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Cougar GX 800W 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. We set ambient temperatures to 35c in our environment to reflect warm 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
1.55
3.35
1.77
5.07
6.66
12.14
0.5
5.07
0.20 -12.02
200W
3.13
3.34
3.48
5.05
13.54
12.10
1.0
5.05
0.30 -12.03
400W
6.17
3.33
7.17
5.04
27.65
12.16
1.5
5.03
0.50 -12.06
600W 9.44 3.32 10.75 5.00 41.29 11.97 2.0 5.01 0.60 -12.08
800W
13.24
3.32
15.08
4.98
55.55
11.94
2.5
5.00
0.80 -12.10

The Cougar GX 800W passes this test, although there is a little droop on the +12v output, dropping from 12.14V to 11.94V across the full range. Not the best set of results we have seen in recent months, but not bad.

Cougar GX 800W Maximum Load
824W

The Cougar CX 800W managed to only deliver another 24W above maximum rated output before it shut down, safely.

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 3.34 1.0 5.07 60.0 11.88 0.2 -12.02 0.50 5.05
165W 15.0 3.30 18.0 4.94 2.0 12.12 0.2 -12.03 0.50 5.04

Cross loading results exhibit a few minor weaknesses. The +12V output dropped to 11.88V when hit with 60A. Likewise the +5V output dropped to 4.94A when hit with 18A.

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 20 15 20 15
200W 20 15 25 20
400W 30 20 35 25
600W 40 30 45 30
800W 50 35 55 35

Ripple suppression is quite disappointing. The +5V output peaked at 35mV which is one of the better results. +12V held well within the rated tolerances, peaking at 55mV at full load. The +3.3V hit 50mV at full load, which is the limit of industry tolerance specifications. A borderline fail, and far from the best we have seen in recent months.

Efficiency (%)
100W
81.43
200W
85.67
400W
91.33
600W
89.42
800W 88.79

The unit achieves a maximum efficiency of 91.33 percent in our tests at 50 percent load, dropping to 88.79 percent 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
29.2
200W
30.3
400W
32.7
600W
34.2
800W 37.4

The large fan is quite quiet until the last 200W of output when it spins faster to compensate for rising temperatures. Still it isn’t too intrusive, especially if you are demanding less than 600W under full load. If you need a power supply to deliver 700W or more on a regular basis, we recommend you pay a little extra for a high quality 1000W rated unit.

Temperature (c)
Intake
Exhaust
100W
37
40
200W
39
44
400W
42
47
600W
44
52
800W
47
56

The temperatures rise as the fan becomes more active. The overall cooling performance is very good.

Maximum load
Efficiency
824W
87.95%

For those interested, we measured efficiency when stressing the unit to breaking point. 87.95% at 824 watts. Not realistic at all, but an interesting closing point.

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