Corsair AX1200 1200W Power Supply Review

paulktreg - 2010-06-10 13:35:19 in Power Supplies
Category: Power Supplies
Reviewed by: paulktreg   
Reviewed on: July 7, 2010
Price: $329.99

Introduction:

Why is the word 'overkill' used so regularly on the forums, with regards to power supply selection? It's a word that could, at times, be equally applied to motherboard, memory and processor selection, so why isn't it? I'll tell you why - because this a site for PC enthusiasts who like to have the latest, the best and most powerful hardware, even if they don't always push it to its full potential. Why are power supplies so different? If a member asks for advice on which power supply will be sufficient to run their proposed new build then give it - although people's opinions will vary. If a member ask for opinions on the best 1200W power supply then give it, but don't go telling them they don't need that much power and they could save some money by going for a 500W unit, because it's not what was asked and it irks some people. It's the member's money at the end of the day and if they want a 1200W power supply for no other reason than because they can, then that's fine by me - that's what enthusiasts do sometimes. A 1200W power supply for a 400W rig brings the added benefits of a stress free, cool running and quiet power supply with a certain level of future proofing, though who knows what's on the horizon? Fit two GTX480 graphics cards in SLI and the 1200W power supply is not overkill in my opinion, but is instead the sensible option - especially if over clocking is your forte.

It'll be no surprise then, that this time around I will be having a look at a 1200W power supply from Corsair. Corsair have been a leading supplier of high-speed memory modules since 1994 and today offer a top quality line of power supplies alongside a wide range of memory products, solid state hard drives and PC enclosures for the mainstream and enthusiast PC market. The AX1200 is Corsair's current flagship power supply, boasting 1200W output and 80 Plus gold efficiency. The AX1200 was designed exclusively by Corsair and you won't find the board used anywhere else - would you release a board whose design brief was to be the best 1200W power supply in the world? Let's put the AX1200 through its paces and see if it can live up to its claims.

 

Closer Look:

The top cover of the box carries a photograph of the modular cable connector panel on the power supply along with model number, main feature list and in the top corner a professional series gold notice. Technical information is given on the back of the box which includes connector types (with photographs) and quantities, specification table, efficiency and fan noise level graphs and a brief description of some of the power supplies features in several different languages.

 

 

 

 

 

 

 

 

 

 

Both side panels carry the model number along with some of the main features in five different languages.

 

 

The box side again gives the model number and photograph of the fan grill. The opposite face carries the exact same image.

 

Not much to see here, a plain brown cardboard box within the box.

 

Lift the lid and the modular cable bag is neatly tucked down the side of the foam protected power supply. The power supply is enclosed in black felt draw string bag for further protection.

 

 

Bag enclosed power supply along with the full box contents, large modular cable box, power cord, user manual, cable ties and power supply fixing screws.

 

 

The Corsair AX1200 power supply is very well packaged with an adequate set of accessories. It is after all, a 'Professional Series' power supply, so you should expect extras, should'nt you? No problems so far, so let's move on and take a closer look at the power supply.

Closer Look:

The Corsair AX1200 power supply is finished off with a coat of very lightly textured matt black paint. This is the way a power supply should look in my opinion and it does a great job of hiding finger prints and provides a certain level of scratch resistance.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The rear of the power supply shows a fairly standard hexagonal-holed exhaust grill along with a standard 13A IEC mains input connector alongside the mains on/off switch. There is nothing worse than routing about at the back of your PC trying to find the switch - large rocker switches are much easier to find, don’t you think? The Corsair AX1200 power supply is fully modular and as you will see in the photograph it requires a lot of modular cable connectors. The circular silver sticker is interesting. The patent number referred to is the property of Ultra Products, who were the first to introduce the fully modular power supply.

 

 

The side panels carry the same label, although it is inverted on the opposite face, presumably so the label is the right way up depending on the power supply orientation/case mounting position.

 

The top of the power supply carries a comprehensive specification label and on the bottom face is the large 140mm cooling fan with the Corsair logo at its centre.

 

 

The modular cable set is large; it has to be to accommodate all the connectors available on this power supply. The motherboard, ATX12V/EPS12V and PCI-E cables are all braided and the peripheral, SATA and floppy disk adapter cables are of the usual Corsair flat black cable design.

 

 

The 140mm cooling fan is a Yate Loon model D14BH-12 rated at 12V 0.7A. What was immediately obvious when the lid was lifted, is that the Corsair AX1200 isn’t your run-of-the-mill power supply. The printed circuit board design, although obviously still a switched mode unit, is quite different from other power supplies I have looked at in the past. The AX1200 employs DC-DC convertors for the 3V3, 5V0 and unusually the +12V rail, no doubt in an effort to drive up the efficiency levels.

 

 

The first photograph shows the modular cable connector panel at the rear. Note the very heavy cables used for the 0V return - the lower the voltage drops the greater the efficiency. The board immediately in front of the 0V return cables is the DC-DC convertor for the +12V rail. Either end of that board are the 3V3 and 5V0 DC-DC convertors, all vertically mounted. The next photograph shows the primary side of the power supply, with the transient filtering stage, power factor correction, mains rectification, smoothing capacitors and heat sinks for amongst other things, the switching transistors.

 

 

The board mounted vertically down the right-hand side of the power supply in the first photograph provides the +5VSB supply and fan speed control. There is a board sandwiched between the +5VSB board and one of the DC-DC convertor boards and the white multiway connector on top, that I believe is responsible for rail protection, over voltage, over current, and so on.

 

 

The Corsair AX1200 power supply comes well packaged with excellent build quality and some novel design features, but how well will it perform? Let’s move on and find out.

Specification:

 

Review Sample: Corsair AX1200 1200W Power Supply, Part Number CMPSU-1200AX.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ratings Table:

Corsair AX1200 1200W (CMPSU-1200AX) Power Supply Specification Table
AC Input
90-264V     15A     50-60Hz
DC Output
+3V3
+5V
+12V
-12V
+5VSB
Maximum Load
30A
30A
100.4A
0.8A
3.5A
Maximum Combined
Wattage
180W
1204.8W
9.6W
17.5W
1204.8W

 

System Protection:

No specific figures are available, so the following sentence is taken from the user manual.

Over-current and over-voltage protection, under-voltage protection, and short circuit protection provide maximum safety to your critical system components.

 

Safety & Agency Approvals:

The safety and agency approvals are quite often listed somewhere in the user manual but not this time - the following agency approval icons are printed on the packaging and/or power supply specification label.

UL, TUV, CE, C Tick, CCC, FCC & RoHS.

 

Power Supply Physical Characteristics:

Corsair AX1200 1200W (CMPSU-1200AX) Power Supply Physical Characteristics
Weight
Length
Width
Height
5.5lbs/2.5kg
7.9"/200mm
5.9"/150mm
3.4"/87mm

 

Power Supply Connectors:

Corsair AX1200 1200W (CMPSU-1200AX) Power Supply Connectors
Connector Type
Qty
Motherboard 20+4 Pin
1
ATX12V/EPS12V 4+4 Pin
2
PCI-E 6+2 Pin
6
SATA Power 15 Pin
16
Peripheral 4 Pin
12
FDD 4 Pin
2

 

Power Supply Cable Lengths:

Corsair AX1200 1200W (CMPSU-1200AX) Power Supply Cable Set
Cable Type
Cable Length/Connector Spacings
Qty
Modular
PSU > 24" > Motherboard 20+4 Pin
1
Modular
PSU > 24" > ATX12V/EPS12V 4+4 Pin
2
Modular
PSU > 24" > PCI-E 6+2 Pin
6
Modular
PSU > 18" > SATA > 4" > SATA > 4" > SATA > 4" > SATA
3
Modular
PSU > 16" > SATA > 4" > SATA
2
Modular
PSU > 18" > Peripheral > 4" > Peripheral > 4" > Peripheral > 4" > Peripheral
3
Adapter
Peripheral > 4" > FDD
2

 

Key Features:

All the following information is taken from the user manual, box packaging and reviewers guide. Lots of information provided, most of which I feel duty bound to pass on!

The Corsair Professional Series Gold AX1200 PSU has been designed from the ground up by Corsair to be the highest performing and most technologically advanced 1200W power supply on the market.

Built using server grade power train architecture, designed for mission critical levels of reliability, the Professional Series AX1200 delivers previously unheard of levels of performance for demanding enthusiasts and gamers.

Combined with exceptionally high energy efficiency, achieving 80 Plus gold certification, a fully modular cable system, and an advanced PCB and cooling design, the AX1200 is also one of the most efficient and quietest power supplies available.

 

Overview of Key Features:

Unique Design, Exclusive to Corsair

The AX1200 has been designed from the ground up by Corsair's power engineering team, and is therefore unique and exclusive to Corsair. It has been designed for one purpose - to be the world's best ATX 1200W power supply.

100.4 Amp Single +12V Rail

The AX1200's massive 100.4 Amp (1204.8W) Single 12V rail makes it the ideal power supply for ultra-high end SLI and Crossfire gaming PCs based around multi-core CPUs.

80 Plus GOLD Efficiency

The sophisticated electrical design, incorporating advanced magnetic modelling 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.

Server Grade Architecture for Outstanding Noise/Ripple and DC Voltage Regulation

The AX1200 features technology previously unheard of in a consumer power supply. Such features include individual DC-DC regulation for 3V3, 5V and 12V rails, and secondary side synchronous rectification, utilizing MOSFETs that have lower losses than the conventional output rectification schemes that utilize Schottky diodes. Plus, the 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 use only those cables that you need, reducing cable clutter and maximising the cooling performance of your PC.

 

Corsair AX1200 Summary of Advantages:

 

Extended Feature List:

The performance had better be good after all that!

Testing:

For more information on how we test our power supplies, please browse our testing methodology.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Electrical Safety:

 

Electrical Safety Test Class 1
Manufacturer/Model
Pass/Fail
Corsair AX1200
Pass

 

Short Circuit Protection:

I short circuited the 3V3, 5V0 and the 12V rail in turn. The power supply did shut down, and once the short was removed and the unit switched off for at least one second, resumed normal operation. Although listed here at the beginning of the testing section, I tend to leave this test until the very end, in case it doesn't quite go to plan.

 

DC Output Voltage Load Regulation:

 

Mains Input Voltage 110VAC

 

 

Corsair AX1200 1200W (CMPSU-1200AX) DC Output Voltage Load Regulation
Supply = 110Vac/50Hz
PSU DC Rail
Measured Voltage(V)
3V3
3.40
5V0
5.08
+12V
12.20
-12V
12.22
5VSB
5.08
Total PSU DC Loading = 0W (0% of Rated Maximum Output Power)

 

Corsair AX1200 1200W (CMPSU-1200AX) DC Output Voltage Load Regulation
Supply = 110Vac/50Hz
PSU
DC Rail
Rail Loading Amps (A)
Rail Loading Watts (W)
Measured Voltage (V)
ATX12V V2.2 Limits (V)
Pass/Fail
+3V3
3.18
10.78
3.39
3.135 – 3.465
Pass
+5V
4.73
23.93
5.06
4.75 – 5.25
Pass
+12V
15.78
192.20
12.18
11.4 – 12.6
Pass
-12V
0.37
4.51
12.20
10.8 – 13.2
Pass
+5VSB
2.08
10.30
4.95
4.75 – 5.25
Pass
Total PSU DC Loading = 241W (20% of Rated Maximum Output Power)

 

Corsair AX1200 1200W (CMPSU-1200AX) DC Output Voltage Load Regulation
Supply = 110Vac/50Hz
PSU
DC Rail
Rail Loading Amps (A)
Rail Loading Watts (W)
Measured Voltage (V)
ATX12V V2.2 Limits (V)
Pass/Fail
+3V3
3.18
10.78
3.39
3.135 – 3.465
Pass
+5V
4.71
23.83
5.06
4.75 – 5.25
Pass
+12V
46.22
562.96
12.18
11.4 – 12.6
Pass
-12V
0.37
4.52
12.21
10.8 – 13.2
Pass
+5VSB
2.03
10.05
4.95
4.75 – 5.25
Pass
Total PSU DC Loading = 612W (51% of Rated Maximum Output Power)

 

Corsair AX1200 1200W (CMPSU-1200AX) DC Output Voltage Load Regulation
Supply = 110Vac/50Hz
PSU
DC Rail
Rail Loading Amps (A)
Rail Loading Watts (W)
Measured Voltage (V)
ATX12V V2.2 Limits (V)
Pass/Fail
+3V3
8.08
27.47
3.40
3.135 – 3.465
Pass
+5V
9.42
47.67
5.06
4.75 – 5.25
Pass
+12V
89.90
1095.88
12.19
11.4 – 12.6
Pass
-12V
0.37
4.52
12.22
10.8 – 13.2
Pass
+5VSB
2.08
10.27
4.94
4.75 – 5.25
Pass
Total PSU DC Loading = 1186W (99% of Rated Maximum Output Power)

 

Mains Input Voltage 230VAC

 

 

Corsair AX1200 1200W (CMPSU-1200AX) DC Output Voltage Load Regulation
Supply = 230Vac/50Hz
PSU DC Rail
Measured Voltage(V)
3V3
3.40
5V0
5.09
+12V
12.20
-12V
12.21
5VSB
5.08
Total PSU DC Loading = 0W (0% of Rated Maximum Output Power)

 

Corsair AX1200 1200W (CMPSU-1200AX) DC Output Voltage Load Regulation
Supply = 230Vac/50Hz
PSU
DC Rail
Rail Loading Amps (A)
Rail Loading Watts (W)
Measured Voltage (V)
ATX12V V2.2 Limits (V)
Pass/Fail
+3V3
3.19
10.81
3.39
3.135 – 3.465
Pass
+5V
4.75
24.03
5.06
4.75 – 5.25
Pass
+12V
15.72
191.47
12.18
11.4 – 12.6
Pass
-12V
0.37
4.51
12.20
10.8 – 13.2
Pass
+5VSB
2.07
10.16
4.91
4.75 – 5.25
Pass
Total PSU DC Loading = 241W (20% of Rated Maximum Output Power)

 

Corsair AX1200 1200W (CMPSU-1200AX) DC Output Voltage Load Regulation
Supply = 230Vac/50Hz
PSU
DC Rail
Rail Loading Amps (A)
Rail Loading Watts (W)
Measured Voltage (V)
ATX12V V2.2 Limits (V)
Pass/Fail
+3V3
3.18
10.78
3.39
3.135 – 3.465
Pass
+5V
4.70
23.78
5.06
4.75 – 5.25
Pass
+12V
46.22
562.96
12.18
11.4 – 12.6
Pass
-12V
0.37
4.52
12.21
10.8 – 13.2
Pass
+5VSB
2.03
10.01
4.93
4.75 – 5.25
Pass
Total PSU DC Loading = 612W (51% of Rated Maximum Output Power)

 

Corsair AX1200 1200W (CMPSU-1200AX) DC Output Voltage Load Regulation
Supply = 230Vac/50Hz
PSU
DC Rail
Rail Loading Amps (A)
Rail Loading Watts (W)
Measured Voltage (V)
ATX12V V2.2 Limits (V)
Pass/Fail
+3V3
8.04
27.34
3.40
3.135 – 3.465
Pass
+5V
9.38
47.46
5.06
4.75 – 5.25
Pass
+12V
89.94
1096.37
12.19
11.4 – 12.6
Pass
-12V
0.38
4.64
12.22
10.8 – 13.2
Pass
+5VSB
2.08
10.27
4.94
4.75 – 5.25
Pass
Total PSU DC Loading = 1186W (99% of Rated Maximum Output Power)

 

Perfect! Rock solid rails that translate to virtually horizontal lines on the graphs. The Corsair AX1200 power supply is probably one of the best regulated power supplies I've tested, so let's move on and see if it can continue to produce excellent results.

Testing:

Efficiency and Power Factor:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Corsair AX1200 1200W (CMPSU-1200AX) Power Factor & Efficiency
Supply = 110Vac/50Hz
DC Load (W)
AC Load (W)
PF
Efficiency (%)
Pass/Fail
0
16
0.66
N/A
N/A
242
281
0.99
86
Pass
612
699
0.99
88
Pass
1186
1398
0.99
85
Pass

 

Corsair AX1200 1200W (CMPSU-1200AX) Power Factor & Efficiency
Supply = 230Vac/50Hz
DC Load (W)
AC Load (W)
PF
Efficiency (%)
Pass/Fail
0
16
0.23
N/A
N/A
241
278
0.93
87
Pass
612
675
0.97
91
Pass
1186
1358
0.99
87
Pass

 

The Corsair AX1200 power supply is the most efficient unit I’ve tested to date following the OCC power supply testing methodology. The 80 Plus gold standard requires efficiency levels of 87%, 90% and 87% efficiency at 20%, 50% and 100% DC loading with a power factor >0.9 at 50%. Power factor levels are fine but the efficiency levels, following the OCC testing methodology, are a little on the low side at 110Vac and just a pass at 230Vac, but for reasons I will explain later, won’t warrant a failure. The test protocol for 80 Plus certification is quite specific, not only for the overall DC load levels, 20%, 50% and 100%, but it also calls for specific loading on the DC rails which I found difficult to attain because of the nature of my test load. Expensive variable electronic loads, like the Chroma, are usually employed for this sort of testing, but because I’m using a network of fixed value wire wound resistors hitting specific rail loads, or at least getting close, it was difficult. The power supply manufacturers design and optimize their units to meet the requirements for 80 Plus, so failing a unit for the sake of a few percentage points, when I can’t quite hit the right loads, would be unfair. The Corsair AX1200 is a very efficient power supply that would I’m sure, with correctly spread DC rail loading, hit peak efficiency and meet the requirements of 80 Plus gold.

 

AC Ripple On DC Outputs:

 

I have consistently found the AC ripple levels on the DC rails to be more or less equal with a 110VAC or 230VAC mains supply. The results given below are for 230VAC only but I will continue to check the levels at 110VAC during testing and publish them below if there are any significant differences.

 

AC ripple/noise on the +3V3 rail at 230VAC

Oscilloscope settings: Amplitude = 5mv/div, Timebase = 10uS/div

 

AC ripple/noise on the +5V0 rail at 230VAC

Oscilloscope settings: Amplitude = 5mv/div, Timebase = 10uS/div

 

AC ripple/noise on the +12V rail at 230VAC

Oscilloscope settings: Amplitude = 5mv/div, Timebase = 10uS/div

 

AC ripple/noise on the -12V rail at 230VAC

Oscilloscope settings: Amplitude = 5mv/div, Timebase = 10uS/div

 

AC ripple/noise on the +5VSB rail at 230VAC

Oscilloscope settings: Amplitude = 5mv/div, Timebase = 10uS/div

 

Corsair AX1200 1200W (CMPSU-1200AX) AC Ripple/Noise
Supply = 230Vac/50Hz DC Loading = 1186W
DC Rail
+3V3
+5V0
+12V
-12V0
+5VSB
ATX12 Max (mV p-p)
50
50
120
120
50
Ripple (mV p-p)
20
20
30
25
20
Pass/Fail
Pass
Pass
Pass
Pass
Pass

 

The noise/ripple levels on the Corsair AX1200 power supply rails all fell well within the limits laid down by the ATX12V V2.2 specification. A noise level on the 12V rail of only 30mV, peak to peak, when over 1kW of energy is being drawn is really excellent. No problems here, so let’s move on.

Testing:

Temperature, Noise Levels and Fan Speeds:

I am not going to give a pass or fail in this section, as the ATX12V V2.2 does not really have any references on which to base a decision.

Temperatures are purely for information only, as there are too many variables involved when installed in a case, which, by the way, it wasn't. Ambient temperature, processor cooling efficiency and case cooling fans all play their part on the temperature of the air entering the power supply, and consequently the temperature of the air leaving it. No valid conclusions can be made from this test.

 

Corsair AX1200 1200W (CMPSU-1200AX) Temperature & Fan Speeds
Supply = 110/230Vac
DC Loading(W)
Temp In (°C)
Temp Out (°C)
Δ Temp (°C)
Fan Speed (RPM)
0
N/A
N/A
N/A
1255/1252
242/241
22.8/22.5
24.1/23,7
1.3/1.2
1267/1276
612/612
23.1/22.6
26.3/25.3
3.2/2.7
1341/1342
1186/1186
23.7/23.7
29.3/29.1
5.6/5.4
1537/1543

 

The Corsair AX1200 temperatures are kept low thanks in no small part to the high efficiency (reduced heat generation) and fan speeds which never drop below the no-load speed of approximately 1250 rpm. The fan noise is relatively quiet and shouldn’t prove too much of a problem even when it ramps up to 1500 rpm at full load.

Conclusion:

 

Price per Watt:

Power Supply Corsair AX1200 at $329.99 = $0.28/Watt (07-2010)

 

The Corsair AX1200 power supply is one of the most efficient power supplies I have tested for OCC, but it gets better. The DC output voltage load regulation was almost perfect with all the rails maintaining their voltage within a 20mV window from zero to full load, whilst keeping ripple/noise levels well within the permitted levels. The Corsair AX1200 power supply could be the best power supply in this class at the moment and it will take some beating.

If I had one complaint to make, then it's Corsairs decision to go fully modular. I won’t mark the unit down because of this, as some enthusiasts like the idea, but it’s a concept I just can’t understand or even justify. If you are going to go out and buy this power supply, then it’s pretty reasonable to assume it’s for an high-end gaming rig running one, or even two powerful graphics cards in SLI or Crossfire, is it not? Why make the 20/24 pin motherboard connector modular, when every PC uses that one, not to mention an ATX12V/EPS12V connector? Two or even four captive (6/8 pin) PCI-E cables would be another sensible option. I know connector failure is rare, but it does happen, so why not decrease the chances?

The Corsair AX1200 uses some unique design ideas to reach 80 Plus gold levels of efficiency, like zero voltage and zero current switching, rectification using MOSFET’s instead of diodes to reduce losses and a four layer printed circuit board with trace optimization. This review isn’t really the place to expand on these technologies, but for any reader that’s interested, there’s an interesting article on the Corsair website that explains them quite well.

The Corsair AX1200 comes highly recommended and I have no hesitation whatsoever in awarding it the OCC Editors' Choice award.

 

Pros:

 

Cons: