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Review: Thermaltake Smart M550W PSU

by Tarinder Sandhu on 17 May 2012, 15:38 4.0

Tags: Thermaltake (3540.TWO)

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Testing results

Our testing procedures can be found at this link.


Load 10pc 25pc 50pc 75pc 100pc
Efficiency 78.5pc 83.2pc 87.3pc 84.1pc 82.9pc

The 10pc load equates to 55W of load - it's not an exact figure as the various lines have to be loaded with particular amps/volts that may not exactly map out to the desired number.

Those who think that such a figure is pointless for a 550W PSU may like to know that an Intel Core-i5 2500K system with 8GB of RAM and a super-high-end GeForce GTX 680 graphics card idles at just 42W, and that's measured at the wall. Knowing efficiency at low-load levels is just as important as at, say, 50 per cent or 75 per cent.

Thermaltake's supply is pretty good in the efficiency stakes, as evaluated with a 240V source. Use it at 50 per cent load - 275W, or full-on gaming with a single high-end graphics card - and there won't be much of a difference between it and a Platinum-rated model.


In terms of regulation, we're looking at just how well the supply is able to hold to the various lines. The ATX spec. has a +/- 5 per cent leeway on all but the -12V line.

Line/Load 3.3V 5V 12V
10 per cent 3.22V 4.97V 11.96V
50 per cent 3.26V 4.90V 11.75V
100 per cent 3.20V 4.82V 11.62V

Give it some healthy load and the supply ends up nearer the lower end of the ATX spec on all three tested lines. Still, it's within specification.

Regulation - cross-load

How about providing uneven loads that stress particular voltage rails? In the first attempt, we've put 40A on the 12V rails, and 1A on the 3.3V and 5V rails. This can actually be somewhat typical for a system heavy on graphics and CPU power. In the second, we've turned the tables and gone for 12A on both the 3.3V and 5V rails - highly unlikely in a real-world environment - and just 2A on the 12V - even more unlikely!

Line/Load 3.3V 5V 12V
Cross-load 12V focus 3.23V 4.95V 11.92V
Cross-load 3.3V/5V focus 3.22V 4.84V 12.02V

Numbers fall within specification and there's little to be worried about. We'd like them closer to the ideal, but even pushing and pulling the supply's power-delivery system can't throw it off.


Line/Load (mv - p-p max) 3.3V 5V 12V
10 per cent 10mV 15mV 30mV
50 per cent 12mV 20mV 45mV
100 per cent 15mV 35mV 70mV

The ATX v2.2 spec states that the maximum permissible ripple is 120mV for the 12V line and 50mV for others.

Keeping the ripple in check requires excellent filtering. The test unit, which we purchased from a retailer, is very good on the 3.3V and 12V lines. It begins to waver just a little when dealing with the 12V AC suppression.


Temperatures Intake Exhaust
10 per cent 30°C 35°C
50 per cent 35°C 37°C
100 per cent 38°C 46°C

Reasonable temperatures from the unit. Tested in an open-air environment with an ambient temperature of 26°C the unit never become too warm, even after bashing it with a continuous 100 per cent load.

The 140mm fan ramps up noticeably once load is increased to 75 per cent of capacity. Keep it at 50 per cent, which is a pretty sensible figure for long-term use, and it can be deemed quiet.

Results recap

The reviewed unit has good regulation and ripple control at everything but 100 per cent load. Stress it to the limit and the regulation drops off a little but remains in specification, as mandated by the ATX certification.