Corsair AX and AXi Series Power Supplies Review: Small Letter Big Difference?

Today we are going to check out two pairs of “Platinum” power supply units with capacities of 760 and 860 watts, which belong to two different series: AX and AXi. Which one should be a preference for those who are looking for the most efficient power source for their systems?

by Dmitry Vasiliev
04/20/2013 | 04:49 AM

Corsair’s 1200-watt power supply units of the AX and AXi series have already been covered in our earlier reviews (the AX one is outdated already, complying with the 80 PLUS Gold standard only), so today we want to tell you about the junior products from these series. They have wattage ratings of 760 and 860 watts.

 

While the 1200W models are both based on a Flextronics platform, the junior ones differ in terms of their contract manufacturer. It is Flextronics for the intellectual AXi series whereas the AX series, occupying a lower position in Corsair’s product hierarchy, is based on a Seasonic platform.

The benefits of the Corsair Link interface implemented in the AXi series were discussed in our AX 1200i review, so we won’t dwell on them here. We’ll just limit ourselves to comparing the electrical parameters of PSUs which employ two different hardware platforms.

Their specifications are almost identical in terms of load capacity of each power rail. Both series comply with the highest efficiency standard 80 PLUS Platinum. But are they that similar in practice?

Testing Methodology

The following article offers a detailed description of our testing methodology and equipment and a brief explanation of what the specified and tested parameters of power supplies mean: X-bit Labs Presents: Power Supply Units Testing Methodology. If you feel overwhelmed with the numbers and terms this review abounds in, refer to the Methodology.

You can also go to our Cases/PSU section to check out reviews of all other PSU models we have tested in our labs.

We will mark the actual power consumption of three system configurations (discussed in our article PC Power Consumption: How Many Watts Do We Need?) in the cross-load diagrams. This will help you see if the tested PSU can meet the requirements of a real-life PC.

Testing Participants

Corsair AX 760 and 860

The two PSUs have identical packaging and accessories except for the wattage rating indicated on the box.

The medium-sized box is painted black and red, just like with the AX 1200i we tested earlier.

On the back of the box you can find a brief description of product features, a list of power connectors, and charts with specified output power, efficiency, and fan regulation algorithm.

The accessories include a bag with detachable cables, a simple fabric pouch for the PSU itself, a Corsair sticker for your computer case, a few single-use cable straps, mounting screws, a user manual and a warranty brochure.

Exterior Design

One glance is enough to identify the actual maker of this PSU. The nonstandard design of the case, the characteristic shape of the Sanyo Denki impeller you can glimpse through the vent grid, the all-modular cable system and the fan controller on the connectors panel are all typical of Seasonic.

These Corsair PSUs can be easily confused with Seasonic’s original ones in some views, but the back view is where every PSU looks very much like any other.

Circuit Design

As you can easily see, there’s not much difference between the two models in terms of their interior design (the top photo shows you the AX760 and the bottom one, the AX860). A couple of components vary in ratings and the higher-wattage model has a few additional capacitors.

We can also note that the hardware platform is similar to Seasonic’s KM3 series we tested recently except for the color which is black as is typical of Corsair products.

So, these Corsair PSUs are based on the updated Platinum-certified XP2 rather than on the XP platform.

The interior design is almost identical to Seasonic’s KM3 series, so there’s no need to delve into details once again.

Like Seasonic’s original products, the Corsair PSUs employ electrolytic capacitors from United Chemi-Con (also known as Nippon Chemi-Con).

Cables and Connectors

The all-modular AX760 and AX860 are equipped with the following connectors:

Each model comes with the same selection of detachable cables:

The cable system of the AX760 and AX860 PSUs is comparable to that of Corsair’s Gold-certified PSUs based on Seasonic’s KM series. They offer more connectors but lack short cables with fewer SATA/PATA power connectors on each.

The power cables for graphics cards have one or two connectors, offering more flexibility. You can power up to three graphics cards with two power connectors each without any adapters. On the other hand, the PSUs may not be able to deliver that much power, which must be the reason why Seasonic only provided four 6+2-pin PCIe power connectors with its original 760W model.

Specifications

The AX760 and AX860 only differ in the load capacity of the +12V power rail. As expected from a modern PSU, they can deliver most of their power via the +12V rail whereas the load capacity of the +3.3V and +5V rails is rather low.

The PSUs comply with the 80 PLUS Platinum standard, which is the strictest efficiency standard applicable to consumer PSUs (there exist even harsher 80 PLUS Titanium requirements for server PSUs).

They come with a 7-year warranty just like their Seasonic counterparts.

UPS Compatibility

Working with our APC SmartUPS SC 620, the AX760 was stable at loads up to 410 watts when powered by the mains but could only switch to the UPS’s batteries at 300 watts or lower loads.

The AX860 was stable at 416 watts when powered by the mains but couldn’t switch to the UPS’s batteries even at 280 watts.

Cross-Load Voltage Stability

The PSUs are both immaculate in this test. Every voltage is within 2% of the required level (as promised by Seasonic for the same PSUs it sells under its own brand) and even within 1% throughout most loads.

The +12V voltage is the most stable with both PSUs. It’s always within 1% with the AX860. The AX760 only allows that voltage to exceed the 1% limit at near-maximum loads.

Output Voltage Ripple

The two PSUs were almost identical in this test, so we only show you the results of the senior model.

The high-frequency voltage ripple is noticeable on every power rail but always stays within the norm.

The low-frequency voltage ripple (at the double mains frequency) is weaker.

Temperature and Noise

The PSUs are cooled by a Sanyo Denki San Ace 120 fan (part number: 9S1212F404; rated speed: 2200 RPM) which is well-known to us by Seasonic’s Gold- and Platinum-certified products. It features a well-balanced impeller and makes little noise. The fan is partially covered with a piece of plastic to optimize air flows.

We tested the cooling system in both available modes: Normal and Hybrid.

In the Normal mode each PSU had its fan working at about 800 RPM throughout a long range of loads. The AX760’s fan began to accelerate at loads of 600 watts and higher whereas the AX860’s fan did the same at a load of 700 watts.

At full load the fans of the AX760 and AX860 worked at 1310 and 1430 RPM, respectively. The high-quality fans employed here are not uncomfortable at such speeds.

In the Hybrid mode the fan doesn’t work at all until loads of 450-550 watts but there is one unpleasant thing about its behavior afterwards. It can occasionally accelerate to 1600 RPM at loads far from maximum, which is audible even with a Sanyo Denki San Ace 120.

So if you prefer to have a quiet PSU at most loads, the Normal mode may be more appropriate. But if your computer works at loads corresponding to the passive cooling mode or if you’ve got other loud sound sources at high loads, the Hybrid mode is surely preferable.

Efficiency and Power Factor

The AX760 was 92.5%, 93.5% and 91.7% efficient at the reference loads of 20%, 50% and 100%. Its peak efficiency of 93.9% was observed at a load of 305 watts.

The AX860 was 91.9%, 94% and 92.6% efficient at loads of 20%, 50% and 100%, respectively. Its peak efficiency of 94.1% was observed in a load range of 370 to 425 watts.

The power factor of each PSU was close to 99% at high loads.

Standby Source

The two PSUs performed similarly in this test. We can see no problems with their standby source.

Corsair AX 760i and 860i

The packaging follows the same style with the previous models except for minor differences (the interior box is painted black, for example).

The layout of the texts and charts has changed on the back of the box, and the cable system information can now be found on the top of the packaging, yet the overall design style is the same.

The accessories now additionally include a Corsair Link adapter and a piece of paper with a web address from where you can download Corsair Link software. The PSU pouch is velvety. Otherwise, the accessories are the same as you get with the above-discussed AX series products.

Exterior Design

The AXi series differs from the AX visually, their exterior resembling the Corsair TX650 model (except for the modular connectors). The paint is less glossy than on the AX series PSUs we described above.

A plaque with model name can be seen on the back panel, far from the mains connector.

Circuit Design

There are even fewer internal differences between the AX 760i and 860i than between the AX series models discussed above (the top photo shows the 760W model and the bottom photo, the 860W model).

Like the AX series, the AXi PSUs feature an LLC resonant converter. The +3.3V and +5V voltages are generated via DC-DC converters.

One DC-DC converter can be found near the side panel of the case behind a daughter card with Corsair Link logic. The other is located between the modular connectors panel and the +12V circuitry.

Corsair refers to the AXi series as “digital” PSUs because the Corsair Link card allows controlling some of the PSU’s parameters.

The mains connector is not screened as carefully as in Seasonic PSUs. We wonder if this can show up in the output voltage ripple tests.

The PSU has few non-solid-state capacitors inside but the components we see here come from many brands. The photo shows Rubycon and CapXon ones while the huge input capacitor is made by Panasonic. There are also Nichicon capacitors inside this PSU.

Cables and Connectors

The all-modular AX760i and AX860i have the following connectors:

Each model comes with the same selection of detachable cables:

The selection of cables is actually identical to what you get with the AX760 and AX860 with the addition of a Corsair Link cable. We can only add that one of the modular connectors for peripheral cables is going to be empty because there are only five SATA/PATA power cables in the box whereas the PSUs offer six such connectors.

Specifications

The specifications are almost identical to those of the same-wattage AX series models except for a tiny increase in the load capacity of the +12V rail – by a mere 0.3 to 0.6 amperes. This must have been done to emphasize the higher position of the “digital” PSUs in Corsair’s product range. It has no practical value since modern computers need 30 to 40 watts from the +3.3V and +5V rails anyway.

Like the above-discussed AX series, the AXi has 80 PLUS Platinum certification and comes with a 7-year warranty.

UPS Compatibility

Working with our APC SmartUPS SC 620, both AXi series PSUs were stable at loads up to 380 watts when powered by the mains but neither could switch to the UPS’s batteries even at 280 watts.

Cross-Load Voltage Stability

The +12V rail is perfect with both AXi PSUs but the other voltages fluctuate more than in the Seasonic-based AX series models. On the other hand, the deflection of 3% (and even 2% throughout the larger part of the load range) is quite acceptable.

Output Voltage Ripple

Like the previous pair, the AXi PSUs behave similarly in this test, so we only show you the results of the higher-wattage model.

The high-frequency voltage ripple is comparable to that of Corsair’s Seasonic-based PSUs even though this Flextronics-based PSU has less electromagnetic shielding.

The AXi series PSU are even better in terms of the low-frequency voltage ripple than their AX series counterparts.

Temperature and Noise

The PSU is cooled by a 120x120x25mm Yate Loon fan (part number: D12BH-12, rated speed: 2300 RPM) which is partially covered with a piece of plastic to optimize air flows.

As opposed to the AX series, the AXi PSUs only have one operation mode for their fan, which differs from both the Normal and Hybrid modes of the AX series.

The fan is idle at low loads. It wakes up at a load of 300-400 watts (i.e. sooner than in the AX series PSUs) and accelerates in a linear manner right away. The start speed is only 400 RPM. The top speed (at full PSU load) is about 1250 RPM, so the AX760i and AX860i are not louder than their AX series counterparts.

We guess that they are less attractive in terms of noisiness, however, because their fan works at a higher speed than in the AX series PSUs at loads of 600 to 800 watts. On the other hand, the Corsair Link feature allows to adjust the speed of the fan, unlike in the Seasonic-based models.

Efficiency and Power Factor

The AX760i was 91.2%, 94.2% and 92.5% efficient at loads of 20%, 50% and 100%, respectively. Its peak efficiency of 94.5% was observed at a load of 402 watts.

The AX860i was 91.3%, 93.9% and 90.7% efficient at loads of 20%, 50% and 100%, respectively. It reached its peak efficiency of 94% at a load of 433 watts.

Thus, these Flextronics-based PSUs are overall more efficient than their Seasonic-based counterparts – by 1% at medium loads. The latter are better in efficiency at low loads, though.

The power factor is over 99% at loads above 50% with both PSUs and reaches 99.8% at full load.

Standby Source

The standby source copes with its job well enough, yet the voltage drop at full load is about 4% compared to 2% of the AX series PSUs.

Conclusion

Both flagship PSU series from Corsair boast very high efficiency, quiet operation and low voltage ripple. There are but minor differences between them.

Based on a Seasonic platform, the AX series is somewhat better in terms of voltage stability, efficiency at low loads, noisiness at high loads and standby voltage. They are also less expensive than their AXi counterparts.

The Flextronics-based AXi PSUs are overall more efficient and have weaker voltage ripple, but their key feature is the Corsair Link interface that offers monitoring and setup opportunities.

Every model we’ve discussed in this review deserves a place in a high-efficiency computer. The AX series is going to be optimal if you need basic functionality without any extras. The extended functionality of the AXi models isn’t so expensive, though. It is about 10% of the PSU price. We guess that’s not much for the opportunity to check out the Corsair Link capabilities. You may find them highly useful.