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Lian Li PE-750 SFX-L 750W PSU Review

Lian Li enters the PSU market again with two new SFX-L models featuring 550 W and 750 W capacities. The PE-750 is under the microscope today. It features modular cabling, a single +12V rail, and a semi-passive fan.

Efficiency, Temperature, And Noise


Our efficiency testing procedure is detailed here.

Using results from the previous page, we plotted a chart showing the PE-750's efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.

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The PE-750's efficiency levels are impressively high under light and normal loads. This platform puts all of the other SFX and SFX-L designs we've tested to shame.

Efficiency At Low Loads

In the following tests, we measure the PE-750's efficiency at loads significantly lower than 10 percent of its maximum capacity (the lowest load the 80 PLUS standard measures). The loads we dialed were 20, 40, 60 and 80 W. This is important for representing when a PC is idle, with power-saving features turned on.

Test #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan SpeedFan NoisePF/AC Volts
11.220A0.481A0.475A0.194A19.5876.91%0 RPM0 dB(A)0.828
22.472A0.970A0.984A0.390A39.6983.75%0 RPM0 dB(A)0.898
33.725A1.464A1.495A5.089A59.8387.41%0 RPM0 dB(A)0.927
44.961A1.964A1.975A0.784A79.7491.29%0 RPM0 dB(A)0.938

Efficiency under light loads is very high, and noise output is zero thanks to a semi-passive operating mode. We couldn't ask for more from a Platinum-rated SFX-L power supply.

5VSB Efficiency

The ATX specification states that 5VSB standby supply efficiency should be as high as possible, recommending 50 percent or higher efficiency with 100 mA of load, 60 percent or higher with 250 mA of load, and 70 percent or higher with 1 A or more of load.

We take four measurements: one each at 100, 250 and 1000 mA, and one with the full load the 5VSB rail can handle. 

Test #5VSBDC/AC (Watts)EfficiencyPF/AC Volts
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The 5VSB rail is highly efficient as well. Enhance does a good job here.

Power Consumption In Idle And Standby

In the table below, you'll find the power consumption and voltage values of all rails (except -12V) when the PSU is idle (powered on, but without any load on its rails), and the power consumption when the PSU is in standby mode (without any load, at 5VSB).

Mode12V5V3.3V5VSBWattsPF/AC Volts
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Phantom power is way lower than the ErP Lot 6 2013 directive's requirements.

Fan RPM, Delta Temperature And Output Noise

Our mixed noise testing is described in detail here.

The first chart below illustrates the cooling fan's speed (in RPM), and the delta between input and output temperature. The results were obtained at 39 °C (102.2 °F) to 46 °C (114.8 °F) ambient temperature.   

The next chart shows the cooling fan's speed (again, in RPM) and output noise. We measured acoustics from one meter away, inside a small, custom-made anechoic chamber with internals completely covered in sound-proofing material (be quiet! Noise Absorber kit). Background noise inside the chamber was below 18 dB(A) during testing, and the results were obtained with the PSU operating at 39 °C (102.2 °F) to 46 °C (114.8 °F) ambient temperature. 

The following graph illustrates the fan's output noise over the PSU's operating range. The same conditions of the above graph apply to our measurements, though the ambient temperature was between at 28 °C (82.4 °F) to 30 °C (86 °F).  

Passive operation lasts up to around 120 W of load. Afterwards, the fan spins slowly up to 500 W. With more than 500 W, its speed increases significantly. Beyond 680 W, the noise exceeds 43 dB(A). If you don't plan on pushing this power supply hard, expect it to run quietly. Otherwise, it can get loud.

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