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be quiet! Straight Power 11 1000W Power Supply Review

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 test ambient temperatures 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
• SkyTronic DSL 2 Digital Sound Level Meter (6-130dBa)
• 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
0.88
3.35
0.90
5.00
7.35
12.02
0.50
5.03
0.20
-12.02
200W
1.60
3.35
1.65
5.00
15.10
12.02
1.00
5.02
0.20
-12.02
500W
3.20
3.35
3.25
4.99
38.60
11.97
1.50
5.01
0.20
-12.01
750W
4.05
3.34
4.15
4.98
58.50
11.95
2.00
5.01
0.30
-12.02
1000W
5.45
3.33
5.50
4.96
78.09
11.92
2.50
5.01
0.30
-12.01

The load regulation of this power supply is solid, holding well within industry rated tolerance levels.

be quiet! Straight Power 11 1000W Maximum Load
1082W

We managed to get another 82W from the power supply before the protection circuitry kicked in! The supply was undamaged and it was ready to fire up again when we were a little more sensible with the load.

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
885W 2.0 3.35 2.0 5.00 72.0 11.94 0.2 -12.00 0.50 5.02
240W 20.0 3.30 24.0 4.87 2.0 12.02 0.2 -12.02 0.50 5.02

The unit survived the cross load test without any issue, although we noticed the +5V rail dropped from 5.00 to 4.87 when hit with 24A.

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 10 10 5
250W 5 10 15 5
500W 10 15 25 5
750W 10 20 35 5
1000W 10 20 40 5

Ripple suppression from this unit is fairly good, peaking at 10mV and 20mV on the +3.3V and +5V rails respectively. The maximum noise from the +12V is 40mV at full load which is well within the industry rated specifications.

Efficiency (%)
100W
88.73
250W
90.75
500W
92.21
750W
91.67
1000W
89.61

The efficiency results are excellent, peaking at 92.2% at close to 50%. This drops to around 89% efficiency at full load. Good results for an 80 Plus Gold rated unit.

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 SkyTronic DSL 2 Digital Sound Level Meter (6-130dBa) 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
<28.0
250W
<28.0
500W
29.3
750W
31.8
1000W 33.4

The be quiet! SilentWings 3 fans are spectacular fan designs and one of the best on the market. I even rate them higher than some of the Noctua fans I have tested in recent years.

The noise levels from this supply are class leading and if owning a quiet power supply is paramount to your purchase decision then the be quiet! Straight Power 11 1000W bears serious consideration. The pitch of these fans is also very unobtrusive which is clearly linked to the design of the funnel shaped fan inlets.

Temperature (c)
Intake
Exhaust
100W
35
39
250W
35
45
500W
38
53
750W
43
59
1000W
46
65

The fan profile is very unaggressive at lower load situations. At around 700 watts load we noticed it ramping up – then incrementally as the load levels continued to rise. At full load, the temperature held at 65c in our environment, which is a good result.

Maximum load
Efficiency
1082W
89.4

Pushing the PSU above its rated limits generates an efficiency level of around 89.4%. This is not a viable ‘real world’ situation, but its interesting nonetheless.

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