Seasonic X-Series 1250W Power Supply Review

1. Introduction2. Seasonic X-Series 1250W (Bundle & Cables)3. Seasonic X-Series 1250W (External) 4. Seasonic X-Series 1250W (Internal)5. Seasonic X-Series 1250W (Super High Gallery)6. Testing Methodology & Results7. Closing Thoughts8. View All Pages

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

DC Output Load Regulation
Combined DC Load	+3.3V		+5V		+12V		+5VSB		-12V
	A	V	A	V	A	V	A	V	A	V
330W	5.52	3.38	5.51	5.04	21.26	12.20	0.87	5.02	0.20	-12.06
620W	11.01	3.36	11.02	5.03	42.51	12.14	1.75	5.00	0.40	-12.09
918W	16.51	3.34	16.52	5.01	63.72	12.13	2.60	4.99	0.60	-12.13
1249W	9.00	3.30	9.37	5.00	96.00	12.07	3.45	4.98	0.80	-12.14

Seasonic X-Series 1250W	Maximum Load
	1346W

We managed to squeeze 1346W out of the unit before it would shut down gracefully.

Cross Load Testing	+3.3V		+5V		+12V		-12V		+5VSB
	A	V	A	V	A	V	A	V	A	V
1190W	1.0	3.34	1.0	5.03	95.0	11.93	0.05	-12.12	0.05	5.01
195W	22.0	3.31	22.0	5.00	1.0	12.14	0.05	-12.11	0.05	5.00

An excellent set of results, highlighting that the design can handle dramatic load changes without any concerns at all. There is a slight dip when quickly loaded with 95A on the +12V, but it isn’t anything which would cause a problem.

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
330W	10	15	15	15
620W	15	20	25	15
918W	15	25	30	20
1249W	15	25	45	20

As we had hoped from the Seasonic design, noise suppression is very good, with the 12v output peaking at 45 mV at full load. All are well within industry tolerance guidelines.

Efficiency (%)
330W	89.47
620W	91.94
918W	90.47
1204W	89.78

Efficiency results are impressive, peaking around 92% at 50 percent load. This falls to just below 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)
330W	28.0
620W	28.0
918W	30.5
1249W	33.8

Accurately reading noise emissions below 28 dBa is difficult without strict laboratory conditions. The unit rated right at the limits of our testing equipment at 28 dBa when at 50 percent load or less. When it is primed to around 900W it becomes audible. These results are very similar when compared against the Protechnic Magic MGA13512YF inside the XFX Pro 1250W Black Edition power supply.

Temperature (c)
	Intake	Exhaust
330W	37	40
620W	39	44
918W	44	52
1249W	47	57

Thanks to the high levels of efficiency, the exhaust temperatures are really good, rising to a 10c above ambient under full load.

Maximum load	Efficiency
1346W	87.79%

For those interested, we measured the efficiency when stressing the unit to breaking point … around 87.79% at 1346W.

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