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Seasonic PRIME 1200W Platinum PSU 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
• 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
120W
0.90
3.34
0.93
5.03
8.95
12.04
0.50
5.01
0.20
-12.03
240W
1.62
3.34
1.63
5.03
18.45
12.04
1.00
5.01
0.20
-12.03
600W
3.00
3.33
3.11
5.03
46.78
12.03
1.50
5.00
0.30
-12.02
900W
4.01
3.33
4.05
5.02
70.86
12.03
2.00
5.00
0.30
-12.02
1200W
5.02
3.33
5.20
5.02
94.57
12.03
2.50
5.00
0.30
-12.01

The load regulation of the Seasonic power supply is very strong, with all the rails holding within 1% of reference levels.

Seasonic PRIME 1200W Platinum PSU Maximum Load
1345 Watts

We managed to get another 145 watts from the power supply before the protection circuitry kicked in. The supply was undamaged and it was ready to fire up again when we dropped the load to a more realistic level. It could deliver 1,300 watts for sustained periods of time, without a problem.

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
1190W 4.0 3.34 3.0 5.03 88.0 11.97 0.2 -12.03 0.50 5.02
240W 19.0 3.32 22.0 5.01 2.5 12.04 0.2 -12.01 0.50 5.01

The Seasonic PRIME 1200W Platinum PSU delivered great results without any discernible issues.

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 10 5
200W 5 5 15 5
400W 5 5 15 5
600W 5 5 20 5
800W 10 5 20 10
1000W 10 5 25 10
1200W 10 5 25 10

Ripple Suppression is excellent, peaking at 25mV on the +12V rail at full load. The +3.3V and +5V rails peak at 10mV and 5mV respectively.

Efficiency (%)
100W
89.5
200W
92.6
400W
93.7
600W
94.2
800W
93.8
1000W 92.6
1200W 91.6

The overall efficiency results are staggeringly high, peaking at 94.2% at close to 600W. This drops to 91.6% efficiency at full load, a very impressive result overall.

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 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
200W
<28.0
400W
<28.0
600W
30.4
800W 32.6
1000W 34.4
1200W 36.5

The Seasonic PRIME 1200W Platinum PSU is a quiet power supply and the fan only really becomes active once it hits around 750 watts load. Under most situations you would be hard pressed to even know it was on, especially as you are likely to be running a single case fan at the same time. The unit does not suffer from any coil whine.

Temperature (c)
Intake
Exhaust
100W
35
38
200W
36
40
400W
38
44
650W
43
50
800W
45
54
1000W 47 59
1200W 50 64

The fan doesn’t really spin much in the first 600-650 watts of power delivery. At higher demands the fan spins up to compensate for rising ambient temperatures. The overall results are very good.

Maximum load
Efficiency
1345W
90.7

Pushing the power supply above its rated limits generates an efficiency level of around 90.7%. Not a realistic situation to be running but interesting nonetheless.

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