SilverStone SX700-G Power Supply Review: 700W of SFX

700W of 80 Plus Gold Power in the Standard SFX Form Factor

SilverStone has been a champion of SFX power supplies for many years. Their current power supply lineup includes over a dozen different SFX/SFX-L models. They also offer a full line of high quality enclosures, cooling components, and accessories for PC enthusiasts.

With a continued focus on smaller physical size and support for small form-factor enthusiasts, SilverStone’s current SF-Gold Series includes five models ranging in power from 500W to 700W. Unlike the larger SX-L units, which are 30mm (1.2”) longer than a standard SFX chassis, the SX700-G retains the original SFX dimensions. We will be taking a detailed look at the SX700-G power supply in this review.

In addition to its small size the SX700-G power supply features high efficiency (80 Plus Gold certified), comes with all modular flat ribbon-style cables, and remains relatively quiet through mid-power.

SilverStone SX700-G PSU Key Features:

• Small Form Factor (SFX) design
• 700W continuous power output
• Fluid Dynamic Bearing (FDB) fan for quiet, reliable operation
• 80 Plus Gold certified for high efficiency
• Powerful single +12V rail with 58.4A capacity
• All-modular, flat ribbon-style cables
• Strict ±3% voltage regulation and low AC ripple and noise
• Support for high-end GPUs with four PCI-E 8/6-pin connectors
• Safety Protections: OCP, OVP, UVP, SCP, OTP, and OPP
• Currently selling for $179.99 USD (Amazon.com)

Specifications

The SX700-G power supply is rated for a combined, continuous output power of 700 watts at 40°C. The PSU incorporates a single +12V rail that can deliver up to 58.4A (700W). The PSU includes universal AC line input (automatically adjusts the AC line voltage) and active PFC, which makes the unit more environmentally friendly to the local power grid.

SilverStone SX700-G PSU Specifications (from the SilverStone website):

Packaging and Parts

The SilverStone SFX Series 700W Gold power supply arrived packed inside a standard retail box showcasing the unit’s features and specifications.

In addition to the power supply, the box contains a power cord, mounting screws, a User Manual, Product Manual, and seven modular cables (plus a 4-pin Molex to HDD adapter).

The flat ribbon-style modular cables handle the power distribution (see table above for more detailed lengths and connector count).

A Detailed Look

The SilverStone SX700-G power supply enclosure is painted with a satin black finish. The power supply measures 100mm deep x 63mm x 125mm. The back panel includes an On-Off switch, AC receptacle and open honey-comb grill.

The power supply uses a 92mm fan made by Globe Fan for cooling. The nine blade fan (SO921512HB) is rated for 0.45A at 12 VDC and features a Fluid Dynamic Bearing (FDB) bearing for quiet operation and long life.

The front panel on the 700W PSU incorporates eight modular cable connectors, all nicely labelled and color coded. Each blue connector supports one cable with two PCI-E 8/6-pin connectors.

All of the modular cables are flat ribbon-style to assist with neat cable routing and to help maximize airflow. Note that all of the cables are intentionally rather short as this power supply is designed for use in small-size cases.

Here are a few pictures showing the layout and components inside SX700-G power supply. SilverStone is once again using High Power as the OEM for the SX700-G PSU. The overall layout, soldering, and build quality all look good.

The power supply features a modern circuit design to meet the 80 Plus criteria for high efficiency and uses DC-to-DC converters on the secondary to produce the +3.3V and +5V rails from the +12V output. All of capacitors used inside the PSU are Japanese made with a mix of solid polymer and electrolytic caps used throughout. For example, the main bulk capacitor is made by Rubycon and rated for 470uF, 420V, and 85°C. We would prefer to see 105°C rated caps in this type of build.

Testing Methodology

Establishing an accurate load is critical to testing and evaluating a PC power supply. PC Perspective’s power supply test bench can place a precise DC load on the PSU under test. Each power supply is tested under controlled, demanding conditions up to its maximum rated load (at 40ºC).

Our current suite of tests includes:

• DC Load Regulation
• AC Ripple and Noise
• Efficiency
• Differential Temperature
• Noise

The SilverStone SX700-G power supply was evaluated on both features and performance. A full range of equipment was used to test the power supply under controlled load conditions.

• (2) CSI3710A Programmable DC load (+3.3V and +5V outputs)
• (4) CSI3711A Programmable DC load (+12V1, +12V2, +12V3, and +12V4)
• (2) 200W Precision resistor load bank (+12V5 and +12V6)
• Switchable precision resistor load bank (-12V and +5VSB)
• Agilent 34401A digital multimeter (Accuracy ±0.0035% vDC)
• Extech 380803 Power Analyzer (Accuracy ±0.5% of full scale)
• DS1M12 “StingRay” digital oscilloscope (20M S/s with 12 Bit ADC)
• Extech Model 407738 digital sound level meter (Accuracy ±1.5 dB)

The following cables/connectors were used to connect the power supply to the PCPerspective power supply test equipment.

• (1) 20+4 pin ATX
• (1) 8-pin EPS/ATX12V
• (4) 6-pin PCI-E
• (6) SATA
• (3) Molex

Test Results

DC Output Load Regulation

To simulate demanding and maximum loading conditions, the SX700-G power supply was connected to the load testers and supplied with a constant 120 VAC. In this test we are interested in seeing how well a PSU can maintain the various output voltages while operating under different loads.

The ATX12V V2.2 tolerance for voltages states how much each output (rail) is allowed to fluctuate and has tighter tolerances now for the +12V outputs. We have included a second table of expanded tolerances (±1% to ±6%) for reference.

The following tables list the DC voltage results for the SilverStone SX700-G PSU while operating on 120 VAC, 60 Hz.

The power supply produced very good voltage regulation on all of the DC outputs with the three main rails staying within ±1% of the recommended ATX guidelines; even better than SilverStone’s claim of ±3%. Impressive!

AC Ripple and Noise on the DC Outputs

The amount of AC ripple and noise present on the DC outputs was checked using a digital oscilloscope. This AC component may be present in the KHz range where most switching power supplies operate or it may be more prevalent at the 60 Hz line frequency. We adjust the O-scope time base to look for AC ripple at both low and high frequencies. The ATX12V V2.2 specification for DC output noise/ripple is defined in the ATX12V Power Supply Design Guide.

Ideally we would like to see no AC ripple (repetitive) or noise (random) on the DC outputs – the cleaner the better! But in reality there will always be some present. I measured the amplitude of the AC signal (in millivolts, peak-to-peak) to see how well the power supply complied with the ATX standard. The following table lists the ripple/noise results during all of the load tests for the main output voltages of interest.

Overall the SX700-G power supply exhibited good AC ripple and noise suppression with the results staying well below the ATX recommended guidelines, even at full load.

Efficiency

Efficiency is defined by the power output divided by the power input and is usually expressed as a percentage. If a PSU were a 100% efficient (which none are) 700 watts of AC power going in would result in 700 watts of DC power coming out (with no waste heat to dissipate).

In the real world there are always inefficiencies and power is lost in the form of heat during the conversion process. Newer revisions to the ATX12V Power Supply Design Guide V 2.2 have continued to increase the efficiency recommendations for PC switching mode power supplies and now lists both required and recommended minimum efficiencies.

We measured the AC power input to the SilverStone SX700-G with an Extech power analyzer while the total DC load was found by adding all the individual +3.3V, +5V, +12V, -12V and +5VSB loads together.

The overall efficiency of the SilverStone SX700-G power supply is also very good and meets the 80 Plus Gold guidelines, even when operating on 120VAC and at elevated temperatures.

80 Plus Program:

Note: Tests conducted at room temperature (25°C).

Differential Temperature and Noise Levels

To simulate a demanding environment, some of the warm exhaust air from the PSU under test is recirculated back to the intake through a passive air duct, which allows the PSU air inlet temperature to increase with load, up to 40°C.

The differential temperature across the power supply was calculated by subtracting the internal case air temperature (T in) from the temperature of the warm exhaust air flowing out the back of the power supply (T out).

Thermocouples were placed at the air inlet and exhaust outlet. The ambient room air temperature was 23ºC (74ºF) +/- 0.5ºC during testing.

• T out = temperature of air exhausting from power supply
• T in = temperature of air entering power supply
• Delta T = T out – T in

Sound pressure level readings were taken 3’ away from the rear of the case in an otherwise quiet room. The ambient noise level was ~28 dBA.

The SX700-G power supply started out quiet and stayed that way through the 50% load test. At full load with an elevated ambient temperature, the cooling fan did speed up and the noise became very noticeable.

Final Thoughts and Conclusions

SilverStone’s SX700-G power supply can easily deliver 700 watts of combined DC output for the small form factor market in a very compact chassis. Its most obvious feature is its small size, but the PSU also delivered very good voltage regulation, good efficiency, with relatively low AC ripple and noise.

The SX700-G features all modular cables, which are intentionally short. At low to mid-power the PSU was quiet thanks to a high-quality 92mm fan with a Fluid Dynamic Bearing. At high power however, the fan noise becomes very noticeable.

While the performance of the SX700-G power supply proved to be very good there were several areas we found to be disappointing. First, the electrolytic capacitors are rated for 85°C instead of 105°C. Some users may miss not having a second 8-pin EPS connector at this power point but I suspect most users will be OK with one. A 3-year warranty seems out of line when most all the competition is offering significant longer warranty periods. And last but not least, the SX700-G is expensive when compared to the competition, especially considering its 80 Plus Gold efficiency and 3-year warranty.

Bottom line it’s hard to recommend the SX700-G when for about $10 more you can buy a Corsair SF750 SFX unit (more power, more cables/connectors, higher efficiency, 105°C caps, and a 7-year warranty). And if you don’t need/want a true SFX size enclosure, consider SilverStone’s SFX-L 700W unit (SX700-LPT), which is currently selling for $172.48 (Amazon.com) with Platinum level efficiency.

The SilverStone SX700-G power supply is currently selling for $179.99 on Amazon.com.

Strengths:

• 700W Continuous DC output in a compact SFX form factor chassis
• 80 Plus Gold efficiency
• Very good voltage regulation (±1% on the three main outputs)
• Good AC ripple and noise suppression
• 92mm Fan with Fluid Dynamic Bearing (FDB)
• Relatively quiet at low to mid-power levels
• All Japanese made capacitors
• All modular cables, flat ribbon style
• Single +12V output can deliver up to 58.4A/700W
• Four PCI-E connectors (6+2 pin)
• Active PFC with universal AC input

Weaknesses:

• 3-Year warranty
• 85°C Rated electrolytic capacitors
• Expensive compared to the competition

Our thanks to SilverStone for sending us the SX700-G PSU to review.