Introduction and Features

The S12 II power supplies from Seasonic offer even better performance and higher efficiencies than the original S12 and now features a solid cap on the +12V output for enhanced reliability.

Seasonic has an excellent reputation in the computer industry for producing very quiet PC power supplies with high efficiencies and stable outputs.  The new S12 II series includes models with output capacities ranging from 330W up to 500W.  The S12 II 500W that we are reviewing today is designed to deliver high efficiency and quiet operation for mainstream users.  Not everyone wants (and few need) a power supply that can deliver 800W to 1,200W of power.  For many PC enthusiasts, a high-quality 500W PSU may be just what they are looking for.


Seasonic S12 II 500W Power Supply Review - Cases and Cooling 32


The S12 II 500W power supply comes with two PCI-E connectors and incorporates a conductive polymer aluminum solid capacitor on the critical +12V output.  Seasonic claims that all of the S12 II power supplies not only meet but surpass the stringent 80 Plus program requirements for efficiency.  Combined with active power factor correction, the total computer system energy usage can be reduced by up to 20%.  The S12 II series power supplies use a single 120mm cooling fan and low noise fan control for near silent operation.  The S12 II meets all EU regulations for RoHS, WEEE and major safety requirements and is backed by Seasonic’s standard 3-year warranty.


Seasonic S12 II 500W PSU Key Features:


  • 500 watts continuous power output (up to 50°C)
  • Supports the latest ATX12V standard
  • Dual +12V outputs (up to 34A combined)
  • Ultra quiet 120mm variable speed fan
  • High-Efficiency (up to 85%) using double-forward switching circuitry
  • Active PFC with Universal AC line input
  • High grade conductive solid polymer capacitor (on +12V output)
  • Dual PCI-E connectors (one 6-pin and one 8-pin)
  • Compact chassis size: 5.9” (W) x 3.4” (H) x 5.5” (L); 150mm x 86mm x 140mm
  • Fully sleeved cables
  • 3-Year warranty 

The Seasonic S12 II power supply arrived securely packed inside a retail box that highlights the power supplies many features.  In addition to the power supply the box also contains a power cord, mounting screws, FDD adapter cable, Seasonic case badge, warranty card, and a printed User’s Manual.


Seasonic S12 II 500W Power Supply Review - Cases and Cooling 33


Establishing an accurate load is critical to testing and evaluating a PC power supply.  PCPerspective’s power supply test bench can place a precise 2,000 watt DC load on the PSU under test.  Each power supply is tested under controlled, real-world conditions up to its maximum rated load (at 40ºC), using both 115 VAC and 240 VAC line voltage.  Our current suite of tests includes:


  • DC Load Regulation
  • DC Line Regulation
  • DC Cross-load (unbalanced load)
  • AC Ripple and Noise
  • Power Factor
  • Efficiency
  • Differential Temperature
  • Noise

Seasonic S12 II 500W Power Supply Review - Cases and Cooling 34


The Seasonic S12 II 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. 


  • (2) CSI3710A Programmable DC load (+3.3V and +5V ouputs)
  • (4) CSI3711A Programmable DC load (+12V1, +12V2, +12V3, and +12V4)
  • FLUKE 87-III True RMS digital multimeter (Accuracy ±0.05%)
  • Extech 380803 Power Analyzer (Accuracy ±0.5% 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 407738 digital sound level meter (Accuracy ±1.5 dB)
  • Custom Lian Li PC60 enclosure to simulate real-world operating conditions


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