Seasonic SS-300TFX Power Supply Review

Introduction and Features

If you are in the market for a solid 300W PSU for a Micro ATX Media Center or Home Theater PC, the Seasonic SS-300TFX deserves a very close look! This is a very different form factor than standard power supplies so stop in and see if it might work for your next HTPC build!

Seasonic has an excellent reputation for producing quiet ATX style PC power supplies with high efficiencies and stable outputs.  Seasonic also has a full line of server style power supplies in both 1U and 2U form factors and a new 300W TFX model.  The TFX form factor is used by the majority of Micro ATX and Mini-ITX Media Center PCs and Home Theater PCs.


Seasonic SS-300TFX Main Features:

•    Complies with TFX12V v2.31 specification
•    80Plus Bronze certified
•    Pentium 4 12V connector
•    Forward converter circuit design
•    High efficiency and reliability
•    Low AC ripple and noise
•    Super low noise fan control
•    Short circuit protection on all outputs
•    Over voltage protection
•    Over power protection
•    100% Hi-pot tested
•    100% Burn-in, high temperature cycled On/Off
•    Patented active transient load 

PSU 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 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, 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


The Seasonic SS-300TFX 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)
•    Extech MultiMaster MM570 digital multimeter (Accuracy ±0.02%)
•    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
•    Extech Model 407750 digital sound level meter (Accuracy ±1.5 dB)
•    Custom PC60 enclosure to simulate real-world operating conditions