Corsair AX 1200w ATX PSU Review Page: 1

Corsair AX 1200w ATX PSU

Introduction & Specs

For many years Wattage has been the male penis extension. Whether it be in the form of insanely loud car audio systems that you need ear plugs to operate, heavily modified car engines being measured in KW on a rolling road, or that unnecessarily high output PC power supply you purchased for your 486 DX2.  Its always been about bragging and trying to go one better than your mates regardless of whether you actually need the power or not.

However, in the PSU scene at least, times are changing. Back in April graphics card manufacturer nVidia released it's eagerly anticipated GTX480 card on the world. With it came word that the card was capable of sapping up to 300w from the wall at full load. Considering that most of the industry had slowly been moving towards 'ECO Friendly' computing this complete change in direction has given PSU manufacturers viable reason to start producing 1kw+ models once more.

Corsair are one such manufacturer that has done exactly this. Up until recently the HX1000 stood at the top of their mantle, being one of the most respected high-output PSU's available. However, due mainly to its now slightly dated design the PSU has started loosing ground to newer modes that can easily better it in areas such as efficiency. Determined not to be left behind, Corsair went back to the drawing board with the intention of creating yet another PSU that would raise the bar once more. What we're looking at today is that very PSU. The Corsair Professional Series Gold AX1200. So let's start with the specs..

*  Supports the latest ATX12V v2.31 and EPS 2.92 standards and is backward compatible with ATX12V 2.2 and ATX12V 2.01 systems
* An ultra-quiet 140mm double ball-bearing fan delivers excellent airflow at an exceptionally low noise level by varying fan speed in response to temperature
* 80 Plus Gold certified to deliver at least 90% efficiency at 50% load
* Active Power Factor Correction (PFC) with PF value of 0.99
* Universal AC input from 90~264V
      o No more hassle of flipping that tiny red switch to select the voltage input!
* A dedicated single +12V rail offers maximum compatibility with the latest components
* Over-voltage and over-current protection, under-voltage protection, and short circuit protection provide maximum safety to your critical system components
* High-quality Japanese capacitors provide uncompromised performance and reliability
* Completely modular cable system allows you to use only the cables you need
      o Power supply upgrade and replacement is easy, as the cables only need to be disconnected at the power supply
* Low-profile, flat cable design reduces air friction and helps maximize airflow through your computer’s chassis
* A seven year warranty and lifetime access to Corsair’s legendary technical support and customer service
* Dimensions: 150mm(W) x 86mm(H) x 200mm(L)
* MTBF: 100,000 hours
* Safety Approvals: UL, CUL, CE, CB, FCC Class B, TÜV, CCC, C-tick

At first glance there's very little to separate the AX1200 from the barrage of other high-end PSU's that pass through OC3D's labs on a monthly basis. Sure you get a 'quiet' 140mm fan, Active PFC, Universal AC input, Jap caps, a handful of safety features and a single +12v rail. But we've seen all that before. However, what does set this unit apart from a lot of the others is Corsair's impressive seven year warranty (which we've tested ourselves a couple of times) and that shiny 80PLUS Gold certification. Corsair will also be quick to tell you that the AX was designed in-house from the ground up, how it has a server grade power train architecture (toot-toot!) and how their Zero Voltage/Current Switching technology has helped the unit to achieve over 90% efficiency at 50% load. For further info be sure to check out their blog.

To put the efficiency side of things into perspective. If you were to run the AX1200 alongside a standard 80% efficiency PSU at at full load there would be a 144w difference in the amount of power that the two draw from the mains. Basically enough power to run a small HTPC, Laptop, TV...or GTX260 for PhysX processing ;)

Corsair AX1200 Rail Layout
DC Output +3.3V +5V +12V1 +12V2 +12V3 +12V4 +12V5 +12V6 -12V +5VSB
30A 30A 100.4A - - - - - 0.8A 3.5A
Max Power 180W 1204.8W 9.6W 17.5W

When it comes to the rail layout, impressive simply is not the word. Considering that the AX1200 is supposed to be a 1200w PSU, it already over-delivers on this rating on the +12v rail alone. 100.4A (1204.8W) on a single rail is pretty insane and would certainly put on an awesome fireworks show if the safety features weren't there to keep everything in check.

Of course, as soon as you start putting load on the +3.3/+5v rails it does eat into this output, and with 30A available to either of the rails a maximum of 180w can be deducted from the 1204w output of the 12v rail. Mind you, this is just theoretical though, because we're willing to bet that the AX1200's max output is a conservative claim. One that will be quickly surpassed when it comes to our testing.

But first let's move on and see what goodies Corsair have bundled in the box...

Corsair AX 1200w ATX PSU Review Page: 2

Corsair AX 1200w  ATX PSU

Packaging & Contents

At OC3D, we often get asked why we spend so much time describing the packaging of products that come in for review. After all, once your latest purchase is handed over by Mr Postie the time it takes for the box to be open, the manual thrown in the bin and the PC in bits on the floor can barely be measured by a stop watch.

However, when you're spending a pretty penny on something like a PSU or Graphics Card, you want to make sure that it arrives in perfect condition. Not only that but peeling back the layers of cardboard, styrofoam and soft velvet bags can add to the excitement much like getting beneath the wife's latest piece of lingerie. Or maybe that's just me?

Corsair AX 1200w ATX PSU Box Front  Corsair AX 1200w ATX PSU Box Back  

Corsair AX 1200w ATX PSU Inner Box  Corsair AX 1200w ATX PSU Padding

If however you feel the same, then we're in for a treat. The AX1200 follows Corsair's usual standard of packaging with the unit being placed inside a plastic bag followed by a velvet drawstring bag to prevent minor scuffs and scratches. Then the unit is encased in custom made styrofoam inserts before finally being placed inside a double walled cardboard box. Even Uma Thurman with a collection of swords would find it immensely difficult to put a scratch on this PSU!

Corsair AX 1200w ATX PSU Contents  Corsair AX 1200w ATX PSU Accessories

Next up is the goodies. To be honest it's very rare to get anything more than some cable ties and a key ring with a PSU purchase, as there's very little margin for profit as it is. However, the past has shown us manufacturers will do anything to win people over, even to the point of throwing in leather suitcases, keyrings, fans, lanyards and other pointless junk!

Corsair on the other hand have kept things 'Professional' by sticking to the basics and providing the AX1200 with some black case screws, a "Powered by Corsair" case badge, a handfull of cable ties and an oh-so-very important mains lead. Of course there's also a goddamn massive bag of modular cables, but I'll talk about that on the next page.



Appearance-wise the AX1200 is pretty much the same as most of Corsair's previous units. It's not dolled up in a wacky colour such as orange, red or blue and it's not got an annoyingly glossy finish that collects finger prints faster than a CSI on amphetamines. It's just a plain and simple matte black powdercoat finish that feels durable and will blend in with your PC regardless of any colour scheme you may have going on.

Corsair AX 1200w  ATX PSU Bottom  Corsair AX 1200w  ATX PSU Fan

Corsair AX 1200w ATX PSU Side  Corsair AX 1200w ATX PSU Top

The stickers on the side and top of the unit are tasteful and help to give it a slightly stylish edge over a completely black box. Corsair have also managed to avoid sticking CE and Hi-Pot stickers all over the unit, instead thoughfully placing them all on the main specification sticker.

Corsair AX 1200w ATX PSU Rear  Corsair AX 1200w ATX PSU Switch

The rear of the unit houses the mains power cord along with a rather beefy rocker switch. This is much more welcome than the smaller 'High school electronics project' style switches used on most other PSU's and should provide many years of reliable arc-free switching. Even if you are one of those people who insists on turning all appliances off at the switch every night before you can get to sleep at night.

Now we've covered every angle but the front of the PSU, let's move on to the next page and see what the modular interface has in store...

Corsair AX 1200w ATX PSU Review Page: 3

Corsair AX 1200w   ATX PSU

Cables & Connectors

As you've probably guessed from the picture at the top of every page, the AX1200 is FULLY MODULAR! Very few manufacturers have managed to pull this off in the past with models from Silverstone and ULTRA receiving mixed press on the effectiveness of the connectors. Why Corsair had the sudden change of heart and decided to go fully modular for the AX series I'm not sure. After all, if you're planning to use the AX1200 as part of a 'normal' PC system you'll be needing the ATX connector at the very least anyway!

Corsair AX 1200w ATX PSU Modular  Corsair AX 1200w ATX PSU Modular

Corsair have, however, instantly improved on the fully modular design used by their competitors. Rather than the main ATX cable being a large 24-Pin connector, Corsair have split it into two connectors (10-Pin and 14-Pin) to help increase the strength of the mating and prevent situations when the pins at the edge of the connector lose contact due to the cable being bent at a tight angle.

Additionally, the whole modular experience has been simplified by splitting the connectors into two groups: Peripheral & SATA and PCI-E & CPU. Basically anything that runs on only 12v (Graphics Cards, Motherboard EPS) goes in one of the eight available 8-Pin connectors, while any other devices that make use of 3.3v/5v (Hard Disks, DVD..etc) go in any one of the six available 6-Pin connectors. Simples!

Corsair AX 1200w ATX PSU Cables in  Corsair AX 1200w ATX PSU Spares

Plugging as many cables into the unit as possible leaves you with two unused modular cables. Obviously depending on whether your system uses more SATA or Molex connectors you can decide which ones exclude. Regardless of the combination you certainly won't find yourself short of connectors though with the AX1200 having a total of 16 SATA and 12 Molex connectors.

Corsair AX1200 Connectors
 ATX Connector Modular
1x 20+4 Pin
 EPS-12v / P4-12v Connector(s) Modular
2x 4+4 Pin
 Molex Connectors Modular 12x
 Floppy Disk Connectors Modular 2x
 SATA Connectors Modular 16x
 PCI-E Connectors Modular 6x 6+2 Pin

Corsair AX 1200w ATX PSU All Cables
  Corsair AX 1200w ATX PSU PCIE

Corsair AX 1200w ATX PSU ATX  Corsair AX 1200w ATX PSU EPS

Much to my relief Corsair have stuck with the flat 'ribbon-style' modular SATA/Molex cables that have been made popular by their HX series. These have a much better bend radius than traditional 'bunched' cables in sleeving with the only slight downside being that they only bend in two directions. However, due to the sheer number of cables needed for EPS and ATX modular cables, Corsair has reverted to sleeving in order to keep them looking tidy. But fear not, there's no ugly rainbow coloured wires anywhere to be seen - so if you're not a sleeving fan, you can happily cut the sleeving off and keep the black wires bunched together using zip ties instead.



Now for the good stuff, and ooh-err this is just a tad different to any other PSU I've seen in the past. It's not a Seasonic, it's not a CWT, it's not a Delta. Could this mean that Corsair really have specc'd this unit from the ground up themselves? Time to put the cameras lens protector on so I can push it right up against some of these tasty looking components..

Corsair AX 1200w ATX PSU Internals  Corsair AX 1200w ATX PSU Internals

First things first, the insides of the unit are more tidy than a female porn stars rhododendron. Everything is perfectly positioned and there's absolutely no cables trailing across the internals or any of that sticky white...glue used to keep components from touching. While this accounts for little in the performance side of things, it does go to show that Corsair have put a lot of thought into the cooling pattern of the fan.

Corsair AX 1200w ATX PSU AC  Corsair AX 1200w ATX PSU Transformer

The AC receptacle at the rear of the unit features a built-in filter that should remove any transients coming in from the mains power line. This also serves as barrier for any noise produced by the transistors inside the PSU from returning back out to mains supply where it may cause interference on other electronic devices. The two main transformers for the unit are rather strange looking fellows too, but are actually part of the +12v VRM.

Corsair AX 1200w ATX PSU VRM  Corsair AX 1200w ATX PSU VRM

The 3.3v and +5v VRM's appear to sit at opposite sides of the PSU and each have a collection of solid state caps. Also pictured in the image on the right is the PCB responsible for a large part of the AX1200's safety features - namely OVP, UVP, OCP...etc.

Corsair AX 1200w ATX PSU Caps  Corsair AX 1200w ATX PSU Caps

The caps on the primary side of the unit are manufactured by Japanese company Nichicon and carry the specs of 470uF / 420v / 105°C. Interestingly over on the secondary side of the unit Corsair has switched to another Japanese manufacturer, Rubycon, for filtering the 12v output.

Corsair AX 1200w ATX PSU Rail  Corsair AX 1200w ATX PSU SOmmit

See those big 12 gauge wires? Well that's where the massive 100A 12v current is distributed to all of the modular connectors at the front of the PSU. Rather than using a standard traces design with the several wires soldered to the back of the PCB, Corsair have opted for solid metal rails that run along the top and down between each of the connectors. This is not only more efficient (as thick lumps of metal tend not to heat up as much as solder traces), but it also means that a considerable amount of amperage can be delivered to connectors that are in close proximity to each other.

Normally at this point I'd show you some pictures of the fan used to keep this beasty cool, but unfortunately I forgot to snap any shots *blushes*. Anyway, I can tell you that the fan is a Yate Loon D14BH-12 with the specs being available here.

Now to put the AX1200 through hell....

Corsair AX 1200w ATX PSU Review Page: 4

Corsair AX 1200w    ATX PSU

Simulated Load Results (Graphs)

For those of you not familiar with the layout of our relatively new graphs, the highest and lowest values on the Y-axis (voltage) represent the maximum and minimum voltages allowed by ATX specifications. If the results should fall outside the graph at any time, then that's an instant FAIL. However, merely staying inside these boundaries does not necessarily indicate a good PSU. In order to display truly great voltage regulation, a PSU must stick as closely as possible to the thick white horizontal line (ideal voltage) as possible.

You will also notice that the graph is split into three sections as depicted by the Green, Amber and Red backgrounds. These indicate normal usage (green), heavily uneven load distribution (amber) and overloading of the PSU (red). For the most part all we need to worry about is how it performs in the green section, but good performance in the other sections will undoubtedly earn the PSU extra brownie points.

For a better understanding of now we conduct our PSU testing and how these results were obtained, please be sure to check out the tabulated results over on the next page.

The +3.3v rail in particular is being used less and less these days with most high current devices relying mostly on the +12v rail and occasionally on the +5v rail. This is reflected somewhat in the results from the AX1200, which while perfectly acceptable and well within tolerances, Isn't quite as tight as it could be.


Despite the appearance of a slightly less steep slope on the +5v rail in comparison to the +3.3v one, the actual change in voltage from 327w to 1206w loads is exactly the same. However, given that ATX guidelines give us a window of ±10% on the baseline voltage, the +5v rail has just a little more leeway in either direction and therefore the +5v rail could be stated as having ever so slightly better performance.

Would you look at that +12v rail though. What a sight for sore eyes (I've got hay-fever). The voltage output stays ever so slightly above our 12v baseline throughout all of the tests, and only has the tiniest of downward slants from idle to full load. Even in the max load test is refuses to budge from 12.04v  showing that this really is a PSU for those who are going to be putting some seriously powerful GPU's in their PC's.

Efficiency....boing! That pretty much sums it up, don't you think? 93% at any anything from ~600-900w load and just shy of 90% efficiency when running at its full rated output. The only areas that push the line towards the bottom of the graph is the cross-load TX1 test (heavy load on +3.3/5v) and the max-load test where the PSU is running way outside of specification. Both these tests don't really mimic real life situations - and certainly aren't part of the standard 80PLUS tests. It's mostly me having fun watching PSU's scream for help.

Corsair AX 1200w ATX PSU Review Page: 5

Corsair AX 1200w    ATX PSU

Simulated Load Results (Data)

If you've seen the simplified graphs over on the previous page you will undoubtedly already have a good idea of how the Corsair AX1200 performs. However, certain results from the test can be too dificult to incorporate into the existing graphs, and for this reason all of the result data is also provided in the table format below. 

All testing is conducting using OC3D's trusty SunMoon SM-268+ DC load tester. This equipment is capable of placing a user specified load on all of the PSU's rails (+3.3v, +5v, +12v, -12v, +5vSB) up to a maximum load of 1680w.  As the maximum load for this device on the +12v rail is restricted to 75A we will also be calling on additional help from our Analogic Series 2000 DC load tester, so that anything up to an additional 166A can be added if necessary. All testing is conducted at 50°C (±5%) with the results being recorded using a Fluke Multimeter and Thermostat.

Corsair AX1200 1200w @ 50°C
   +3.3v  +5.0v  +12v  +5vSB  -12v  AC Watts /
 DC Watts
 Efficiency  Intake /
Δ Temp
5.50A 5.50A 21.25A 0.87A  0.20A 356w /
91.85% 50.0°C /
3.36v 5.03v 12.18v 5.02v  -12.28v
11.00A 11.00A 42.50A 1.75A  0.40A

661w /

93.64%  50.0°C /
3.32v 4.98v 12.12v 4.95v  -12.31v
16.50A 16.50A 63.75A 2.62A  0.60A 980w /
 93.36% 50.2C /
3.26v 4.94v 12.06v 4.89v -12.32v
22.00A 22.00A 85.00A 3.50A 0.80A 1347w /
89.53%  50.2°C /
3.23v 4.90v 12.04v 4.84v -12.31v
22.00A 22.00A 1.00A 0.00A 0.00A 235w /
82.12% 50.1°C /
3.27v 4.95v 12.20v 5.05v -12.30v
 1.00A  1.00A  62.00A  0.00A  0.00A 1300w /
91.61% 50.0°C /
3.35v 5.02v 12.08v 5.03v -12.32v
 22.00A 22.00A 114.00A 3.50A 0.80A 1760w /
86.47% 51.0°C /
3.22v 4.90v 12.04v 4.84v -12.32v

OK. Before we even talk about anything else, I think you should take a look at the DC Watts being pulled in test TMax1. Yes, you did read that right. That's a whopping 1522W that the AX1200 can output continuously. At one point I even got it up to 1600W, but unfortunately it turned off after a few minutes. This is also testament to the OCP functioning properly on the unit. No matter how much I overloaded it by, or how many times I switched it straight back on after it had cut out, the AX1200 WOULD NOT GO BANG!

The rest of the results speak for themselves to be honest. Good voltages (especially on +12v) throught all of the tests, no weird voltage see-saw results during the cross-load tests, no exhaust temperatures suitable for stripping paint from your walls and efficiency levels that would give Captain Planet a reason to retire.

Corsair AX1200 Scope Results @ 50c
   +3.3v  +5.0v  +12v
Corsair AX 1200w  ATX PSU Corsair AX 1200w  ATX PSU Corsair AX 1200w  ATX PSU
Corsair AX 1200w  ATX PSU Corsair AX 1200w  ATX PSU Corsair AX 1200w  ATX PSU
Corsair AX 1200w  ATX PSU Corsair AX 1200w  ATX PSU Corsair AX 1200w  ATX PSU
Corsair AX 1200w  ATX PSU Corsair AX 1200w  ATX PSU Corsair AX 1200w  ATX PSU
Corsair AX 1200w  ATX PSU Corsair AX 1200w  ATX PSU Corsair AX 1200w  ATX PSU
Corsair AX 1200w  ATX PSU Corsair AX 1200w  ATX PSU Corsair AX 1200w  ATX PSU
Corsair AX 1200w  ATX PSU Corsair AX 1200w  ATX PSU Corsair AX 1200w  ATX PSU


Ripple.....what bloody ripple. I almost felt like that idiot who stands up on the stage saying "is this thing on" into the microphone. Tests 1-4 are flat, flat, flat and flat with no more than 24mV being recorded at any stage. The cross-load tests are also equally as uninteresting, and it's only when we get to the max-load test and seriously give the AX1200 a kicking that it puts out a still quite measly 42mV on the +12v rail. Awesome job Corsair!

Corsair AX 1200w ATX PSU Review Page: 6

Corsair AX 1200w      ATX PSU


Just when it looked like the rest of the PSU market was finally catching up to the highly acclaimed HX series, Corsair have come out with yet another PSU range that moves the bar even further out of their sight. Without any shadow of doubt the AX1200 is by far the best PSU that has come through OC3D's labs to date, and the very fact that Corsair designed the unit from the ground up makes that achievement a whole lot more meaningful.

Starting with the efficiency, the AX1200 lives up to its 80Plus Gold certification by providing up to 93% efficiency at 600-900w loads and around 90% efficiency at all other load levels. In fact, the AX1200 is pretty much tapping on the door of an 80PLUS Platinum certificate, which is very impressive indeed.

Then there's the ripple results....well more precisely, the lack of them. 22mV of ripple on the +12v rail when the load tester is pulling over 85A through it is simply awesome. No scratch that, it's phenomenal. Only when the PSU is pushed way beyond its rated output does the ripple on any of the rails start to budge, but even then we're only talking 25-30mV on the +3.3/5v rails and 42mV on the +12v rail which is better than most other PSU's can hope to get at ordinary load levels.

The only area for any improvement (and this is me being picky) is in the stability of the +3.3v and +5v rails. While both are more than acceptable with only 0.13v drop from idle to full load, I can't help but feel that with the AX being Corsair's new flagship model, these could have been made a little more solid. That said though, the stability of the all-important +12v rail is perfect. No massive over-volting at idle, no drooping below the +12.00 marker and solid results under cross-load and maximum load situations.

Did I also mention that it is capable of holding a 1522w load at 50°C and even peaking at 1600w for a minute or two? Yum.

At the end of the day the AX1200 is an all-round belter of a PSU. It's got the looks, the performance, the warranty and even the packaging. The price is at the high end of what I'd consider acceptable for any wattage PSU (£245 @ Scan), but you get what you pay for and this certainly rings true for the AX1200. 

The Good
- Absolutely amazing ripple suppression.
- Extremely powerful +12v rail.
- Gold level efficiency only a whisker away from Platinum.
- Fully modular for those neat freaks.
- Lovely modular cables.
- Silent (as far as I could tell with 3000w of testing equipment in the background!).
- Shuts down safely when overloaded (which kicks in at over 1500w!).
- Well packaged.
- 7yr Warranty.

The Mediocre
- +3.3v and +5v rails could be a little tighter

The Bad
- Not a sausage.

In recognition of the AX1200's excellent all-round performance, I am pleased to award it our coveted "Best In Class" award for Power Supplies rated from 1000-1500w.

Thanks to Corsair for providing the AX1200 for review. Discuss in our forums.