Introduction & Packaging
Corsair is one of the most recognisable brand names in the PC market. They’ve huge a vast range of chassis, peripherals, storage, memory, power supplies and more! As well as years of history with consumers and a fiercely loyal fan base that has served them pretty well too. Their power supplies are some of the most popular around, especially their budget friendly models, which have been a prime choice with system builders around the world.
Today, we’ll be taking a look at their HX750i, a high-end 80 Plus Platinum rated unit that will be well suited to powerful single GPU systems and even some dual-GPU systems. The extremely efficient power delivery is certainly appealing, but will come at a premium, but you’ll also find Corsair Link, fully modular cables, a Zero RPM fan mode, a 7-year warranty and more, so Corsair is certainly doing a lot to tempt you to invest in a high-end unit.
“HXi Series power supplies give you extremely tight voltage control, virtually silent operation, and a fully modular cable set. With all Japanese 105°C capacitors, they’re a great choice for high performance PCs where reliability is essential. 80 PLUS Platinum efficiency reduces operating cost and excess heat, and together with Zero RPM Fan Mode technology, gives you virtually silent operation.” – Corsair
The packaging is really nicely designed, with a clear image of the PSU on the front, showing off those fully modular connectors.
Around the back, a few technical details about the efficiency and the zero RPM fan mode.
In the box, you’ll find a large and durable component bag, which houses all of the cables for the PSU. This is handy for storing any you’re not using, should you need them in the future.
You’ll also find a user manual, warranty guide, an AC power cable, a few cable ties and the PSU mounting screws; everything you’re likely to need to get set up.
A Closer Look – Exterior
Power Supply Unit
First impressions of the HX750i are very promising, as it feels like a very durable unit, has a good weight to it and even the exterior paint work looks and feels premium. Of course, I’m not overly fussed with how my PSU “feels”, but in terms of aesthetics, this one should blend in with most system builds quite nicely. There’s a large fan intake on the top, with a stylish metal grille and lines on the chassis to match the grille design, giving it a nice flowing and uniform appearance.
Down the side, nothing overly interesting, just a big sticker with the branding on it.
There’s a large sticker on the base showing the PSUs ratings. As you can see, we’ve got a powerful 62.5A +12v rail, perfect for those who need to power high-end hardware. It’s also QC passed, that’s usually a good start, right?
Lots of interesting things going on here! There’s Corsair Link on the left, with either the proprietary cable or MicroUSB cable available for this. Honestly, most consumers aren’t going to need or want this, but enthusiasts who want to take absolute control over fan profiles and rail voltages will welcome it with open arms. The PSU features a hybrid fan mode, allowing it to run at zero-RPM at low loads, this could mean your fan rarely spins, so if you’re worried it has broken, you can press the fan test button to check it. There are five 8-pin connectors, five 6-pin and a split 24-pin ATX connector.
Loads of ventilation around the back, which will no doubt help with the passive fan mode. There’s also a sticker here advising you that the fan not spinning may be part of the normal operation of the unit.
All of the included cables are of a very high quality, with black cables and black connectors, giving them a sleek and uniform appearance. Even the 24-pin is flat, which is a bit of a rare thing and this will help greatly with cable routing/management.
There’s even a couple of Molex to floppy adaptors, rather than have them directly on one of the longer cables, which should help keep things neat and tidy for those who don’t need the floppy adaptors.
The interior of this PSU has a lot going on, but you can see a lot of care has gone into this CWT manufactured unit, as it’s very neat and tidy in here. There’s a good amount of space between all major components too, which should help greatly with both the passive cooling and fan assisted cooling of the unit.
There are two main bulk capacitors, each rated for 400V, 390uF and 105c. It’s worth mentioning now, all the capacitors in this unit are high-quality Japanese capacitors, so performance and reliability should be very good overall.
Taken a closer look at any part of this PSU, it quickly becomes apparent that the soldering is superb. I’ve seen a lot of high-end units that look a little untidy on the PCBs and various connections, but that’s simply not the case here. As can be seen on the PCB below, which features the PWM and PFC management hardware.
This is the Corsair Link PCB, which features a small processor and a few cable headers that run to the connectors at the back of the unit, as well as one for the fan which we have disconnected.
The rear output PCB looks neat and tidy, with thick and shielded cables running to the output connectors.
A few extra caps down the front for voltage regulation and power for some of the power voltage rails.
The EM line filtering and AC input at the rear of the unit.
The fan is a Corsair NR135P, which features a fluid dynamic bearing and PWM header, so it should be nice and quiet, even at higher RPM.
At eTeknix we take the power supply testing procedure very seriously and have invested a lot of resources into acquiring the appropriate testing equipment. For all power supply reviews we test the power supplies with dedicated power supply testing equipment. This means we are able to get the most accurate results from our testing as opposed to using software benchmarks (such as OCCT) or multi-meter readouts which are broadly inaccurate.
Our test machinery is as follows:
- Sunmoon SM-5500ATE Active Load Tester (1200W rated)
- Stingray DS1M12 USB Oscilloscope
- Voltcraft DT-10L laser tachometer
The eTeknix test procedure involves:
- Testing each power supply at 20/40/60/80/100% load (with balanced load across all rails) and measuring PFC (power factor correction), efficiency (actual power divided by power “pulled at the wall”) and voltage regulation (deviance from expected voltages of 3.3/5/12 on the main rails).
- Measuring ripple with an oscilloscope at 20/40/60/80/100% load.
- Measuring fan speed after a stabilisation period of five minutes at each load scenario using the Voltcraft DT-10L laser tachometer and a reflective strip on the fan.
- Testing each power supply’s OPP (Over Power Protection) mechanism and seeing how many watts each power supply can deliver before shutting down
Other things to consider are that
- We recognise that a single yellow 12 volt cable can provide only 6 Amps before overheating (which corrupts voltage regulation and efficiency) and so we used an adequate number of cables for each power supply to ensure there is not efficiency loss from poor cables selection
- Our Sunmoon SM-5500ATE power supply tester is not capable of testing more than 300W on each of the 12 volt rails so where a power supply provides more than 300W on a 12 volt rail that power is distributed over multiple 12 volt rails on the load tester. For example a power supply with one 12 volt rail supplying 750 watts would be spread equally over three 12 volt rails on the load tester, a power supply with two 450W 12v rails would be spread over four 12v rails on the load tester, two 225W 12v rails for each of the 12v rails on the unit.
- We use the same time scale and horizontal millivolt scale on our oscilloscope for all ripple tests, that is a 20ms T/DIV (horizontal) and a 0.02 V/DIV (vertical) meaning the scale is from -80mV to +80mV, ATX spec dictates that the 12v rail must fall within 150mv of ripple and the 3.3/5 within 50mv so that scale allows us to include both 150 and 50mV peaks. (Some older PSU reviews use different scales which were later ditched as the visual representation they give is inadequate, in these reviews written measurements are provided only).
- Deviance is the terminology used to represent the way voltages diverge from the expected values
Efficiency, PFC and Voltage Regulation
To test voltage regulation we load the power supply to five different load scenarios that give an equal spread of load across every single rail. So that means 20% on all rails, 40% on all rails and so on. We then calculate the average deviance of each rail from its expected voltage.
As we’ve seen with many modern Corsair PSUs, but voltage regulation is absolutely fantastic, with remarkably consistent voltages throughout. Especially on the +12v rails, which are some of the tightest readings I’ve ever seen!
Power efficiency is measured by calculating actual supplied wattage divided by the wattage drawn at the wall/plug, multiplied by 100 to give a percentage. We then compare that to the particular 80 Plus certification the company claims to see if it meets that. You can see the 80 Plus certifications below, we always test 230v power supplies.
The efficiency is superb, sitting comfortably within the 80 Plus Platinum rated and actually running 2% more efficient that the rating at low loads.
Power Factor Correction
Power Factor Correction is the ratio of the real power flowing to the load, to the apparent power in the circuit. The aim of PFC is to make the load circuitry that is power factor corrected appear purely resistive (apparent power equal to real power). In this case, the voltage and current are in phase and the reactive power consumption is zero. The closer the number to one the better as this allows the most efficient delivery of electrical power (Source – Wikipedia).
The PFC on this unit is incredible, as a rule, the closer to 1, the better and these are some of the closest results I’ve seen.
Noise and Ripple can easily be measured by an oscilloscope. These show how much voltage fluctuation there is on a particular rail. We tested the rail stability of the 3.3 volt, 5 volt and 12 volt rails using an identical time and millivolt scale for all graphs. millivolt ripple is measured by the peak to peak size of the voltage curve.
The latest ATX 12 volt version 2.3 specifications state that ripple from peak to peak must be no higher than 50 millivolts for the 3.3 volt and 5 volt rails, while the 12 volt rail is allowed up to 120 millivolts peak to peak to stay within specifications. Millivolt figures are stated to the closest increment of 5 given their variability.
|Load (%)||3.3V Ripple||5V Ripple||12V Ripple|
Knocking it out of the park again, this PSU has extremely tight ripple suppression, with results that are a very well within the allowances for each rail.
3.3 volt @ 100%
5 volt @ 100%
12 volt @ 100%
Over Power Protection and Max Wattage
Power supplies often quote as having various protection mechanisms such and the most important of these is Over Power Protection. In our testing we crank up the power draw until the power supply either shuts down (meaning the OPP mechanism is present and working) or blows up (meaning it is either not present or not working). We then note the maximum power consumption before the power supply shut down (or blew up).
Very good OPP protection, as we managed to push over 950W through this unit before it shut down, so you should be able to handle the odd power spike when benchmarking or gaming without any major issue. Also, the OPP kicked in, preventing the unit from exploding, that’s always a welcome feature.
When testing in a power supply laboratory it is difficult to take fan noise readings as the noise from the Sunmoon test equipment and air conditioning corrupts everything. The next best thing in our circumstances was reading off the fan speed with a tachometer to get an idea for the noise. The ambient temperature during testing held constant at 22 degrees, with 1 degree of variation. Each power supply had a consistent time period of 5 minutes to stabilise between each load scenario.
In my experience the following general relationships apply between noise levels and fan speeds, though it can vary greatly between the type of fan used.
- Below 800 RPM – Inaudible/Silent
- 800 to 1000 RPM – Barely audible
- 1000 – 1200 RPM – Audible but still quiet
- 1200 – 1400 RPM – Moderately noisy
- 1400 – 1800 RPM – Noisy
- 1800 RPM or higher – Intolerable
The fan didn’t run at all until we got up to 60% load, meaning the PSU remained completely silent and should do for most day-to-day operation. Even when we got it to 100% load, the fan was still little more than a whisper and you’ll likely never hear it once it’s installed in a chassis.
The Corsair HX750i 750W Plus Platinum Digital Power Supply is available from most major retailers and Corsair stock is often in plentiful supply almost everywhere you look. You can pick this unit up from Overclockers in the UK for £126.95 while readers in the US can get it from NewEgg for $149.99. The price is about average for this rating, sitting between some units from SuperFlower and Seasonic in terms of price.
Another day, another review and another fantastic unit from Corsair. It’s easy to see why Corsair is a popular choice with system builders, they certainly tick a lot of boxes and as we saw with this unit today, the performance is superb. That’s not to say other manufacturers make junk units, but Corsair certainly have the goods to go head-to-head with anyone else out there.
Let’s start with the efficiency, this unit is right on the 80 Plus Platinum rating and that’s a great place to be, as it means this PSU will end up using less power than most, saving you a little bit of money on your electricity bill. It’s not going to pave your house with gold via the savings, but every little helps and it’s also a little more green by not burning up extra power for nothing. The high-efficiency is backed up by exceptional PFC and ripple suppression, meaning that you’ll have efficiency and squeaky clean power delivery throughout.
The use of high-quality components really shines through here. The soldering on the PCB is neat and tidy, components are well spaced and mounted neatly, the internal cables are thick and well shielded, all capacitors are high-quality and Japanese made, all of which adds up to a lot. The PSU runs cool, incredibly quiet and smoothly, without letting performance slip and that’s exactly what you want from virtually any bit of PC hardware.
The inclusion of Corsair Link, the fan testing button, zero RPM modes, all black flat-style and fully modular cables and a 7-year warranty are just icing on the cake, making this a perfect choice for anyone planning a high-end gaming system or workstation.
- Fully modular cables
- Seven-year warranty
- Excellent ripple suppression
- Zero RPM fan mode
- Extremely quiet fan at full load
- Fan-test button
- Corsair Link
- Switchable single/multiple 12v rail
- Platinum efficiency
- Tight voltage regulation
“The HX750i from Corsair is as good as you could expect a PSU to be and would make a fantastic addition to anyone system build. Highly recommended!”
Thank you Corsair for providing this review sample.