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FSP Twins 500W Redundant PSU Review

The FSP Twins series combines the usability of a normal ATX PSU and the advanced features of a redundant server unit. The Twins 500W we're evaluating today addresses users that need an ultra-reliable PSU and are willing to pay for it.

Ripple Measurements

To learn how we measure ripple, please click here.

The following table includes the ripple levels we measured on the Twins 500W's rails. The limits, according to the ATX specification, are 120mV (+12V) and 50mV (5V, 3.3V and 5VSB).

Test12V5V3.3V5VSBPass/Fail
10% Load53.7mV13.7mV22.2mV12.5mVPass
20% Load53.1mV13.7mV22.0mV13.7mVPass
30% Load53.1mV13.5mV22.5mV13.7mVPass
40% Load53.9mV13.6mV22.5mV14.0mVPass
50% Load57.6mV13.5mV22.9mV14.5mVPass
60% Load61.7mV13.6mV23.2mV15.3mVPass
70% Load62.8mV13.5mV24.0mV15.8mVPass
80% Load61.5mV13.3mV23.8mV16.7mVPass
90% Load63.2mV13.4mV24.5mV16.9mVPass
100% Load63.8mV14.2mV25.8mV17.6mVPass
110% Load67.4mV14.3mV26.4mV18.0mVPass
Cross-Load 161.9mV15.7mV25.9mV15.2mVPass
Cross-Load 266.9mV15.3mV22.8mV16.0mVPass
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Ripple suppression at +12V isn't that good, but it's great on the 5V and 5VSB rails. It's decent at 3.3V, too.

Ripple Oscilloscope Screenshots

The following oscilloscope screenshots illustrate the AC ripple and noise registered on the main rails (+12V, 5V, 3.3V, and 5VSB). The bigger the fluctuations on the screen, the bigger the ripple/noise. We set 0.01 V/Div (each vertical division/box equals 0.01V) as the standard for all measurements.

Ripple At Full Load

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Ripple At 110-Percent Load

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Ripple At Cross-Load 1

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Ripple At Cross-Load 2

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Aris Mpitziopoulos
Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.