Nexus NX-5000 Silent PSU

Nexus has had PSUs in SPCR’s silent circle before. The NX-5000, a modest 530W model with fairly high efficiency, is the latest to enter the select winners circle.

Dec 27, 2009 by Mike Vass

Product	Nexus NX-5000 R3 530W Power Supply
Manufacturer	Nexus
Market Price	~US$100

Nexus has offered a variety of computer components for a decade, and presently have a plethora of cases, heatsinks, fans, and power supplies for the consumer market. Nexus has always been focussed on quiet computing gear since their inception; we use some of their fans as references in our reviews.

SPCR has reviewed several Nexus power supplies in the recent past, including both the
old and improved NX-8060
600W, the amazingly quiet Nexus
Value 430 (430W), and the high-end RX-8500
(850W). Under scrutiny now is a medium power offering from Nexus, the NX-5000
(Revision 3), that promises to be "Real Silent" while delivering enough
power (530W) for high-end dual-GPU gaming rigs.

PACKAGING & FEATURES

The box is reminiscent of the RX-8500, with a convenient carrying handle and a subtle feature listing in the bottom-left. The back of the box highlights efficiency and "silent" operation.

Nexus NX-5000 FEATURE HIGHLIGHTS (from the web product page)
Highlight	Our comment
530 Watt true power	"True power" as opposed to peak or apparent power, one assumes.
Single 12V Rail	Preferable to multiple lines, in our view.
82% efficiency; complies with 80 PLUS BRONZE specifications	82%, 85%, 82% efficiencies at 20%, 50%, and 100% loads.
Inaudible performance	We will find out.
Sleeved cables with X-mesh	This is neXus branding; the sleeving is wrapped nice and tight.
Active PFC	This is important if you buy by the Volt-Ampere, rather than the Wat, but a very common feature nowadays.
Real Silent 12cm fan	The phrase "real silent" has always been annoying but perhaps it markets better than the grammatically correct "really silent".
Excellent airflow, honey-comb grill	The entire back panel is a honey-comb grille, which is nice, but again not uncommon.
Full range automatic; no voltage selection has to be set	This is common in power supplies with Active PFC circuitry.
Multiple safety features such as: overvoltage and short-circuit protection	These features help to protect your downstream components.
Ball bearing fan	Better for longevity in hot conditions but usually noisier than sleeve bearing.
Version ATX 2.2	OK.
Complies to WEEE & RoHS	Mandatory for EU. RoHS and WEEE set rules regarding hazardous substances and end-of-life recovery targets, respectively.
Size:150x86x125mm / 5.9×3.4×4.9in	125mm deep is actually short, and good for case organization.

VISUAL TOUR

Inside the box are a handful of accessories and a loose foam block assisting
a bubble-wrap bag in protecting the power supply. This is minimal compared to
other power supplies, which have sometimes included monographed velvet bags
and foam frames, but we prefer it: Less packaging means less waste.

Simple packaging and accessories.

The power supply was further wrapped in another, harder plastic
bag, likely for scratch resistance, though almost comically redundant. The only
included accessories were a set of four uncoloured mounting screws and the AC cable.

Additional bag, likely for scratch resistance, along with twist-tied power cables and mounting screws. Hexagonal exhaust holes along the entire back panel, assisting airflow. The cable sleeves are adorned with an "X" pattern. Also, a back grille that in some configurations might pump some hot air back into the case.

There is no UL file number listed anywhere on the case to check at the UL
Online Certifications Directory, meaning there is no easy way to determine
the OEM. We could dig through the printed circuit board for well known transformer
components and silkscreen board revision numbers, but most readers don’t really
care; the main issue is electrical and acoustic performance.

OUTPUT CABLES

Unlike the NX-5000’s cousin, the RX-8500, there are no modular cables; All
power cables are fixed on the NX-5000.

1 – ATX connector (mm) 20+4 pin
1 – EPS/ATX12V 4 pin connector (mm)
1 – EPS/ATX12V 4-8 pin connector (mm)
1 – PCIe (mm) 6 pin
1 – PCIe (mm) 6+2-pin
2- Three SATA connectors (mm)
2 – Three 4-pin peripheral connectors with one floppy drive connector (mm)

The length of each cable is quite generous, which can be equally convenient
and annoying for a fixed-cable PSU depending on the layout of one’s case.

INSIDE

The NX-5000’s case is a classic stamped steel C-shell case. The fan cable is secured
to the main power cable bundle very closely with little slack (to avoid bending
and interfering with the fan’s blades).

The fan blade color continues the black and white motif used throughout the case design. Relatively small heatsinks are used on each power stage.

The topology and case look similar to the Nexus Value 430, although
with some obvious part changes, and lacking the trimpots seen on the Value 430.
The main capacitor is a Teapo rated at 270uF to 400V and 85ºC, unlike the Value
430’s 220uF / 450V.

The fan is a Muhua Industrial Co. Ltd. MH1225M12D

Nexus is continuing to use fans from Muhua Industrial, in this
case the MH1225M12D, rated to 12V @ 0.26A. This fan is noted to be a ball-bearing
fan, with a "D" in the place of the "S", which probably indicates
a sleeve bearing on the Value 430’s MH1225L12S. Similar to that fan, the support
struts are parallel to the trailing edge of the blades, suggesting high tonal
noise, but with the excellent noise results of the Value 430, we’re optimistic.

TESTING

For a fuller understanding of ATX power supplies, please read
the reference article Power
Supply Fundamentals. Those who seek source materials
can find Intel’s various PSU design guides at Form
Factors.

For a complete rundown of testing equipment and procedures, please
refer to SPCR’s
PSU Test Platform V4.1. The testing system is a close simulation of
a moderate airflow mid-tower PC optimized for low noise.

Acoustic measurements are now performed in our anechoic chamber with ambient level of 11 dBA or lower, with a PC-based spectrum analyzer comprised of SpectraPLUS software with ACO Pacific microphone and M-Audio digital audio interfaces.

In the test rig, the ambient temperature of the PSU varies proportionately
with its output load, which is exactly the way it is in a real PC environment.
But there is the added benefit of a high power load tester which allows incremental
load testing all the way to full power for any non-industrial PC power supply.
Both fan noise and voltage are measured at various standard loads. It is, in
general, a very demanding test, as the operating ambient temperature of the
PSU often reaches >40°C at full power. This is impossible to achieve
with an open test bench setup.

The 120mm fan responsible for "case airflow" is deliberately
run at a steady low level (6~7V) when the system is run at "low"
loads. When the test loads become greater, the 120mm fan is turned up to a higher
speed, but one that doesn’t affect the noise level of the overall system. Anyone
who is running a system that draws 400W or more would definitely want more than
20CFM of airflow through their case, and at this point, the noise level of the
exhaust fan is typically not the greatest concern.

Great effort has been made to devise as realistic
an operating environment for the PSU as possible, but the thermal and noise
results obtained here still cannot be considered absolute. There are too many
variables in PCs and too many possible combinations of components for any single
test environment to provide infallible results. And there is always the bugaboo
of sample variance. These results are akin to a resume, a few detailed photographs,
and some short sound bites of someone you’ve never met. You’ll probably get
a pretty good overall representation, but it is not quite the same as an extended
meeting in person.

REAL SYSTEM POWER NEEDS: While we test the PSU to full
output in order to verify the manufacturer’s claims, real desktop PCs simply
do not require anywhere near this level of power. The most pertinent range of
DC output power is between about 40W and 300W, because it is the power range
where most systems will be working most of the time. To illustrate this point,
we
conducted system tests to measure the power draw of several actual systems
under idle and worst-case conditions. Our most power-hungry overclocked
130W TDP processor rig with an ATI Radeon X1950XTX-512 graphics card drew ~256W
DC peak from the power supply under full load — well within the capabilities
of any modern power supply. Please follow the link provided above to see the
details. It is true that very elaborate systems with the most power hungry dual
video cards today might draw as much as another 200W, but the total should
remain under 500W in extrapolations of our real world measurements.

INTERPRETING TEMPERATURE DATA

It important to keep in mind that PSU fan speed varies with temperature,
not output load. A power supply generates more heat as output increases, but
it is not the only the only factor that affects fan speed. Ambient temperature
and case airflow have almost as much an effect. Our test rig represents a challenging
thermal situation for a power supply: A large portion of the heat generated
inside the case must be exhausted through the power supply, which causes a corresponding
increase in fan speed.

When examining thermal data, the most important indicator of cooling
efficiency is the difference between intake and exhaust. Because
the heat generated in the PSU loader by the output of the PSU is always the
same for a given power level, the intake temperature should be roughly the same
between different tests. The only external variable is the ambient room temperature.
The temperature of the exhaust air from the PSU is affected by several factors:

The thermal rise in the power supply is really the
only indicator we have about all of the above. This is why the intake temperature
is important: It represents the ambient temperature around the power supply
itself. Subtracting the intake temperature from the exhaust temperature gives
a reasonable gauge of the effectiveness of the power supply’s cooling system.
This is the only temperature number that is comparable between different reviews,
as it is unaffected by the ambient temperature.

TEST RESULTS

The ambient temperature was 22~23°, and the ambient noise
level was 11 dBA. Please bear in mind that our testing platform utilizes separate
loading apparatuses for 12V1 and 12V2, and data is collected accordingly, but
in the NX-5000 12V1 and 12V2 are the same line, and they are treated accordingly
in all data analyses.

1. EFFICIENCY — This is a measure of AC-to-DC
conversion efficiency. The ATX12V Power Supply Design Guide recommends 80% efficiency
or better at all output power loads. 80% efficiency means that to deliver 80W
DC output, a PSU draws 100W AC input, and 20W is lost as heat within the PSU.
Higher efficiency is preferred for reduced energy consumption and cooler operation.
It allows reduced cooling airflow, which translates to lower noise. The 80 Plus
Bronze standard requires 85% efficiency at 50% of rated load, and 82% efficiency
at both 20% load and full rated load.

As with many modern power supplies, the NX-5000 has an efficiency
curve that peaks around roughly half its rated load, and dropped off slightly
towards zero and maximum load. Efficiency at about 65W, a reasonable idle load
for modern systems, was a typical 77%. At about 90W, efficiency reached 81.8%,
and we can expect that it would reach 82% by its 20% load of 106W, passing its
first 80 Plus Bronze requirement. At 250W
efficiency was greater than 85% with a measured peak of 85.9% at a 200W load. At at a 50% rated load of 265W, the efficiency
would remain above 85% as specified.

Efficiency dropped down to 80.2% at the maximum load of 530W,
which is below the 82% required for 80 Plus Bronze certification. This is caused
by the demanding thermal environment of our test fixture, compared to the open-air
tests performed for 80 Plus certifications. In our open-air tests, the NX-5000
still fell just short of the 82% efficiency target, at 81.5% at full load, but
it’s close enough that the anomaly can be written off to sample or test measurement
variance.

2. VOLTAGE REGULATION refers to how stable the output voltages
are under various load conditions. The ATX12V Power Supply Design Guide calls
for the +12, +5V and +3.3V lines to be maintained within ±5%.

The NX-5000 performed very well, keeping all voltage lines within
at least 3.4% of their rated value at all times throughout the tests. All lines
experienced a maximum voltage overshoot at low loads, with a 0.92% peak on the
12V line, 3.4% peak on the 5V line, and 3.2% peak on the 3.3V line. The crossload
test did not reduce the performance of the NX-5000’s voltage regulation on any
lines.

3. AC RIPPLE refers to unwanted "noise"
artifacts in the DC output of a switching power supply. It’s usually very high
in frequency (in the order of 100s of kHz). The peak-to-peak value is measured.
The ATX12V Guide allows up to 120mV (peak-to-peak) of AC ripple on the +12V
line and 50mV on the +5V and +3.3V lines. Ripple on all the lines was quite
modest, with a peak ripple of 35mV on the 12V line measured at full load, and
peak ripples of 23mV and 21mV measured with a 400W load for the 5V and 3.3V
lines, respectively.

4. POWER FACTOR is ideal when it measures 1.0. In the most
practical sense, PF is a measure of how "difficult" it is for the
electric utility to deliver the AC power into your power supply. High PF reduces
the AC current draw, which reduces stress on the electric wiring in your home
(and elsewhere up the line). It also means you can do with a smaller, cheaper
UPS backup; they are priced according to their VA (volt-ampere) rating. The
NX-5000 maintained a good Power Factor throughout the test, above 0.9 beyond
40W, and staying above .94 beyond 40W to full load. Though not the best power
factor performance we’ve seen in a power supply with Active PFC, it’s definitely
good enough for 80 Plus Bronze certification.

5. LOW LOAD TESTING revealed no problems starting at very
low loads. Our sample had no issue starting up with no load, either, and the
power draw was very reasonable. Unexpected shutdowns were seen when the 12V
line was suddenly unloaded to 0A, even when other lines were still drawing power,
but this situation is extremely unlikely to occur with modern computer components, and
their predominant use of the 12V line for motors, fans, and additional power
for CPUs, GPUs, and many other components.

6. LOW & 240 VAC PERFORMANCE

The power supply was set to a 400W load with 120VAC through the
20A variac in the lab. The variac was then dialed 10V lower every 5 minutes.
This is to check the stability of the PSU under brownout conditions where the
AC line voltage drops from the 120V norm.

Most full-range input power supplies achieve higher efficiency
with higher AC input voltage. SPCR’s lab is equipped with a 240VAC line, which
was used to check power supply efficiency for the benefit of those who live
in 240VAC mains regions.

Efficiency improved around 4.2% with 240VAC input at this load.
The NX-5000 performed without any problems all the way down to 100VAC, with
an efficiency drop of 2.9% at 100VAC from 120VAC. Neither voltage regulation
nor ripple changed appreciably during the test.

7. TEMPERATURE & COOLING

The NX-5000 remained fairly cool throughout testing. The airflow across the back grille was not
very uniform, which may have had an effect on exhaust temperature readings.
Relatively large intake temperatures were also seen, possibly due in part to
the fan pushing air back into the test setup via its front grille.

8. FAN, FAN CONTROLLER and NOISE

We attempted to monitor the fan voltage for the 2-wire Muhua fan,
but found that the voltage remained railed to the 12V line throughout the test,
in spite of audible cues that the fan was spinning faster. This implies PWM
control, or some kind of ground level control, so instead we relied solely on
the more relevant SPL readings and our hearing to monitor the fan performance.

The slowly spinning Muhua fan did not register on our measurement
system, the SPL remaining unchanged at the ambient of 11 dBA@1m from idle all
the way up to 150W. It was barely audible from even 30cm in our anechoic test
chamber. The fan finally started speeding up around 200W, a fractional increase
rounded up to 12dBA@1m, with no real perceivable difference in the sound.
The first perceivable difference was heard at 250W (31ºC intake), where
the fan finally sped up to a slightly more audible, calm "wooshing"
sound at 14 dBA@1m, more from air turbulence than the fan’s bearing.

The fan’s noise increased most noticeably at 300W (32ºC intake),
to a more audible 22 dBA@1m. To take a reading in the anechoic chamber, the cooling fans in the loading apparatus must be turned off to ensure they do not contribute
to the noise level. This decreases the amount of heat pushed into the "hot
box" test fixture, decreasing the thermal stress on the power supply under
testing. Very soon after the loading apparatus’ cooling fans were
turned off, the NX-5000’s fan would slow down, implying that a 32ºC intake
is perhaps a threshold for the NX-5000’s fan controller. Above 32ºC/300W, the fan
noise increased steadily, up to a maximum of 25 dBA@1m at full load. Even this
noise level is just a quiet, smooth rustle of moving air, which is very impressive
for a 530W PSU at full load.

The screen captures below from the SpectraPLUS audio spectrum
analyzer should be self-explanatory. Note that the noise floor of the anechoic
chamber is just under 11 dBA. The red line is the ambient level of the chamber
without any noise sources.

Idle to about 200W. Peaks are seen at 400Hz and 200Hz, and are related to commutator buzz and what little turbulence is audible at this level. At 250W, the fan becomes slightly more audible at 14dBA@1m, with smooth, low tones dominant. At 300W, a very noticeable jump in fan noise is seen, with a broad spectrum that translates to something more like a fuzzy white noise. As the noise increases past 400W, we mostly hear increasing volume on the lower pitched hum from blade turbulence and the bearing.

Outside the Hot Box

In a modern high performance case that has independent cooling airflow
for the power supply, thermal conditions are much milder than in a conventional
case or in our test box. The PSU does not have to work nearly as hard to exhaust
hot air from the downstream components. As in our most recent PSU reviews,
a noise/load test was performed out of the hot box to simulate noise performance
in a modern, high performance case.

Nexus NX-5000 SPL: In Hot Box vs. Out
Power load	200W	250W	300W	400W	530W
in hot box	12	14	22	24	25
out	12	12	12.5	14	19
Measurements are SPL in dBA@1m

On the test bench with ambient room temperature at 23°C, the Muhua
fan managed to stay under a barely audible 14 dBA@1m all the way up to 400W,
and peaked at 19 dBA@1m, which is noticeably quieter compared to its already
superbly quiet performance in the test box.

COMPARISONS

The comparison table below shows the SPL versus Power Load data on all the PSUs tested in the anechoic chamber thus far.

Comparison: Various PSUs Noise Vs. Power Output in Anechoic Chamber
Model	90W	150W	200W	250W	300W	400W	500W	6-700W	850W
Seasonic X-650	<10	11	12	14	16	31	31	32	n/a
Nexus Value 430	11	11	16	18	18	19	n/a	n/a	n/a
Nexus NX-5000	11	11	12	14	22	24	25	n/a	n/a
Antec CP-850	12	12	12	14	14	26	40	44	45
Enermax Eco80+ 500W	<11	12	16	19	26	32	33	n/a	n/a
Seasonic M12D 850W	14	14	14	14	14	24	37	42	42
Enermax Modu82+ 625*	13	13	14	15	16	26	36	37	n/a
Coolermaster M700W	14	14	18	21	25	27	34	34	n/a
Chill Innovation CP-700M	15	15	15	15	17	30	34	34	n/a
Antec Signature 650	15	15	15	18	18	28	36	47	n/a
SilverStone DA700	18	18	18	18	23	32	35	41	n/a
Nexus RX-8500	14	14	17	22	28	32	32	33	33
NesteQ ECS7001	22	22	22	21	23	25	36	37	n/a
PCPC Silencer 610	20	24	24	24	24	30	40	50	n/a
Corsair CX400W	22	26	32	35	35	35	35	n/a	n/a

The Nexus NX-5000 is one of the quietest power supplies reviewed in the anechoic
chamber, and though it is louder than the Nexus Value 430 at 300~400W, it’s
practically inaudible below that power load, and still has reserve to spare
for dual-GPU systems, 8 hard disks, or whatever other components you feel it
must power.

Caution: Please keep in mind that the data in the above table is specific to the conditions of our test setup. Change the cooling configuration, the ambient temperature and any number of other factors, and you could change the point at which the fans start speeding up, as well as the rate of the rise in speed. The baseline SPL is accurate, however, probably to within 1 dBA.

MP3 SOUND RECORDINGS

These recordings were made as 24-bit / 88 kHz WAV files with a high
resolution, lab quality, digital recording system inside SPCR’s
own anechoic chamber (11 dBA ambient), then converted to LAME 128kbps
encoded MP3s. We’ve listened long and hard to ensure there is no audible degradation
from the original WAV files to these MP3s. They represent a quick snapshot of
what we heard during the review.

These recordings are intended to give you an idea of how the product sounds
in actual use — one meter is a reasonable typical distance between a computer
or computer component and your ear. The recording contains stretches of ambient
noise that you can use to judge the relative loudness of the subject. Be aware
that very quiet subjects may not be audible — if we couldn’t hear it from
one meter, chances are we couldn’t record it either!

Each recording starts with 6~10 seconds of room ambient, followed
by 10 seconds of the product’s noise. For the most realistic results,
set the volume so that the starting ambient level is just barely audible, then
don’t change the volume setting again while comparing all the sound files.

• Nexus
  NX-5000 at various loads in anechoic chamber at one meter
  — Low Load – 11 dBA@1m
  — 250W (14 dBA@1m)
  — 400W (24 dBA@1m)

Sound Recordings of PSU Comparatives
in the Anechoic Chamber

CONCLUSIONS

The Nexus NX-5000 lived up to its claims of being
"Real Silent" (taken figuratively, not literally, which is a
whole ‘nuther discussion) while delivering 530W. It scored very high in
both electrical and noise characteristics, demonstrating low ripple, extremely
good voltage regulation over its entire range of load tests and crossload tests,
good efficiency characteristics over its entire working range, and perhaps most
importantly, managed to stay quiet across its entire operating range, with a
peak of just 25 dBA@1m after thermally stabilizing at its full load of 530W.
Running a PSU continuously at full load is an
extremely demanding test and unlikely to ever happen "naturally" in practice, so it is similarly unlikely
that users of this power supply will ever hear such fan speeds in their own
system. The small, unobtrusive physical aspect adds to the impression of a quiet,
efficient, and professional "demeanour".

It’s hard to find fault with this PSU, aside from perhaps the
lack of modular cabling. The NX-5000 is a great addition to Nexustek’s midrange
power supplies and a very strong contender in the "silent" computing
enthusiast market. It fully deserves SPCR’s Editor’s Choice Award.

Nexus NX-5000 Balance Sheet
Likes * 80 Plus Bronze efficiency * Almost inaudible @ low-med loads * Quiet (<25dBA) at max load * Solid voltage characteristics * Reliable at high test temperatures	Quibbles * No modular cabling

Nexus NX-5000 Power Supply

SPCR Editor’s Choice Award

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SPCR Articles of Related Interest:
Power Supply Fundamentals

Recommended Power Supplies
SPCR PSU Test Rig V.4
Enermax Eco80+ 500W PSU
Nexus Value 430 PSU:
Affordable Silence
X-650: Seasonic
hits Gold

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