Cougar GX-F750W PSU Review

Efficiency, Temperature & Noise


Our efficiency testing procedure is detailed here.

Using results from the previous page, we plotted a chart showing the GX-F750's efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.

The unit's efficiency is close to this category's average under normal loads. Under light loads, it falls quite low.

Efficiency At Low Loads

In the following tests, we measure the GX-F750'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 80W. This is important for representing when a PC is idle, with power-saving features turned on.

Test #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan Speed
PSU Noise
PF/AC Volts
11.195A0.501A0.477A0.196A19.72357.321%735 RPM
20.7 dB(A)
22.432A0.999A0.986A0.391A39.76877.358%725 RPM
20.2 dB(A)0.957
33.667A1.496A1.497A5.100A59.86882.640%750 RPM
21.3 dB(A)0.975
44.891A2.003A1.981A0.784A79.79984.902%795 RPM
22.8 dB(A)0.975

With 20W load, the GX-F750's efficiency is very low. At the other three load levels, its efficiency looks normal for an 80 PLUS Gold-rated PSU. Strangely, the first sample we tested (the one that broke during our overload test) achieved a notably higher efficiency level (64.546%) under 20W of load.

5VSB Efficiency

The ATX specification, along with CEC, ErP Lot 3 2014 and ErP Lot 6 2010/2013, states that 5VSB standby supply efficiency should be as high as possible, recommending 75 percent or higher with 550mA, 1A, and 1.5A of load. The PSU should also achieve higher than 75% efficiency at 5VSB under full load, or with 3A if its max current output on this rail is higher than 3A.

We take six measurements: one each at 100, 250, 550, 1000, and 1500mA, and one with the full load the 5VSB rail can handle.

Test #5VSBDC/AC (Watts)EfficiencyPF/AC Volts

The 5VSB rail's efficiency is decent, but nowhere near as good as implementations from CWT and FSP.

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

The vampire power that we measure with our analyzer is low under 115V and 230V inputs.

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 30°C (86°F) to 40°C (104°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 hemi-anechoic chamber. Background noise inside the chamber was below 6 dB(A) during testing (it's actually much lower, but our sound meter’s microphone hits its floor), and the results were obtained with the PSU operating at 30°C (86°F) to 40°C (104°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 30°C (86°F) to 32°C (89.6°F).  

Cougar's fan profile is clearly aggressive; from almost 10W of load, the PSU lands within the 25-30 dB(A) noise zone. But because of its low-speed fan, maximum noise barely exceeds 40 dB(A) with 660W and higher loads.

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