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80 Plus hits Retail: Silverstone's Element ST50EF-Plus

September 24, 2006 by Devon
Cooke

Product
Silverstone Element ST50EF-Plus

80-Plus Certified 500W ATX12V 2.2 Power Supply
Manufacturer
Silverstone
Market Price
US$95~120

The 80 Plus certification
program
for high efficiency power supplies has been well covered by SPCR,
and the name should be familiar to most of our regular readers. However, actually
buying an 80 Plus power supply is not easy. The reason for this is simple:
The 80 Plus rebates are available only to system integrators who use approved
power supplies in complete PCs. Few 80 Plus models are available in retail channels
— the program simply isn't targeted at the retail market.

However, consumer recognition that 80 Plus certification is a sign of a good
power supply is beginning to change that. FSP's fanless Zen
power supply
was the first retail package model to be approved, but now there are quite a few on the 80 Plus list. Silverstone has two 80 Plus approved models, 400W and 500W versions in their Element line. These are 120mm fan power supplies. The test sample's 500W capacity should be enough to satisfy
those who don't think that 300W
is enough
.



The "Plus" in the name and the 80 Plus logo differentiate it from the regular 500W Element.



The Element comes with ATX and AUX adapters instead of the more common "split"
connectors.

Feature Highlights of the Silverstone Element Plus
(from
SilverStone's
web site
)
FEATURE & BRIEF COMMENT
Shorter cables designed for SFF and Micro-ATX cases
Not on our sample. Silverstone
makes a special version with shorter cables. Details
here
.
Efficiency over 80%
(20% to 100% loading)
80 Plus certification
gives this claim a lot more weight than usual.
Dual +12V rails for advanced systems
We're a little sick of
seeing this feature advertised as "special". It's a requirement
of ATX12V 2.x, and it seems to cause more problems than it solves.
Dual PCI-E connectors (support SLI or CrossFire)
Essential (and very common)
for a recent high end power supply.
Silent running 120mm fan
Silent
is a dangerous word to use. We'll settle for quiet.
Support for ATX12V 2.2 Support for the latest
standard.
Active PFC
Allows smaller UPS units
to be used and may save some users money in utility bills.

OUTPUT SPECIFICATIONS: Silverstone Element Plus ST50EF-PLUS
AC Input
90V ~ 264V @ 47Hz ~ 63Hz (Auto Range)
DC Output
+3.3V
+5V
+12V1
+12V2
-12V
+5VSB
Minimum Output Current
0.5A
0.3A
1.0A
1.0A
–
–
Maximum Output Current
25A
25A
18A
18A
0.3A
3.0A

Maximum Combined

150W
432W (36A)
3.6W
15.0W
500W

As we would expect of a 500W power supply, all of the voltage rails have generous
capacities. Both +12V rails are specified at 18A, and the combined rating should
allow both to supply that amount of power simultaneously.

The minimum output ratings are of more concern. Our
investigation of power distribution
across the various voltage rails did
not reveal any systems that would trigger the minimum load protection on the
+3.3V and +5V rails, but the +12V rails are another matter. Of the six systems
we tested, four drew less than 1.0A on one of the +12V rails at idle.

We saw a similar trend when we
examined CPU power consumption in detail last April
: Of 15 systems examined,
10 drew less than 1.0A from
the +12V2 rail
. These included several mobile processors and every single
AMD chip we looked at. In fact, the only systems that required more than
1.0A at idle used Intel's now-obsolete P4 architecture. With the release of
Intel's Core 2 Duo chips, it may not be unrealistic to say that just about every
new system will run afoul of the 1.0A minimum load at some point.

So, what to make of this conflict between Silverstone's specifications and
real systems? It is unlikely that Silverstone has released a product that
will not work with the majority of systems, so it seems logical to treat the
minimum load specifications as wrong. However, regular (and / or cautious) readers
should be aware that some high efficiency power supplies have had stability issues
for exactly this reason.

There is no guarantee that the Element will not run into any compatibility issues in this time of transitions in CPUs and motherboards, but we
can say that the Element had no issues running with no load at all, which
means that the minimum load requirements are not as strict as they are specified.

EXTERNAL OVERVIEW

The Element Plus closely resembles another 80 Plus power supply we've looked
at: Enhance's OEM-only ENP-5136GH.
In fact, the two power supplies appear to share the same external casing, right
down to the matte black finish. It's not a secret that Silverstone's power supplies are made for them by Enhance,
so the resemblance is no surprise.

The most distinctive feature of the casing is a vent that occupies the top
quarter of the back panel, allowing some air to flow in this awkward-to-cool
part of the casing. While this may recirculate some air into the system, the
additional cooling provided by this vent is probably well worth it.



The external casing is identical to another power supply...



...The Enhance ENP-5136GH.



The rear vent is fully open, but the mesh is tighter than most.

INTERIOR

The resemblance to Enhance's power supply continues with the cover off: The
layout of the PCB and the style of the heatsinks are very similar. The main
differences seem to be component selection and the position of the thermal sensor
that controls the fan speed.



Circuit topology is similar to models we've seen before.

The heatsinks are made of anodized aluminum, and are made of a relatively small
number of thick, stubby fins. They look both cheap to manufacture and effective
for cooling, without restricting airflow too much. Most power supplies use two large heatsinks, but the Element
has a third heatsink off to one side that cools a large transistor along the left side.



New heatsinks. Are they improved?



The heatsink fins are widely spaced and allow air to flow easily between
them.

FANS

The fan is sourced from ADDA,
a well known and well reputed manufacturer. It is a high speed version
of the fan found in Seasonic's S12 series and the Enhance ENP-5136GH —
both of which are close to inaudible at low loads. Hopefully, the starting voltage
will allow the Element to be just as quiet.



The Element uses a high speed version of the fan found in Seasonic's quiet
S12 series.

CABLES AND CONNECTORS



Accessory cables are very long... Silverstone also sells a special
edition with shorter cables.

The individual cable sets are listed below:

  • 21" cable for main 24-pin ATX connector
  • 22" cable for auxiliary 8-pin +12V EPS AUX connector
  • 2 x 22" cable for 6-pin PCIe connector
  • 2 x 39" cable with three SATA drive connectors
  • 2 x 42" cable with three 4-pin IDE drive connectors and one floppy
    connector
  • 6" 24-pin to 20-pin ATX adapter
  • 6" 8-pin to 4-pin AUX adapter

The main cable sets — ATX, AUX and both PCIe cables — are all standard
length and are sleeved in black vinyl mesh. For some reason, the drive cables
(both for IDE and SATA drives) are not sleeved, and are quite a bit longer than
usual. In fact, they are so long that Silverstone sells a
"Short Cable" version of the Element Plus
that is designed for
Small Form Factor and Home Theater systems that do not have room for the extra
cable bulk.

Another oddity is the way the Element deals with the two different kinds of
ATX connectors. Instead of the elegant "20+4" connector than allow
the same connector to be used for both 20 and 24-pin systems, Silverstone includes
a 6 inch adapter cable that converts the 24-pin connector into one that is usable
with older 20-pin systems. A similar adapter is used for the AUX connector,
which is an 8-pin EPS connector by default. Because most systems use the 4-pin
connection, the AUX adapter will probably be used more frequently than not,
so the cable set can be considered to be 28" long.

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 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.

Note that the low speed 80mm fan responsible for "case airflow" in the thermal simulation rig is deliberately kept at a steady low level (~6V) even when the PSU is operating at very high power and the PSU fan is spinning fast enough to drown out any noise contribution of the "case fan". This is to keep a level playing (thermal) field for all the PSUs tested, but it is admittedly somewhat unrealistic. Most users will want to increase airflow in the case if their system is drawing that much power from the PSU frequently or on a long term steady-state basis. Keep in mind that some PSUs will actually perform more quietly in a real system with higher case airflow than in our low airflow thermal test box.

Great effort has been made to devise as realistic a quiet 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 20°C and 18 dBA, with 121VAC/60Hz input.

OUTPUT & EFFICIENCY: Silverstone Element Plus ST50EF-Plus











DC Output Voltage (V) + Current (A)

DC Output Power

AC Input Power

Calculated Efficiency
+12V1
+12V2
+5V
+3.3V
-12V
+5VSB
12.02
0.95
12.00
1.70
5.02
0.97
3.36
0.95
0.0
0.2
40.9
55
73.8%
12.01
1.88
12.00
1.70
5.02
2.88
3.36
1.83
0.0
0.4
65.6
84
78.0%
12.01
1.87
11.98
3.26
5.02
2.87
3.36
2.74
0.1
0.5
88.8
112
79.6%
12.00
3.75
11.97
4.92
5.02
4.63
3.36
4.61
0.1
0.9
148.3
179
82.7%
11.98
5.57
11.93
6.59
5.01
6.36
3.36
5.36
0.1
1.2
202.4
237
85.4%
11.97
6.52
11.91
8.00
5.01
7.99
3.35
7.60
0.2
1.5
248.7
293
84.9%
11.97
8.56
11.89
9.46
5.01
8.86
3.35
9.31
0.2
1.8
301.9
358
84.3%
11.93
12.12
11.86
11.04
5.00
13.00
3.34
13.19
0.2
2.4
399.0
485
82.3%
11.89
14.76
11.79
15.27
4.98
15.05
3.32
15.02
0.3
3.0
498.9
628
79.4%
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


OTHER DATA SUMMARY: Silverstone Element Plus ST50EF-Plus
DC Output (W)
40.9
65.6
88.8
148.3
202.4
248.7
301.9
399.0
498.9
Intake Temp (°C)
23
25
28
33
37
39
42
43
45
Exhaust Temp (°C)
25
26
29
35
41
45
47
49
53
Temp Rise (°C)
2
1
1
2
4
6
5
6
8
Fan Voltage (V)
4.5
4.5
4.5
4.5
4.5
4.9
6.8
10.3
11.6
SPL ([email protected])
23
23
23
23
23
25
34
41
43
Power Factor
0.95
0.97
0.97
0.99
0.99
0.99
0.99
0.99
1.00
AC Power in Standby: 0.4W / 0.06 PF

AC Power with No Load, PSU power On: 5.5W / 0.42 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. LOW LOAD PERFORMANCE

Despite the warning about minimum loads, the Element Plus had no problems running
with no load — and it drew a very respectably low 5.5W while doing so. Lower
quality power supplies can draw as much as 15~20W just by being turned on, so
the low no-load performance is impressive (just don't try to calculate efficiency).

Although it would run with no load, we were able to trigger a shutdown
condition by loading either the +5V or the +3.3V line without putting a load
on the +12V line. The reverse was not true — the power supply remained
stable when the only load was on the +12V line. Every system draws some
power from +12V, so it is unlikely that this will lead to any misbehavior powering a real system.

2. VOLTAGE REGULATION was excellent — within 2% across the board,
and within 1% for all but the two highest power test points. The +5V and +3.3V line varied
by just 0.04V each. This is well within spec for both the 5% tolerance required
by ATX12V and the 3% tolerance required by EPS12V.

3. EFFICIENCY was topnotch — not that we really expected anything different
from an 80 Plus power supply. Efficiency peaked surprisingly early in the test
at just above 85%. Most systems will not consume the 200W required to reach
this peak, but efficiency was excellent even at lower outputs. 74% efficiency
at 40W output may not hit the magic 80% number, but its still very impressive
— the more so because it is representative of the power consumption in
a typical system.

4. POWER FACTOR stayed close to the ideal value of 1.00 thanks to active
power factor correction.

5. TEMPERATURE & COOLING were good throughout the most commonly used output range. The thermal
rise through the power supply stayed below 5°C until the fan ramped up at
~250W output, and it never exceeded 10°C. The high efficiency and excellent
voltage regulation at full load both suggest that the power supply never came
close to overheating, and the 45°C intake temperature was within the 50°C
thermal specifications.

6. FAN, FAN CONTROLLER and NOISE

The residual noise level was a little higher than it could have been, mainly
because the starting voltage for the fan was a little too high. 23 [email protected] is
very quiet, but it was still clearly audible in our test lab — unlike the
best power supplies, which are just barely audible at one meter. Even so, the
fan noise was smooth and inoffensive, characterized mostly by a low growl that
blended easily into the background.

Of more concern was the wheezing electronic squeal that the power supply gave
off when there was not enough load on the +5VSB line. The squeal was high pitched
and very irritating, and it was present whenever the power supply was running
unless at least 0.3A were applied to the +5VSB line. Smaller loads would affect
the pitch and rhythm of the squeal, but would not eliminate it entirely. It's
not clear how serious this issue is. 0.3A represents just 1.5W, and all motherboards
require a little power in standby mode. Exactly how much is an open question
— as far as we know, nobody has looked at it in detail.

The fan slope was excellent. The fan speed didn't even start to increase until the
intake temperature approached 40°C, during the 250W test point. The vast
majority of systems fit into this power envelope, which means that the fan noise
should stay low and constant no matter what load is placed on the system. Only
very powerful gaming systems with dual graphics cards are likely to require
more power — and even then the noise may still go unnoticed, as cooling
of the components demanding over 250W total will probably require other fans (like the CPU fan, the case fan and the VGA fan) to be spinning at considerable speed and concomittant noise.

MP3 RECORDINGS

Each of these recording have 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

Despite a few quibbles the Element Plus has proved itself a worthy product,
with very strong fundamentals. It's well regulated, highly efficient, and didn't
start to get noisy until 300W output. What's not to like?

We did mention a few quibbles... Yes, it is fairly quiet, but we know
other power supplies that are quieter — we know that Adda's fans start reliably
at voltages below 4.5V, so we would have liked to see that taken advantage
of. Also, the odd squealing when the +5VSB line was underloaded may prove to
be a problem... or it may just be a meaningless artifact of testing — we
won't know until people start using the unit in real systems.

The high minimum load requirements — and the fact that we could readily
ignore them — make us question just how meaningful the load specifications
are. We are very thankful that these specifications did not seem to be hard-and-fast
requirements, as a large number of systems would violate them.

All in all, the Element Plus is a big improvement over the
last Silverstone power supply we looked at
, especially in the acoustics
department. The 80 Plus certification was suggestive, but our test confirms
it: The Element Plus can stand with the best.

*

SPCR Articles of Related Interest:

Power Supply Fundamentals & Recommended
Units


Power Distribution within Six PCs

Desktop CPU Power Survey,
April 2006


Silverstone Strider ST56F Power Supply

FSP Zen Fanless 300W Power
Supply (80 Plus)


Enhance ENP-5136GH 360W PSU:
A New 80 Plus Brand


Seasonic SS-400HT Power Supply,
80 Plus Version

* * *

Much thanks to Silverstone
for the opportunity to examine this power supply.

Discuss
this article in the SPCR Forums.

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