XFX Pro Series 750W Power Supply Review

1. Introduction2. The XFX Pro Series 750W Power Supply (Bundle)3. The XFX Pro Series 750W Power Supply (External)4. The XFX Pro Series 750W Power Supply (Internal)5. Testing Methodology and Results6. Closing Thoughts7. 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
• 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
75W	1.22	3.35	1.19	5.05	4.90	12.13	0.50	5.06	0.20	-12.11
150W	2.18	3.35	2.80	5.04	10.00	12.12	1.00	5.05	0.30	-12.10
375W	6.15	3.33	6.00	5.04	26.10	12.08	1.50	5.04	0.50	-12.08
565W	10.30	3.32	10.87	5.03	38.34	12.06	2.00	5.02	0.60	-12.06
750W	10.74	3.31	13.86	5.00	53.51	12.02	3.00	4.99	0.80	-12.01

A very good set of results for the XFX Pro Series 650W, all of the primary rails are holding within 2.5% of the nominal voltage.

XFX Pro Series 750W	Maximum Load
	812.7W

We managed to push 812.7W out of the Power supply before it shut down, gracefully. The protection circuitry performs well.

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
734W	1.0	3.34	1.0	5.04	60.0	12.04	0.2	-12.08	0.50	5.03
154W	15.0	3.31	15.0	5.00	2.0	11.99	0.2	-12.02	0.50	5.01

The XFX Pro Series 750W has no problems with our crossloading tests and even with a 60a load on the 12V output it held steady. With such a high load voltages can often fluctuate but the XFX 750W PSU performed well. This is down to the DC to DC converter design which produces +3.3V and +5V outputs from the +12 rail.

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 XFX unit complied with the ATX standard.

AC Ripple (mV p-p)
DC Load	+3.3V	+5V	+12V	5VSB
75W	5	5	5	5
150W	5	5	10	5
375W	5	5	15	10
565W	5	5	20	10
750W	10	10	25	15

Ripple results are well within the parameters set down in the ATX12V Ver 2.2 standard. +3.3V and +5V are extremely impressive and the +12V rail is also very stable, peaking at 25mv.

Efficiency (%)
75W	85.23
150W	86.74
375W	87.64
565W	84.96
750W	83.42

These efficiency results are great for a 80 Plus Bronze certified supply, hitting 87.64% at around 50% load. At full load the efficiency drops to just over 83%, which is still very impressive.

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)
75W	27.3
150W	29.4
375W	29.5
565W	33.4
750W	35.3

Our noise results are very close to the XFX Pro Series 650W PSU we reviewed last week. At around 70% load, the PSU become audible, rising to a maximum of 35.3 dBa at 100% load. It isn't the world's quietest PSU by a long shot, but at realistic load levels it should not annoy the user base.

Temperature (c)
	Intake	Exhaust
75W	35	37
150W	35	37
375W	38	43
565W	42	51
750W	45	53

The large fan pushes a lot of airflow under load which helps to keep the components in check. At around 70-80% load, the fan speeds start increasing considerably. At full load we reach a 8c above ambient intake threshold.

Maximum load	Efficiency
812.7W	80.7

Pushing the PSU above its rated limits generates an efficiency level of around 80.7%. This is not a viable ‘real world’ situation, but its interesting nonetheless.

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