BitFenix Whisper M Series 850W PSU Review

1. Introduction2. Bundle and Cables3. External4. Internal5. Methodology and Testing6. Closing Thoughts7. View All Pages

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 run at 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

We test in a single +12V configuration.

DC Output Load Regulation
Combined DC Load	+3.3V		+5V		+12V		+5VSB		-12V
	A	V	A	V	A	V	A	V	A	V
85W	0.87	3.37	0.88	5.07	6.05	12.00	0.50	5.00	0.20	-12.03
170W	1.61	3.35	1.64	5.05	12.40	12.00	1.00	5.01	0.20	-12.02
425W	3.18	3.33	3.15	5.02	32.40	11.98	1.50	5.01	0.20	-12.03
638W	4.00	3.30	4.04	4.98	48.94	11.95	2.00	5.01	0.30	-12.03
850W	5.00	3.34	5.20	5.05	65.68	11.92	2.50	5.01	0.30	-12.03

Load regulation is superb with all rails exhibiting very minor fluctuation under load.

BitFenix Whisper M Series 850W	Maximum Load
	875W

We managed to get the power supply to deliver 875W before it would shut down, delivering around 25W 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	11.93	0.2	-12.03	0.50	5.01
165W	15.0	3.30	18.0	4.98	2.0	12.02	0.2	-12.02	0.50	5.00

The power supply exhibited some fluctuation dealing with our intensive Cross Loading test. It was tasked with 60A on the +12V rail and it held at 11.93V. The other rails delivered excellent 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	5	10
225W	5	5	15	10
450W	5	5	15	15
675W	5	10	20	15
850W	10	10	25	20

Noise suppression results are surprisingly good, hitting 10mV on both the +3.3V and +5V rails. The +12V rail peaks at 25mV under full load conditions. Great results really overall.

Efficiency (%)
100W	90.87
225W	91.45
450W	92.21
675W	91.37
850W	89.88

Efficiency is extremely impressive, peaking at 92 percent at 50 percent load. This drops to around 90 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	<28.0
225W	<28.0
450W	29.2
675W	35.3
850W	39.1

The large fan spins relatively slowly under most load conditions, it is only in the last 250 watts of rated power output that it spins up and can be audible. It is a little louder than many 850 watt supplies we have tested within the last year, so if you are hyper sensitive to noise then we would recommend you look elsewhere.

Temperature (c)
	Intake	Exhaust
100W	37	39
225W	38	42
450W	40	44
675W	45	52
850W	47	58

The high levels of efficiency of this unit help reduce expelled heat. At full load we measured a +11c variable.

Maximum load	Efficiency
875 watts	89.5

At 945 watts, the efficiency level measures 89.5%. Not a practical situation to be running 24/7, but worth noting.

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