Network audio will run and run. The more we learn, the
better equipped we will become, and the better able to help readers optimise
this new kind of system.
This issue's project covers a variety of topics which were
largely dealt with in a rewarding listening test marathon. While complex and
time consuming, these delivered clear and repeatable results. The procedures
were inevitably time consuming, because many of the changes and substitutions
required the network to be reset. (In the case of the Naim UnitiServe,
this involves a full power down and power up of the operating system.)
Swapping interconnects is so much easier in the analogue domain!
We were intrigued by the results of auditioning several NAS
(network-attached storage) drives, reported in Vol5
No3, concerning the differences between internal processors, and
the sound quality variations found between different data drives, whether
solid state or disc. The effect of the recommended gigabit switch at the (data
replay) streamer end of the chain needed verifying, and also the influence of
the type of network cable type joining it all up.
Talk to computer people (especially those at Hydrogen
Audio), and such ideas are derided as pure heresy. These people consider that 'bits are
bits' and that a NAS cable (of sufficient bandwidth, which all
are of course) cannot possible influence results. However, we do not indulge
in such prognostications, which are seemingly made as an article of
pseudoreligious faith. Rather, we observe and report on the differences that
we find, if any, with a view to understanding better how these connected
systems behave, and to seek answers.
Naim UnitiServe Revisited
We were lent a second UnitiServe,
this time the -SSD solid state
version, and made careful comparisons against the established standard unit
with hard disk drive (HDD). We also tried and report on an unofficial
substitution for the UnitiServe 12V
6A external plug-in power supply. In fairness Naim do not claim audiophile
status for the UnitiServe, and
in truth it performs very well just as it is, even justifying my use of high
end DACs such as the MSB Platinums.
But I wanted to hear the effect of using an external plug-in 12V linear supply
in place of the standard, if line filtered, switch-mode type. It's possible
that Naim will release an upgraded power supply for the UnitiServe,
having appreciated its potential, but I can make no promises in this regard.
The final audio tests exploited the fine USB input feature of the UnitiServe
to assess two contentious Red Book audio rips which have a
not just limited to CD format audio or its internal storage. It can also
replay audio from a USB memory stick and will scan the network for music
stored on NAS drives or other network-linked shared files, in WAV, AIFF, FLAC,
ALAC, OGG Vorbis, AAC, WMA and MP3 formats at up to 24bit/192kHz resolution.
The UnitiServe-SSD has
no internal hard-disk storage and is intended for use in network systems where
ripped data is stored exclusively on the network (most commonly a NAS drive).
Music access and control is available via multiple
interfaces, including the NServe computer
based control software, or the Apps on iPhone,
iPod or iPad
platforms. It also responds to a conventional infrared remote
control, though connecting an accessory display to the UnitiServe
is essential to get the most out of this mode.
Comparing the hardware of the two UnitiServes,
the official story (and it is a good one) tells of the awful inevitability of
hard drive failure, its endlessly spinning mechanism running quite hot from
hub, actuator motors and related power supplies. Indeed, it's amazing that
hard drives run as well as they do. Naim fits good ones, selected and
certainly heavy duty (though not the slower and very costly examples made for
commercial servers). HDD failure is measured in years rather than months, but
the consequences could nevertheless be severe. Spend a month or so ripping say
800GB of music to the hard disk UnitiServe,
and you could be lucky and enjoy years of replay pleasure with no other store
required, just a simple network control to choose albums and tracks. I have
done this for many months now, well aware of the risks. Breakdown might even
be benign, and Naim might be able to recover the tracks and re-compile them
when carrying out the repair. But maybe not, and ripping the whole lot again
would not be a welcome task.
Protection stage one is therefore to couple up temporarily
to a computer via NaimNet software and make a 'mirror' backup copy, say
on a portable USB-connected terabyte drive (£90 or less). Then UnitiServe
drive failure can be addressed by reading back from these copy
files, simply by plugging that USB drive into the back of the repaired UnitiServe.
Only Naim can reload the files since its internal drive is set to read-only as
far as the customer goes. (This is quite deliberate to prevent the UnitiServe
becoming corrupted, the resulting defect in practice no different
from any mechanical or electrical failure.) Going for the solid state version
of the UnitiServe sounds like good advice, even though this version
costs about 15 per cent extra. Using a 16GB Single Level Cell (SLC) 'Enterprise
Drive', it has just a fraction of the HDD version's memory
capacity, but that's not what it's about. With no moving parts 'it
should never fail', but that's actually not quite true: the number of
possible read/write cycles does have a finite limit, even though Naim fits the
top grade of SS memory. Memory operation requires moving the data around the
chips resulting in 'electrical wear' to the charge storage property.
However, internal routines aim to protect the memory, and if it is relatively
little used (as is done in the UnitiServe,
for example mainly for the resident operating system programming), a long 5-10
years estimated life is likely.
Cited further advantages for the SSD
are lower power consumption, and hence lowered electrical noise; no
moving parts, so lower acoustical noise and vibration, and therefore
potentially cleaner CD rips and therefore the promise of better sound quality.
A most convenient feature when ripping CDs is that it uploads straight to the
NAS drive; where correctly connected to the internet it can look up the
metadata and augment the file information.
The HDD and the SSD UnitiServes
sounded fundamentally similar, with very good detail and a strong sense of
rhythm and drive. They were substantially involving musically when compared to
so much digital audio replay out there, especially that emanating from
computer style CD ROM drive machines, rather than classic Red Book 'realtime' players.
Operating with the Naim DAC
for example, both UnitiServe versions
delivered a solid performance that matched the standalone Naim CDX-2,
while those power supply upgrades for the Naim DAC
continue to chase the sound quality dragon. This continued right up
to the heroic 555PS, though I
felt this final step was bordering on the side of diminishing returns.
did sound different, not by much but enough for us to determine a preference.
However, our result is not claimed to be universal. The SSD
initially seemed to have an advantage, but we had walked into a
trap. While it seemed to have higher definition, sounding more evenly
tempered, sophisticated, certainly a little clearer and also somehow more
vitally connected, there was also an slightly foreign processed quality,
almost a coloration – not quite a 'glare' but more as if the lights at
the recording venue had been turned up a little too much. Direct comparison
with the HDD version showed that the SSD's
subtle 'halo' effect was indeed less natural. And the HDD version has a
clear advantage on one aspect of sound quality: music flowed a little better
and timing was superior too, with more natural dynamic expression. So despite
the SSD's advantage in clarity
and audible sophistication, in the end we considered that the hard disk
version beat the SSD by about
13% – a significant margin in a HIFICRITIC
review context, though in another system the SSD
might be preferred.
The SDD can
undoubtedly provide great sound quality, but the regular hard drive version
certainly sounded a little better in our review system. The SSD
is physically silent, the HDD very nearly so, and while the SSD
sounds cool, sophisticated, pure, smooth, vital, almost crystal
clear, it ultimately lacks the full quotient of musical drive and rhythm that
we know is possible from our test programme, due, we believe, to a touch of 'processed
sound' detachment. That said, we have no hesitation in
Recommending both the standard hard drive and the SSD
Switch-Mode Versus Linear Supplies
As standard, both UnitiServe
models come supplied with switch-mode power supplies. Since such
supplies tend to affect system sound quality adversely, we thought it would be
interesting to try them with an alternative non-Naim linear supply. We won't
go into the extended detail involved in getting the comparisons right,
including whether one or both the units were on and which type of supply fed
which type of UnitiServe.
Perhaps inevitably either or both of the standard switchmode supplies
moderately degraded the overall system sound quality, a factor which until now
had been accepted as an inevitable component of the overall UnitiServe
sound quality. Indeed, the latter is inherently so good that it
simply survives this factory choice of power supply.
It is only when these UnitiServes
are assessed individually with the two different supplies that the magnitude
of the performance gain with the linear supply becomes obvious. For these
tests I used an inexpensive (less than £100) non-audiophile, semiindustrial
12V 10A Elektro-Automatik PS 2012-10 supply.
It was slightly modified to minimise residual fan noise when located near the
listening position (ideally such a supply would be convection cooled), and I
had to fit a cable with Naim-compatible DC plug. The full benefit of the
linear supply was not achieved until the second UnitiServe
was powered down, and its switch-mode supply disconnected from the
In my audio system context the sound quality of both types
of server improved by no less than 30 per cent when used with the linear
supply. (Incidentally, it's a tribute to the MSB Platinum
Signature DAC used for monitoring these changes that such effects
were so readily heard and easily scaled.) With linear supply the HDD UnitiServe
sounded more upbeat and flowing, with a purer quality overall and
noticeably reduced grain and sibilance – surprisingly, since little such
error could be detected prior to the change. The midrange sounded still more
natural, with more expressive yet unforced vocals, while rhythmic power
increased and bass tune playing was clearer at low frequencies. Reference
programme examples in particular sounded closer to the master tape experience.
The UnitiServe-SSD with
linear supply showed improved image depth and still greater clarity and
sweetness. That slightly unreal tinge of 'glare' was significantly
reduced, while the low frequency quality was also improved. There's still a
hint of 'processing' and a slightly less than natural quality about its
sounds, but all was rendered with greater overall definition. It sounded
substantially more upbeat with better flow than when using the standard
supply, and was now rated very good in this respect, though we still felt that
the HDD version had the advantage here. However, I cannot rule out the
possibility that some listeners may prefer the particular quality of sonic
precision available from the SSD Naim
UnitiServe when using a superior
A Gigabit Switch
Linn amongst others recommends that a fast gigabit switch is
placed in the network cable line close to the network music player, to buffer
and accurately shape the signals fed to the player, since the NAS drive could
be sited some distance away.
Such a switch is likely to have a plug-top switchmode supply
(as in our Netgear example), and such a supply is undesirable if sited so
close to audio system electronics. Replacing this supply with a generic linear
(transformer) supply did lift system sound quality 3% to 5%. However, deleting
the switch from the chain altogether brought a 10% improvement in sound
quality, which for me was an important discovery.
A streamer local gigabit switch is only required if there
are further local network components to support and provide shared connection,
so we did use it in comparative testing when running two UnitiServes
Most network audio websites and also manufacturers involved
discount the idea that the choice of network cable can affect the sound,
either because they are sure it does not, or simply because this is a
convenient view to take. Since 15m of network cable costs about £13, it was
easy to buy two lengths of Belkin Snagless UPTP
(unshielded and recommended for audio use) in Cat5e and Cat6
varieties. They arrived in tight coils and needed to be stretched out for a
day or two to 'relax' and lay flat before gently smoothing out the bends.
With the network audio system up and running, the two test cables were used
between the NASconnected router a hard disk drive Naim UnitiServe.
Patience was required, as the system had to synchronise after each
disconnection. Multiple trials were carried out, but this was not really
necessary, as the differences were not trivial. Using Cat6 as the reference,
reversion to Cat5e dropped sound quality by around 20 per cent – jaw
dropping in view of the trivial cost involved, especially when compared with
the price of the whole audio system.
Variations in the sound of digital audio replay don't
necessarily correlate with those in the analogue domain; sometimes different
terms are needed. By comparison, Cat5e sounded 'greyer', with less
contrast and somewhat dulled detail. Specifically, low level detail and image
depth were impaired, unwanted grain and sibilance were increased, and there
was a shortfall in coherence and involvement. Dynamics were softened and the
sense of rhythm was significantly reduced. Three DACs were tried (the Metrum Octave,
the MSB Platinum Signature and
the Naim DAC), all with very
similar results, so I do not think that the differences are down to failures
of the DACs to re-clock or reject jitter, nor the S/PDIF performance of the UnitiServe,
which has proved a first rate source of data in this format.
"Most network audio
websites and also manufacturers involved discount the idea that the choice of
network cable can affect the sound, either because they are sure it does not,
or simply because this is a convenient view to take"
We therefore believe that network cables have a significant
influence on audio replay. (Incidentally, we have been warned against using
screened types.) Other factors may well affect performance too, such as the
quality of termination to the plugs and the fit and tightness of these plugs
for these not wholly reliable 'telephone' connectors. And we hope to try
out some 'audiophile' network cables soon.
New Zealand LOG Rips
Many enthusiasts will be aware that different ripping drives
and software do sound different upon replay, despite working to a common and
specified lossless format. A contentious test CDR known to HIFICRITIC
has 23 different error-checked lossless rips from various
unmodified computers, drives and ripping software, and nearly all of these can
be subjectively differentiated from one another. (We are planning a report on
some ripping software and its sound quality.) Furthermore, brief experiments
with the UnitiServe's built-in
audio grade ripper have revealed small differences in the rip quality
resulting from changes in the power supply or the support environment.
Kethel had ripped three versions of the Private
Investigations track using a ROM drive with various upgrade power
supply arrangements, including a shunt regulated version based on a John
Linsley Hood design. The files were EAC error checked, zipped, sent to the UK
over the internet, unzipped, HDD stored in my computer, and EAC checked again
to be sure they were all numerically the same. They were then copied onto a
USB stick, and replayed via a
Naim UnitiServe and MSB Platinum
Signature /Diamond Power Base into an Audio Research Reference
5/Krell Evo 402e/Wilson
Audio Sophia 3 analogue replay
system, with accessories and supports to match. We made careful comparisons
with eight repeats in all, judging as if we were playing the CD which we know
very well; we felt the sound quality differences between the files were
somewhat like changing CD players.
This gave a sound that was rather mid-fi CD in character. It might be
considered perfectly good by those who haven't heard anything better, but
for us it was not very communicative or involving. We decided to give this a
50% approximate sound quality score as a reference.
Sounded less dull, more detailed and more transparent than Rip
1, with more precise dynamics and better bass definition. There was
now more musical expression with better clarity, listener involvement, and
unquestionably higher resolution (I have experienced the master tapes). The
score was now a comparative 75%, and the sound was considered very natural,
accurate, with firmer clearer bass lines, greater depth and atmosphere.
Instrumental decays were better extended into the deep silences.
Initially considered better still in some respects but not others, Rip
3 showed more convincing micro dynamic resolution in the far depth
plane, and still more detail and focus. But it was not quite as relaxed,
flowing and musically involving, and sounded slightly artificial and mannered
with what we call a 'spotlit' character. In consequence the score dropped
to around 65%. Kethel had believed that Rip
3 would be the best, as he had made further changes to the ripping
drive supply. Whereas we had 'correctly' and reliably identified the
improvements with Rip 2, with no
foreknowledge of what changes had been made, we were now in disagreement over Rip
3. Subsequent further tests confirmed that we had been correct, and
that Kethel had not completed the final modification to the optimum standard
for this rip.
particularly interesting to try and understand the means by which the power
supply quality for a ripper's drive mechanism can be transmitted as sound
quality differences via error-proofed
WAV music files. Computer people tell us: "this is not possible" and "we
must be imagining it". However, we are merely reporting what we have found.
Ripping hardware and programs simply cannot be taken for granted, even if and
when the software reports 'zero errors'.
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