Corsair AX1200 Power Supply Review

1. Introduction2. The Corsair AX1200 Supply (External)3. The Corsair AX1200 Supply (Internal)4. Testing Methodology and Results5. Closing Thoughts6. View All Pages

Corsair are well known as one of the leading suppliers of high quality memory for the discerning enthusiast and in recent years they have expanded their range into other areas such as cooling and power supplies. The Corsair motto seems simple, create the best products they can without compromising … it has worked well for them so far as their name is more highly regarded now than it has ever been.

Corsair's high level presence in the power supply market has been undoubtedly aided by strong partnerships with CWT and Seasonic with top level support and testing regimes in place to ensure the products have achieved their standards. The HX range for instance was a huge success and granted them an elusive position in this competitive sector. With further expansion into other ranges such as the CX, TX and VX it seemed there was no stopping them.

Today we look at the new range of units – specifically the Corsair Professional Series Gold AX 1200 which is the flagship model in the range and is in fact the largest capacity power supply that they have ever released. What is particularly interesting is the fact that the model has been created in conjunction with a new supplier –  Flextronics International Ltd.

It is worth delving a little into the background of Flextronics as many people will never have heard of them. They are an electronics manufacturing services provider who were founded in 1969 and have an HQ in Singapore. They provide a wide range of manufacturing, logistical support and supply chain management and offer technical support to industries such as medical, automotive and consumer electronics. Their customer base includes Microsoft, SUN, HP, Samsung, Apple, Siemens, RIM, Lego Group, Lenovo and many more. In 2005 they founded a subsidiary group called FlexPower and are now the ‘4th largest power supply company in the world'. The power supply we are looking at today is one of their first within the SMPS (switching mode power supplies) market place for the enthusiast audience.

As we all know on KitGuru, the power requirements of gaming PC's are constantly increasing and in the last year with the release of high performance graphics cards such as the nVidia GTX480 and processors like the Core i7 980X from Intel … it shows no sign of slowing down. Power supplies have always been a massively important aspect of a system build, but finally even the mass enthusiast audience is beginning to understand this.

The Corsair unit we are looking at today is based on a server grade powertrain architecture which incorporates state of the art features many of which are unique in the consumer power supply market. Corsair Marketing manager Gareth Ogden has produced a detailed post on the technology which you can read over here. It really is worth a look if you are interested in what Corsair have achieved by working with Flextronics.

Unique Design, Exclusive to Corsair The Professional Series Gold AX1200 has been designed from the ground-up by Corsair’s power engineering team, and is therefore unique and exclusive to Corsair. 100.4 Amp Single +12V Rail The AX1200’s massive 100.4 Amp (1204.8 Watt) single +12V rail makes it the ideal power supply for ultra-high end NVIDIA SLI™ and ATI CrossFireX™ gaming PCs based around multi-core CPUs. 80 Plus® Gold Efficiency The sophisticated electrical design, incorporating advanced magnetic modeling during development in order to optimize magnetic component performance, delivers exceptionally high energy efficiency (90% and above). This meets or exceeds the requirements for 80 Plus Gold certification. Outstanding Noise/Ripple and DC Voltage Regulation The AX1200 features individual DC-DC regulation for 3.3V, 5V and 12V rails, and secondary side synchronous rectification, utilizing MOSFETs that have lower losses than the conventional output rectification schemes. An advanced 4-layer modular connector board PCB ensures a better ground return plane, lower resistance and low voltage drops. This, combined with circuit trace optimization, also helps to minimize ripple and noise. Fully Modular Cable System The fully-modular, low-profile cable system provides maximum flexibility when building or upgrading your PC, and maximum airflow through your chassis. This allows you to utilize only the cables that you need, reducing cable clutter and maximizing the cooling performance of your PC. Zero Voltage Switching / Zero Current Switching Technology The Corsair AX1200 utilizes ZVS / ZCS technology to switch at near 0V and 0A, which ensures there are minimal switching losses, thereby maximizing efficiency and further reducing waste heat. Ultra Low Noise Design The AX1200 utilizes a low-noise, thermally-controlled 140mm fan, and employs sophisticated techniques to enhance cooling performance and reduce noise. This includes a specially designed PCB that channels airflow to reduce back-pressure and maximize the fan’s cooling ability.

The Corsair AX1200 arrives in one of the largest power supply boxes we have ever seen, and just for reference we placed a Blackberry phone beside it. Its huuuggee.

Inside the box there is a manual, reviewers guide (which you won't get if you buy one obviously) and a bag with all the modular cables inside. They also supply mounting screws and cable ties to neaten up your system build.

The reviewers guide explains about synchronous rectification on the outputs and Zero voltage and zero current switching on the primary side to help the unit reach the remarkable quoted efficiency levels.

The storage bag within the box is extremely big and all the cables are supplied inside.

Type Of Connector	Corsair AX1200
ATX Connector (600mm)	20+4pin
6+2 Pin PCIe (610mm)	6
SATA (400mm+90mm)	4
SATA (440mm+90mm+90mm+90mm)	12
4+4 Pin EPS12V/ATX12V connector (610mm)	2
5.25″ Drive (460mm+110mm+110mm)	12
5.25-3.5″ Drive Adapter (100mm)	2

There are enough cables included to support even the most demanding of system builds. Some are sleeved ribbon design and others are flat black ribbon.

The power supply itself is wedged between two heavy duty blocks of styrofoam and it is encased within a felt bag . When you remove the PSU from the felt bag, yes there is another protective cover. We would be safe in saying that if this unit arrives damaged, then your postman needs a slapping.

Corsair AX1200	+3.3V	+5V	+12V	-12V	+5VSB
	30A	30A	100.4A	0.8A	3.5A
Max Power	180W		1204.8W	9.6A	17.5W
	1204.8W

Yes you read that right, 100.4A on the 12V rail. This is a simply staggering level of power to be delivering down a single line and is without a doubt the highest we have seen. Even the Silverstone Zeus ZM1200M which resides in our labs falls short of this mark.

Is this enough connectivity for you? Yes we thought so.

The top is home to a 140mm fan – we like the aesthetics of the unit, its a simple ‘black' design throughout, no controversial gold fans here (opps sorry Enermax).

A detailed overview of the unit's performance characteristics as discussed earlier.

As we have seen on many high quality power supplies recently, the fan of choice is a Yate Loon model. This particular one is the D14BH-12 which is rated at 12v 0.7A. This is very similar (from memory) to what I remember inside the previous HX1000W.

This power supply is unlike any design we have seen before as the printed circuit board design is very unusual. The AX1200 utilises DC-DC converters for the 3V3, 5V0 and +12 rail, this is clearly to help increase overall unit efficiency.

The images above show the heavy duty cables for the 0V return and the board in front of the 0V return cables is the DC-DC converter for the +12V Rail.

The heatsink layout is very interesting with most of them in the area of the fan above which wisely ensures that the airflow will be strong to keep things in check. The image above, bottom right is the rear end of the 5VSB circuit board.

The overall design is very clean with an unusual topology design from Flextronics.

The primary side is home to the majority of the input filtering along the back edge of the PCB right next to the exhaust area. These primary side power components are connected to heatsinks between the coils and capacitors. The unit also is supplied with a line filtered AC receptacle, which is similar to many high grade server units. These incorporate many components found in a standard AC transient filter and places them all into a single box as well as the receptacle itself.

Special mention also goes to soldering on the unit which is some of the finest we have yet to see.

The capacitors used for the PFC stage are Nichicon based rated at 420v 470uF 105C. This Corsair unit boosts efficiency by minimising the loss in the PFC stage by switching the primary power on and off when the cycle is at 0 voltage and 0 current.

The secondary stage uses a synchronous rectification DC-DC Design – it uses DC-DC VRM's for the minor rails and also for the 12V rail. The PCB is a 4 layer design which means it will deliver lower resistance. Corsair also deserve some credit for component selection as they are using highest grade Rubycon electrolytics. We also noticed several shunt resistors on the design which we assume means that Corsair could add a switch for multirail selection.

The board down the right hand side in the first image above provides the +5VSB supply as well as fan speed control. There is also a board between the +5VSB board and one of the DC-DC converter boards which handles over current and over voltage regulation (Weltrend WT7527S).

The AX1200 uses a VRM design to handle the three primary rails. A single 1587A, two K0391's and two K0394's are seen above.

Above are some transient filtering components. A MOV, four V capacitors, two coils and two X capacitors.

In case you missed it earlier, there is a double VRM for the 12V rail – on each side is a 2812 controller.

Additional technical assistance: Peter McFarland and Jeremy Price.

Correctly testing power supplies is a complex procedure and KitGuru have configured a test bench which can deliver up to a 2,000 watt DC load. Over the coming months this configuration is likely to be adjusted further and fine tuned. Ambient room temperatures are kept to a ‘real world' realistic condition of 25c with air conditioning.

We use combinations of the following hardware:
• SunMoon SM-268
•  CSI3710A Programmable DC load (+3.3V and +5V outputs)
•  CSI3711A Programmable DC load (+12V1, +12V2, +12V3, and +12V4)
• Extech Power Analyzer
• Extech MultiMaster MM570 digital multimeter
• Extech digital sound level meter
• Digital oscilloscope (20M S/s with 12 Bit ADC)
• Variable Autotransformer, 1.4 KVA

DC Output Load Regulation
Combined DC Load	+3.3V		+5V		+12V		+5VSB		-12V
	A	V	A	V	A	V	A	V	A	V
330W	5.50	3.37	5.50	5.02	21.25	12.20	0.87	5.03	0.20	-12.20
620W	11.00	3.35	11.00	5.02	42.50	12.18	1.75	4.99	0.40	-12.21
918W	16.50	3.31	16.50	5.01	63.75	12.06	2.62	4.97	0.60	-12.24
1204W	22.00	3.25	22.00	4.95	85.00	12.02	3.5	4.94	0.80	-12.30

Corsair AX1200	Maximum Load
	1545W

Incredibly we managed to wrangle 1545W from the unit – and what is even more stunning is that it was happy to run at this for some time. If we loaded it higher than this it would shut off after a short while. We are pleased to report that the Overcircuit protection system works wonders as the unit didn't POP and just shut off safely until we restarted with lower load. The results in the table above speak for themselves, no unusual lowering or raising of figures as we increased the load.

Next we want to try Cross Loading. This basically means loads which are not balanced. If a PC for instance needs 500W on the +12V outputs but something like 30W via the combined 3.3V and +5V outputs then the voltage regulation can fluctuate badly.

Cross Load Testing	+3.3V		+5V		+12V		-12V		+5VSB
	A	V	A	V	A	V	A	V	A	V
1190W	1.0	3.33	1.0	5.01	62.0	12.05	0.05	-12.25	0.05	5.03
195W	22.0	3.30	22.0	4.98	1.0	11.98	0.05	-12.20	0.05	5.03

A stellar sets of results for the AX1200, it deals well with the crossloading tests, very little fluctuation throughout.

We then used an oscilloscope to measure AC ripple and noise present on the DC outputs. We set the oscilloscope time base to check for AC ripple at both high and low ends of the spectrum.

ATX12V V2.2 specification for DC output ripple and noise is defined in the ATX 12V power supply design guide.

ATX12V Ver 2.2 Noise/Ripple Tolerance
Output	Ripple (mV p-p)
+3.3V	50
+5V	50
+12V1	120
+12V2	120
-12V	120
+5VSB	50

Obviously when measuring AC noise and ripple on the DC outputs the cleaner (less recorded) means we have a better end result. We measured this AC signal amplitude to see how closely the Corsair unit complied with the ATX standard.

AC Ripple (mV p-p)
DC Load	+3.3V	+5V	+12V	5VSB
330W	5	5	10	5
620W	10	10	15	10
918W	10	10	20	15
1204W	20	20	25	20

These are outstanding results and without a doubt, class leading. We recorded only 25mV of noise on the 12V line fully loaded – remember this is with 1200W of energy being drawn!

Efficiency (%)
330W	92.21
620W	93.78
918W	93.54
1204W	90.67

Once again, we have never seen efficiency figures anywhere near this level and even under full load it still managed to achieve a 90%+ efficiency rating which is mind blowing. These efficiency figures are basically off the chart.

We take the issue of noise very seriously at KitGuru and this is why we have built a special home brew system as a reference point when we test noise levels of various components. Why do this? Well this means we can eliminate secondary noise pollution in the test room and concentrate on components we are testing. It also brings us slightly closer to industry standards, such as DIN 45635.

Today to test the Corsair Power Supply we have taken it into our acoustics room environment and have set our Digital Sound Level Noise Decibel Meter Style 2 one meter away from the unit. We have no other fans running so we can effectively measure just the noise from the unit itself.

As this can be a little confusing for people, here are various dBa ratings in with real world situations to help describe the various levels.

KitGuru noise guide
10dBA – Normal Breathing/Rustling Leaves
20-25dBA – Whisper
30dBA – High Quality Computer fan
40dBA – A Bubbling Brook, or a Refridgerator
50dBA – Normal Conversation
60dBA – Laughter
70dBA – Vacuum Cleaner or Hairdryer
80dBA – City Traffic or a Garbage Disposal
90dBA – Motorcycle or Lawnmower
100dBA – MP3 player at maximum output
110dBA – Orchestra
120dBA – Front row rock concert/Jet Engine
130dBA – Threshold of Pain
140dBA – Military Jet takeoff/Gunshot (close range)
160dBA – Instant Perforation of eardrum

Noise (dBA)
330W	26.4
620W	28.9
918W	29.8
1204W	32.3

These are a great set of results, and while Corsair rate the AX1200 maximum noise output at 30dBa we measured slightly higher at 32.3dBa, which is still not that noticeable under real world conditions, more than likely drown out by several case fans (if you could load it over 1kW). Very good set of results, yet again.

Exhaust Temperature (c)
330W	26
620W	28
918W	40
1204W	44

The power supply delivers a great combination of very low noise with reasonable levels of heat being removed. The 140mm preset fan settings throughout the range seem to be well adjusted by Corsair.

Maximum load	Efficiency
1545W	87.12%

For those interested, we measured the efficiency when stressing the unit to breaking point.over 87% at 1545W, are you impressed yet?

The HX series from Corsair paved the path for others to follow and while many have caught up to this elusive model, Corsair have just released a power supply that has blown everything out of the water, and then some. The AX1200W power supply from Corsair isn't just their best unit, its easily the best power supply on the market right now and we think it will be some time before we see results like these again. We were so surprised with some of the results that we reran them multiple times over a period of several days – just in case our eyes, and testing equipment were playing tricks with us.

The efficiency ratings are off the charts, with results over 93% between 600 and 900W and over 90% even at full load. These really are staggering results which we never thought we would see, not for some years anyway.

Ripple is class leading, there is no doubt about it and most of the time the rails just hold a flat line, as if its just died on the test bench. Rail stability is another of the many strong points with miniscule movement even under heavy cross loading.

When you see a KitGuru lab technican with an incredulous smile on his face as he says “Hey, this is holding at 1545W!” you realise that this is something very special indeed. It is a modern day work of art. It would have scored 10/10 but we have to leave a little room for their next unit, because as incredible as it sounds, it might be even better.

The only downside is the asking price – Scan in the UK are taking preorders and it will set you back £245 inc vat when it is released next month … which to be perfectly honest is actually a very good price for a unit which has redefined just what is possible from a high end power supply.

KitGuru says: Redefines the high end market.

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