SilverStone offers a great variety of both cases and power supply units, but they are nonetheless primarily known for their numerous small form factor cases and non-standard designs. Designs such as these often require very careful consideration of the hardware that will be installed in them, or even special versions of hardware exclusively designed for such systems. We have reviewed a number of their cases in the past, but it is products like the Milo ML04 and ML05 that really stand out when it comes to offbeat, specialized form factors. Meanwhile given their unusual form factor, Silverstone also supplies products like their SFX PSUs and slim optical drives to fit such designs.

In fact Silverstone supplies a surprisingly large range of products for their small form factor designs, giving their cases quite a bit more flexibiltiy than one would normally expect. On the PSU side for example, the company currently offers five different SFX form factor PSUs, ranging from 300 to 600 Watts, suitable for driving everything from the true HTPC to portable gaming machines.

To that end, today we'll be looking at the most powerful of these SFX PSUs, the SX600-G. The tiny SFX PSU measures just 125mm × 63.5mm × 100mm, or a bit less than half the size of a standard ATX power supply. Yet in that space Silverstone has built a PSU capable of supplying 600 Watts with 80Plus Gold certification and modular cables as well, allowing it to power even the most power-demanding system that could fit in a case that requires such a power supply.

Packaging and Bundle

We received the SilverStone SX600-G SFX PSU in a relatively small cardboard box, yet large and sturdy enough for the small PSU. The artwork seems a bit excessive, combining abstract and geometric patterns along with a picture of the unit itself. The most basic features of the PSU can be read at the front side of the box and more details are printed on the back.

For the most part the SX600-G's included bundle is rather plain, with Silverstone shipping the necessary mounting screws, an AC power cable, and a manual. Unexpected however, SilverStone also provides one extra and rather interesting item alongside with the SX600-G SFX PSU: an SFX to ATX mounting adapter. Our best guess is that SilverStone is also looking to sell this PSU for use in small ATX cases, where space is similarly an issue. However, the very short cables supplied with the PSU are going to be an issue with that concept.

This is a fully modular design so every cable can be detached, including the 24-pin ATX cable. All of the cables are "flat", ribbon-like, including the thick 24-pin ATX cable, with SilverStone apparently aiming to cut down on cable slack and save as much space as possible in the process. Be warned that these cables are much shorter than those of a regular ATX PSU, with the ATX power cable being just 30 cm (11.8") long. Every cable is made by using black wires and black connectors, with the sole exception of the PSU-side connector of the PCI Express power cable, which is blue.

Overall the number of connectors is actually very low for a PSU with this high of a power output rating. This means that the SX600-G will typically operate with plenty of headroom, as it would be difficult to completely load down a 600W PSU off of only single high-power video card and CPU.

External Appearance

The SilverStone SX600-G SFX obviously is very small compared to an ATX PSU, measuring in at the SFX standard dimensions of just 125 × 63.5 × 100 mm (W×H×D). Due to the limited internal volume the SFX form factor affords, most SFX PSUs come with a 60mm fan, so imagine our surprise at finding an 80mm fan in the SX600-G. Having a larger cooling fan fit into the SFX form factor and on top of that managing to fit large enough components to reach an output of 600 Watts with 80Plus Gold efficiency levels seems like quite an engineering feat. Meanwhile the small body is sprayed with a satin black paint that is fingerprint resistant.

SilverStone made the odd move to punch their company logo at the top side and place the sticker with the electrical specifications and certifications on the left side of the chassis. It is likely that the company expects the top of the PSU to be more frequently visible than its side, but such aesthetic improvements are of questionable value on such products, as SFF and desktop cases rarely have windowed panels anyway.

Meanwhile there is nothing of importance at the rear side of the unit, not even an on/off switch. Apparently, every bit of space does matter and even a switch would not easily fit inside such a densely packed design. The few connectors for the modular cables can be seen at the front of the PSU.

Internal Design

The thin 80 mm fan of the SX600-G SFX PSU is supplied by ADDA, one of the most renowned fan manufacturers. The AD0812UB-D91 is a very high speed model, capable of reaching a maximum speed of 4800 RPM at 12V input. And although that sounds like a scary number compared to the speeds of 120/140 mm fans found in larger PSUs, it is not dramatic for an 80 mm fan. As with the vast majority of such high speed models, it has a ball bearing.

The OEM behind the very densely packed design you see below is Enhance. Enhance is not a very common manufacturer for high output PSUs, but they do specialize on SFX/SFF and proprietary PSU designs. It is so densely packed that it is very difficult to make head or tails of what components are being used without at least partially dismantling it. There is a PCB attached to the back of the AC receptacle with half of the filtering stage components on it, while the other half is on the main PCB. There are a total of four Y capacitors, two X capacitors and two filtering inductors. For safety, there is also a metal oxide varistor and a simple glass fuse for limited surge protection.

Due to space restrictions, Enhance had to keep things relatively simple. The SX600-G is based on a simple half-bridge active rectification design, with two MOSFETs feeding the main transformer. The rectifiers at the secondary of the main transformer generate only a 12V line and the minor 3.3V/5V lines are converted from it using DC-to-DC conversion circuits. By replacing passive components (diodes) with active components (transistors) and using DC-to-DC circuits for the minor voltage lines, Enhance improved the efficiency of the SX600-G without having to use "exotic" technologies or much more expensive parts.

The primary APFC capacitor is a high quality product supplied by Nippon Chemi-Con (450V/330μF), but there is complete chaos at the other side of the transformer, with the rest of the capacitors coming from no less than six different brands. We saw electrolytics from Elite, Teapo, Rubycon, SunCon and Su'Scon, while the polymer capacitors are supplied by Gemmy Electronics and G-Luxon. It appears as if half of Asia came together to build this PSU. The assembly quality is rather good, considering the very small proportions and density of the unit.

Cold Test Results

For the testing of PSUs, 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 - 2014 Pipeline post.

The efficiency of the SilverStone SX600-G is very good but it does not actually meet the 80Plus Gold certification standards under 230V AC input. It is very likely that it does with an input of 110V/60Hz AC, which admittedly is what was used to certify this PSU in the first place. We measured a maximum efficiency of 91.2% at 50% load and an average efficiency across the entire nominal load range (20% to 100% of the unit's capacity) of 89.2%. It is interesting to note that the low load efficiency of the SX600-G is quite good, with an efficiency reading of nearly 79% at just 5% load.

This PSU sports a semi-fanless design, meaning that the fan will start only after the temperature exceeds a certain point. For a densely packed SFX unit, that point as it turns out is not very high, with the fan kicking in shortly after 200W in our room temperature environmental test. Still, the internal temperatures of the SX600-G remained relatively low and the fan did not have to get loud. Even at maximum load, the fan stopped at 39.1 dB(A), a clearly audible but borderline comfortable figure. 

Hot Test Results

Moving on to our hotbox testing, the SX600-G is only rated for operation up to 40°C, and as we can quickly see in our results it's for a good reason - its performance plummeted once placed in our hotbox. We do not get to review lower power units often here at AnandTech, yet these may be the worst hotbox electrical performance figures we have seen in recent years.

Overall voltage regulation is acceptable, at 2.5% for the 3.3V line and 3.3% for the 5V and 12V lines. The power quality however is terrible. At maximum load, the two minor voltage lines even failed the 50 mV specification limit and the 12V line reached the borderline 114 mV figure with a limit of 120 mV. With the PSU heavily cross-loaded, the 12V line failed the power quality limit as well, registering a ripple of 162 mV. Apparently Enhance just does not expect this PSU to be so heavily loaded under such hot conditions (and, considering the very limited number of connectors, it cannot really be).

We need to stress that this is a PSU rated at 40°C and we perform our testing at temperatures higher than 45°C - we could reduce the ambient temperature of our hotbox testing but we chose not to do so as the results would then not be comparable to those of our previous reviews.

Alongside the regulation and power quality, the energy conversion efficiency plummets as well. The average efficiency reduction is 1.9%, with a high drop of 3.3% at 100% load. The active parts of the PSU are good and such an efficiency loss cannot be attributed solely to them, as they have to cope with very high internal temperatures that reduce the performance of even the best of parts.

This time, the fan of the SX600-G started right away, as the ambient conditions likely were already too harsh for the PSU. With the unit being so densely packed and heavily loaded, the fan has to keep spinning faster and faster in order to cope with the increased thermal demand. It does, maintaining safe operating temperatures for the SX600-G even under the harshest conditions. The strange thing is that even at 100% load, the fan did not reach it maximum rotational speed. With our laser tachometer registering 4200-4300 RPM, it indicates that the fan has headroom to spin even faster if the conditions get harsher than this. Still, it reaches 46.6 dB(A) under maximum load, which the vast majority of users will find intolerable for everyday use. 

Conclusion

Unlike the more flexible ATX solutions, the SilverStone SX600-G SFX PSU is a rather narrowly focused product, designed for a very specific group of users. Frankly, the number of users that would even want a 600 Watt PSU inside their tiny desktop/SFF case is very small, let alone the number of those users who could use that much power given the component limitations imposed by such small case dimensions. Which is not to say that there's not a place for a 600W SFX PSU, only that it's definitely a niche role on the whole.

Unsurprisingly then, for this 600W unit SilverStone is trying to expand their customer base a little bit with the inclusion of the SFX to ATX frame adapter. After all, even if a small form factor case can take a full size ATX PSU, a very compact design might benefit from the presence of a smaller SFX PSU. Unfortunately in trying to serve two masters, Silverstone's included modular cables are still designed first and foremost for the smaller SFX form factor, meaning that they don't offer much slack for actually reaching an ATX motherboard. We fell victim to this as well, during our recent review of SilverStone's own Fortress FT05. Despite the small proportions of the case, the CPU power connector could not get anywhere close the motherboard header.

Meanwhile when it comes to performance, it would be entirely unfair to compare the SilverStone SX600-G to any ATX PSU and, frankly, we do not have enough data to compare it against any other SFX PSU either. High performance SFX PSUs are quite rare, and most are built by Enhance anyway.

What we can point out however is that the SilverStone SX600-G SFX struggles to deliver its maximum power output inside a hot environment and, unlike a good gaming tower case, we do expect a small desktop/SSF case to get rather warm given the lack of airflow in most home A/V cabinets. In a hot, enclosed space, the PSU struggles to meet its efficiency certification levels and the power quality is, to put it mildly, not good. As one might expect noise levels in hot conditions are not very good either, as the included 80mm fan has to work rather hard to keep component temperatures in check.

What this means is that the SX600-G is not a very forgiving PSU. If put in a well ventilated room temperature environment the PSU does well enough, you just need good ventilation to start with. Particularly if driven to its full capacity, great care needs to be taken to make sure that the SX600-G and the system it's placed in are well ventilated in order to get suitable performance out of the PSU (and likely the rest of the system as well)

Ultimately there were clearly some tradeoffs made to get a 600W PSU into such a small form factor design, with ambient temperature sensitivity being chief among them. If we were to compare its performance with an average ATX PSU retailing for half the price, the SX600-G clearly falls short. It is not however made to be compared to ATX units, and rather this is one of the highest outputs you can get in the SFX form factor.

Moving on, the quality of the SilverStone SX600-G SFX PSU is troubling at times as well. Enhance does a fine job as an OEM and we have no complaints about the design or the quality of the assembly. For the most part, the quality of the components is good. The active components are of good quality and the primary capacitor is supplied by a very respectable manufacturer. When we check the secondary components however, it is pure chaos, with the capacitors being supplied by over half a dozen manufacturers despite the fact that this is a small SFX PSU.

Of course, the number of suppliers means very little. The fact that many of them are not exactly favorites among enthusiasts however, does. Most of those versed in power electronics would agree that products from, for example, Su'Scon and Elite, are not exactly ideal for what is supposed to be a high performance $130 product. For what amounts to a premium retail price, one would expect better quality. Then again, we can only imagine what it would do to the already premium price of the PSU if Silverstone went with even more expensive top class components.

Wrapping things up, although it's not perfect, the SilverStone SX600-G SFX PSU is still going to be the PSU of choice for those that need a high power output inside a very confined environment. It comes at the steep price of $130 including shipping, but there is virtually no other product that can match its power output in such a small size. But with that said, this is a PSU best reserved for SFX form factor users. If a case can accept a normal ATX PSU, an ATX PSU is probably the better and cheaper option.