Silverstone SST-SX550 550W PSU Review

1. Introduction2. Silverstone SST-SX550 (Bundle & Cables)3. Silverstone SST-SX550 (External)4. Silverstone SST-SX550 (Internal)5. Testing Methodology and Results6. Closing Thoughts7. View All Pages

Today we take a look at one of the latest power supplies from Silverstone – the SST-SX550. This is an SFX power supply designed to fit inside small form factor cases. It features 80 PLUS gold certification, a single +12V rail with a substantial 45A rating and it supports dual PCI-E 6+2 pin connectors. It is also rated to deliver a constant 550 watts while operating at 50C, 24/7.

One of the big problems with SFX power supplies are small cooling fans – which usually means a fair amount of noise under load. Silverstone have fitted a small 80mm fan inside the power supply which they claim will be silent when idle and can provide ‘adequate cooling during high loading conditions'. We will test these claims later in the review.

SilverStone SST-SX550 specifications:

• Supports standard SFX form factor.
• 550W continuous power output at 50℃ operating temperature rated for 24/7 operation.
• High efficiency with 80 PLUS Gold certification.
• Class-leading single +12V rail with 45A.
• Silent running 80mm fan with 18dBA minimum.
• Support dual PCI-E 8/6 pin connectors.
• Active PFC.

The SilverStone SST-SX550 box artwork shows a close up of the fan grill, at an angle. The product name is clearly listed bottom right at the front of the box.

The rear of the box lists some technical data including PSU load and fan speeds under load. SilverStone are clearly focusing on noise levels, given the diagrams on the box.

Inside the box is a user manual, cable ties, mounting screws and a regional specific power cable.

Connectors:

1 x 24 / 20-Pin motherboard connector（300mm）
1 x 8 / 4-Pin EPS / ATX 12V connector（400mm）
2 x 8 / 6-Pin PCIE connector（”400mm / 150mm” x 2）
3 x SATA connector（300mm / 200mm / 100mm）
2 x 4-Pin Peripheral connector（300mm / 200mm）
1 x 4-Pin Floppy connector（300mm / 200mm / 200mm）

Cable quality is good, they are all sleeved – although not completely into the chassis itself, as seen in the images above. They include two 6+2 pin PCI connectors to handle one or two graphics cards.

The SilverStone SST-SX550 is a diminutive SFX power supply measuring 125 mm (W) x 63.5 mm (H) x 100 mm (D). It weighs only 1.1kg. The paintwork is quite good and proves fairly resistant to scratching. This is a non modular power supply so all the cables are hardwired into the chassis. Call me old fashioned, but I would have preferred if SilverStone had sleeved the cables all the way into the chassis, rather than stopping short. It does look a bit naff.

The small fan grill is clearly seen on one side of the power supply, shown above. Strangely there is no SilverStone badge in the center position, like we would normally expect to see.

One side of the power supply is vented to support airflow. There is a power connector and switch close by.

Silverstone SST-SX550 550W
DC Output	+3.3V	+5V	+12V	-12V	+5Vsb
Max Output	21A	22A	45A	0.3A	2.5A
Total Power	120W		540W	3.6W	12.5W
	550W

The Silverstone SST-SX550 delivers a very capable 45A via the single +12V rail, more than enough for a single high powered graphics card, or two lower demand models in SLI or Crossfire.

The 80mm fan is made by Protechnic Electric with part number MGA8012YS-A15. This fan is rated 12V 0.28A. Little information can be found online although some investigation would indicate that fan speed peaks at 3,800 rpm. We do hope it doesn't spin close to this speed, as it will likely be rather loud, given the small physical dimensions.

This Active PFC power supply is an FSP OEM design for SilverStone. I thought initially this might be an active clamp with group regulation configuration. There is a DC to DC daughterboard shown close to the bunch of hard wired cables. The two primary capacitors are rated 420V 150uF and secondary stage capacitors are rated 105c which is good to see, especially in such a space restricted design. General soldering quality is decent, if unremarkable.

The SST-SX550 has Over Current Protection, Over Power Protection, Over Voltage Protection, Short Circuit Protection and Over Temperature Protection.

Correctly testing power supplies is a complex procedure and KitGuru have configured a test bench which can deliver up to a 2,000 watt DC load. Due to public requests we changed our temperature settings increasing ambient temperatures by 10c (to 35c) in our environment to greater reflect warmer internal chassis conditions.

We use combinations of the following hardware:
• SunMoon SM-268
• CSI3710A Programmable DC load (+3.3V and +5V outputs)
• CSI3711A Programmable DC load (+12V1, +12V2, +12V3, and +12V4)
• Extech Power Analyzer
• Extech MultiMaster MM570 digital multimeter
• SkyTronic DSL 2 Digital Sound Level Meter (6-130dBa)
• Digital oscilloscope (20M S/s with 12 Bit ADC)
• Variable Autotransformer, 1.4 KVA

We combine all +12V output for the results below.

DC Output Load Regulation
Combined DC Load	+3.3V		+5V		+12V		+5VSB
	A	V	A	V	A	V	A	V
110W	1.18	3.33	1.18	5.01	8.02	12.09	0.50	5.03
220W	2.06	3.33	2.07	5.00	16.13	12.08	0.50	5.02
340W	3.05	3.32	3.06	4.99	25.14	12.06	1.00	5.03
445W	4.12	3.32	4.06	4.98	33.25	12.04	1.50	5.02
550W	5.15	3.31	5.02	4.97	41.05	11.97	2.50	5.03

Silverstone SST-SX550	Maximum Load
	630W

Load regulation is good across the output range. The power supply delivered 630 watts of power before it would shut down, safely.

Next we want to try Cross Loading. This basically means loads which are not balanced. If a PC for instance needs 500W on the +12V outputs but something like 30W via the combined 3.3V and +5V outputs then the voltage regulation can fluctuate badly.

Cross Load Testing	+3.3V		+5V		+12V		-12V		+5VSB
	A	V	A	V	A	V	A	V	A	V
493W	1.0	3.33	1.0	5.02	40.5	11.96	0.2	-12.03	0.50	5.02
153W	15.0	3.30	15.0	4.98	2.0	12.08	0.2	-12.01	0.50	5.02

The unit passed the Cross Load test without any concerns.

We then used an oscilloscope to measure AC ripple and noise present on the DC outputs. We set the oscilloscope time base to check for AC ripple at both high and low ends of the spectrum. ATX12V V2.2 specification for DC output ripple and noise is defined in the ATX 12V power supply design guide.

ATX12V Ver 2.2 Noise/Ripple Tolerance
Output	Ripple (mV p-p)
+3.3V	50
+5V	50
+12V1	120
+12V2	120
-12V	120
+5VSB	50

Obviously when measuring AC noise and ripple on the DC outputs the cleaner (less recorded) means we have a better end result. We measured this AC signal amplitude to see how closely the unit complied with the ATX standard.

AC Ripple (mV p-p)
DC Load	+3.3V	+5V	+12V	5VSB
110W	5	5	10	10
220W	5	10	20	10
340W	15	10	25	10
445W	20	15	30	15
550W	20	15	40	15

Noise suppression is good with the +3.3V and +5V rail peaking at 20mV and 15mV respectively. The +12V rail peaks at 40mV under full load conditions.

Efficiency (%)
110W	88.75
220W	89.88
340W	91.71
445W	90.88
550W	89.45

Efficiency is excellent, peaking at around 91.8% at 50% load. At full load, this drops to around 89.5%. Solid results.

We take the issue of noise very seriously at KitGuru and this is why we have built a special home brew system as a reference point when we test noise levels of various components. Why do this? Well this means we can eliminate secondary noise pollution in the test room and concentrate on components we are testing. It also brings us slightly closer to industry standards, such as DIN 45635.

Today to test the Power Supply we have taken it into our acoustics room environment and have set our SkyTronic DSL 2 Digital Sound Level Meter (6-130dBa) one meter away from the unit. We have no other fans running so we can effectively measure just the noise from the unit itself. That said, measuring lower than 28dBa proves very difficult, unless in strict laboratory conditions.

As this can be a little confusing for people, here are various dBa ratings in with real world situations to help describe the various levels.

KitGuru noise guide
10dBA – Normal Breathing/Rustling Leaves
20-25dBA – Whisper
30dBA – High Quality Computer fan
40dBA – A Bubbling Brook, or a Refrigerator
50dBA – Normal Conversation
60dBA – Laughter
70dBA – Vacuum Cleaner or Hairdryer
80dBA – City Traffic or a Garbage Disposal
90dBA – Motorcycle or Lawnmower
100dBA – MP3 Player at maximum output
110dBA – Orchestra
120dBA – Front row rock concert/Jet Engine
130dBA – Threshold of Pain
140dBA – Military Jet takeoff/Gunshot (close range)
160dBA – Instant Perforation of eardrum

Noise (dBA)
110W	<28.0
220W	<28.0
340W	33.4
445W	36.4
550W	38.9

The small 80mm fan doesn't have much work to do until around 350-400 watts is demanded from the unit. It starts to actively spin up at this point. Its certainly audible at around 450 watts load, and the fan quickly spins up to around 3,750 rpm (our own readings of the fan speeds) as load rises to 550 watts. You really wouldn't want to be running this unit at 550 watts continuously however.

Using a slightly larger 92mm fan would have helped reduce noise levels, but we imagine SilverStone are reserving the larger, quieter fans for their higher cost units (SX500-G and SX650-G).

Temperature (c)
	Intake	Exhaust
110W	36	39
220W	37	42
340W	41	47
445W	45	53
550W	47	59

The small fan has to work hard in the last 30 percent of total load, but the internal temperatures are actually pretty good.

Maximum load	Efficiency
630W	88.7

Pushing the power supply above its rated limits generates an efficiency level of 88.7%. This is not a viable ‘real world’ situation, but its interesting nonetheless.

The Silverstone SST-SX550 is a high quality SFX power supply created for specific space restricted chassis designs. It is reasonably priced around the £70 point, and is capable of delivering a sustained 620 watts when pushed hard.

While it is beneficial to buy a power supply that is fully modular, it is clear Silverstone are trying to keep the price point down, without compromising too much on quality. It may be a little more work routing all the cables out of sight, but it isn't a critical, deal breaking issue.

The quality of the paint work is very good, and its a rather inoffensive monochromatic design suited to fit into any system build.

Technically, the unit is capable, if unremarkable. Load regulation is solid, and the SST-SX550 passed our cross load test without an issue. Ripple suppression is pretty good, as is the efficiency for an 80 Plus Gold rated unit.

The single +12V rail is powerful (rated to 45A), and capable of handling a demanding graphics card for a gaming system build. There will be no problems using the SX550 at the heart of a new GTX1080 based gaming system.

My only real concern is the operation of the small 80mm fan under duress. When load hits above 400 watts, it has to spin up to ensure there is adequate air flow throughout the chassis. At close to 500 watt demand, it is clearly audible and somewhat annoying. SilverStone have decided to only fit the larger 92mm fans in their more expensive SX500-G and SX650-G models.

That said if you know the load of your system is closer to 300/350 watts (and many are), then it won't be such a problematic issue long term. These load demands will also help achieve closer to optimum efficiency.

The SilverStone 550 W SST-SX550 is available today from Scan in the United Kingdom for £71.46 inc vat HERE.

Pros:

• good price point at £70 in the UK.
• quality finish.
• technically capable unit.
• 45A via the single +12V rail.

Cons:

• 80mm fan can get loud if the supply is pushed harder (over 400 watts).
• cable sleeving doesn't go into the chassis itself, stopping short.

Kitguru says: The Silverstone SST-SX550 is a well priced and capable unit. I would prefer a 92mm fan rather than 80mm, but unless you need to drive a constant 400 watt+ load, its not too much of an issue.

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