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TEST RESULTS
For a fuller understanding of ATX power supplies, please read our article Power
Supply Fundamentals & Recommended Units. Those who seek source materials
can find Intel's various PSU design guides, closely followed by PSU manufacturers,
at Form Factors.
For a complete rundown of testing equipment and procedures, please refer to the
article
SPCR's Revised PSU Testing System. It 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 actual output load, which is exactly the way it is in a real PC
environment. But there is the added benefit of a precise 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 loads. It is, in general, a very demanding test, as the operating
ambient temperature of the PSU often reaches 40°C or more at full power.
This is impossible to achieve with an open test bench setup.
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 far too many variables in PCs and far 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 reasonably good overall impression of that person, but it is not quite the same as an extended meeting in person.
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. All other noise sources in the room were turned off while making the sound recordings.
Ambient conditions during testing were 20°C and 20 dBA, with input of 120 VAC
/ 60 Hz measured at the AC outlet.
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FSP Blue Storm AX500-A TEST RESULTS
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DC Output (W)
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65
|
90
|
150
|
200
|
250
|
300
|
400
|
460
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AC Input (W)
|
83
|
114
|
190
|
250
|
315
|
390
|
515
|
597
|
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Efficiency
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78%
|
79%
|
79%
|
80%
|
80%
|
78%
|
78%
|
77%
|
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Intake Temp (°C)
|
25
|
27
|
29
|
32
|
32
|
32
|
34
|
37
|
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PSU Exhaust (°C)
|
31
|
35
|
41
|
43
|
45
|
48
|
52
|
57
|
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Fan Voltage
|
5.3
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5.4
|
6.0
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7.8
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10.3
|
11.0
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12.0
|
12.0
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Noise (dBA/1m)
|
26
|
26
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29
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36
|
42
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43
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45
|
45
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Power Factor
|
0.63~0.67
|
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NOTE: The ambient room temperature during testing
varies a few degrees from review to review. Please take this into account
when comparing PSU test data.
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ANALYSIS
As mentioned above, despite the "500" in the model number and the
500W marketing blurb on the retail box, the Blue Storm is rated up to 460W.
Because of the discrepancy between these two numbers we feel that the 460W rating
may be more conservative (and truthful) than the ratings specified by many other
companies. This speculation is borne out by the fact that efficiency began to
rapidly decline at around the 460W mark. Many other power supplies exhibit this
rapid decline before their rated spec, indicating that they are operating beyond
their capabilities.
1. VOLTAGE REGULATION was good, ±4% or better on all lines at any of the test loads. The ATX 2.2 standard specifies voltage regulation of ±5%
on a positive lines, so ±4% is a reasonable margin of error
-
+12V: 12.11 to 12.45
-
+5V: 4.78 to 4.91
-
+3.3V: 3.19 to 3.30
2. EFFICIENCY was just short of top notch. The highest efficiency power
supply that we tested
peaked at 88%. However, its efficiency peaks at 300W, and at 90W, the efficiency is a much lower 76%.
By comparison, the Blue Storm has an extremely flat efficiency curve, and its
peak efficiency is between 150W and 250W: right in the typical
power range. There are other power supplies that have
a higher peak efficiency, but these units typically reach this peak at wattages
that are beyond what most systems draw. Furthermore, the difference between
the highest and the lowest measured efficiency for the whole 460W range was
just 3%. Our measurements place the Blue Storm well above its rated efficiency
of >70%, and it is 10-17% more efficient than the last Fortron PSU we tested,
the FSP350-60PN
"Aurora".
3. POWER OUTPUT: The Blue Storm had no trouble meeting its specified
maximum of 460W. It even ran for about 20 minutes at almost double its 160W
maximum rating for the +3.3V/+5V combination before we realized that we had
overloaded it. The wattage ratings of this power supply
may be more conservative than most, and this is a good thing.
NOTE on PCI-E CURRENT CAPACITY: There was some question about the maximum output capacity for PCI-Express because of the recent changes in the spec by Intel and nVidia. So to avoid confusion, a quick call was placed to Fortron. They confirmed that up to 75W was available on for PCI-e. The latest spec demands as much as 150W. As far as we know, PCI-e VGA cards that demand that much power are not on the market yet, but you should be aware that 75W is the recommended maximum on this PSU.
4. POWER FACTOR: There is no mention of power factor in any of the Blue
Storm's marketing material or its specification sheets. However, its power factor
is in line with other units with passive power factor correction, which ranges between 0.63
and 0.67.
5. FAN & FAN CONTROLLER: The Blue Storm is unusual for a Fortron power
supply because its fan is manufactured by Protechnic rather than Yate Loon.
While the Protechnic is not the quietest fan we have heard, it is quite smooth,
and because it is a sleeve-bearing, it does not exhibit the clicking
so common in ball-bearing fans. A lower airflow version of this fan would have
been a better choice from an acoustics point of view, but given how "soon" the fan controller brings it up to
12V, this may not have been viable from a cooling standpoint.
The fan controller is quite responsive. Changes in temperature are quickly
mirrored by changes in fan voltage. The rate of change is close to the threshold
of perception. Listening closely, it is possible to hear the fan slowly increasing
in speed. However, it is unlikely that the changes in fan voltage are sudden
enough to be noticeable as background noise. Unless one is specifically listening
for the change in fan speed it is unlikely to be noticed.
There are two concerns that we had with the fan controller on the Blue Storm:
- One is the start voltage. The low floor for the fan voltage seems to be around
5.3 volts. Many competitive quiet PSUs start below 5V. In a system that is otherwise quiet, this difference
is audible with the typical mid-to-low speed 12V fan employed in quiet PSUs.
- The other concern is that it increases in voltage too soon. The
fan voltage begins to increase at about 150W output, and by 200W output the
fan voltage is 7.8V and it produces 36 dBA at one meter: No longer quiet. This is an active power range where changes
in fan speed are likely to be audible. While this may be good design from
a cooling standpoint, it is not such a good design from a low noise point of
view.
6. NOISE: The noise of the Protechnic fan starts out mostly as airflow.
There is a small amount of low frequency motor hum that is noticeable
in an otherwise silent room, but it is fairly constant and inoffensive. As fan
voltage increases, the hum becomes more evident and increases in pitch, bringing
the noise further into the range of frequencies to which humans are most sensitive.
In a case, the starting noise level (and, most likely, the idle level) is pretty low, and probably good enough for most users. You may not want to sleep next to it, but during
daylight hours the ambient noise would probably be loud enough to cover it.
At higher loads, the hum of the motor could easily become irritating
as a background drone. It is the volume of the noise that is the problem, not
the character, so using this power supply in a low power system might be viable.
But, then again, why use a 460W power supply in a low power system?
CONCLUSIONS
The Fortron Source Power Blue Storm AX500-A is a great improvement over
the last Fortron PSU that we reviewed. Efficiency is definitely this power supply's greatest strength.
Noise levels between the Blue Storm and the FSP350-60PN
Aurora measured within two dBA, but the Blue Storm
is quieter subjectively.
In a wider comparison with power supplies from other acoustics-focused manufacturers, the Blue
Storm fares less well. There are units with quieter fans and fan controllers
that output less voltage to a higher power output level, although few of them
will beat the Blue Storm in efficiency. Kudos to Fortron for using
a sleeve-bearing fan instead of a ball-bearing model, which would have been noiser. Still, this sleeve bearing fan was not really quiet enough to push the Blue Storm into the top ranks of quiet PSUs.
The retail pricing seems quite attractive for its power rating, but this is such a variable that it is difficult to comment on with confidence. The inclusion of Molex connectors with grips is also a point in the Blue Storm's
favour. We look forward to seeing this feature on more power supplies from Fortron,
and hope that such connectors become industry standard.
Overall, the Blue Storm is a well-rounded power supply that suits many applications. Its flat efficiency
curve makes it suitable for use in both high and low power applications. Although
the noise it produces at higher output levels would be unacceptable to a hardcore
silencing enthusiast, it is likely that in a high powered system there would
be other, greater sources of noise.
* * *
Much thanks to Fortron
Source for the opportunity to examine the Power Blue Storm AX500-A.
Discuss this article in the SPCR Forums.
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