Corsair is a company that needs no introduction. They are one of the oldest names in the PC industry and, although they initially only marketed memory-related products, nowadays the company has diversified into most segments of the PC market, with products ranging from PC hardware components to office/gaming chairs.

The company has been particularly active in the PC power supply (PSU) market. It was one of the first markets the company diversified into, and their first few products that the company released over a decade ago were a huge success. Nowadays Corsair is one of the biggest players in the PC PSU market, with dozens of competitive products covering every want and need.

The company places a lot of weight on their PSU division, which has been one of the innovation leaders during the past decade, always coming up with new features and/or technological upgrades. It is no chance that Corsair's units were always amongst the first to meet the new 80Plus programme certifications when they were being introduced. Corsair has always been trying to be a technological step ahead of their competition, striving to bring the best out in the market first.

It is somewhat of a tradition for Corsair to always have one pinnacle product, a PSU that has no equal in the market, regardless of the cost. For quite some time this PSU was the AX1500i, a behemoth PSU with 80Plus Titanium certification. While the 80Plus Titanium certification is rare and costly even today, Corsair achieved it four years ago. As the electrical performance of the AX1500i already was outworldish and there are no better quality or efficiency certifications to be earned, the top-tier PSU market has been lethargic for quite a long time, with hardly any new products coming out for years.

Suddenly, a few months ago Corsair announced the release of the AX1600i, an upgrade of the original AX1500i, boasting that it is even more efficient and with improved overall performance. There is no official certification higher than the 80Plus Titanium that the AX1500i already had, but since we did review the AX1500i back in 2014, we can compare the two units and see what has been improved and by how much.

And without spoiling too much in advance here, the true highlight of the AX1600i is not its total capacity, but its efficiency. Corsair enabled an unparalleled super-high efficiency design for the AX1600i by equipping the PSU with Gallium Nitride (GaN) MOSFETs. These are expensive, but afford an extra bump to the brand; no other consumer power supply has these, and we take a close look at them over the next few pages. If these work well, they could easily be a game changer for the industry as other providers use them.

Packaging and Bundle

Corsair is using their usual yellow/black artwork for the packaging of the AX1600i, with the only major difference compared to the packaging of less powerful models being the massive size of the box. The box is very strong and should provide ample shipping protection and inside we found the power supply well protected between thick foam paddings.

Unlike most of their other PSUs and older versions of the AX series units, the AX1600i comes with a fairly rich bundle. The first thing that stands out is the C19 power cable, which is necessary because the input amperage of the AX1600i can surpass the rating of regular C13 cables in countries where the grid voltage is low. Corsair also supplies black 3M mounting screws, a case badge, some short cable ties, a few cable straps, and side stickers in three different colors (red, white, and blue).

The AX1600i is a fully modular design and all of its cables come neatly organized in a rolled-up storage pouch. All of the connectors and wires are black. SATA/Molex/Floppy/USB cables are "flat", ribbon-like cables. The thicker PCIe, EPS, and 24-pin ATX cables are additionally covered into black sleeving and hide extra filtering capacitors.

External Appearance

Corsair managed to design the AX1600i to be a visually imposing product with an elegant, yet not extravagant design. Amazingly, even with its increase in power output, the AX1600i actually is physically smaller than the AX1500i. The chassis of the AX1600i measures 205 mm × 150 mm × 86 mm (D × W × H), making about two centimeters shorter than the AX1500i. The chassis has chamfered edges and embossed ridges create a subtle decorative effect. The ridges are also aligned with the design of the fan's finger guard, improving aesthetics even further.

A chromed sticker with the company's logo can be seen at the top side of the unit and grey decorative stickers cover the largest portion of its sides. The side stickers can be (permanently) replaced with those supplied with the unit's bundled items. The sticker with the unit's specifications and certifications has been moved to the right side of the chassis, hidden away in cases that have a windowed left side panel - unless the PSU is installed with its fan facing upwards, that is.

The rear side of the AX1600i seems typical for a computer PSU but closer inspection reveals some secrets. A small power switch can be seen next to the C20 receptacle, yet it's far too small for a unit with this kind of output. The switch does not cut off the AC input but signals the inrush current relay, deactivating it and completely isolating the PSU from its AC connection. A small badge of the unit's model can also be seen towards the right side of the unit.

As expected, the front of the chassis is littered with the modular cable connectors. There are ten connectors for the PCIe and EPS cables alone, six for SATA/Peripheral cables, and two split connectors for the 24-pin ATX cable. It is easily noticeable that the connectors for the 24-pin cable actually sum up to 30 pins. That is because of the extra voltage sensing wires that the design is using to adjust its output in virtually real time. There is also a self-test button that forces the PSU to start and run a basic operational test, as well as a micro-USB connector for the Corsair Link interface.

Internal Design

The AX1600i is one of Corsair's few units that is using a full-size 140 mm fan instead of a 135 mm fan. It is a Corsair-branded fluid dynamic bearing (FDB) fan. No detailed specifications regarding the fan can be found but our instruments measured a maximum speed of about 2100 RPM and a maximum air volume flow of about 75 CFM.

Although we honestly expected that the AX1600i would be just a small update of the AX1500i, that could not have been further from the truth. The AX1600i practically is an entirely new platform. The OEM of the power supply is Flextronics, the same company behind the AX1500i, but the AX1600i is drastically different.

The filtering stage begins at the rear of the AC receptacle and continues on the main PCB. We counted a total of six Y capacitors, two X capacitors and four inductors. There is also a X capacitor discharge IC that improves the overall performance of the X capacitors, increasing their efficiency and reducing the inductor requirements.

The AX1600i does not have a "classic" PFC circuit but a digital "bridge-less" converter similar to the one we saw in AX1500i. In theory, classic APFC designs top out at 96% efficiency and the Totem-Pole Bridgeless PFC design that Corsair is using could reach up to 99%.

Corsair however took things a bit further and, in what's easily the most interesting aspect of the PSU's design, replaced the normal MOSFETs with Gallium-Nitride (GaN) MOSFETs, which are even more efficient. GaN has long been under development for use as a replacement for silicon in transistors, and that development is finally paying off with consumer products. Which isn't to say that this is the sole innovation of the AX1600i or even the only element contributing to its improvements, but it's easily the most exciting.

In any case, buffering these new MOSFETs we find three very large capacitors, two from Nippon Chemi-Con (450V/470μF) and one from Rubycon (450V/680μF) are present here.

Moving towards the primary inverter, we find a full-bridge design with an LLC resonant controller. Aside from the ultra-high efficiency MOSFETs, there is nothing about the primary side that we have not seen in many other high efficiency designs. At the secondary side of the transformers we find a synchronous converter - or two, as the topology essentially resembles that of two circuits working together in parallel. Synchronous converters are also common but not one with sixteen MOSFETs for the 12V line alone. The 5V and 3.3V lines are generated via additional DC to DC converters. The secondary side electrolytic capacitors are all provided by Nippon Chemi-Con. Most of the polymer capacitors are also provided by the same company but a few Nichicon products can be spotted as well.

Both the primary and the secondary side of the AX1600i are digitally controlled via their own digital controllers. A microcontroller unit is also present, providing the Corsair Link interface capabilities.

The Corsair Link Software

The Corsair Link is a unified software that allows for the monitoring and control of multiple Corsair products. The software is capable of identifying and monitoring system sensors, such as the CPU temperature or fan speeds, and can use that information for the programming of user-specific performance profiles. For instance, you can program the lighting of the Hydro H100i to change according to a temperature reading.

In the case of the AX1600i, the Corsair Link software fully monitors the input and every output of the power supply, as well as its temperature and fan speed. The accuracy of the readings is adequate for typical use.

Screenshots of the Corsair Link software while the PSU was attached to our electronic loads. The displayed system configuration is that of a laptop and does not in any way correspond to the load of the PSU.

The Corsair Link software adds some extra functionality to the AX1600i. It is possible for the user to forgo the single 12V line over current protection (OCP) and create virtual OCP's per connector, limiting the current that will be available to certain devices. This can protect certain devices as, in the case of a temporary fault, the PSU will shutdown instead of supplying them with a massive current that would permanently damage them. The user can also adjust the cooling profile of the PSU's fan, or the cooling profiles of other fans based on the PSU's load.

Cold Test Results

For the testing of PSUs, we are using high precision electronic loads with a maximum power draw of 2700 Watts, a Rigol DS5042M  40 MHz oscilloscope, an Extech 380803 power analyzer, two high precision UNI-T UT-325 digital thermometers, an Extech HD600 SPL meter, a self-designed hotbox and various other bits and parts. For a thorough explanation of our testing methodology and more details on our equipment, please refer to our How We Test PSUs - 2014 Pipeline post.

Even though it received its 80Plus Titanium certification with an input of 115V AC (and lower requirements), the new Corsair AX1600i easily meets the stricter requirements for a 230V AC input as well. The maximum efficiency we measured was 96.6% at 50% load, with the unit surpassing the 90% point with just a 7.5% load. Even with a load of just 80 Watts (5% of the unit's rated capacity), the AX1600i has an efficiency of nearly 88%, outperforming the best possible efficiency of most budget-level PSU designs. The average efficiency within the nominal load range (20% to 100% of the unit's capacity) is an astonishing 95.4%.

The outworldish efficiency of the Corsair AX1600i allows it to deliver similarly astonishing thermal performance as well. Our test sample barely even got warm while testing in room temperature, even while operating at maximum output. The fan of the AX1600i is not even bothered to start before the load surpasses the 600 Watts mark and barely becomes audible when the load is over 1.1 kW. As it would take a system with at least three powerful GPUs to reach that kind of power demand, it is highly unlikely that the AX1600i will ever be noticeable over the cooling fans of the graphics cards and the system.

Hot Test Results

The Corsair AX1500i already was the benchmark of electrical quality, leaving very little room for improvement. Although the AX1600i might appear to deliver a little bit better power quality, the truth is that we would need very high precision equipment to tell the difference between the two, and any difference would be unimportantly small. However, that does not lessen the fact that the AX1600i delivers possibly the best power quality that can be bought at this point of time. For the most part, the voltage ripple of any line is less than ten millivolts. The maximum ripple on the 12V line is just 14 mV and that is with a massive current draw of almost 124 amperes. The voltage regulation is equally impressive, with a variation of just 0.2% on the 12V line across the nominal load range. Voltage regulation is a little bit worse on the 3.3V/5V lines, at 0.4%/0.25% respectively, which figures still are a lot better than what most current high-performance PSUs can achieve.

When it comes to adverse ambient conditions, the Corsair AX1600i is a true fortress. Operating the AX1600i inside our hotbox had virtually no impact on its electrical performance and/or efficiency. Even though the ambient temperature was well over 45 °C, the efficiency drop across the entire range was a mere 0.1%. This suggests that the components of the AX1600i are far from getting thermally overstressed, even with the PSU operating at maximum output under these adverse conditions.

The only thing inside the AX1600i that is affected by the high ambient temperature is the cooling fan. It will still not even start with a load below 460 Watts but it is livelier once it does start, increasing its speed at a higher rate as the load increases. It ultimately reaches about 45.5 dB(A) at maximum load, which would be a low figure even for a mainstream PSU with an output of some hundred Watts, yet the AX1600i manages to maintain comfortable noise levels operating at maximum load with an ambient temperature of over 48°C. The internal temperatures of the PSU also are very low taking its power output and low fan speed into account.

Conclusion

Corsair's intent behind the creation of the AX1600i was to create a product that is technologically and qualitatively superior than anything else in the consumer's market, with little regard for its production cost and, ultimately, the retail price. It is the kind of product aiming to please just a select few who want to build top-tier gaming systems or workstations regardless of the monetary cost.

Technologically, the AX1600i undoubtedly is the most advanced PSU that is currently available to consumers. The Gallium Nitride (GaN) parts are smaller, lighter, and significantly more efficient than their classic silicon-based counterparts. Their use allowed Flextronics (and ultimately Corsair) to design a platform that combines better overall performance and higher output into a smaller chassis. The end result is a PSU that is no larger than most 800W designs and yet is capable of delivering twice that power output without flinching. GaN parts are greatly more expensive than their silicon-based counterparts but the final product's cost was partially offset by the reduction in size and cooling requirements, allowing Corsair to maintain the price of the AX1600i at relatively reasonable levels.

The overall performance of the AX1600i is incomparable to that of classic PSU designs. Even the top tier models from other known manufacturers would have a hard time competing with the AX1600i on a single performance aspect - let alone every aspect. The power quality is textbook, with barely any voltage ripple appearing on any of the lines and under any load, while the voltage regulation is practically ideal. The very high electrical efficiency of the platform not only minimizes energy waste but also allows the PSU to operate very quietly and maintain low internal temperatures even when heavily loaded. Its very high quality parts are almost completely unaffected by environmental factors, ensuring that the AX1600i will perform 100% even in harsh environments. Taken altogether this means that the AX1600i has no peer; simpy put, its performance is unparalleled.

Corsair's flagship combines the best possible overall performance with exceptional quality parts, fashioning the best consumer PSU that money can buy. However, the AX1600i's true enemy is itself. With a price tag of $500 and a power output of 1600 Watts, the PSU is both preposterously expensive compared to regular designs and has a power output that will be vastly oversized for almost every kind of user. Only a system with a very powerful CPU and at least four top-tier graphics cards will be able to reasonably load an AX1600i, and these systems are quickly becoming a relic as NVIDIA scale back on SLI & CrossFire support. Instead we'd be looking at edge cases such as heavily overclocked systems with a smaller number of video cards, or someone who needs a lot of Titan Vs for productivity purposes.

Still, Corsair's move to GaN components signifies a very important milestone, as it is very likely that we will be seeing them implemented in less powerful units in the near future. They will be especially useful in SFX designs, as they will be able to deliver a high power output very efficiently, allowing the creation of quiet SFX units for living room gaming systems.