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Corsair VX450W: Quiet Value PSU

August 16, 2007 by Mike Chin

Product
Corsair VX450W

ATX12V v2.2 / v2.01 power supply
Manufacturer
Corsair Memory
Market Price
US$75~80

Corsair Memory is a brand best known for high performance memory, but they made a big splash when they entered the PSU market last year with the HX series 520W and 620W power supplies. The combination of excellent performance and very low noise made them a hit with both overclockers and silent PC enthusiasts. The only downside seemed to be low level humming with a small number of units, which caused frustrations among the silent enthusiasts. However, Corsair's user support has been excellent, with buzz/hum complainants quickly issued replacement units.

The new VX450W is a lower powered, less ambitious model that seeks to fill a value niche. It's one of two models in the VX series; the other being a 550W version that has yet to be released. The VX450W does not feature detachable modular cables like those found on the HX series. Corsair's marketing makes a big deal about the unit's eco-friendliness, emphasizing the high efficiency and active correction for very high power factor. These features are hardly unique to the VX450W, however, and could be found in numerous PSUs even dating back a couple years. The packaging is very similar to the HX series, with a classy, understated look that suggests a lot of time, money and attention have been paid to this aspect. There's little doubt that Corsair's marketing/PR is on the ball.




Classy understated retail package.



Inside, the PSU is cradled in a cloth drawstring bag lined with bubble-plastic. A user's manual, screws, plastic cable straps, AC cable and a detailed reviewer's guide completed the sample package.

FEATURE HIGHLIGHTS AND SPECIFICATIONS

Corsair VX450W Feature Highlights (from the Corsair
web site)
FEATURE & BRIEF COMMENT
Supports the latest ATX12V v2.2 standard and is backwards compatible with ATX12V 2.01 systems.
Very good; unlike the HX series, the VX is not EPS12V compliant. This has to do with dual-video card support.
Guaranteed compatibility with dual-GPU configurations. To be expected.
Double forward switching circuitry design offers high efficiency, up to 85% under wide load range.
Sounds good and familiar, though the percentage has jumped from the 80% claimed for the HX series.
Active Power Factor Correction with PF value=0.99 provides clean and reliable power to your system. Well, it has little to do with the outputs and everything to do with the input, but it's a good thing.
Universal AC input 90~264V automatically scans and detects the correct voltage. No more hassle of flipping that tiny red switch!
Fairly standard, but the 90V input is lower that the usual 100V, which is good.
Ultra quiet 120mm double ball-bearing fan delivers excellent airflow at an exceptionally low noise level by varying the RPM in response to temperature.
OK.
Dedicated single +12V rail offers maximum compatibility with latest components. The straight-up honesty is refreshing.
High quality Japanese capacitors provide uncompromised performance and reliability.
To assure savvy buyers who may be aware of the bad cap fiasco that's plagued China-made electronics for some years.
Over Current/Voltage/Power Protection, Under Voltage Protection, and Short Circuit Protection provide maximum safety for your critical system components. About par for the high end course.
Standard ATX/PS2 size: 5.9"(W) x 3.4"(H) X 5.9"(L)

150mm(W) x 86mm(H) x 150mm(L)
Not oversized is good.
MTBF: 100,000 Hours That's a long time. Wonder how it's calculated...
Safety Approvals: UL, CUL, CE, CB, FCC Class B, TÜV, CCC, C-tick. The more the merrier.
Five year warranty with 24/7 support. Very nice.

OUTPUT SPECIFICATIONS: Corsair VX450W
AC Input
90-264VAC, 5-9A, 47-63Hz
DC Output
+3.3V
+5V
+12V
-12V
+5VSB
Maximum Output Current
20A
20A
33A
0.8A
3A
Maximum Combined
140W
396W
9.6W
12.5W
450W

Corsair provides two graphs that show noise and efficiency curves with a high degree of resolution. Most similar data presented in marketing materials don't really tell much; these are much better than usual.

The noise curve above show a steady noise level of around 21~22 dBA (at 1m, presumably), and a hinge at 400W, at which point the noise ramps almost vertically. This is the most extreme "hinged" noise/fan speed to load curve we've seen in any power supply, and it promises that the VX450W will be quieter at higher power than any other PSU tested to date. We have to assume that the load refers to typical temperatures reached at the plotted power levels, since every PSU we've tested only ties fan speed to temperature, not actual power output.

The efficiency curves shown above are also very detailed and show a realistic midrange peak with falloff at either extremes. The 2~4% advantage in efficiency at 230VAC jibes perfectly well with our own comparison tests of PSU efficiency at 110~120 / 220~240 VAC.

EXTERNAL TOUR

The exterior of theVX450W is archetypical black.



Nothing out of the ordinary here.



No vents
other than the fan intake and backside exhaust grill.

A single 120mm fan draws air into the power supply from below, blows it across the heatsinks, then out the low-impedance back grill. A wire grill protects the fan while providing a low resistance
to the airflow.



The label.

We know that Corsair is not the manufacturer, but the E307858 UL file number marked on the label does belong to Corsair. The HX series are made by Seasonic; there's little reason to doubt that the VX450W is also made by Seasonic.

OUTPUT CABLES



All the output cables are sleeved.

They are long and plentiful. There are a total of eight cable sets:

  • 22" cable for main 20+4-pin ATX connector
  • 22" cable for 2x12V AUX12V
  • 22" cable for 4x12V AUX12V
  • 24" cable for 6-pin PCIe connector
  • 2 x 35" cable with one floppy drive and three 4-pin IDE connectors
  • 2 x 28" cable with three SATA drive connectors

INTERIOR

The internal layout of the components on the PCB is neat and tidy, and the black (painted, most likely) heatsinks are quite small. The main transformer brand, the layout, the inductors, the dual-ball bearing 120mm Adda fan, the power switch and related components — in short, just about everything inside the PSU — identifies this unit as one made by Seasonic.



Nice clean layout.



Relatively small heatsinks.



One unusual feature is a piece of stiff, clear plastic that blocks about a quarter of the fan's exhaust side (on the inside of the PSU). What might its function be? A look at exactly which portion of the fan it blocks gives us an idea. The purple area in the photo below is the portion covered by the plastic sheet. It seems designed to ensure that airflow from the fan doesn't simply silp out the back without travelling across the heatsinks, as the area closest to the exhaust actually does not contain any components at all. It is an airflow control baffle.



The clear plastic is a baffle to prevent any airflow "short circuit."

The main capacitor is rated for 105°C, not the more common 85°C.



A closer look at the primary cap and main transformer.

The medium speed ball bearing fan is made by Adda, similar to others used in previous Corsairs (and Seasonics).



Familiar Adda fan.

TESTING

For a fuller understanding of ATX power supplies, please read the reference
article Power Supply Fundamentals & Recommended
Units
. 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
V.4
. The testing system is a close simulation of a moderate airflow
mid-tower PC optimized for low noise.

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 our testing loads the PSU to full output
(even 600W!) 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 65W and 250W, 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 maximum power draw that an actual system can draw
under worst-case conditions.
Our most power-hungry Intel 670 (P4-3.8) processor
rig with nVidia 6800GT video card drew ~214W DC 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 video card today could draw as much as another
60~100W, but the total still remains well under 400W in extrapolations of our
real world measurements. As for high end dual video card gaming rigs... well,
to be realistic, they have no place in silent computing today.

SPCR's high fidelity sound
recording system
was used to create MP3 sound files of this PSU. As
with the setup for recording fans, the position of the mic was 3" from the exhaust
vent at a 45° angle, outside the airflow turbulence area. The photo below shows
the setup (a different PSU is being recorded). All other noise sources in the
room were turned off while making the sound recordings.

INTERPRETING TEMPERATURE DATA

It important to keep in mind that fan speed varies with temperature,
not output load. A power supply generates more heat as output increases, but
is not the only the only factor that affects fan speed. Ambient temperature
and case airflow have almost as much 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

Two samples were tested. The results were virtually identical, with less than 1% variance for every parameter. One was picked at random to post results for, as neither could be said to be better or worse. Ambient conditions during testing were 23°C and 18 dBA. AC input was 119V,
60Hz.

Note that even though the VX450W has only one 12V line, two separate load banks were used for the 12V loading. The SPCR load tester does not have the capacity to load up 33A on a single 12V line. Hence the 12V1 and 12V2 columns.

OUTPUT, VOLTAGE REGULATION & EFFICIENCY: Corsair VX450W







DC Output Voltage (V) + Current (A)

Total DC Output

AC Input

Calculated Efficiency
+12V1
+12V2
+5V
+3.3V
-12V
+5VSB
12.20
0.97
12.20
0
5.05
0.97
3.26
0.93
0.1
0.1
21.5
35
61.3%
12.20
0.97
12.20
1.72
5.05
0.97
3.26
0.93
0.1
0.2
42.9
59
72.8%
12.20
1.89
12.20
1.72
5.05
1.94
3.26
1.79
0.2
0.4
64.1
81
79.1%
12.20
1.86
12.20
3.45
5.05
2.85
3.26
1.79
0.2
0.5
89.8
112
80.1%
12.20
4.77
12.20
4.96
5.05
2.85
3.32
3.58
0.2
0.6
150.4
182
82.6%
12.20
5.61
12.20
6.67
5.05
4.45
3.30
5.10
0.4
1.1
199.2
235
84.8%
12.10
8.43
12.10
6.65
4.98
6.98
3.30
7.17
0.4
1.4
252.5
303
83.3%
12.08
9.23
12.08
9.55
4.96
6.99
3.28
8.21
0.5
1.7
302.9
365
83.0%
12.08
10.91
12.08
11.12
4.95
7.84
3.26
9.06
0.6
2.0
351.4
427
82.3%
12.08
10.98
12.00
12.81
4.93
10.47
3.35
10.73
0.7
2.4
394.1
482
81.8%
12.08
12.90
11.93
14.11
4.91
12.71
3.32
12.78
0.7
2.5
451.0
563
80.1%
Crossload Test
11.65
16.55
11.65
16.00
5.15
0.98
3.27
0.9
.5
2.0
398.2
484
82.3%
+12V Ripple (peak-to-peak): 18mV @ 90W ~ 39mV @ 451W (max)
+5V Ripple (peak-to-peak): 15mV @ 90W ~ 18mV @ 451W (max)
+3.3V Ripple (peak-to-peak): 9mV @ 90W ~ 12mV @ 451W (max)
NOTE: The current and voltage for -12V and
+5VSB lines is not measured but based on switch settings of the DBS-2100
PS Loader. It is a tiny portion of the total, and potential errors arising
from inaccuracies on these lines is <1W.


OTHER DATA SUMMARY: Corsair VX450W
DC Output (W)
21.5
42.9
64.1
89.8
150.4
199.2
252.5
302.9
351.4
394.1
451.0
Intake Temp (°C)
23
23
24
25
27
28
29
31
33
33
33
Exhaust Temp (°C)
26
26
28
32
36
39
43
45
46
49
49
Temp Rise (°C)
3
3
4
7
9
11
14
14
13
16
16
Fan Voltage (V)
4.06
4.06
4.06
4.06
4.08
4.10
4.84
5.80
7.70
9.52
11.1
SPL ([email protected])
21
21
21
21
21
21
22
26
35
44
50
Power Factor
0.94
0.99
1.00
1.00
0.99
0.99
1.00
1.00
1.00
1.00
1.00

AC Power in Standby: 0.5W / 0.13 PF

AC Power with No Load, PSU power On: 11.6W / 0.81 PF
NOTE: The ambient room temperature during
testing can vary a few degrees from review to review. Please take this
into account when comparing PSU test data.

 

ANALYSIS

1. EFFICIENCY was excellent across the board. Even at the super low output load of just 21,5W, it was a surprisingly high 61%. This compares favorably with the HX620W's 49.5% efficiency at the same power load. By ~40W, efficiency had reached 73%. The benchmark 80% efficiency was seen at 90W output, but as the 64W load showed 79.1%, it's possible that the 80% mark was reached as low as 70 or 75W. The peak of ~85% was centered at about 200W, and >80% efficiency was maintained to full rated 450W output. Both samples could have qualified for 80 Plus (although neither have official 80 Plus certification).

2. VOLTAGE REGULATION was excellent. At virtually all loads, all the voltages were just about dead on, within a minuscule -0.1V and +0.2V range. The worst voltage drop of 0.35V on the 12V line occurred during the extreme crossloading test. This represents a drop of 2.9%, which excellent for the very worst single variance, as up to 5% (0.6V) is allowed.

3. RIPPLE (measured peak-to-peak) fell well within the limits specified by the ATX standards.
The highest ripple occurred at full load, where it reached 39mv on the 12V lines.
To put that in perspective, the ATX12V requires +12V ripple to be below 120
mV, and below 50mV on the +5V and +3.3V.

4. POWER FACTOR was excellent thanks to the active power factor correction
circuit, staying at or very close to the theoretical maximum of 1.0.

5. LOW LOAD PERFORMANCE

Standby and no-load performance were both reasonably efficient, with standby
coming in well under one watt, and no-load at 11.6W and 15.5W for the two samples. Neither sample had any issues starting up with no load at all.

6. LOW AC VOLTAGE PERFORMANCE

The power supply was set to 351W load with 120VAC through the hefty variac in the lab. The variac was then dialed 10V lower every 10 minutes. The VX450X is rated for operation 90~260VAC, a wider range than the usual 100~240VAC. We pushed it down to 80VAC. We also checked the efficiency at 240VAC input for the sake of readers in the 220~250VAC world.

Low VAC Test: Corsair VX450W @ 351W Output
VAC
AC Current
AC Power
Efficiency
244V
1.73A
410W
85.6%
120V
3.56A
426W
82.4%
110V
3.88A
430W
81.6%
100V
4.24A
432W
81.2%
90V
4.80A
437W
80.3%

80V

5.43A

443W

79.2%

The VX450W stood up to the drops in AC voltage admirably, even when
operating at 80VAC. Neither voltage regulation
nor ripple changed measurably during the test, and efficiency dropped only marginally. At 244VAC, efficiency improved at the 351W load to 86.2% (from 82.4% for 120VAC). That's a 3.2% advantage compared to the 120VAC input.

7. TEMPERATURE & COOLING

The cooling worked well, especially considering the slow speed of the fan through much of the load range. Temperature rise remained modest and did not reach double digits until about the 200W mark. From 250W to 450W, the temperature rise stayed at about 13~16°C. This suggests a reasonably well-cooled PSU despite the low fan speeds.

8. FAN, FAN CONTROLLER and NOISE

Upon turn on, the PSU fan started at just below 4V, then stabilized at 4.06 within a minute or two. The Sound Pressure Level (SPL) reading was 21 [email protected], which was audible at 1m, but quiet and smooth.
I listened carefully for any audible buzzing with both samples from a meter away. There was none at this distance above the fan noise at any load. When the fan was stopped with a plastic wire tie jammed into the blades, a bit of buzzing could be heard from about a foot away, but this was about at the same level as fanless PSUs we've tested. In other words, audible buzzing or humming was not an issue with these samples.

The fan noise and voltage remained essentially unchanged in our thermal test rig all the way to about 250W output load. This is extremely quiet performance, close to the very best we've encountered in any PSU.

Beyond 250W, the fan speed and noise climbed quickly, as expected. The overall noise at high loads were actually higher than measured on the HX520/620 samples from last year, despite the fan in the VX450W being rated at lower top speed. A closer look at the measured SPL of many other tested PSUs show lower readings than the VX450W at very high load. In the comparison table below, the >30 [email protected] readings are highlighted in light green.

Comparison: Various PSUs Noise Vs. Power Output
Model
90W
150W
200W
250W
300W
400W
450W
Corsair VX450W
21
21
21
22
26
44
50
Corsair HX520/620
22
22
22
22
22
29
40
Seasonic S12-430
20
22
25
29
32
37
37
Seasonic S12 Energy Plus 550/650
20
20
20
21
26
38
40

Antec EarthWatts 430
22
22
24
29
37
41
43

Zalman ZM600
25
27
29
30
31
36
40

The above comparison table should not be taken as an absolute. It shows sound pressure levels recorded on SPCR's test platform. The ambient temperature varies a bit, in a range of 20~23°C, and some of the PSUs may have the small advantage of lower ambient temperature during testing. This can help lower the overall noise curve, and more importantly, increase the power level at which the noise starts getting seriously louder. Still, at higher power levels, the temperature in the test box is determined mostly by the load. In any case, in the above test data, several models are about equally quiet up to ~200W load. But only the Corsair HX series has lower measured SPL at 300W. Above 300W, the HX and most other models remain quieter than the VX450W.

For those who do better with graphical representations of data, here's the same information, plotted as curves on a graph. Note that not every PSU was measured at every 50W interval; some data points were interpolated.

With regard to the graph, it should be noted that...

  • In real use, at idle in most PCs in most environments, all the Corsair PSUs, the Seasonics and the Antec Trio 550 would have about the same subjective loudness. All would be perceived as very quiet. It's only with the temperature rise that occurs when the load exceeds 150W that any significant acoustic differences show up among these models.
  • You can see clearly that both the Zalman ZM600 and the Nexus NX8060 have linear fan speed controllers, compared to the other models, all of which have a distinct hinged curve.
  • You can also see how much higher the hinge point has moved, and how much steeper the slope has become in the curves for Seasonic-built PSUs since the S12-430. This is related to improvements in efficiency and cooling, and a continuing focus by Seasonic on PSU acoustics.

Getting back to the Corsair VX450W, the higher SPL readings at higher loads are clearly caused by its plastic fan baffle. It is not a factor when the fan RPM is low, but considerably more turbulence is created when the fan blades are spinning fast in such close proximity. The additional noise at high loads is not meaningful for most silent PC enthusiasts who are unlikely to run systems that draw >200W DC. In such systems, the VX450W will be about as quiet a fan-cooled PSU as you can find on the market. However, for systems that routinely pull over 250W, there's some acoustic benefit to going with the HX series, which is as quiet as the VX450W at lower loads and remains quieter to a higher load.

If you want the best noise performance from the VX450W, use it in a system that draws no more than 300W (DC), and/or ensure that its immediate environmental temperature does not climb much above 30°C. Note that 31°C was the air temperature at the intake side of the VX450W with 300W load. A system with such parameters is not difficult to build today, especially for energy-savvy PC enthusiasts.

MP3 SOUND RECORDINGS

Each of these recording start with 6~10 seconds of silence to let you hear the ambient
sound of the room, followed by 10 seconds of the product's noise.

Sound Recordings of PSU Comparatives

HOW TO LISTEN & COMPARE

These recordings were made
with a high resolution, studio quality, digital recording system, 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. Two recordings of each noise level were made, one from a
distance of one meter, and another from one foot
away.

The one meter recording
is intended to give you an idea of how the subject of this review sound
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. For best results, set your volume control so that the
ambient noise is just barely audible. 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!

The one foot recording is
designed to bring out the fine details of the noise. Use this recording
with caution! Although more detailed, it may not represent how the subject
sounds in actual use. It is best to listen to this recording after you
have listened to the one meter recording.

More details about how
we make these recordings can be found in our short article: Audio
Recording Methods Revised
.


CONCLUSIONS

The new Corsair VX450W is not aimed at the dual-video card, power-demanding, PC gaming user, but for a much bigger audience: Everyone else. The VX450W delivers clean, stable power that's much more than adequate for the vast majority of PC systems today. Like the HX series, it's among the quietest fan-cooled PSUs we've tested. They are very energy efficient, matching and even surpassing many of 80 Plus certified models we've tested. The
sleeved cables are long enough for large cases, and there are enough connectors for very ambitious systems. Corsair's five year warranty remains the longest for any computer power supply we know of.

The best way to take advantage of the VX450W's quiet qualities has already been mentioned: Ensure that the PSU intake air does not exceed 30°C often, nor demand more than ~300W DC output. With a decent case and well selected components, these are easy requirements to meet these days. Following these guidelines will reward you with a PSU that's always very quiet, making the basis for a very quiet computer.

We stated on our review of the Corsair HX520/620 that.... "about the only thing SPCR could ask for are a couple more lower power models for those of us who seek to make a high efficiency, quiet, yet highly capable computer. 300W would be plenty for such a PC in these days of improving CPU efficiency." 450W is considerably higher than what we asked for, but that's OK, as everything else, including price, is certainly right.

Final words: Another great PSU, Corsair.

* * *

SPCR Articles of Related Interest:

Power Supply Fundamentals

Recommended
Power Supplies



Power Distribution within Six PCs

SPCR PSU Test Rig V.4

Seasonic S12 Energy Plus 550 and 660

Silverstone Element Plus ST50EF-Plus

Zalman ZM600 heatpipe-cooled modular PSU

Seasonic M12-700

Corsair HX520 & HX620





* * *

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this article in the SPCR Forums.

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