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Corsair Professional Series AX760i and AX860i 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. Due to public requests we have changed our temperature settings recently – previously we rated with ambient temperatures at 25C, we have increased ambient temperatures by 10c (to 35c) in our environment to greater reflect warmer internal chassis conditions.

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
1.56
3.39
1.78
5.07
6.67
12.18
0.50
5.07
0.20 -12.01
225W
3.73
3.37
3.87
5.05
15.59
12.14
1.00
5.06
0.20 -12.03
450W
7.52
3.35
8.36
5.04
30.77
12.12
1.50
5.04
0.30 -12.07
675W 11.31 3.34 12.37 5.03 47.48 12.07 2.00 5.04 0.50 -12.09
860W
1.60
3.32
1.16
5.02
65.00
12.03
0.50
5.02
0.20 -12.13

No concerns with the load regulation, holding well across all output stages.

Corsair AX860i Maximum Load
997W

We managed to get the PSU to achieve 997W before it would shut down, delivering around 137W more than rated specifications.

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 3.37 1.0 5.07 60.0 12.05 0.2 -12.04 0.50 5.04
165W 15.0 3.33 18.0 5.02 2.0 12.16 0.2 -12.05 0.50 5.03

The Corsair AX860i exhibited no problems when dealing with our intensive Cross Loading test. It was tasked with 60A on the +12V rail and it held at 12.05V. The other rails delivered good results also.

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 unit complied with the ATX standard.

AC Ripple (mV p-p)
DC Load +3.3V +5V +12V 5VSB
100W 5 5 10 5
225W 5 10 10 10
450W 10 10 15 10
675W 15 15 20 15
860W 20 20 25 15

Noise suppression results are yet again excellent, peaking at 25mV on the +12V rail when under full load. The other rails fell between 5mV and 20mV across the full range of loads. Well within industry tolerance specifications.

Efficiency (%)
100W
88.87
225W
90.77
450W
93.89
675W
92.44
860W 91.61

Efficiency is excellent, peaking at almost 94 percent at 50 percent load. Efficiency falls down to around 91.5% at full load.

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 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 Refrigerator
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
<28.0
225W
<28.0
450W
30.5
675W
32.4
860W 33.2

The fan is disabled at the lower power levels, below 40%, making the AX760i and AX860i ideal for quiet running systems such as a high powered media center.

Under 400W translated to a silent experience, and the fan only started to speed up shortly afterwards. At 650W, the fan was clearly audible, although never intrusive. Great all round results for the AX860i.

Temperature (c)
Intake
Exhaust
100W
37
43
225W
38
46
450W
43
54
675W
46
56
860W
48
61

Exhaust temperatures are good, especially considering the low spinning fan which never generates much noise at all, even under full load. The AX860i rises to a maximum 13c above ambient threshold at full load.

Maximum load
Efficiency
997 watts
87.78

At 977 watts, the efficiency level measures 87.78%. Not a practical situation to be running 24/7, but worth noting.

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