Linear Power Supply for NAIM Unitiserve

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  • Fully Regulated Design
  • 12V DC at 5 amps
  • Proven design
  • Money back if not delighted

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MCRU introduce the XLCR Fully Regulated Linear Power Supply to fit the Naim Unitiserve. Improves sound quality, proven by customer feedback. The unit has been reviewed by respected UK audiophile Jason Kennedy, here is the review on Jason's website "The Ear"

The XLCR power supply is designed and manufactured in the UK by Longdog Audio who are also responsible for a multitude of award winning power supplies sold by MCRU. EVERY product we have submitted for review in the UK Hi-Fi press has won the top accolade, with several  hundred power supplies sold throughout the world this is a well proven design.

The XLCR was designed specifically to power the Naim Unitiserve which requires 12V DC at 4.8 amps. Un-like the existing power brick supplied with the unit our supply is a fully regulated linear design and according to the first customer to use it it makes the sound much better as we would expect. It is well documented that switch mode power supplies can degrade sound quality, a linear design takes away a lot of the grunge that a smps injects into the mains system resulting in far better sound quality which after all is why we listen to music in the first place.

The Longdog Audio 5A power supply is designed as a high quality low noise power source for the current generation of computer based audio components. Even the most costly digital audio source from established high quality audio manufacturers are supplied as standard with a small, efficient (and cheap) switch mode power supply (SMPS). Modern SMPS's are wonders of electrical technology, offering many features, small size, wide range of input voltages, high current output. But the one thing the all fail at to some extent is the job they are actually used for, providing smooth, quiet, regulated power to feed the audio sources. Looking at the output of a typical SMPS (using an oscilloscope), shows they produce a sea of noise on top of the direct current. A typical 12v DC power supply may produce 500mv or so of wide band noise. As someone in the HiFi industry was heard to say, many years ago, "source first". Well, to the digital
components that we are using today, the original source of any audio that it produces starts with the power supply. Yes, its possible to clean up the noise to some extent by the use of filtration, but for every reduction of noise the filter will add a corresponding increase in power supply impedance, and that means that the power supply is less able to cope with the changing demands of the component.

As the demands of the component change, the DC level of the supply changes at the same time. This is a phenomenon that is beloved in the guitar amplifier world, and there its called "Sag". In guitar amps it increases the distortion and adds more "character" to the sound. But "character" and distortion are the last thing we want to introduce to our HiFi components. Longdog Audio has been supplying solutions to the problems of SMPS's for some years now, we have been making small ultra low noise linear power supplies and providing them to power DAC's and other small source components. However getting such a low noise with a linear (non switching) supply does come with a cost, that cost is efficiency. Each of the regulation stages in a LDA linear supply requires 3 volt or so of headroom to work with. So a 12v output supply, will need to start with a 18v source. The supply discards the excess voltage in the form of heat. That works just fine
if the supply is expecting to supply 500ma or so of current. A 12v 500ma supply will be creating 3W of heat, noting troublesome to dissipate from the casework of the supply. However if we try and simply scale this solution up to 5A or more, we start having to deal with 30W-80W of heat. Suddenly our nice quiet power supply starts to resemble a large class A amplifier, and starts to grow large heatsinks to dissipate this unwanted energy.

The Longdog Audio 5A supply avoids this problem by making use of the latest semiconductor technology. High current MOSFET transistors are now available that can be used to regulate power
with less than half a volt voltage drop, that means a 12v 5A supply can operate with only 2.5W of wasted heat. However to control these devices, we need a voltage that is still much higher than the required output voltage. So to provide the quietness of a linear supply with the efficiency of a SMPS, the LDA design makes use of voltage doubling techniques to get the best of both worlds.
High current, high efficiency and quiet power. The LDA design is so efficient that it does not require the use of external heatsinks, making use of its quality aluminium casework to dissipate the
small amount of heat generated. This means that the supply can be operated continuously at full power yet still only become warm to the touch

The unit is made in 230V and 120V versions, we ship globally and supply the appropriate mains power cable to suit your country in with the package. The unit connects to your Unitiserve via a short cable terminated with a 4 pin DIN connector to connect to the power supply and an audiophile Oyaide DC plug to connect to your Unitiserve. The lead is 1 metre long as standard.

On/off switch and IEC mains power inlet on the rear, the unit has a green LED on the front panel. Specially chosen rubber feet are fitted to absorb micro vibrations.

Dimensions 205mm wide | 320mm deep | 130mm tall.

230V | 120V AC Input

12V DC 4.8 amps output 


Here are some positive thoughts from the latest owner of the Power Supply Mr Harvey....

The old saying goes, you don’t miss something until it is gone.

When I first unpacked my Naim UnitiServe, being a typical bloke, I didn’t read the instructions and hooked it up with the rest of my system. As an upgraded mains cable convert, I treated the supplied mains transformer with a MCRU cable. I was immediately rewarded with a massive amount of interference coming out of my B&W speakers. I then read the instructions, which clearly stated only use the supplied filtered mains cable. I fitted the filtered Naim mains cable and the interference was gone. So the first point is that the UnitiServe is very sensitive to mains interference. I ripped a few CDs and had a listen. The sound was OK, but I guess best summed up as thin and compressed. After spending £2200 I was a little disappointed, but resigned to the fact that the penalty for a conveniently ripped CD collection, was compromised sound.
A couple of weeks later, reading an online forum, I discovered Teddy Pardo linear mains supplies. I ran the proposed purchase past my wife, she said no, so I ordered a Teddy Pardo power supply anyhow.  As soon as it arrived I replaced the Naim transformer with the Tedy Pardo, connected it to the mains with a MCRU No. 85 cable. The result was a smoother and warmer sound, with no hint of interference. I still felt the sound was compressed and the midrange harsh, particularly with female vocals. Overall an improvement had been found.
Two months later, I had ripped all my CDs and had even found time to listen to some of them on the Naim/Teddy Pardo combination. I had grown to accept the resulting sound. Then, by chance, I phoned David at MCRU for a chat about cables or fuses or something. I mentioned that I was a little disappointed with the UnitiServe sound, despite fitting a linear power supply. David informed me about the new MCRU UnitiServe linear power supply. I explained I was happy with the Teddy Pardo, but David insisted on me listening to his new power supply. When I received it, the first thing that stood out was it’s large size and the very well built aluminium case. I connected it to my HiFi and oh my word, I was completely shocked. My digital HiFi had become analogue. The soundstage was massively increased, the base deeper, the treble controlled and all harshness in the midrange had gone. The silence between musical passages was actually silent. I have heard people describe high end hifi set ups as creating black silence - I now know what this means. 
In summary, if you have a UnitiServe, please listen to the MCRU linear power supply. You have the option of a 30 day trial. The improvement in sound is incredible, not subtle. I cannot pretend to understand how the linear power supply works, except that it smooths the DC supply to what is a very sensitive UnitiServe. As the UnitiServe works hard, playing, ripping or backing up, the power supply can be heard working equally hard. The result is amazing.
Do I miss the old compressed digital sound? You bet I don’t. Maybe the old saying is wrong. (On the other hand, my wife spotted the new black box and is currently living with her mother. I do miss her cooking.)


By on 26 Jan. 2015 :

Title : It's as good as they say !
Comment : I have an original Uniti and a UnitiServe connected via a Gigaswitch using Audioquest Cinnamon CAT 7 cable, driving a pair of PMC Twenty.21 speakers - so "bottom range" Hi-Fi (according to some). The linear supply has taken the whole system to a new level. More fine detail, better bass, with transients that can make me jump ! An amazing improvement straight from the box. I've just got all the bits to make a linear supply for the gigaswitch, a bit easier than for the UnitiServe, I can't believe it will make much difference but I'm certainly willing to try it out. Not cheap, but good value, in my system at least.
(Linear Power Supply for NAIM Unitiserve)

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