SilverStone SX650-G PSU Review: Lots Of Power In A Small Form Factor

Efficiency, Temperature & Noise


Our efficiency testing procedure is detailed here.

Using results from the previous page, we plotted a chart showing the SX650-G’s efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.

Measured efficiency under normal loads was high enough. However, it didn't look as good under light loads, at least compared to competing models with similar specifications.

Efficiency At Low Loads

In the following tests, we measure the SX650-G's efficiency at loads significantly lower than 10 percent of its maximum capacity (the lowest load the 80 PLUS standard measures). The loads we dial are 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
11.207A0.491A0.475A0.196A19.70063.287%1117 RPM
19.4 dB(A)
22.436A0.980A0.983A0.391A39.74967.701%1117 RPM19.4 dB(A)0.967
33.672A1.475A1.494A5.093A59.86881.586%1117 RPM19.4 dB(A)0.977
44.895A1.975A1.974A0.786A79.78183.941%1117 RPM19.4 dB(A)0.981

With 20W and 40W of load, we would like to see efficiency levels close to 70% and 80%, respectively. Also, the fan's speed was fairly high in these tests. It could have started spinning at a slower speed.

5VSB Efficiency

The ATX specification (revision 1.4), 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 maximum current output on that 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 achieved high efficiency scores with 115V input.

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 SX650-G's power consumption in standby is low enough with 115V input and a bit higher with 230V.

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 37°C (98.6°F) to 47°C (116.6°F) ambient temperature.   

The next chart shows the cooling fan's speed (again, in RPM) and output noise. We measure acoustics from one meter away, inside a hemi-anechoic chamber. Background noise inside the chamber is below 6 dB(A) during testing (it's actually much lower, but our sound meter’s microphone hits its floor), and the results are obtained with the PSU operating at 37°C (98.6°F) to 47°C (116.6°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 is between 30°C (86°F) to 32°C (89.6°F).  

The PSU's lowest output noise was less than 20 dB(A). At normal operating temperatures, it remained there up through 270W of load. With 40 to 50W more, the 30 dB(A) mark was passed quickly. And beyond 390W, the SX650-G found itself in the 35-40 dB(A) region.

SilverStone's fan profile could be tuned better. After all, noise output increased by 15 dB(A) within a 50W range. We did notice that if load on the minor rails remained below 70W combined, the fan spun slower (even under high operating temperatures).

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