In the world of PC enthusiasts, Lian Li is a name synonymous with top-quality aluminum cases. The company introduced their first PC cases back in the 90’s, when PCs still were a rare find in living rooms. Their minimalistic designs and all-aluminum constructs were a jewel at the time of crude steel cases with beige plastic faceplates. Lian Li today is one of the most reputable case designers and manufacturers on the planet.

Introduction

For decades, Lian Li stood almost completely focuses on the design and manufacturing of top-tier PC cases. A few years ago, it entered the market with SFX-L power supplies, but the demand wasn't quite there. It was not until last year that the company took a significant step towards diversification with the introduction of all-in-one liquid cooling solutions. Apparently, the company found that diversification attempt successful and they are taking yet another step this year, with the introduction of a new SFX power supply this time around.

In today’s review, we are having a look at the SP750, Lian Li’s first-ever SFX PSU that rated at 750 W with an 80 Plus Gold certification. Lian Li certainly takes a peculiar diversification approach here, as their new PSU is not a regular-sized power supply, but an SFX unit, and one with a very high-power output to boot. This is a PSU for compact high-power gaming systems, quite possibly designed to match Lian Li’s own small case designs.

Packaging and Bundle

We received the Lian Li SP750 in a cardboard box that is typical for consumer power supplies. There is nothing special about the box but it does provide enough protection to the unit for shipping. The aesthetic design also is relatively simple, with colored edges and based on a picture of the unit itself. It is apparent that Lian Li placed just as much effort as it was needed to create a proper modern packaging and no more than that.

Inside the box, we found a minimalistic bundle, even as far as a PSU is concerned. Aside from a gratitude card, and a very simple user’s manual, Lian Li only included the four black mounting screws. There are no cable ties or any other accessories accompanying this unit.

The Lian Li SP750 is a fully modular PSU and every cable can be detached, including the 24-pin ATX cable. All of the connectors and wires are black. The 24-pin ATX, the EPS, and the PCI Express cables are all individually sleeved as well, but the SATA and Molex connector cables are not. It is obvious that the cables are quite a bit shorter than regular ATX PSU cables, which is reasonable for an SFX power supply. This is a realistic choice considering that the PSU may be installed in very confined spaces where every millimeter counts but could become an issue for users wanting to use the PSU with a regular ATX case. What is strange here is the presence of three PCI Express connectors, because the SP750 clearly has the power output for two middle-range graphics cards but the lack of a fourth connector deprives users from that choice. The cables are supplied in a simple but effective storage pouch.

The Lian Li SP750 750W SFX PSU

External Appearance

Perhaps the greatest feature of the Lian Li SP750 is its size – the company managed to get that high a power output out of a standard 125 × 63.5 × 100 mm / 4.92 × 2.5 × 3.94 in (W×H×D) SFX form factor design, making the PSU compatible with virtually every SFX case in the market. SFX cases designed to fit top-tier graphics cards usually can accommodate an SFX-L PSU as well, yet ensuring compatibility with any SFX-compliant case regardless of its target market definitely is a good thing.

Lian Li spent plenty of time worrying about the aesthetics of their new PSU. Parts of the chassis are brushed aluminum, with stickers covering most of the unit’s sides. A beautifully made label with the company logo can be seen right next to the cooling fan. The designer went as far as choosing screws with polished heads.

Despite the compact dimensions of the unit, the designer managed to place a small on/off switch next to the AC cable on the rear side of the PSU. The front side is densely populated with the connectors for the modular cables. The connectors are not color-coded but there is a basic legend printed on the chassis indicating what each connector is for. Besides, it is practically impossible for a user to insert a cable into the wrong connector, as each cable type has a different connector and the connectors are keyed.

Internal Design

The fan responsible for the cooling needs of the SP750 is a low-profile 92 mm product made by Yate Loon, a company whose products we frequently see in PC power supplies. There is nothing too special about this fan, as it has a simple double-bearing engine and a very high theoretical maximum speed of 3000 RPM. Double bearing fans are rare in high-quality PSUs because of their high noise output but they are extremely reliable.

The OEM behind the creation of the Lian Li SP750 is Helly Technology, a company we rarely encounter. The interior of the SP750 is densely packed, which was to be expected for an SFX design with that much power output. The filtering stage starts on the back of the AC receptacle, consisting of two Y capacitors, two X capacitors, and two filtering inductors in total. It is a simple filtering stage, which ought to be just as efficient as necessary.

There is only one bridge rectifier, on its own heatsink – if anyone can call that tiny piece of metal a heatsink. The heatsink is but a small flat piece of metal, smaller than the chip itself. Space is an issue in such a design and a larger heatsink would obstruct the installation of the switch but we have the feeling that the designer could do a little better here.

The APFC circuit is textbook, with the active components on the large heatsink across the edge of the PCB, one filtering coil, and a single capacitor. The large 400V/470μF capacitor is made by Nippon Chemi-Con, as all electrolytics in the unit are. There are two primary side inversion MOSFETs that form the heart of an LLC resonant half-bridge design.

On the secondary side, we can see the unit’s relatively huge main transformer surrounded by a thin metallic plate that acts as a heatsink for the 12V generating MOSFETs. As with all modern PSU designs, the 3.3V and 5V lines are derived via DC-to-DC conversion circuits. Most of the capacitors are polymer and are made by Beryl or, for those interested in the full name of the company, Zhao Qing Beryl Electronic Technology Ltd. Although this is the first time we have seen their products in a commercial PSU, Beryl is a reputable manufacturer, with a significant R&D division and global research collaborations on the advancement of, mainly polymer, capacitors.

Read on for our testing of this power supply.

Cold Test Results (Room Ambient Temperature)

For our power supply testing, we are using high precision electronic loads with a maximum power draw of 2700 Watts, a Rigol DS5042M 40 MHz oscilloscope, an Extech 380803 power analyzer, two high precision UNI-T UT-325 digital thermometers, an Extech HD600 SPL meter, a self-designed hotbox and various other bits and parts. For a thorough explanation of our testing methodology and more details on our equipment, please refer to our How We Test PSUs post.

The efficiency of the Lian Li SP750 is good – and it had to be, considering the very high output and its small size. The unit meets the 80Plus Gold certification limit of 90% efficiency at 20% load when powered from a 230V AC source. When powered from a 115V AC source, the low load efficiency is actually even higher, easily granting the SP750 its 80Plus Gold certification. The average efficiency of the SP750 across its nominal load range is 91.3% when powered from a 230V AC source, or 89.7% when powered from a 115V AC source.

Lian Li has the SP750 designed so as to operate without turning on its fan up to 40% load (300 Watts). To be exact, the thermal control of the PSU is tuned so as to turn on the fan when the internal temperature of the unit reaches 60°C. At a room temperature of 25°C, that would happen when the load is about 300 Watts, hence Lian Li’s specification. With our higher room temperature, the fan started earlier, with the thermal control circuit starting the fan almost exactly at an internal temperature of 60°C.

The 92 mm fan started when our load was just over 200 Watts, with relatively low noise figures for a fan this size. Its double ball bearing engine is audible just as soon as the fan starts but stays at comfortable levels unit the load reaches about 550 Watts. At higher loads, the fan will be clearly audible from a distance, yet not unexpectedly so all things considered.

Hot Test Results

For our power supply testing, we are using high precision electronic loads with a maximum power draw of 2700 Watts, a Rigol DS5042M 40 MHz oscilloscope, an Extech 380803 power analyzer, two high precision UNI-T UT-325 digital thermometers, an Extech HD600 SPL meter, a self-designed hotbox and various other bits and parts. For a thorough explanation of our testing methodology and more details on our equipment, please refer to our How We Test PSUs post.

The energy conversion efficiency of the Lian Li SP750 is remarkably stable, dropping an average of just 0.4% with the unit operating inside our hotbox. The degradation is greater at higher loads, naturally, but there are no signs of significant thermal stress.

The cooling fan of the Lian Li SP750 starts almost immediately after powering on the PSU into our hotbox, as expected from its thermal control circuitry. Noise levels are tolerable at first but the speed of the fan increases quickly, reaching maximum speed with a load of about 400 Watts. As the fan cannot spin any faster, the internal temperature of the units starts climbing even faster, reaching very uncomfortable temperature figures when the PSU is fully loaded in such an environment. The protective circuits did not shut down the unit and there was no indication of excessive stress to any of its performance indicators, yet we would not recommend allowing the PSU to ever run anywhere near that hot.

Power Supply Quality

As part of our testing, we also check output parameters are within specifications, as well as voltage ripple and line noise.

Even though they complied with the design power quality guidelines, earlier SFX PSU designs displayed poor power quality figures. However, more recent models, like the SilverStone SX700-LPT and Corsair’s SF450, were greatly improved. Lian Li’s even more powerful SP750 now delivers excellent power quality figures, easily comparable with those of very good ATX units.

We recorded a maximum voltage ripple of 38 mV on the 12V line under maximum load but much lower figures at lower loads, suggesting that the components were getting thermally stressed. Ripple figures on the 3.3V and 5V lines are lower, barely reaching 18 mV. The voltage regulation of the 12V line is impressive, at just 0.75%, but Lian Li somewhat neglected the 3.3V and 5V lines, the regulation of which is slightly above 3%.

Conclusion

Lian Li took a very strange approach for their first SFX entrance into the power supply market with the development of a premium PSU with a very high-power output. The SP750 is an SFX design meant to power systems that could even be featuring an RTX 3090 – assuming that one can find and afford such a card in the market today. The use for small form factor 750W units powering big cards is small, as few users actually build very powerful yet compact machines, however there are only a few companies that develop and market similar high-output SFX PSUs, meaning that the SP750 does not have as much competition as an ATX PSU would. The use of Helly Technology as the OEM is also a question mark, as we do not often see them used for consumer power supplies.

The quality of the Lian Li SP750 is excellent. Both externally and internally, Lian Li’s designers were very careful with their selection of components and with the manufacturing process. As a result, the SP750 is not just reliable but also very aesthetically pleasing. It is actually strange that Lian Li only covers the SP750 with a 5-year warranty, whereas most other manufacturers offer up to 10 years for products of just as good quality.

When it comes to performance, the Lian Li SP750 does not disappoint. It offers excellent electrical performance, with power quality figures that we expect to see only with top-tier PSU designs. The energy conversion efficiency is exceptional, with the unit easily justifying its 80Plus Gold certification. What is even more impressive is its resilience to high internal temperatures, which hardly affect the unit’s conversion efficiency. The only troubling performance aspect of the SP750 is the cooling fan, which will easily become audible when the PSU is heavily loaded, even with the unit inside a relatively cool system.

Lian Li is targeting a niche market with the release of the SP750 and we believe that the company expects most of their sales to be in conjunction with their own SFX-compliant cases – after all, the SP750 aesthetically is a perfect match for them. Even though the high-performance SFX PSU market is very small, there are also very few competitors right now, meaning that Lian Li only has to worry about a handful of other products and not hundreds of them. The retail price of the SP750 is $140, a very reasonable tag for an SFX PSU with that high a power output.