The well-known memory brand morphed in recent years to become a major player in retail power supplies. While Corsair offers kilowatt PSUs, a 400W model rounds out the opposite end of its line.
Dec 15, 2009 by Mike Vass
Product | Corsair Power 400W (CMPSU-400CX) Computer Power Supply |
Brand | Corsair |
Market Price | US$50 – $65 |
Corsair has been offering power supply units, based on Seasonic and Channel
Well platforms, for the past three or so years. SPCR reviewed a handful of them
— the VX450W,
TX650W, and
both the HX520W
and HX620W — and reported consistently excellent performance. Naturally,
the lineup has expanded, mostly upwards to the kilowatt level… but the CX400W
is a counterpoint to the rest of the Corsair power line, with just 400W maximum
power at a very modest price. As you might expect, Corsair claims the CX400W
makes no sacrifices on performance.
A 400W-rated PSU is generally seen today as a “low-end” model, though
we’ve seen in the
past that many very capable systems don’t draw more anywhere close to 400W.
It’s the inclusion of high end gaming cards, particularly two or more such cards,
that makes the power demand jump. Some manufacturer rebates have pulled the
price of the CX400W under $50 this holiday season, so it really does compete
in the lowest price category of power supply units.
Like the VX450W and TX650W, but unlike the HX520W and HX620W, the power cables
on the CX400W are permanently attached. This is expected for such a low cost
model, and has the theoretical advantage of reducing overall voltage drops through
the cabling.
PACKAGING & FEATURES
The box features minimalistic artwork, with less focus on feature listings compared to previous Corsair models. |
Corsair CX400W FEATURE HIGHLIGHTS (from the web product page) | |
Features | Our comment |
Supports the latest ATX12V v2.2 standard and is backwards compatible with ATX12V 2.01 systems. | Good to see. |
Rated up to 400W of continuous power output at 40ºC | Notice the 40ºC: A realistic operating temperature. |
Extra long fully sleeved cables to support full tower chassis and assist with flexible cable routing. | In leiu of modular cables, this is a nice feature to have. |
Ultra-quiet 120mm double ball-bearing fan delivers excellent airflow at an exceptionally low noise level by varying the RPM in response to temperature. | Of course, the airflow has to turn 90º to exhaust, but this is pretty typical. Hopefully the fan is indeed “ultra-quiet” |
High efficiency topology to ensure energy savings. | The CX400W is branded basic 80Plus, so expect good efficiency, not stellar efficiency. |
99% Active Power Factor Correction provides clean and reliable power to your system. | This is important if you buy by the Volt-Ampere, rather than the Watt. |
Universal AC input 90~264V automatically scans and detects the correct voltage. No more hassle of flipping that red switch! | Nice to know about the switch. Notice the 90V lower limit. This is very good. |
Dedicated single +12V rail offers maximum compatibility with latest components | The honesty about a shared 12V line is nice! |
Over Current/Voltage/Power Protection, Under Voltage Protection, and Short Circuit Protection provide maximum safety to your critical system components. | OK. |
Standard ATX PS/2 size: 5.9″(W) x 3.4″(H) X 5.5″(L); 150mm(W) x 86mm(H) x 140mm(L) | Yep, this is pretty standard. |
MTBF: 100,000 Hours | 11.4 Years. I like the optimism! |
SPECIFICATIONS
Power specifications are shown on a convenient sticker right
on the top of the unit:
Corsair CMPSU-400CX (CX400W) Specifications | |||||
AC Input | 100-240V – 7A 50/60Hz (Differs from website) | ||||
DC Output | 3.3V | 5V | 12V | -12V | 5Vsb |
20A | 20A | 30A | 0.8A | 2.5A | |
130W | 360W | 9.6W | 12.5W | ||
400W |
Strangely, the AC Input specifications vary with respect to
the website’s specs for the same supply: 100-240V – 7A – 50/60Hz written on
the label, versus 90-264V – 5-9A – 47-63Hz on the website. That 10VAC on the
lower end could make a difference in brownout conditions.
Our sample lacked any 80 Plus labelling, but it is clearly among
Corsair passed models listed
at the 80 Plus web site. Keep in mind that the testing for 80 Plus
approval is done at normal ambient room temperature. The 80
Plus Testing Guidelines (PDF) specify only that “ambient temperature
shall be maintained at 23°C ± 5°C throughout the test.”
In contrast, the ambient temperature of the SPCR test system is directly proportionate
to the load. At low load, the air intake is at or just above room temperature,
but as load is increased, the temperature rises steadily. Typically, with
a fan-cooled PSU, the intake temperature in our test system reaches 45~50°C
at >600W loads. This is an extremely tough test condition, as PSU efficiency
naturally drops off at high and low loads; combine high load with high temperature
and it’s essentially a torture chamber. It does replicate reasonably well
the conditions that prevail in a typical tower PC. For full details, please
refer to SPCR’s PSU Test Platform
V4.1.
VISUAL TOUR
Opening up the retail box, a modest packaging scheme was revealed. Cutting
the costs of fancy velvet drawstring bags, custom monographed velcro cable bags,
and solid foam enclosures leaves the CX400W with a plain bubble-wrapped bag
and simply retained cabling and accessories.
Modest packaging and accessories |
Accessories include a region-appropriate AC cable, 4 mounting
screws, a bag of cable ties, and the User’s Manual.
2-piece interlocking C-shaped casing, scratch-resistant black with a modest debossed Corsair logo. Also, note the neatly bundled cables.
|
OUTPUT CABLES
1 – ATX connector (640mm) 20+4 pin
1- EPS/ATX12V 8-4 pin connector (600mm) 4×2 (8-pin)
1- PCIe 6-pin (640mm)
2- Three SATA connectors (760mm)
2- Three 4-pin peripheral connectors with one floppy drive connectors (900mm)
The length of each cable is quite generous, and the included zip ties will
be required for cable management in most cases.
INSIDE
Four screws on the table, and we’re in. Looking at the topography inside, we
see… a VX450W with different parts.
Notice the “CX” on the yellow filter cap near the bottom, sandwiched between two toroids. Hints aside, it’s pretty hard to tell apart from the VX450W. Good sized heatsinks on all the power stages. |
Unlike the VX450W, there is no plastic baffling near the exhaust
port, which implies it is not necessary. Another important difference is the
lower value filtering cap: 270uF @ 400V versus the VX450W’s 330uF @ 400V. This
is a cost cutting measure, and whether it is important will be seen in the voltage
regulation and ripple tests. Like the VX450W, the CX400W uses an ADDA AD1212MB-A71GL
120mm fan, rated for 85.2CFM at 2200rpm and 39.1dB/A.
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 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 150~200W, 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:
- Intake temperature (determined by ambient temperature and power output
level) - Efficiency of the PSU (how much heat it generates while producing the
required output) - The effectiveness of the PSU’s cooling system, which is comprised of:
- Overall mechanical and airflow design
- Size, shape and overall surface area of heatsinks
- Fan(s) and fan speed control circuit
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 21~23°, and the ambient noise
level was 11 dBA. Note that our testing platform utilizes separate loading apparatuses
for 12V1 and 12V2, and data is collected accordingly, but in the CX400W 12V1
and 12V2 are the same line, and they are treated accordingly in all data analyses.
There is no downside to our method.
OUTPUT, REGULATION & EFFICIENCY: Corsair CX400W | ||||||||||||
DC Output Voltage (V) + Current (A) | DC Output | AC Input | Calculated Efficiency | |||||||||
+12V1 | +12V2 | +5V | +3.3V | -12V | +5VSB | |||||||
12.38 | 0.98 | 12.38 | 0 | 5.1 | 0.98 | 3.38 | 0.97 | 0.1 | 0.1 | 22.1 | 35 | 63.2% |
12.35 | 0.98 | 12.35 | 1.71 | 5.11 | 0.98 | 3.38 | 0.97 | 0.1 | 0.1 | 43.2 | 59 | 73.2% |
12.35 | 1.93 | 12.35 | 1.73 | 5.1 | 1.94 | 3.38 | 1.85 | 0.1 | 0.4 | 64.5 | 83 | 77.8% |
12.35 | 1.92 | 12.35 | 3.43 | 5.1 | 1.95 | 3.38 | 2.74 | 0.2 | 0.5 | 90.2 | 111 | 81.2% |
12.34 | 3.82 | 12.34 | 4.93 | 5.09 | 4.53 | 3.38 | 2.66 | 0.3 | 1 | 148.6 | 181 | 82.1% |
12.3 | 5.67 | 12.3 | 6.54 | 5.08 | 5.4 | 3.38 | 5.27 | 0.4 | 1 | 205.2 | 244 | 84.1% |
12.27 | 7.67 | 12.27 | 7.91 | 5.08 | 5.5 | 3.39 | 5.32 | 0.5 | 1.5 | 250.6 | 293 | 85.5% |
12.26 | 8.63 | 12.26 | 9.43 | 5.07 | 7.89 | 3.39 | 7.82 | 0.6 | 1.8 | 304.1 | 364 | 83.6% |
12.25 | 11.34 | 12.25 | 9.52 | 5.07 | 9.42 | 3.39 | 8.66 | 0.7 | 2.1 | 351.6 | 427 | 82.3% |
12.2 | 13.04 | 12.2 | 11.01 | 5.05 | 10.93 | 3.39 | 10.1 | 0.7 | 2.1 | 401.7 | 493 | 81.5% |
Crossload Test | ||||||||||||
11.88 | 13.52 | 11.88 | 14.94 | 5.22 | 1 | 3.38 | 0.95 | 0.1 | 0.1 | 348.2 | 420 | 82.9% |
+12V Ripple (peak-to-peak): <16mV @ <400W +5V Ripple (peak-to-peak): <4.4mV @ <400W +3.3V Ripple (peak-to-peak): <5.6mV @ <400W | ||||||||||||
NOTE: The current and voltage for -12V and +5VSB lines is not measured but based on switch settings. It is a tiny portion of the total, and errors arising from inaccuracies on these lines is <1W. |
OTHER DATA SUMMARY: Corsair CX400W | ||||||||||||
DC Load (W) | 22 | 43 | 64 | 90 | 148 | 205 | 250 | 304 | 351 | 401 | ||
Intake °C | 21 | 21 | 24 | 25 | 30 | 30 | 29 | 30 | 31 | 36 | ||
Exhaust °C | 24 | 25 | 29 | 31 | 35 | 37 | 38 | 40 | 45 | 51 | ||
Temp Rise °C | 3.0 | 4.0 | 5.0 | 6.0 | 5.0 | 7.0 | 9.0 | 10.0 | 14.0 | 15.0 | ||
Fan Voltage | 4.2 | 4.2 | 4.2 | 4.2 | 6.2 | 10.2 | 11.2 | 11.2 | 11.3 | 11.3 | ||
SPL (dBA@1m) | 19 | 19 | 19 | 19 | 26 | 32 | 35 | 35 | 35 | 35 | ||
Power Factor | 0.86 | 0.96 | 0.98 | 0.997 | 1 | .99 | 1 | 1 | 1 | 1 | ||
AC Power in Standby: 0.7W / 0.087 PF AC Power with No Load, PSU power On: 9W / 0.68 PF | ||||||||||||
NOTE: The ambient room temperature during testing can vary a few degrees from review to review. Please take this into account when comparing our PSU test data. |
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
standard also requires 80% efficiency at 20% of rated load or higher.
At a minimal and unrealistic 20W load, efficiency was poor at
63.2%. By 65W, which is a nominal idle load for most systems these days, efficiency
rose to about 78%. Better than 80% efficiency was seen at all loads over 90W
up to the maximum rated load, and a 85.5% peak was reached at 250W. As we’ve
seen in many other power supplies, efficiency began to drop as maximum rated
power output was reached, likely due to the rising temperatures at those loads.
These are good results, although 80%+ efficiency is reached a
little beyond the 80W load that represents 20% of maximum load. Note that the
80 Plus testing is done at typical room temperature (18~28°C) while our
test conditions feed the heat of the PSU output back into its operating ambient,
which makes for a much hotter, more demanding high power load test. In spite
of this, the CX400W efficiency remained above 80% even to full load.
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 CX400W performed magnificently, with maximum overshoot and
undershoot seen at no load and crossload conditions, respectively. The worst
on the 12V line was an overshoot of 3.17% at no load, and crossload conditions
only managed to drop the voltage 1%. The 5V line, similarly, was 2.2% over at
no load, but reached around 4.4% over during the crossload test, still within
spec. Both lines tended to get closer to their target voltage as the load increased,
decreasing percentage overshoot. The 3.3V line acted contrarily, increasing
overshoot as the load increased, reaching a maximum of 2.72% at maximum load,
and generally unaffected by the crossload test.
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 Power Supply 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 ridiculously good at all power levels, staying under 16mV on the 12V line
over the entire range, and under 4.4mV and 5.6mV on the 5V and 3.3V lines, respectively.
Close to the best ripple we’ve measured in the past, and fantastic at the price.
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. Power
factor was good for this PSU, running no lower than 0.96 for every point above
50W, though a PF of 0.86 was measured for 20W. At this low power, however, the
difference the power factor makes is not nearly as significant as at, say, 400W.
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 modest.
6. LOW & 240 VAC PERFORMANCE
The power supply was set to 300W load with 120VAC through the
hefty 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 when the
AC line voltage drops from the 120V norm. Given the difference between the web
specifications and the specifications written on our power supply, we tested
down to 90V.
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.
Various VAC Inputs: CX400W @ 300W Output | ||
VAC | AC Power | Efficiency |
240V | 347W | 87.6% |
120V | 360W | 84.4% |
110V | 363W | 83.7% |
100V | 365W | 83.3% |
90V | 368W | 82.6% |
Efficiency improved around 3.2% with 240VAC input at this load.
The power supply also performed appreciably all the way down to 90V as promised,
still staying above 80% efficiency. Neither voltage regulation nor ripple changed
appreciably during the test.
7. TEMPERATURE & COOLING
The CX400W stayed reasonably cool throughout the test, demonstrating
a double digit temperature rise around 300W, and staying at a stable 15ºC
rise at maximum load. This is quite impressive for the price point, but the
tradeoff is higher fan speed, as explained below.
8. FAN, FAN CONTROLLER and NOISE
The fan voltage was monitored via a small wire soldered onto the
positive terminal of the Adda fan. With no load, all the way up to about 90W,
the fan remained at a quiet 4.18V, audible from 1m but generally a low, unoffensive
hum, registering 22dBA@1m. Commutator chatter could only be heard with a discerning
ear at less than a foot away, and did not seem to increase at higher speeds.
At 150W and above, however, the fan sped up to maintain reasonable cooling,
increasing to a lightly audible 26dBA@1m at 150W. The noise increased to a plainly
audible, turbulent 32dBA@1m after running for some time at 200W. At 250W, the
fan hit its maximum voltage of 11.2V, generating a very noticable hum at 35dBA@1m,
all the way up to and throughout maximum load.
The screen captures below from our 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.
At around 150W, the fan noise became plainly audible, with higher frequency components becoming audible and apparent, and the sound gaining more broadband noise. |
In a modern high performance case with independent cooling airflow
for the power supply, thermal condition 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, we
performed a noise/load test out of the hot box to simulate noise performance
in a modern, high performance case.
Corsair CX400W SPL: In Hot Box vs. Out | |||||||||
Power load | 90W | 150W | 200W | 250W | 300W | ||||
in hot box | 19 | 26 | 32 | 35 | 35 | ||||
out | 19 | 19 | 24 | 30 | 35 | ||||
Measurements are in dBA@1m |
On the test bench with ambient room temperature at 23°C, the fan
in the CX400W stayed quietly below 30dBA@1m until 250W. The overall noise-to-power
curve is still considerably steeper than most of the top rated PSUs to emerge
from SPCR testing, but it’s considerably better than inside the hot box, as
expected. With some care in thermal design and keeping maximum component power
demand to no higher than ~200W, a DIY system builder should be able to assemble
a very quiet PC with the Corsair CX400W.
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 |
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 | 19 | 26 | 32 | 35 | 35 | 35 | 35 | n/a | n/a |
*Guesstimates based on the Modu82+ 425’s idle in the chamber and the Modu82+ 625’s load test.
The Corsair CX400W is obviously one of the noisier power supplies we’ve tested
in the past year. It stopped performing “quietly” (<30dBA@1m SPL)
at a rather low 200W load. It may not be quiet enough for silent PC enthusiasts,
but it will likely be quiet enough for many mainstream users, especially in
systems without power hungry video cards..
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.
- Corsair
CX400W at various loads in anechoic chamber at one meter
— Ambient of chamber – 11 dBA@1m
— 90W (19 dBA@1m)
— 150W (25 dBA@1m)
Sound Recordings of PSU Comparatives in the Anechoic Chamber
- Nexus
Value 430 at various loads in anechoic chamber at one meter
— idle to >150W (11 dBA@1m)
— 200 (16 dBA@1m)
— 250 (18 dBA@1m)
— 400 (19 dBA@1m) - Enermax
Eco80+ at various loads in anechoic chamber at one meter
— idle to >90W (11 dBA@1m)
— 200W (16 dBA@1m)
— 250W (19 dBA@1m)
— 300W (26 dBA@1m)
CONCLUSIONS
Electrically, the Corsair CX400W performed solidly throughout
the testing, including the cross-loading. It produced amazingly low ripple and
noise, and maintained excellent voltage regulation throughout. It had no trouble
producing full rated power and staying cool on the cool test bench or inside
the extremely hot test box. Our sample lived up to all but one of the selling
features that we could test (11.4 years MTBF, really?).
Acoustics was the only aspect of its performance that was not
remarkable. A couple of years ago, below 25 dBA@1m at up to 150W would have
been enough to qualify a PSU as a genuinely quiet model. But standards have
improved, and the overall noise of the quietest PSUs in the marketplace is now
not only lower but lower to a high power load than ever before. In this context,
the CX400W feels a little dated. Its controller sped up the fan speed at a much
lower power level than we expected.
Keep in mind that this is a bargain-priced power supply, in the
lowest price bracket of brand name power supplies, and the CX400W’s idle noise
is still quite low. Its electrical performance (other than efficiency) up to
rated power is competitive with the very best PSUs money can buy. At $50, an
80 Plus-certified, rock solid power supply that is quiet at low power draw is
quite a value — and a good candidate for fan modding in a silent PC enthusiast’s
special project. The CX400W cleanly rounds out the lower-end PSU offerings from
Corsair.
Corsair CX400W Balance Sheet | |
Likes * >80% efficiency in typical use | Quibbles * Steep noise/power curve |
Our thanks to Corsair
for the review sample.
* * *
SPCR Articles of Related Interest:
Power Supply Fundamentals
Recommended Power Supplies
SPCR PSU Test Rig V.4
Sparkle Power’s 250W ATX12V
80 Plus SPI250EP
Enermax Eco80+ 500W PSU
Corsair VX450W: Quiet Value
PSU
Nexus Value 430 PSU: Affordable Silence
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