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Silverstone SX600-G: SFX 80+ Gold PSU

Product
SX600-G

SFX 80 PLUS Gold PSU
Brand
Silverstone
Price
$129

Virtually all consumer IT products have been shrinking for some years, and
Silverstone is one long-established case maker that's keenly aware of the trend.
Their latest big gaming cases are considerably smaller than previous generations
(compare, for example, this year's Raven RV5 to the original Raven), and they've
made a concerted effort to introduce HTPC and other small cases utilizing SFX
power supplies rather than the much bigger ATX PSUs. The dearth of good SFX
power supply options has more or less forced Silverstone to come up with their
own, which is a good thing for IT consumers in general and silent PC enthusiasts
in particular.

We've looked (in Silverstone case reviews) at their 300W and 450W SFX models,
both quite useful and quiet enough, especially at lower power loads. There are
four SFX models in the lineup now: 300W Bronze 80 PLUS, 450W Bronze, 450W Gold,
and the 600W Gold model under review here. This 600 watter is unique in a number
of ways: Gold 80+ efficiency, completely detachable output cables, and the highest
rating of any SFX PSU ever.

At Computex in Taipei a couple months ago, Tony Ou, Silverstone's PR/Marketing
lead man, was talking up a new metric for power supplies: Power per volume.
Specifically, watts per liter. The typical ATX PSU has a volume of ~1.9 liters,
which means a 600W PSU offers roughly 315W/liter. Going up the power scale results
in higher power density, as the power supplies still have to fit at least in
the 8.5 x 15 cm back exhaust plate of every ATX case. So a super power PSU with
a deep casing like the Silverstone ST1500 is 529W/L. Make it more efficient
and fit it into a smaller casing, like the ST1500-GS, and W/L goes up, to 646W/L.
The very small SX600-G being examined here only occupies about 0.8 liters, which
gives a whopping power density of 756W/L.






Watts per liter is Silverstone's new metric, touted on PSUs displayed
at Computex Taipei 2014.

So aside from this highlight, what are the salient features of this SX600-G
PSU? Here's the summary from Silverstone:

Silverstone SX600-G HIGHLIGHTS

from
the product page
FEATURE & BRIEF Our comment
Intelligent semi-fanless operation Usually means the fan won't start till
a certain temperature is reached
Support standard SFX form factor and
ATX via included bracket

Same type of flat plate that accompanies
Seasonic PSUs
High efficiency with 80 PLUS Gold certification Very good
100% modular cables

Very handy during installation
All cables made with flexible flat arrays

Also much shorter than usual, for small
cases
600W continuous power output
at 40ºC operating temperature rated for 24/7 operation
Impressive in such small package
Class-leading single +12V
rail with 50A
It's just what ATX12V calls
for
Strict ±3% voltage
regulation and low ripple & noise
Tight might be a better term
than strict
Support dual PCI-E 8/6pin
connectors
OK


Silverstone SX600-G SPECIFICATIONS
AC Input
90~264VAC, 47~63 Hz
DC Output
3.3V
5V
12V
-12V
5Vsb
20A
15A
50A
0.3A
2.5A
90W
600W
3.6W
12.5W
600W

The product web page is notable for its comprehensiveness; the
SX600-G is more thoroughly spec'd than most retail computer PSUs.

Silverstone SX600-G: Other Technical Details
PFC Active PFC(PF>0.95 at full load)
Efficiency

87%~90%(20% to 100% loading - 80 PLUS
Gold)
MTBF 100,000 hours
Operating temperature 0°C ~ 40°C
Protection

Over current protection

Over power protection

Over voltage protection

Over Temperature Protection

Under voltage protection

Short circuit protection

No load operation
Connectors 1 x 24 / 20-Pin motherboard
(300mm)

1 x 8 / 4-Pin EPS / ATX 12V (400mm)

2 x 8 / 6-Pin PCIE (400mm / 150mm)

4 x SATA (300mm / 200mm / 100mm / 100mm)

2 x 4-Pin Peripheral (300mm / 200mm)

1 x 4-Pin Floppy (300mm / 200mm / 200mm)
Color Black(Lead-Free Paint)
Cooling Single 80mm silent fan
Noise Level 0 ~ 40 dBA
Dimension 125 (W) × 63.5 (H) ×
100 mm (D)
Weight 1.45 kg
Form factor SFX

DETAILS

The SX600-G continues its smaller-is-better theme in its packageing, which
is about as small as it can be. Included with the PSU and its cables are the
ATX adapter plate, a user manual, and a general PS guide.



The package is small, too.




Contents include a user manual as well as a generalized PSU guide.




PSU in center, along with ATX adapter plate, AC & output cables.




The main label on the PSU.




The main ATX cable is cleverly folded to make it easy to fit. This is
the approximate length of all the cables — usefully short for small
cases.

 

TESTING

For a fuller understanding of computer 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.

SPCR's
PSU Test Platform V4.1
. is the basic setup for the testing. It is a close simulation of
a moderate airflow mid-tower PC optimized for low noise. There is one major change: The primary testing is done with the PSU NOT inside the hotbox but atop it, out of the heat path. This is in recognition of several realities that prevail today:

  • In SPCR's earlier test platforms, the internal temperature varied proportionately
    with output load. The tested PSU was subject to this heat, and operating ambient
    temperature rose with increased load, reaching >40°C and often much
    higher at full power. This was a realistic simulation of a mid-tower PC case
    where the PSU is mounted conventionally at the top back portion of the case.
  • Today, the vast majority of "serious" PC cases for the home builder
    no longer position the PSU at the top back corner. The PSU is most often located
    at the bottom/back corner, out of the path of heat from the other components
    in the case. This design concept took root with the Antec P180, and now dominates
    the DIY case arena. This means the PSU generally has to dissipate only its
    own heat.

So, we've reversed our approach: The PSU is tested briefly in
the hotbox only to check what happens to noise, fan speed and temperatures when
it is used in an outmoded case design.

Acoustic measurements are performed in our own anechoic
chamber
with ambient level of 11 dBA or lower, with a PC-based
spectrum analyzer
comprised of SpectraPLUS
software with super-low noise 1" diaphragm ACO
Pacific
microphone and M-Audio 24-bit digital audio interfaces.

REAL SYSTEM POWER NEEDS: While we test the PSU to full
output in order to verify the manufacturer's claims, real desktop PCs generally
do not require this level of power. The most pertinent range of DC output power
is between about 20W and 400W, because it is the power range where most systems
will be working most of the time. It is true that very elaborate systems with
the most power hungry dual video cards today might draw as much as another 150~400W,
but the total usually remains under 700W.

TEST RESULTS

The ambient temperature was ~22°, and the ambient noise level
was ~10 dBA.

Silverstone SX600-G Test Results

DC Output (W)

AC Input

(W)
Heat loss

(W)

Efficiency %
Power Factor
Exhaust
21.2
33
11.8
64.4
0.89
24°C
<11
40.2
54
13.8
74.4
0.95
25°C
15
64.8
80
15.2
81.1
0.98
26°C
15
90.2
107
16.8
84.3
1.00
27°C
15
149.8
171
21.2
87.6
1.00
28°C
16
200.5
225
24.5
89.1
1.00
29°C
19
299.5
325
25.5
92.2
1.00
34°C
29
400.2
433
37.8
92.4
1.00
37°C
32
495.5
545
49.5
90.9
1.00
40°C
34
601.7
685
83.3
87.8
1.00
44°C
34
Crossload Test

(1A on 5V and 3.3V lines; the rest on 12V line)
400.5
431
31
92.9%
1.00
44°C
<11
+12V Ripple: <20mV @ <250W ~ <47mV
@ 600W
+5V Ripple: <12mV @ <250W ~ <20mV @ 600W
+3.3V Ripple: <11mV @ <250W ~ <20mV @ 600W
AC Power in Standby: 0.5W

AC Power with No Load, PSU power On: 8.7W / 0.52 PF




1. EFFICIENCY — This is a measure of AC-to-DC
conversion efficiency. As an example, 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
Gold standard requires 87% efficiency at 20% load, 90% efficiency at 50% of
rated load, and 87% efficiency at full rated load.

At the super low 20W load, efficiency was 64.4%. It rose quickly
to 74% at 40W and 84% at 90W. The required 87% mark at 130W was probably reached,
judging by the 87.6% measured at 150W. Peak efficieny was reached at 300~400W,
where it exceed 92%, well above the 90% efficiency at 50% load required by 80
PLUS Gold. At full load it was 87.8%, still over the required 87% efficiency.

There was no issue with crossloading. With over 90% of a 400W
load on 12V, efficiency improved a smidgen over the standard loading.

Despite its small physical size, the power efficiency curve holds
true to the 600W output rating. This PSU does not reach very high efficiency
till some 25% of its rated load, over 150W. In this regard, it is similar to
ATX12V PSUs of the same power and efficiency rating.

2. VOLTAGE REGULATION refers to how stable the output voltages are under
various load conditions. The Power Supply Design Guide calls for the +12, +5V
and +3.3V lines to be maintained within ±5%.

Voltage Regulation

Silverstone SX600-G
Line
Max
Min
%
12V
12.02V
11.75V
+0.2, -2.1
5V
5.02V
4.80V
+0.4, -4.2
3.3V
3.35V
3.22V
+1.7, -2.5

The critical 12V line was well regulated. It was right on the
money through the bottom half of the power range and began drooping at ~300W,
to 11.92V, gradually dropping to the low of 11.75V at full power. The 5V line
was also dead accurate at lower power, starting at 5.02V and dropping only at
very high load, to a low of 4.8V, which percentage-wise, is the worst spec here
but still well within recommended guidelines. The 3.3V line went from 3.35V
at lower loads to 3.22V (-2.5%) at full load. This is good performance. Computer
components easily tolerate wider voltage variations.

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 m easured.
The PSU Design 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 modest
at lower power levels, staying under 20mV on 12V at all power levels up to around
250W and increasing gradually with power to <47mV at full load. The ripple
on the 5V and 3.3V lines was consistently ~50% lower than on the 12V line.

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 is excellent, running 1.0 through most of the loads.

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 of 8.7W was modest. The 0.5W power draw in standby (power switch
on but computer off) is very low.

6. LOW & 240 VAC PERFORMANCE

The power supply was set to 400W load and the AC input voltage
varied. Most full-range input power supplies achieve 2~3% higher efficiency
with 220~240 VAC, compared to 110~120 VAC. SPCR's lab is equipped with a 240
VAC line, which is used to check power supply efficiency for the benefit of
those who live in higher mains voltage regions. We also used a hefty variac
to check the stability of the PSU under brownout conditions where the AC line
voltage drops from the 120V norm.

Various VAC Inputs:

Silverstone SX600-G
VAC
AC Power
DC Output
Efficiency
242V
420W
400W
95.2%
120V
433W
92.4%
100V
439W
91.3%

The 95.2% efficiency reached at 400W load on 242VAC input matches
the highest efficiency we've measured, previously on the 80 PLUS Platinum
Rosewill Silent Night 500. It's the reduced efficiency at low and maximum
loads which keeps Silverstone SX600-G from the Platinum category, not the
maximum efficiency at mid power.

7. COOLING

The temperatures measured for this unit during operation seem
lower than usual. Normally, for a fan-cooled PSU, a thermal sensor is moved
around a bit during warmup at ~200W load to find the "hot spot" on
the exhaust grill where is attached using friction. This provides consistent
enough readings of the exhaust air temperature. For whatever reason, the exhaust
air never seemed to get that high. It's important to note, however, that the
semi-passive fan, which is tied to an internal temperature of 45°C in a sensor
somewhere inside the unit, started at just 40W load after about 15 minutes,
when the exhaust temperature read only 26°C.

8. NOISE

No noise of any kind was heard or detected at 20W load in the
anechoic chamber with the microphone a meter away. Even from virtually inches
away, only a trace amount of buzz could be reliably heard.

The fan started spinning at a much lower power load and external
temperature than expected, as detailed in section 7. Once the fan began spinning,
it did not stop at any time during testing, even after switching on/off; presumably
the internal sensor to which the fan operation is tied never had a chance to
cool off below 45°C.

The minimum noise of the fan measured about 14.5 dBA @ 1m. This
is very quiet, likely inaudible in most installations. The quality of the noise
was not entirely smooth, however, as the 80mm fan exhibited a small degree of
tonality and some periodic clicking. Again, the volume was at a low enough level
that this should not be considered significant for most users, even among SPCR's
highly sensitive audience.



The SX600-G frequency spectrum at low loads.

The fan speed did not appear to increase until around 200W load,
when it slid up to 19 dBA. The sound quality was actually a bit smoother than
at the lowest speed, as most of the periodic noises had disappeared, and the
primary component was the broadband woosh of airflow.

From this point on up, the fan speed/noise rose more or less in
sync with power load. 300W saw a 10 dBA jump, but then beyond that, the noise
level rose 7 dBA to a maximum of just under 35 dBA at 500W. This level did not
change all the way to full power. 35 dBA @ 1m is plainly audible, but the quality
of the noise is relatively benign, being a fairly smooth broadband noise with
little or no tonality.



This is the frequency spectrum at 500W+ loads.

Overall, the noise performance is not quite as good as one of
SPCR's top-rated ATX power supplies, which benefit from 120mm or larger fans,
but the SX600-G is still a very quiet power supply, certainly to ~200W load.
Above that power level, it becomes increasingly and plainly audible but not
highly intrusive, due to the relatively smooth quality of the noise. There's
very little or no electronic noise (such as buzz, hum or whine) to be perceived.

9. COMPARISONS

The comparison table below shows the SPL versus Power Load data on PSUs tested
in ambient room temperature, typically 20~24°C. The Silverstone SX600-G is the
lone SFX PSU on this table, and the only one with an 80mm fan; naturally it
falls to the bottom. However, note that while not quite as quiet at very low
load, above ~250W, it actually runs significantly quieter than the Seasonic
G360.

PSU Noise ([email protected]) vs. Power in Ambient
Room Temperature
Model
90W
150W
200W
250W
300W
400W
500W
6-700W
850W

Seasonic 520 Platinum
<11
<11
<11
<11
<11
<11
<11
n/a
n/a

Rosewill Silent Night 500
<11*
<11
<11
<11
<11
<11
12
n/a
n/a

Kingwin Lazer Platinum LZP-550
<11*
<11
<11
<11
<11
<11
16
n/a
n/a

bequiet! DPP 10 550W
<11
<11
<11
<11
<11
12
15
n/a
n/a

Seasonic X-400 Fanless
<11*
<11
<11
<11
<11
<11
n/a
n/a
n/a

Enermax Platimax 60v0W
<11
<11
<11
<11
<11
12
18
24
n/a

Enermax Modu/Pro87+ 500
11
11
11
11
11
11
18
n/a
n/a

Corsair AX850
<11
<11
<11
11~13
12
13
17
24
35

Seasonic X-650
<11
<11
<11
<11
<11
16
27
32
n/a

Nexus NX-5000
11
11
12
12
12.5
14
19
n/a
n/a
Antec CP-850
12
12
12
12
12
14
20
24
40

Enermax Eco80+ 500W
<11
12
12
16
20
23
28
n/a
n/a

Antec TP-750
12
12
12
14
15
27
31
40
n/a

Seasonic G360
<13
<13
18
24
34
39
n/a
n/a
n/a
CoolerMaster Silent Pro M2 720W
15
15
15
15
15
16
22
31
n/a
Cougar GX-700
15
15
15
17
21
25
35
35
n/a
Silverstone SX600-G (SFX)
15
16
19
n/a
29
32
35
35
n/a

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.

CONCLUSIONS

The Silverstone SX600-G SFX power supply delivers very
good performance in a package just half the size of a typical ATX PSU. Its voltage
regulation, noise and ripple, and efficiency are all very good, with the peak efficiency
being as high as I've measured in any PSU thus far. The >95% efficiency at
400W load with 240VAC input means this PSU produces just a measly 20W of heat
at that power level.

This sample produced virtually no audible electronic noise under
~200W. Above that power level, any rise in electronic noise is masked by the
broadband fan noise. In comparison with ATX PSUs of the same power rating, the
small SX600-G runs louder at mid & higher power level, though its subjective
volume is still moderate; this is the price you pay for for high power in a
small package.

The most likely application for this SFX power supply is in a
small, mini-ITX, single video card, high performance gaming rig. The SX600-G
is ideally suited for this purpose, in one of the dozen or so SFX-based cases
Silverstone offers. The short, flat-profile, completely detachable output cables
are very useful for assembling such a computer. It might also be useful with
its ATX adapter plate to use in place of an ATX power supply in cases where
the power supply limits space for the CPU heatsink. In summary, SX600-G is a
useful addition to Silverstone's roster of power supplies, as its is entire
SFX line.

Much thanks to Silverstone
for the review sample.



Silvertsone SX600-G SFX PSU is Recommended by SPCR

* * *

SPCR Articles of Related Interest:

Power Supply Fundamentals


Recommended Power Supplies

SPCR PSU Test Rig

Seasonic Platinum
Fanless 520W


Fanless PSU Torture
Test Roundup


Fanless
PSUs: Kingwin Stryker STR-500 & Silverstone ST50NF


Seasonic G360

* * *

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