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SilverStone SFX 650W Gold Power Supply Review

Author: Lee Garbutt
Manufacturer: SilverStone

DC Load Regulation and AC Ripple

Testing Methodology

Establishing an accurate load is critical to testing and evaluating a PC power supply.  PCPerspective’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:

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

The SilverStone SX650-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
•    (5) SATA
•    (3) Molex

DC Output Load Regulation

To simulate demanding and maximum loading conditions, the SX650-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.

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The following tables list the DC voltage results for the SilverStone SX650-G PSU while operating on 120 VAC, 60 Hz.

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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%.

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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.

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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.

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Overall the SX650-G power supply exhibited very good AC ripple and noise suppression with the results staying well below the ATX recommended guidelines, even at full load.


December 3, 2017 | 11:27 AM - Posted by Smitty (not verified)

Thanks for the review. I'm a customer looking to purchase this SX650 or the Corsair SF600 and I noticed you have reviewed both units. However, there seems to be little direct comparison in your review between the two, even though they are direct competitors.

1) Is the fan in the Silverstone removable without cutting and soldering wires? It doesn't appear so but just looking to confirm.
2) It seems the SX650 runs hotter and louder than the SF600 based on comparing the two tables between reviews. However, this is a test where you are recycling hot air back into the intake. Many cases are designed where the PSU intake is bringing in fresh/cool outside air. Do you think this will affect the temperatures in a different way?

December 3, 2017 | 11:28 AM - Posted by Smitty (not verified)

One additional question:
3) The Corsair cables in the SF600 are often accused of being stiff and difficult to work with. Based on your review the SX650 have similar length and variety of cables. Are they also 'too stiff' or are they more flexible and easier to route?

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