Test Setup

All measurements were performed using two Chroma 6314A mainframes equipped with the following electronic loads: six 63123A [350 W each], one 63102A [100 W x2], and one 63101A [200 W]. The aforementioned equipment is able to deliver 2500 W of load, and all loads are controlled by a custom-made software. We also used a Rigol DS2072A oscilloscope kindly sponsored by Batronix, a Picoscope 3424 oscilloscope, a Picotech TC-08 thermocouple data logger, two Fluke multimeters (models 289 and 175), and a Yokogawa WT210 power meter. We also included a wooden box, which, along with some heating elements, was used as a hot box. Finally, we had at our disposal three more oscilloscopes (Rigol VS5042, Stingray DS1M12, and a second Picoscope 3424), and a Class 1 Bruel & kjaer 2250-L G4 Sound Analyzer which is equipped with a type 4189 microphone that features a 16.6 - 140 dBA-weighted dynamic range. You will find more details about our equipment and the review methodology we follow in this article. We also conduct all of our tests at 40°C-45°C ambient to simulate the environment seen inside a typical system with a higher accuracy, with 40°C-45°C being derived from a standard ambient assumption of 23°C and 17°C-22°C being added for the typical temperature rise within a system.

Primary Rails Voltage Regulation

The following charts show the main rails' voltage values, recorded over a range from 60 W to the maximum specified load, and the deviation (in percent) for the same load range.

5VSB Regulation

The following chart shows how the 5VSB rail deals with the load we throw at it.

Hold-up Time

Hold-up time is a very important PSU characteristic and represents the amount of time, usually measured in milliseconds, a PSU can maintain output regulations as defined by the ATX spec without input power. In other words, it is the amount of time the system can continue to run without shutting down or rebooting during a power interruption. The ATX specification sets the minimum hold-up time to 16 ms with the maximum continuous output load. In the following screenshot, the blue line is the mains signal and the yellow line is the "Power Good" signal. The latter is de-asserted to a low state when any of the +12V, 5V, or 3.3V output voltages fall below the undervoltage threshold, or after the mains power has been removed for a sufficiently long time to guarantee that the PSU cannot operate anymore.



The hold-up time was higher than the minimum, so all is good here.

Inrush Current

Inrush current or switch-on surge refers to the maximum, instantaneous input-current drawn by an electrical device when it is first turned on. Because of the charging current of the APFC capacitor(s), PSUs produce large inrush-current right as they are turned on. Large inrush current can cause the tripping of circuit breakers and fuses and may also damage switches, relays, and bridge rectifiers; as a result, the lower the inrush current of a PSU right as it is turned on, the better.



Inrush current was also low, which is in no small part due to the good design. Nice work, CWT!

Voltage Regulation and Efficiency Measurements

The first set of tests revealed the stability of the voltage rails and the efficiency of the HX750i. The applied load was equal to (approximately) 10% - 110% of the maximum load the PSU can handle, with 10% steps.

We conducted two additional tests. In the first test, we stressed the two minor rails (5V and 3.3V) with a high load while the load at +12V was only 0.10 A. This test reveals whether the PSU is Haswell ready or not. In the second test, we dialed the maximum load the +12V rail could handle while the load on the minor rails was minimal.

The HX750i's voltage regulation is tight on all rails, with its 5VSB rail setting a new record in the category. Despite the very high efficiency, CWT managed to offer a truly high-end class load regulation along with a dead-silent operation under even extremely tough conditions. As you can see in the table above, we pushed the unit hard by having it deliver more than its full power at 47.5°C. Though you could easily say we totally abused the unit, it also did operate flawlessly throughout those tests. It is always great to see such good platforms perform as well with such high ambient temperatures. It was also very quiet since its fan hardly spun up. However, such might also reduce the HX750i's longevity, but CWT's and Corsair's engineers must have no such concerns or it wouldn't come with a hefty 7-year warranty.

The HX750i also exhibited incredible efficiency and ultra-tight load regulation, and it is silent enough to please even please those looking to put together a very quiet system. Add to all the above that Corsair Link's efficiency readings were close enough to those we measured with our very expensive power analyzer and there is nothing more to ask of a product with such a price tag.

Corsair Link Screenshots

Several screenshots of the Corsair Link software, which we took during our test sessions, follow. The order of these screenshots is the same as the order of the tests in the table above (10% load to Cross-load 2 test).