen to in ‘off duty’ periods, which to me is a pretty good indicator of the worth of a product: the appeal is visceral, not merely academic.

Having added the second 555 PS to this tried and tested set-up, I’m not at all sure why there was any suggestion that doing so wouldn’t bring distinct benefits: compared with the player with a single supply – and most obvious when switching back – was an effect not at all removed from that of switching to a more powerful amp and better speakers, such was the added resolution of detail, the extended and more tightly controlled bass, and the sheer dynamic impact.

That this was true via relatively modest amplification – for ‘operational reasons’ not entirely disconnected with other reviewing commitments, I used my Naim Supernait3/HiCap DR combination as much as I did my NAC52/52PS/NAP250’ olive set-up – was even more striking. Not only did this show that the idea of ‘source first’ is alive and well, but it also demonstrated just how well-sorted an integrated amp is the SN3. Yes, a totally ‘mullet’ system, but with such musical rewards!

In truth, I didn’t find a single album (or indeed track) that sounded better without the extra power supply in place; the weight of the Roger Waters live recordings on Us + Them [Columbia/Legacy] went from impressive to jaw-dropping, with even greater insight into the instruments being played backed up with a great big, tight bass. At the same time, at the other end of the scale, the gentle trio jazz of the new Espen Eriksen Trio set, End of Summer [Rune Grammofon] gained immensely from the tighter focus brought about by the twin-powered Naim.

Not only was every move of drummer Andreas Bye clearly delineated, from the subtlest swish of brush on skin to the punch of his bass drum, but also the resonance of Lars Tormod Jenset’s bass sang out through the mix. But the most astonishing revelation was Eriksen’s piano, which sounded not just like a recording of the instrument but actually as though it was sitting in the space before me, taking me all the way back to the experience of hearing the trio from a front-row seat in a small jazz club. Well, actually in the upstairs room of a well-heeled Surrey golf club, but you get the idea.

The lazy, sleazy groove of the Stones’ Goat’s Head Soup, in its latest remastered DSD64 form [Polydor Japan], sounds magnificently louche with the twin-powered ND 555 delivering the tune, with all the lush layers of guitars, strings and more revealed: the ND 555 with single PSU almost gets there, but this is the full-on effect. Meanwhile, Bach’s anything but ‘Little’ Prelude and Fugue in D major, played by Ulrich Böhme on Rondeau, shows just how well the supercharged network player can bring out not only the sheer air-shifting power of those lower manuals but also deliver the way the sound interacts with the space in which it’s being played. JSB certainly knew how to write a bass-line!

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