Review Index:

SilverStone ST50EF-Plus High-Efficiency Power Supply Review

Manufacturer: Silverstone

Introduction and Features

SilverStone recently introduced three new power supplies in the Element Series, which are designed for high efficiency operation.  The new models include one 400W and two 500W units that are particularly well suited for use in SFF and HTPC cases.  We will be taking a detailed look at the ST50EF-Plus, which has been tested and approved by the 80 Plus program to deliver greater than 80% efficiency across all loading conditions (from 20% to 100%).  As a result of greater efficiency, the power supply generates less waste heat.  This allows the 120mm cooling fan to operate at minimal speeds, ensuring near silent operation for most applications.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />



SilverStone is based in <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />Taiwan with a sales office in California.  They specialize in designing low acoustic and high performance PC and HTPC enclosures, power supplies and other accessories for the PC enthusiast market. 


SilverStone Element ST50EF-Plus 500W PSU Key Features:


  • High-Efficiency operation, greater than 80% (from 20% to 100% load)

  • 500 watt continuous DC power output (up to 50°C operating temperature)

  • Virtually silent, temperature controlled 120mm fan

  • ATX12V v2.2 compliance

  • Dual +12V outputs (up to 36A combined)

  • Dual PCI-E connectors (nVIDIA SLI and ATI CrossFire ready)

  • Active PFC with Universal AC line input

  • 3-Year warranty 

In addition to the power supply the box also includes a power cord, mounting screws, wire ties, a detailed manual and two adapter cables.



The Element ST50EF-Plus 500W 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.  In addition to measuring the power going in and coming out I looked at voltage regulation, electrical noise (AC ripple), sound level, efficiency and cost.  Here is a list of the equipment used during testing.



  • FLUKE 87-III True RMS digital multimeter (Accuracy +/- 0.05%)

  • WattsUp? Pro — digital wattmeter (Accuracy 3% of full scale)

  • Hitachi V-650F 60 MHz dual trace oscilloscope (Accuracy +/- 3%)

  • Powerstat Variable Autotransformer, 1.4 KVA, 0-140 VAC

  • FLUKE  52-II digital thermometer (Accuracy +/- 0.3ºC/0.5ºF)

  • Extech Model 407736 digital sound level meter (Accuracy +/- 1.5 dB)

  • AccuLab V1-10kg digital balance (Accuracy +/- 1g)

  • Homemade PSU load tester — selectable loads (up to 470W)

  • Seasonic PSU load tester (up to 137W)

Establishing a controlled load is critical to testing and evaluating a PC power supply.  I built my own power supply load tester using 13 wire-wound, ceramic resistors of various sizes.  This unit can now place up to a 470 watt combined load onto the power supply being tested and includes independent +12V1 and +12V2 loads.  Different combinations of resistors can be switched in or out to select various loads.  In addition to my own load tester, I also used a load tester manufactured by Seasonic (75W and 137W loads).


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