Seasonic X-Series 850W Power Supply Review

1. Introduction2. Seasonic X-Series 850W (Bundle & Cables)3. Seasonic X-Series 850W (External)4. Seasonic X-Series 850W (Internal)5. Seasonic X-Series 850W (Super High Res Gallery)6. Testing Methodology7. 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
100W	1.56	3.35	1.77	5.04	6.65	12.08	0.50	5.06	0.20	-12.00
225W	3.73	3.34	3.85	5.02	15.58	12.05	1.00	5.04	0.20	-12.04
450W	7.52	3.33	8.34	5.00	30.77	12.02	1.50	5.03	0.30	-12.08
675W	11.31	3.31	12.33	4.99	47.47	12.00	2.00	5.00	0.50	-12.09
850W	1.50	3.30	1.16	4.98	63.51	11.99	0.50	4.99	0.20	-12.11

No concerns with the load regulation, holding well across all output stages.

Seasonic X-Series 850W	Maximum Load
	1,033W

We managed to get the PSU to achieve 1,033W before it would shut down, delivering around 183W more than rated specifications! We could almost say this is a 1,000Watt power supply in disguise.

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	3.35	1.0	5.04	60.0	12.00	0.2	-12.02	0.50	5.02
165W	15.0	3.31	18.0	4.98	2.0	12.08	0.2	-12.03	0.50	5.01

The Seasonic X-Series 850w exhibited no problems when dealing with our intensive Cross Loading test. It was tasked with 60A on the +12V rail and it held at 12.00V. The other rails delivered good 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	15	5
225W	5	10	15	10
450W	10	10	20	10
675W	15	10	25	15
850W	15	15	30	15

Noise suppression results are very good, peaking at 30mV on the +12V rail when under full load. The other rails fall between 5mV and 15mV across the full range of loads. Well within industry tolerance specifications.

Efficiency (%)
100W	84.13
225W	87.87
450W	91.88
675W	90.82
850W	88.35

Efficiency is excellent, peaking at almost 92% at 50% load. Efficiency falls down to just over 88% 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	29.3
675W	31.7
850W	33.8

The fan activity is temperature controlled, disabling if a certain threshold is maintained. Therefore a portion of the fan activity will be related directly to the ambient room temperature.

In our room we found that loads under 500W translated to an almost silent experience. The fan spins up when the load gets higher and subsequently ambient temperatures increase accordingly. Over 700W and the fan would be audible in a quiet room, although likely drowned out inside an enthusiast system configuration.

Temperature (c)
	Intake	Exhaust
100W	37	40
225W	38	43
450W	42	49
675W	45	54
850W	47	59

As we mentioned earlier there are very few heatsinks inside the Seasonic power supply, so the efficiency and fan performance is important. The temperatures are controlled well however, rising to a maximum 12c above ambient threshold at full load.

Maximum load	Efficiency
1,033 watts	83.77

At 1033 watts, the efficiency level measures 83.77%. Not a practical situation to be running 24/7, but worth noting.

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