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Corsair AX850 Power Supply Review

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 23c 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
100W
1.58
3.35
1.77
5.02
6.64
12.18
0.50
5.00
0.20 -12.15
225W
3.70
3.34
3.83
5.02
15.55
12.17
1.00
5.01
0.20 -12.17
450W
7.50
3.34
8.37
5.01
30.68
12.16
1.50
5.01
0.30 -12.18
675W 11.30 3.34 12.39 5.01 47.46 12.12 2.00 5.00 0.50 -12.18
850W
1.29
3.33
1.10
5.00
71.03
12.11
0.50
5.00
0.20 -12.20

The AX850 deliverd excellent load regulation on all output channels across a wide range of loads. These are exceptional results and the +3.3V and 5V rails remained firmly within +/-2% of the nominal voltage instead of the recommended +/-5% and the +12V rail held within +/- 1%, even when it was forced to deliver over 70 Amps. Massively impressive results indeed.

Corsair AX850 Maximum Load
1045W

We managed to force the PSU to 1045W before it turned off which is almost 200W more than the rating. It was able to run at 1045W for quite some time before shutting down safely. We are again very happy to report that the overcircuit protection system is working perfectly as the unit didn't fizzle and die it just shut down and waited until we acted more sensibly with our testing equipment.

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
760W 1.0 3.32 1.0 5.06 65.0 12.01 0.2 -12.18 0.50 5.02
165W 15.0 3.29 18.0 5.03 2.0 12.02 0.2 -12.15 0.50 5.01

Once again the Corsair AX850 does not fail to deliver the goods with very little fluctuation when cross loaded.

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
100W 5 10 10 5
225W 10 10 10 10
450W 10 10 15 10
675W 15 20 20 15
850W 15 20 20 15

The AX850 ripple results are just as impressive as the AX1200 model, in fact we noticed slightly lower (5mV) on the +12V and 5VSB readout. Once again Corsair seem to have nailed this perfectly as we know from previous experience that the older TX850 was registering around 90 mv on the 12V reading.

Efficiency (%)
100W
90.12
225W
90.33
450W
92.28
675W
91.74
850W 90.26

While efficiency is not quite as high as the AX1200, it is still reading over 90% throughout the entire range of readings which easily puts this into the upper echelons of efficiency performance on the market. Remember Gold Certification requires a 87% efficiency rating at 100% load. 3.26% higher based on our testing which is exceptional.

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)
100W
0
225W
17.3
450W
23.2
675W
28.7
850W 34.8

Another strong set of results with the unit only becoming audible over 80-85% load. Standard case fans are likely to even drown this out. The San Ace 120 really is an exceptional fan.

Exhaust Temperature (c)
100W
23.9
225W
27.3
450W
29.8
675W
32.3
850W 35.9

Exhaust temperatures were what we expected after using the PSU for several days before testing, very cool indeed. The high efficency rating helps this unit to run really cool internally and this is reflected by the air being expelled. Once again, excellent results.

Maximum load
Efficiency
1045W
86.1%

For those interested, we measured efficiency when stressing the unit to breaking point. Over 86% at 1045W, higher than some units rated to over 1000W.

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24 comments

  1. These Corsair PSUs really are leading the way. Nice temperature results too. I used to read reviews with PSUs outputting over 50c.

  2. that is great. the pricing is good too £90 less than the 1200W.

  3. Corsair really do deliver such great products. this is an ideal next purchase for a buddy of mine who is building a high spec gaming rig with a GTX480 in it.

  4. Excellent review, seems to be a killer product all round. Price isnt bad considering. I know PCpower used to charge 300 quid for their 1200W and over 200 for a 850/900w

  5. Man this site is active, every day one or two reviews on it !

  6. The fan in that seems pretty much the best you could use. great job by Corsair and they deserve to be getting a good rep in this market. Box art is brilliant.!

  7. Well this is sweet. bit more than I like to pay, I got an enermax last year for 100, still working great 🙂

  8. Im really glad this unit came out. the AX1200 was a great showcase of technical ability, but it was so expensive, I think only people who have dual GTX480s would buy it.

    This seems much more valid for todays market, and while its 150, its ‘affordable’, If you think about it, this should last 3 years easy even with new hardware, so its a long term investment. I wish a video card I would buy now for 150 would still be a good option in 3 years..

  9. Yeah, always stuns me when people build a great gaming system then buy a no name 800w brand for 35 quid in their local store. Then bitch when the system crashes every 5 minutes.

  10. This is my next PSU, without question. should last me to 2014 🙂

  11. Gimmie some sugar

    Brilliant review. cross loading results are superb.

  12. Been waiting on this one for a bit now 🙂 hasnt disappointed.

  13. I need a new PSU, but do you think they will release one at £80 🙂 ?

  14. Excellent, most excellent. Now I just need to rob a bank.

  15. These designs are so efficient and its really setting them apart. Enermax should have an answer soon however.

  16. Corsair are having such a great year. them and MSI seem top of the field.

  17. 150 is out of my price point. normally. I might try and make an exception this time, funds permitting. I need something I can rely on to last me for years also

  18. Another kick ass product from the Corsair group. They really are pumping them out lately. efficiency is great.

  19. over 90 percent efficiency is impressive shit. Would save quite a bit of money with this over the year, Once I convince my wife that is why I need it however,

  20. Another top review KG. I think this is going to sell very well for corsair. I hope they bring out a 650W model and can get it under £100

  21. Seems this range is breaking all records in the PSU industry. How many more models are they going to make, or is it just two ?

  22. Excellent product from a company who seem to be really putting a lot of resources into delivering the best possible units to market.

  23. Very impressive testing results. much better value than the 1200 unit in the same family

  24. The hybrid fan feature is great as it should mean the psu fan stays silent when you’re not gaming or folding or something like that. More psus should do this!