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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
75W
1.25
3.37
1.20
5.07
4.97
12.17
0.50
5.05
0.20
-12.05
150W
2.15
3.35
2.85
5.05
10.04
12.14
1.00
5.03
0.30
-12.07
375W
6.14
3.33
6.03
5.04
26.12
12.11
1.50
5.02
0.50
-12.09
565W
10.33
3.31
10.84
5.03
38.31
12.08
2.00
5.01
0.60
-12.10
760W
10.78
3.30
13.91
5.01
54.02
12.05
3.00
5.00
0.80
-12.12

Regulation is excellent, with all the rails holding steady, even at full load.

Corsair AX760i Maximum Load
893W

We managed to reach around 893W before the unit would shut down gracefully, after the protection kicked in.

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
734W 1.0 3.36 1.0 5.05 60.0 12.03 0.2 -12.03 0.50 5.02
154W 15.0 3.31 15.0 5.01 2.0 12.13 0.2 -12.03 0.50 5.01

The Corsair AX760i excelled with our cross loading tests. We hit the power supply with 60A on the +12V rail and it held at 12.03v. Other rails also exhibited fantastic results.

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
75W 10 10 5 10
150W 10 10 10 10
375W 10 10 10 10
565W 15 10 20 15
760W 20 15 25 15

Ripple results are very good on all the rails, holding well within the tolerance guidelines. The 12V+ output is particularly impressive, peaking at 25 mV.

Efficiency (%)
75W
88.33
150W
90.56
375W
93.87
565W
92.22
760W
91.53

The Corsair power supply certainly doesn’t exhibit any efficiency concerns, peaking at just under 94 percent at 50 percent 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)
75W
<28.0
150W
<28.0
375W
30.3
565W
31.2
760W 32.8

The Corsair AX760i is very quiet, even at full load, peaking just below 33 dBa. At under 40%, the fan stops spinning completely, making it ideal for a low noise media center or enthusiast system build. Corsair have tuned the fan profile to be very passive indeed.

Temperature (c)
Intake
Exhaust
75W
36
42
150W
38
45
375W
39
48
565W
45
53
760W
47
59

Exhaust temperatures are excellent, reaching a maximum delta of 12c above intake at full load. Corsair have tuned this unit to spin the fan slowly, even when fully loaded.

Maximum load
Efficiency
893W
87.4

For those interested, we measured efficiency when stressing the unit to breaking point. 87.4 percent efficiency at 893W … hardly practical, but interesting regardless.

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