SilverStone SX700-PT SFX Power Supply Review: SX700 Series Re-Examined

Introduction

Earlier this year, we took a detailed look at SilverStone’s SX700-G SFX power supply, which provides up to 700W of DC power in a compact SFX enclosure with an 80 Plus Gold efficiency rating. While the overall electrical performance proved to be very good (voltage regulation, efficiency, and AC ripple suppression) we felt the power supply came up a little short in the areas of component quality (85°C rated electrolytic capacitors versus 105°C), warranty support, and pricing.

Our earlier review of the SilverStone SX700-G SFX Gold Power Supply can be found here.

SilverStone recently released a new version of the SX700; this time with 80 Plus Platinum certification, for even higher efficiency. Once again this is a true SFX power supply and not one of the longer SFX-L versions. By tweaking a few key components they were able to push the SX700 to Platinum level efficiency (at least 92% efficient at a 50% load). Another difference between the new SX700-PT and the previous SX700-G is the addition of a second 8/4-pin EPS/ATX12V cable. The SX700-PT power supply features two of these cables/connectors.

And finally the SX700-PT now comes with a 5-year warranty instead of the SX700-G unit’s 3-year coverage. Otherwise, the two power supplies appear to be nearly identical. Please refer to the previous SX700-G review for info on packaging, parts, and a more detailed description. In this review we are going to focus on the test results of the new SX700 Platinum PSU.

Key Features

• 80 Plus Platinum certified for high efficiency (92% at 50% load)
• Small Form Factor (SFX) design: 63.5 x 125 x 100mm
• 700W continuous power output at up to 40°C
• Fluid Dynamic Bearing (FDB) fan for quiet, reliable operation
• Powerful single +12V rail with 58.4A capacity
• All-modular, flat ribbon-style cables
• All Japanese made capacitors
• Strict ±3% voltage regulation and low AC ripple and noise
• Support for high-end GPUs with four PCI-E 8/6-pin connectors
• Two 8/4-pin EPS/ATX12V cable/connectors
• Safety Protections: OCP, OVP, UVP, SCP, OTP, and OPP
• 5-Year warranty

Specifications

Test Results

The following cables/connectors were used to connect the SX700-PT power supply to the PCPerspective power supply test equipment.

• (1) 20+4 pin ATX
• (2) 8-pin EPS/ATX12V
• (4) 6-pin PCI-E
• (6) SATA
• (3) Molex

Internally the new SX700-PT power supply appears very similar to the previous SX700-G we reviewed earlier this year. SilverStone said they were able to increase the efficiency by upgrading a few key components to higher quality, more efficient parts. However, we were disappointed to see that didn’t include upgrading the electrolytic caps to 105°C versions while they were making improvements.

DC Output Load Regulation

To simulate demanding and maximum loading conditions, the SX700-PT 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-PT PSU while operating on 120 VAC, 60 Hz.

Once again the power supply produced very good voltage regulation on all of the DC outputs with the three main rails staying within ±2% of the recommended ATX guidelines; even better than SilverStone’s claim of ±3%.

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-PT power supply exhibited good AC ripple and noise suppression with the results staying well below the ATX recommended guidelines, even at full load with an elevated operating temperature.

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-PT 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-PT power supply proved to be excellent and complies with the 80 Plus Platinum guidelines, even when operating on 120VAC and at elevated temperatures; just as SilverStone claims.

80 Plus Program

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

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 ~27 dBA.

One of the first things we noticed during testing was the SX700-PT runs slightly cooler than the previous SX700-G; just what you would expect with higher efficiency and less waste heat. The SX700-PT 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 to keep the temperatures under control and the noise became quite noticeable.

Final Thoughts and Conclusions

As we mentioned in the introduction, the focus of this review is primarily on the changes and improvements made to SilverStone’s new SX700-PT Platinum rated SFX power supply. Compared to the SX700-G Gold we reviewed earlier this year, the new SX700-PT is different in three ways. First, the circuitry has been tweaked to deliver higher efficiency, meeting the 80 Plus Platinum level criteria instead of Gold. The second difference is the addition of another 8/4-pin EPS/ATX12V cable/connector for a total of two. And finally SilverStone has upgraded the warranty from 3-years to 5-years for the SX700-PT Platinum. Other than that the two power supplies appear to be nearly identical.

The electrical performance of the SX700-PT power supply was very good, just like we saw with the previous SX700-G. And thanks to the higher efficiency, the SX700-PT runs slightly cooler and remains relatively quiet through much of the load range. While higher efficiency and a second EPS cable are nice, in our opinion the most notable improvement was increasing the warranty period from three to five years.

However, SilverStone did not address two of the other issues we noted during the earlier SX700-G review. First, while SilverStone upgraded some components for higher efficiency, the electrolytic capacitors are still rated for 85°C instead of moving up to 105°C parts like we would expect to see in a premium power supply. And unfortunately, the SX700-PT is still relatively expensive. The SilverStone SX700-PT power supply is currently selling for $186 USD on Amazon.com (as of 12/02/2019).

Once again it’s hard to give the SX700-PT a strong recommendation when for about $10 less you can buy a competing unit with more power, 105°C caps, and a 7-year warranty (Corsair SF750 SFX). Alternatively, if you don’t need/want a true SFX size power supply, you might consider SilverStone’s SX700-LPT unit, which is selling for $169.99 USD (Amazon.com).

• 700W Continuous DC output in a compact SFX form factor chassis
• 80 Plus Platinum level efficiency (92% at 50% load)
• Very good voltage regulation (±2% on the three main outputs)
• Good AC ripple and noise suppression
• Fluid Dynamic Bearing (FDB) fan
• 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)
• Two 8/4-pin EPS/ATX12V cable/connectors
• Safety Protections: OCP, OVP, UVP, SCP, OTP, and OPP
• Active PFC with universal AC input
• 5-Year warranty

• 85°C Rated electrolytic capacitors
• Relatively expensive

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