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Silentmaxx Fanless 400W MX460-PFL01 power supply

Another addition to the fanless ranks looks very familiar. In fact, it’s well nigh identical in appearance to the fanless Fortron Zen 300W PSU we reviewed last year. This one is branded with a different name and rated a hundred watts higher, with a bigger price tag. Is it still silent, and efficient enough to be 80 Plus?

April 2, 2006 by Devon
Cooke

Product
Silentmaxx Fanless 400W
MX460-PFL01
400W ATX12V 2.01 Fanless Power Supply
Manufacturer
Silentmaxx

Market Price

US$175

Low noise computer equipment is a market segment of its own, with different
values and requirements from the gaming, server or workstation markets. “Fanless”
is a keyword; in the past year or so, we’ve seen fanless heatsinks, fanless
cases, fanless video cards, and fanless power supplies all proliferate. Manufacturers have recognized the low noise segment as significant,
and are responding with suitable products.

One of these products is the Silentmaxx Fanless 400 Watt. It looks almost identical to the
FSP Zen
reviewed last year, but is rated for an extra 100W of capacity. Silentmaxx is a
German company that markets to the low noise market. It does not seem
to be well established outside of Germany, and its web site is in German only.
Nevertheless, its products are labeled in English as well as German, and its
products are available worldwide from QuietPC’s
numerous web sites
.

The similarity to the FSP Zen is more than skin deep. It’s clear that
FSP is the OEM for Silentmaxx. There are similarities everywhere, from the size and
shape of the window on the retail box to the internal heatsinks and the general
layout of the PCB. The only major difference seems to the higher output rating. It’s about the highest rated fanless power supplies we know of. Most
other fanless models are in the 300-350 watt range.


A large, retail-friendly package with a window.

FEATURE HIGHLIGHTS

Feature Highlights of the Silentmaxx Fanless 400 Watt
MX460-PFL01
(from a Google translation of
Silentmaxx’s
web site
)

FEATURE & BRIEF COMMENT
Efficiency greater than 89% Probably too high to be
realistic, but still a good sign.
Separate 12V lines
for more stability (ATX 12V V2.01)
Whether or not they improve
stability is debatable, but they’re required by ATX12V 2.01
Error protection (over-voltage, under-voltage, short-circuit, over-current,
overload, over-temperature
)
The more the better,
but surely over-current and overload protection are the same thing…
Punched housing for optimized heat transfer The casing is
very open to the surrounding air. Whether that’s good or bad depends on
system airflow.
Very large and highly efficient cooling fins The trademark of fanless
power supplies: Large heatsinks.

Aside from the usual cables, screws, and a fully illustrated bilingual manual,
the Silentmaxx Fanless 400 Watt also comes with… a fan. This seems like an odd freebie to include with a fanless power supply, but perhaps Silentmaxx
is engaging in a little social engineering here. The fan is a subtle hint that
at least a little airflow is needed. In this respect, the Silentmaxx
is no different from any other fanless power supply; every one of them requires
help from system airflow to be cooled safely.

OUTPUT SPECIFICATIONS

SPECIFICATIONS: Silentmaxx Fanless 400 Watt (from Silentmaxx’s
web site
)

AC Input

100~240 VAC / 50~60 Hz

Maximum AC Input Current

6A

DC Output

+3.3V

+5V

+12V1

+12V2

-12V

+5VSB

Maximum Output Current

30A

28A

14A

15A

0.8A

2.0A

Maximum Combined

145W
168W
180W
9.6W
10W
380W

400W (460W peak)

PHYSICAL BASICS

Most of the casing is made of a fine mesh that should allow air — and
heat — to pass easily in and out of the power supply. The exact behavior
of the airflow will depend on the system as a whole, but the casing is open
enough that there should always be some airflow to remove heat.
A system with no fans at all might prove to be a problem, but such systems are
rarely feasible.


The exterior casing is open to the surrounding air…


…with the exception of the top panel, which must be solid enough to
provide a base for the electronic circuitry.

In spite of the wide-open casing, the amount of space that is open to the
air outside the system is actually quite limited. Most power supplies use a
hexagonal mesh that covers almost all of the back panel, but the mesh on the
back panel of the Silentmaxx is more restrictive and covers less space. It seems
that most of the airflow around the internal heatsinks will come from the surrounding
air inside the system. As with any other fanless power supply, the waste heat
will need to be exhausted from the case in some way to avoid overheating.

INSIDE

While the exterior of the Silentmaxx was almost indistinguishable from the
FSP Zen — only a slightly different shade of blue gave the difference away
— there is an immediate visual difference when the cover is removed. Instead
of the expected silvery aluminum heatsinks, the Silentmaxx’ heatsinks are hot
pink. The resulting pink-and-blue color scheme is quite garish, though it might
be at home in a case full of blacklights and LEDs. Personally, I’m glad I don’t
have to look at it after it’s been installed. It reminds me too much of a certain
trend in skiwear that was popular in the early ’90s.


The heatsinks are very… pink.

The color scheme isn’t just for looks, though (thank goodness!). The pink finish
comes from anodizing the aluminum to increase the amount of heat that it radiates.
In a fanned power supply, this would have little effect, since the vast majority
of the heat is removed via the process of forced convection. However, without
airflow, that method of removing heat drops dramatically, making direct radiation
a more significant factor in the amount of heat transferred by the heatsinks.
Insignificant as it seems, changing the color of the heatsinks could be where
Silentmaxx has managed to find some of those extra 100W of capacity.


Real men use pink heatsinks.

With the heatsinks removed, the Silentmaxx turns out to be a pretty conventional
power supply. The usual transformers and coils are all present. There do seem
to be far more MOSFETs than usual, grouped in clusters around the base of each
heatsink. MOSFETs are often the most heat-sensitive components in a power supply,
so it makes sense to have many operating in parallel to keep their individual
temperatures at a minimum.


Nothing too unusual here…


…except for the numerous MOSFETs clustered around each heatsink.

FAN


In keeping with the color scheme, the bonus case fan is clear blue.

The bonus 80mm case fan is branded with Silentmaxx’ logo, and a google search
of the model number did not prove to be helpful in discovering the OEM. The
current rating indicates a medium-low speed fan, and a quick listening test
showed this to be the case. The noise level was quite acceptable, even at full
speed. Quieter fans are available, but the compromise between airflow and noise
was surprisingly good for a fan that was tossed in as an extra.

On the other hand, the fan felt a bit flimsy and brittle, as though it would
be easy to break. It also comes with a two-pin header that will not fit on a
three-pin motherboard headers without modification.

CABLES AND CONNECTORS

All cable sets were sleeved, and all of the IDE plugs had grips for ease of
removal.

  • 18″ Sleeved cable for main 20+4-pin ATX connector
  • 14″ Sleeved cable for auxiliary 4+4-pin 12V AUX connector
  • 15″ Sleeved cable for 6-pin PCIe connector
  • 23″ Sleeved cable with two SATA drive connectors
  • 27″ Sleeved cable with two 4-pin IDE drive connectors and one floppy
    connector
  • 26″ Sleeved cable with three 4-pin IDE drive connectors
  • 17″ cable with a thermally controlled, nonstandard 2-PIN fan header

The individual cable sets seemed a little shorter than usual. This was a complaint
we had with the FSP Zen as well, but we were pleased to see that the problem
seemed less severe with the Silentmaxx than the FSP Zen. In particular, the
main ATX cable is a much more standard length in the Silentmaxx.

Another difference from the FSP Zen is the inclusion of what appears to be
a fan header. Unfortunately, the tiny two-pin header does not match any of the
fans that we could find in the lab, nor does it match the fan header on the
bonus case fan. For all intents and purposes, it appears to be useless, which
made us wonder whether we had correctly identified its purpose. A quick chat
with Dave Williamson at Quiet
PC USA
(our supplier) confirmed that it is meant as a fan header:

“The 2-wire connector is designed to operate a separate case fan if needed.
It is temperature controlled from the PSU. Most of the time the 2-pin connector
will not have power, however when the PSU becomes extremely hot it will activate
the auxiliary fan connector providing power to operate a separate case fan.”

Apparently, the header is meant to power an emergency backup fan. Hopefully,
the next revision will replace the connector with one that is a little more
standard — perhaps one that works with the included case fan.

TEST RESULTS

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.3
. 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 open design of the Silentmaxx required a little modification of the test
rig to keep the thermal simulation as accurate as possible. Because the power
supply is designed to be installed in a case, only the rear panel is designed
to be exposed to the open air. However, our test bench left one whole side of
the power supply open that would not be open in an ordinary system. To correct
this, a piece of cardboard was taped over the offending side to prevent any
air from flowing through it.


The side vent was blocked off with cardboard to keep the thermal simulation
accurate.

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 powerful 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 SLI could draw as much as another 100W, perhaps more, but the total
still remains well under 400W in extrapolations of our real world measurements.

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.

On to the test results…

Ambient conditions during testing were 22°C and 20 dBA, 123V/60Hz.

OUTPUT & EFFICIENCY: Silentmaxx Fanless 400 Watt
MX460-PFL01






DC Output Voltage (V) + Current (A)

Total DC Output

AC Input

Calculated Efficiency
+12V1
+12V2
+5V
+3.3V
-12V
+5VSB
12.00
0.95
11.98
1.71
5.06
0.97
3.38
0.00
0.1
0.2
39.0
55
70.6%
11.99
1.87
11.98
1.71
5.06
1.94
3.37
2.59
0.1
0.3
64.2
84
76.6%
11.99
1.87
11.96
3.27
5.05
2.87
3.36
2.58
0.2
0.5
89.6
113
79.6%
11.97
3.71
11.93
4.92
5.04
4.56
3.36
5.09
0.3
0.8
150.8
184
81.9%
11.95
6.41
11.92
4.93
5.02
6.27
3.35
7.05
0.4
1.0
200.3
238
84.1%
11.93
7.51
11.91
6.33
5.01
8.75
3.34
8.44
0.5
1.3
249.5
298
83.7%
11.91
8.45
11.86
8.00
4.99
10.35
3.31
11.46
0.6
1.5
299.8
359
83.5%
11.86
11.89
11.78
11.00
4.95
12.62
3.25
14.20
0.8
2.0
400.1
492
81.3%

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: Silentmaxx Fanless 400 Watt
MX460-PFL01
DC Output (W)
39.0
64.2
89.6
150.8
200.3
249.5
299.8
400.1
Intake Temp (°C)
24
27
31
35
39
40
45
50
Exhaust Temp (°C)
29
32
38
44
50
56
63
70
Temp Rise (°C)
5
5
7
9
11
16
18
20
Power Factor
0.95
0.95
0.96
0.99
0.99
0.99
0.98
0.98

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. VOLTAGE REGULATION was very good, within ±3% throughout the
test and often within ±1%. As a general rule, voltages fluctuated very
little. Only when we pressed it to the very maximum load did the voltages drop
in any significant way.

2. EFFICIENCY was excellent, although it did fall a little short of
the 89% efficiency that was claimed. Regardless, the Silentmaxx deserves a high
recommendation. We’ve only tested three power supplies that are more efficient,
one of which is the FSP Zen. The other two are 80
Plus
certified Seasonic models that are not easy to find on the retail
market. Of these only one managed to beat the Silentmaxx across all of the data
points tested. The differences between these four top-runners were close enough
that they are all at more or less equally efficient.

Compared to the FSP Zen, the Silentmaxx appears to be biased towards efficiency
at close to full capacity. Thus, the FSP Zen is more efficient below 250W —
where the vast majority of systems spend their time — and the Silentmaxx
is more efficient at 250W and above. The Zen earned 80 PLUS certification with >80% efficiency at 20, 50 and 100 percent of rated power (and >0.9 PF). With efficiency measured at 79.6% at 89.6W in our test, this Silentmaxx will probably reach 80% at 100W (20% load), so it too, can probably earn 80 PLUS certification.

3. POWER FACTOR was excellent thanks to the active power factor correction
circuit. Power factor stayed close to the theoretical maximum of 1.0 throughout
testing.

4. TEMPERATURE & COOLING

The temperature rise across the Silentmaxx was fairly high in ordinary terms,
but that is no surprise for a fanless unit. In comparison to other fanless power
supplies we’ve tested, the 20°C rise that we measured at full load is fairly
typical: High, but still within the bounds of safety. In comparison with the
FSP Zen, the temperatures were better by a few degrees across the board —
enough to make us think that the Silentmaxx is a slightly better performer,
but not enough to rule out slight variations in the test procedure as a possible
cause of the difference. Thermal performance was also roughly on par with the
fanless Antec Phantom 350.

5. NOISE

The nice thing about fanless power supplies is they generally don’t make any
noise. A very slight hum or buzz could be heard within a few centimeters, but
no noise was audible from a normal operating position.

COMPARISON

The similarity between the Silentmaxx and the FSP Zen just begs for a direct
comparison. Similarities have already been noted in the sections on efficiency
and temperature, but a side-by-side comparison makes for a more complete picture.


EFFICIENCY COMPARISON:
FSP Zen FSP300-60GNF vs.
Silentmaxx Fanless 400 Watt MX460-PFL01

Target Output

40W

65W

90W

150W

200W

250W

300W

400W

Efficiency

Silentmaxx
70.6%
76.6%
79.6%
81.9%
84.1%
83.7%
83.5%
81.3%

FSP Zen
76.6%
80.4%
83.0%
84.6%
84.6%
83.6%
82.9%
–

The FSP Zen is clearly more efficient in the lower range. The Zen carries an advantage of 3-6 percentage points
all the way up to 150W output, which is about the most a non-gaming system will
ever draw. The Silentmaxx does gain the upper hand as the output increases,
but even then the difference is never more than 0.6 points. Presumably, this
difference would widen if the Zen were capable of outputting 400 watts, but
any advantage at this level is almost entirely theoretical. Nobody except overclockers
with SLI are likely to need this much power consumption.


THERMAL COMPARISON:
FSP Zen FSP300-60GNF vs.
Silentmaxx Fanless 400 Watt MX460-PFL01

Target Output

40W

65W

90W

150W

200W

250W

300W

400W

Temperature Rise

Silentmaxx
5°C
5°C
7°C
9°C
11°C
16°C
18°C
20°C

FSP Zen
6°C
10°C
9°C
13°C
15°C
18°C
20°C
–

The situation is reversed when the thermal results are compared. The Silentmaxx
holds a slight advantage across the whole range of output, typically in the
2~4°C range. Oddly enough, the difference is greatest in the 65~150W range
where the Zen holds the greatest advantage in efficiency. This result may be that the anodizing treatment of the heatsinks in the Silentmaxx helps… or maybe it’s just a testing anomaly.

CONCLUSIONS

The Silentmaxx Fanless 400 Watt and the FSP Zen are brethren, both on the surface and beneath the skin. Our impressions of the two power supplies are similar. In other words,
the Silentmaxx is impressive. Efficiency in
particular is excellent… though it missed the claimed
89%. Voltage regulation was also very good.

As with all fanless power supplies, the thermals are a bit of questionable. The Silentmaxx runs warmer than most fanned power
supplies, but it doesn’t appear to be much better or worse than any of the competition.
How much the pink anodized heatsinks do for cooling is hard to say; we are
cautiously optimistic that they help a little.

One difference between the two that we were pleased to notice was that the
main ATX cable on the Silentmaxx was a full 18 inches long — a roughly
standard length, and about four inches longer than the FSP Zen.

We are confused by the external fan header.
The nonstandard connector makes it useless — it won’t even power the included
case fan. All thing considered, the odd fan connector is a pretty small bone to pick but we hope to see this fixed in a future revision.

Overall, we came away with a fairly positive impression, grounded in the solid
electronics that are the starting point for any good power supply. If you seek a fanless PSU and understand how to make the best of this one, it may be worth the steep $175 asking price.

* * *

Much thanks to Quiet
PC USA
for the opportunity to examine this power supply.

*

SPCR Articles of Related Interest:
Power Supply Fundamentals & Recommended Units
Power Distribution within Six PCs
Fortron Zen fanless 300W Power Supply
Antec Phantom 500 “Hybrid” PSU
SilverStone ST30NF Fanless ATX PSU
Seasonic S12-430

* * *

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