Test SetupAll measurements are performed utilizing ten electronic loads (seven Array 3711A, 300W each, and three Array 3710A, 150W each), which are able to deliver over 2500W of load and are controlled by a custom made software. We also use a Picoscope 3424 oscilloscope, a CHY 502 thermometer, a Fluke 175 multimeter and an Instek GPM-8212 power meter. Furthermore, in our setup we have included a wooden box, which along with a heating element is used as a Hot Box. Finally, we have at our disposal four more oscilloscopes (Rigol 1052E and VS5042, Stingray DS1M12 and a second Picoscope 3424) and a CEM DT-8852 sound level meter. In this article you will find more details about our equipment and the review methodology we follow. Finally, if the manufacturer states that the maximum operating temperature of the test unit is only 40°C then we try to stay near this temperature, otherwise we crank up the heat inside the hotbox up to 45-50°C.
Voltage Regulation ChartsThe following charts show the voltage values of the main rails, recorded over a range from 60W to the maximum specified load, and the deviation (in percent) for the same load range.
5VSB Regulation ChartThe following chart shows how the 5VSB rail deals with the load we throw at it.
Efficiency ChartIn this chart you will find the efficiency of SP-750M at low loads and at loads equal to 20-100% of PSU’s maximum rated load.
Voltage Regulation and Efficiency MeasurementsThe first set of tests reveals the stability of voltage rails and the efficiency of SP-750M. The applied load equals to (approximately) 20%, 40%, 50%, 60%, 80% and 100%, of the maximum load that the PSU can handle. In addition, we conduct two more tests. In the first we stress the two minor rails (5V & 3.3V) with a high load, while the load at +12V is only 2A and in the second test we dial the maximum load that +12V can handle while load at minor rails is minimal.
| Voltage Regulation & Efficiency Testing Data |
|Test||12 V||5 V||3.3 V||5VSB||Power|
Despite the 40°C limit that Thermaltake states in its specs the PSU managed to deliver its full power even at over 50°C ambient, something very good of course. Also the efficiency readings we got were pretty high for a merely Bronze PSU since with medium loads they reached 89%. Voltage regulation at +12V ideally should be lower than 2% and at 3.3V close to 3%. On the 5V rail the deviation was low enough since it didn't exceed 3%.
Regarding output noise, even with 20% load the fan made its presence felt. With 40% load it was significantly louder and with 50% load and above it was annoyingly loud and could be easily heard across the room, while all fans of the electronic loads were operating at full speed. So the final verdict is that this unit is equipped with a really noisy fan which however is highly effective and probably essential for the cooling of the fets that rectify +12V.
Efficiency at Low LoadsIn the next tests, we measure the efficiency of SP-750M at loads much lower than 20% of its maximum rated load (the lowest load that the 80 Plus Standard measures). The loads that we dial are 40, 60, 80 and 100W (for PSUs with over 500W capacity). This is important for scenarios in which a typical office PC is in idle with power saving turned on.
| Efficiency at Low Loads |
|Test #||12 V||5 V||3.3 V||5 VSB||Power|
Efficiency at low loads is at the levels we expected from a Bronze 750W unit; however with 40W load we would like to see an over 70% reading. The SP-750M needs at least 100W load to surpass the 80% mark, so surely it is not the best choice for a system that consumes less than 60-80W at idle but considering its official efficiency rating we cannot be very demanding in these tests.
5VSB EfficiencyATX spec states that the 5VSB standby supply's efficiency should be as high as possible and recommends 50% or higher efficiency with 100mA load, 60% or higher with 250mA load and 70% or higher with 1A or more load.
We will take four measurements, three at 100 / 250 / 1000 mA and one with the full load that 5VSB rail can handle.
| 5VSB Efficiency|
|Test #||5VSB||Power (DC/AC)||Efficiency||PF/AC Volts|
At the first two tests efficiency is amazing while on the last two it is quite good and easily surpasses the 70% mark. All in all the 5VSB rail performs excellent since it registers tight enough voltage regulation and good efficiency.
Power Consumption in Idle & StandbyIn the table below you will find the power consumption and the voltage values of all rails (except -12V), when the PSU is in idle mode (On but without any load at its rails) and the power consumption when the PSU is in standby (without any load at 5VSB).
| Idle / Standby |
|Mode||12 V||5 V||3.3 V||5VSB||Power (AC)||PF/AC Volts|
Vampire power is really low in this PSU and doesn't even exceed 0.1W! This is why efficiency with low loads at 5VSB is so high. Excellent results here even surpasses that of units that are rated for higher efficieny.