Hardware Reviews

Longdog Audio XLCR Naim Unitiserve power supply


The Naim Unitiserve is a dedicated music server made by a company with a track record for high quality and back up, Naim is also renowned for offering power supply (PSU) upgrades for its preamplifiers and source components. Thus far however it has not made one for the Unitiserve, which is supplied with an inline supply of the switching variety. It’s a bit bigger than you would get with a decent computer company NAS drive, the Unitiserve is essentially a very good NAS drive with disc ripping abilities, but uses the same technology. Switching mode power supplies (SMPS) are brilliant things if you want to reduce mains voltage to the sort of levels required by all manner of devices; they are inexpensive, quiet and don’t produce lots of heat. What’s not to like, well the noise that they add to the voltage supplied and the noise that they inject into the mains which then spreads to other components in the system. As Linn and others have proved it is possible to make a great sounding SMPS but not at sensible prices. The alternative is a linear power supply with a transformer such as is found in Naim’s HI-CAP and other supplies, but since these are not made for the Unitiserve Long Dog Audio’s Nick Gorham decided to make a version of his 5A supply for this purpose.

The Unitiserve requires 12 volts of DC at 4.8 amps, which can result in a supply that’s as large and hot as a power amplifier, so Nick used high current MOSFET transistors in a voltage doubling arrangement to create a sensibly sized supply that doesn’t require heat sinking. The full technical story can be had from Nick or David at distributor MCRU, but the resulting Long Dog XLCR comes in a reasonably compact case that’s about the same width as the Unitiserve but twice the height. It’s small enough to sit alongside it on the rack and that’s the important thing, actually the aluminium used for the job is important too but you wouldn’t mistake it for a Naim box. This partly because it has a green LED on the front that’s rather brighter than you get with contemporary Naim kit. On the back there’s an IEC mains inlet for 120V or 230V depending on which versions you choose. Output is via a short lead with a four pin DIN at the supply end and an Oyaide DC plug for the server.

linear power supply 3

One thing to scorch into your memory if you own a Unitiserve is never turn it off without using the proper shut down procedure. Casual switching off on the back or unplugging from the wall often results in damage, sometimes pretty catastrophic. As you might be able to tell I learned this the hard way. Switching in another PSU is therefore slower than most changes you can make but with the Long Dog you could have left it all day, the differences it brings are not what you would call subtle. In a revealing system they are seriously dramatic, during a review of a big Meridian system I contrasted the Long Dog with the standard supply via my Resolution Audio Cantata in UPnP streamer mode. With a well known piece of chamber music (La Folia by the Gregorio Paniagua) the change was jaw dropping. The amount of acoustic space that appeared was shocking, I had to check the volume and the track to make sure nothing had changed. Then it became clear that the noise floor had disappeared to reveal a bed of tape hiss on this analogue recording that I’ve not previously encountered. This combination of opening up of the recording meant that the dynamics took on a vigour that made the standard PSU sound gutless. The change this power supply brings about is nothing short of boggling, admittedly the Meridian system is pretty revealing which helps but it is such a big difference that this is second time I have put fingers to keyboard to report my findings. The first time I hadn’t heard it via Meridian but my regular system and the changes were nearly as dramatic, with Melanie de Biasio’s (No Deal) sultry tones the highlighting of the voice increases alongside a general improvement in transparency. It opened up the soundstage and revealed surprising amounts of detail because once again the noise floor had been pushed down to expose quieter sounds, the fine details that combine to make reverb last longer and instruments and voices sound more real.

Ask someone from the Naim inner circle about using a third party supply and they will nod their head sagely and say, yes very nice but they screw up the timing. As it happened I had a member of that exclusive society around to try something else and they had to admit that the timing did not suffer. I would go further and say that it improves because of the all round transparency increase, this reveals the nature of leading edges more clearly, so you can appreciate the way that different instruments sync together. When you can hear more you can hear where more notes stop and start, so timing is a natural benefactor. Transparency does not necessarily equate with better timing but in this case it clearly does. Essentially you are hearing more of what the server can do and less of the noise that the standard supply injects into the wall, it’s this double bonus that makes the result so compelling.

linear power supply side

Going back to the SMPS results in harder edged, smaller scale sound that is more akin to old style Naim, a sound that some prefer it has to be said but I’m not among them. I love the way that the soundstage opens up with the Long Dog, it ushers in genuine 3D imaging as well as enhancing the drive in the music. I played one of Brendel’s Beethoven Piano Sonatas and that had considerably more life and vigour thanks to the dynamics that this supply allows the Unitiserve to serve up, and this combined with the brilliance of the playing made for far a longer session than expected.

It’s disconcerting that a PSU upgrade to a music file server should have so much effect, but we are still discovering what counts in computer audio and this is certainly an important area. Power supplies are the lifeblood of reproduced music, if you want to hear more they need to be good and the Long Dog is clearly rather good.


Dimensions 205mm wide | 320mm deep | 130mm tall.
230V | 120V AC Input
12V DC 4.8 amps output

Price when tested:
Manufacturer Details:

Long Dog Audio
T 07812 249747


Linear power supply


Jason Kennedy

Distributor Details:

T 07908 056978

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