1. Introduction2. Bundle & Cabling3. External4. Internal5. Testing Methodology and Results6. Closing Thoughts7. View All Pages

During the height of the Covid pandemic getting hands on a quality power supply proved problematic, but in recent weeks we have seen stock levels improving in the UK. With this in mind, Seasonic sent us a newly released power supplier – the SGX-750. This is a fully modular 80 Plus Gold unit targeting a wide audience of enthusiast user.

Seasonic told us there are a range of power supplies launching at the end of February 2022- The SPX 650, SPX 750 and SPX 750 in White, along with the SGX 550, SGX 650 and SGX 750 which we review today. Seasonic confirmed that the SGX 750 we are reviewing today will be priced around £145 inc. VAT in the United Kingdom.

Seasonic SGX Overview:

• 80 PLUS® Gold efficiency
• Available power output: 750, 650 and 550 W
• FOCUS SGX- Fully modular
• Compact SFX Size @ 100 mm deep
• Ideal fit for smaller chassis
• Smart and Silent Fan Control (S3FC)
• Protection features: OPP, OVP, UVP, SCP, OCP, OTP
• 10-year warranty

The Seasonic box artwork is unlikely to set the world alight but it does at least highlight the 10 year warranty terms on the front along with the basic specifications of the unit.

The rear of the box showcases the 80 Plus Gold Efficiency along with the smart and silent fan control. There is almost mention of the Compact SFX size and the use of a 92mm FDB (Fluid Dynamic Bearing Fan).

Inside the box is some literature on the unit, along with a $50 Steam eGift offer.

The small power supply is encased inside two blocks of foam with the cables supplied in another bag. There are some cable ties included, along with a PSU mount shroud and a regional specific power cable. Our sample didn't come from the UK, but anyone buying this unit should get the right power cable.

The SGX 750 is supplied with two 6+2 pin PCIe connectors and 6 SATA connectors across 2 cables. These cables are high quality, flat ribbon style, for ease of routing.

The unit is nicely finished with a simple black and white aesthetic, making it ideal for a variety of themed builds. It is only 100mm deep making it an ideal partner for a small form factor build.

There is a 92mm fan fitted on top of the unit, with a Seasonic badge in the center behind the grill.

One side of the power supply is home to the modular bay – neatly laid out, and labelled for ease of connection during the building phase.

The other side of the unit is home to the power connector, power button, and honeycomb panel to aid with airflow.

The Seasonic SGX 750 power supply is able to deliver 62A on the +12V rail and 20A on both +3.3V and +5V rails for a total of 750W.

Seasonic supply a Hong Hua 92mm fan inside the unit. This is a FDB fan rated at 0.46A @ 12V with a maximum rotational speed of 3,500rpm.

Below - a High Resolution Gallery of the internal layout of the Power supply.

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This power supply is an inhouse Seasonic design with high grade Japanese capacitors throughout primary and secondary stages. The primary stage Japanese Capacitor is made by Rubycon, rated 105C, 420V and 440uF. There is a single heatsink which gets cooled directly from the fan above. The soldering across the board is very good throughout.

The unit is equipped with OPP, OVP, UVP, SCP, OCP and OTP protection.

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
75W	0.95	3.33	0.93	5.02	5.13	12.06	0.50	5.02	0.20	-12.01
150W	1.65	3.33	1.66	5.02	10.61	12.05	1.00	5.02	0.20	-12.02
375W	3.00	3.33	3.02	5.02	28.11	12.02	1.50	5.01	0.30	-12.01
565W	4.05	3.33	4.07	5.02	42.94	12.00	2.00	5.01	0.30	-12.02
750W	4.90	3.33	5.24	5.02	57.48	11.97	2.50	5.00	0.50	-12.02

Load regulation proves to be excellent, holding within 1%.

Seasonic SGX-750	Maximum Load
	832W

We managed to reach around 832W before the unit would shut down gracefully, after the protection kicked in. This is around 82 watts more than the rated output.

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	3.33	1.0	5.02	60.0	11.96	0.2	-12.02	0.50	5.01
154W	15.0	3.31	15.0	4.97	2.0	12.05	0.2	-12.01	0.50	5.02

The unit passes our Cross Load testing without any problems. When hit with 60 AMPS the +12V rail held at 11.96 which is a strong result. It is unlikely in a real life situation you would be doing this, but it is good to see the design is holding up extremely well under demanding situations.

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
75W	5	5	10	5
150W	5	5	10	5
375W	5	5	15	5
565W	5	5	15	5
750W	10	10	20	10

Noise suppression results are superb, peaking at 10mV on the +3.3V and +5V rail under full load. The +12V rail peaks at 20mV under full load conditions. A solid showing all round and well within industry rated tolerance levels.

Efficiency (%) 240V
75W	89.6
150W	91.4
375W	92.5
565W	91.8
750W	90.5

Efficiency is good for an 80 Plus Gold unit, peaking at around 92.5% at 50% load. At full load the power supply maintains an 90.5% efficiency level, which is 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 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)
75W	<28.0
150W	<28.0
375W	30.5
565W	31.7
750W	33.5

The fan in this unit is very quiet under most load conditions, and it is only in the last 10% of power deliver that the fan spins up becoming audible. Generally this unit is very quiet under normal load conditions.

Temperature (c)
	Intake	Exhaust
75W	36	39
150W	38	42
375W	39	48
565W	45	55
750W	47	58

The fan works well to expel heat out the rear of the chassis. These are a solid set of results.

Maximum load	Efficiency
843W	90.2

At 832 watts, the efficiency level measures 90.2%. Not a practical situation to be running 24/7, but worth noting.

Seasonic have been releasing award winning power supplies now for as long as we can remember, and their latest SGX-750 modular power supply scored very highly in our test results during the review process.

This is a fully modular unit, designed with a small physical footprint (100mm deep) to ensure maximum compatibility with small form factor chassis. As we would expect from Seasonic, the outer chassis is finished to a very high level and the neutral colour scheme will appeal to enthusiast users focusing on a themed build.

Technically the SGX-750 succeeded in a clean set of test results. Ripple suppression was well within industry tolerance levels at full load. Load Regulation was stellar, and the unit passed the intensive cross load procedures without any issues.

Internally the design is clean and soldering quality is excellent throughout. The use of high grade 105C capacitors in the primary stage show that corners have not been cut to save a few dollars. In reality the unit was able to hold a 800 watt+ load for extended periods of time without issue.

While we have no etailers showing this unit for sale as we go to press – however stock is said to be available by the end of February. Seasonic have told us that the SGX-750 is set to be priced at £145 inc vat when it hits the UK market with a 10 year warranty in place to give peace of mind.

Discuss on our Facebook page HERE.

Pros:

• Fully modular.
• Small form factor ideal for SFX builds.
• high build quality.
• quiet under normal load conditions.
• 105C Japanese capacitor.
• 10 year warranty.

Cons:

• It is quite expensive.

KitGuru says: Another quality power supply from Seasonic. It passed all our tests with flying colours and should be top of your list if you are looking for a low noise, fully modular power supply for a small form factor SFX build.

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