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Cooler Master Silent Pro Hybrid 850W 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. 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

12V output is combined for our testing.

DC Output Load Regulation

Combined

DC Load

+3.3V
+5V
+12V
+5VSB
-12V
A
V
A
V
A
V
A
V
A V
100W
1.50
3.37
1.77
5.09
6.65
12.21
0.50
5.09
0.20 -12.19
225W
3.76
3.35
3.80
5.05
15.55
12.18
1.00
5.05
0.20 -12.17
450W
7.50
3.33
8.33
5.02
30.79
12.11
1.50
5.02
0.30 -12.12
675W 11.30 3.32 12.31 4.96 47.52 12.05 2.00 5.00 0.50 -12.09
850W
1.47
3.28
1.15
4.88
63.49
12.01
0.50
4.95
0.20 -12.03

The supply produces decent load regulation across the +12V output. The +5V output drops to 4.88 at full load however, which is not ideal.

Cooler Master Silent Pro Hybrid 850W Maximum Load
911W

We managed to get the PSU to achieve 912W before it would shut down, delivering around 61W more than the 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 5.09 60.0 11.99 0.2 -12.06 0.50 5.05
165W 15.0 3.27 18.0 4.86 2.0 12.18 0.2 -12.03 0.50 5.03

The power supply passed the cross load tests, although their was a noticeable variable from the +5V output, dropping 0.23 when loaded 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 5 5 15 5
225W 10 10 20 10
450W 10 10 30 10
675W 10 10 35 10
850W 15 15 45 15

Ripple results are extremely impressive across all output with the +3.3V and +5V output peaking at only 15 mV. The +12 output peaks at 45 mV at 100% load. These results are very good.

Efficiency (%)
100W
87.33
225W
89.21
450W
91.77
675W
90.45
850W 89.10

The efficiency of the power supply is very good, hitting almost 92 percent at 50 percent load, dropping back to 89 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 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
29.0
225W
31.4
450W
32.1
675W
34.2
850W 35.3

The power supply is silent at 100W-150W, and when the fan kicks in this rises to an average emission around 32 dBa under general use. This translates to a power supply which is inaudible between 10% and 60% load. When loaded with 650W+ the fan spins up to compensate for rising temperatures. The noise levels peak at 35.3 dBa at full load which is clearly audible.

That said, the user could balance the noise levels manually via the supplied controller, but we really don’t recommend anything but a very minor ‘tweak’ to slightly lower fan noise if you are loading the power supply at 600W or more when gaming.

Temperature (c)
Intake
Exhaust
100W
35
39
225W
37
43
450W
42
49
675W
43
53
850W
47
57

The large fan performs reasonably well, peaking at a maximum 10c above ambient threshold at full load.

Maximum load
Efficiency
911W
87.5%

At 911w, the efficiency level is still strong, measuring 87.5%. Not a practical situation to be running 24/7, but worth noting.

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