Golden Silence: Seasonic and SilverStone Fanless PSUs

How do you get rid of the noise from the PSU fan? Right: get rid of the fan! Our today’s article will discuss two fanless PSU models: Seasonic X-400 Fanless and SilverStone Nightjar.

by Oleg Artamonov
11/28/2010 | 04:22 PM

I am going to test two rather specific power supplies in this review. Despite being high-wattage units, these products from SilverStone and Seasonic have no fans and rely on convection for their cooling, which makes them absolutely silent.

Testing Methodology

 

Click the following link for a description of our testing methodology and equipment and a brief explanation of what the specified and tested parameters of power supplies mean: X-bit Labs Presents: Power Supply Units Testing Methodology In-Depth. If you feel overwhelmed with the numbers and terms this review abounds in, refer to that article.

You can also go to our Cases/PSU section to check out reviews of all other PSU models we have tested in our labs.

We will mark the actual power consumption of three system configurations (discussed in our article PC Power Consumption: How Many Watts Do We Need?) in the cross-load diagrams. This will help you see if the tested PSU can meet the requirements of a real-life PC.

SilverStone Nightjar SST-ST45NF

First goes the 450-watt unit from SilverStone. Although the Nightjar series has been produced for a second year already, Silverstone doesn’t yet offer an alternative. That’s understandable because fanless PSUs are very specific products and their developers focus on achieving high efficiency and use reliable and durable components. Such PSUs have a long lifecycle as the consequence.

The Nightjar series also includes a 300W (SST-ST30NF) and a 400W (SST-ST40NF) model.

 

The PSU comes in a black-and-gray box on which its absolute noiselessness is indicated.

Exterior Design

 

The Nightjar SST-ST45NF has the typical appearance of a fanless PSU: a meshed case with a massive aluminum heatsink as the top panel. The heatsink has a lot of low fins, so it is best cooled by a rather slow stream of air, for example from a system case fan. Theoretically, fanless PSUs can work with no active cooling at all, but you should have at least one low-speed fan inside your computer to make life easier for your PSU, mainboard and hard disks.

Besides the heatsink, the bottom panel is blank, too. It is blank because there is the printed circuit board behind it which would block the airflow anyway. Moreover, the PCB has dangerous voltages up to 400 volts.

There are two LED indicators next to the power connector: one signals that the PSU is working and another, that the PSU is not overheat (the indicator changes its color to red in case of overheat). I guess this is a useful thing. The green color will calm down many users who have no experience with fanless PSUs and do not know what temperature should be considered safe.

Circuit Design

I didn’t see much when I took the cover off this PSU. I mean, all the innards are hidden under the huge aluminum heatsinks that fill up the entire interior and press against the heat-spreading cover with their flat tops.

I don’t use destructive investigation methods in my PSU tests with the help of a soldering iron, therefore I can’t tell you much about the circuit design of the Nightjar SST-ST45NF. I just couldn’t see most of it. The cables are all laid out neatly and the soldering is neat, too. There are heat-conductive and electrical insulating pads between the external and internal heatsinks. So, I can’t find any fault with this PSU’s manufacturing quality.

The actual developer and manufacturer of this PSU is Etasis Electronics Corp.

Cables and Connectors

The Nightjar SST-ST45NF is equipped with the following cables and connectors:

The CPU cable is rather too short. It should be at least 60 centimeters to avoid any problems with connecting and laying that cable out in an ATX system case with a bottom PSU bay. Otherwise, the selection of connectors is perfectly normal for a 450W power supply.

Specifications

The Nightjar SST-ST45NF has a solid (no splitting into multiple virtual lines) +12V power rail with a load up to 420 watts. According to the manufacturer, the Nightjar can work at its full specified load, which is 450 watts, at an air temperature up to 40°C in a 220V power grid. In an 110V power grid the max load is specified to be 400 watts, which is due to the twice higher currents in the high-voltage circuitry and, consequently, higher heat dissipation at the same load.

Temperature and Noise

Working at its full load of 450 watts (outside a system case but with no active cooling), the hottest spot on the PSU’s top panel was 60°C. This temperature feels almost scorching, but is quite acceptable for electronics.

My sample of the PSU did not produce any electronic noise (clicks or hiss or anything) at work.

UPS Compatibility

The Nightjar SST-ST45NF worked with my uninterruptible power supply (APC SmartUPS SC 620) at loads up to 370 and 345 watts when powered by the mains and batteries, respectively. There were no problems when the pair would switch to the UPS’s batteries and the UPS was perfectly stable.

Output Voltage Stability

The PSU boasts superb voltage stability, keeping the +12V voltage within 1% of its nominal value. The other two voltages deflect somewhat more, but never exceed the allowable limits.

Output Voltage Ripple

The high-frequency ripple on the +5V rail is close to the permissible limit.

Besides, there is low-frequency pulsation of 60-70 millivolts on the +12V rail (the allowable maximum is 120 millivolts).

Efficiency and Power Factor

Although the manufacturer says this model is up to 86% efficient, its actual efficiency is as high as 90%! Of course, this is due to my testing it in a 220V power grid. However, I don’t think the efficiency of this PSU is going to drop below 87-88% even at an input voltage of 110 volts.

+5Vsb Standby Source

The standby source copes with its job well. Its output voltage is never lower than 4.9 volts.

Summary

I couldn’t find any serious flaw in the SilverStone Nightjar SST-ST45NF. It is an excellent fanless PSU with high (for its class) wattage, very high efficiency, stable output voltages, and a good selection of connectors. If you want a silent PSU, you should definitely take a look at the Nightjar series.

Seasonic X-400 Fanless SS-400FL

While SilverStone’s Nightjar series has been around for a while, the Seasonic X-400 Fanless has been released just recently. It is the junior model of a series we already covered in our previous review.

The PSU comes in a small black-and-yellow box.

Exterior Design

The X-400 looks somewhat unusual for a fanless PSU. Yes, its side panels are all perforated but where is the huge heatsink instead of the top panel? I have invariably seen it in all fanless PSUs such as the FSP Zen, SilverStone Nightjar and even in the semi-fanless Antec Phantom. This PSU even looks suspiciously empty inside.

Like every other X series model, this one has detachable cables, including the mainboard cable. Interestingly, there is a warning here that you should install this PSU with the meshed panel up. This is obviously meant to ensure effective ventilation through convection: the hot air will be rising up and going out of the PSU case rather than staying in between its components.

The PSU mounting holes are not symmetric in the ATX standard. Therefore the X-400 Fanless has two sets of mounting holes so that you could install it into any system case with the vent panel up.

However, you should be aware that system cases in which there is a blank panel right above the PSU bay won’t be good for the X-400 as that panel will block its ventilation. The best choice is a system case with a bottom PSU bay (which is the coldest zone) and without a horizontal partition that divides the interior into two compartments.

If you do not trust the passive cooling, you may want to install a low-speed fan on top of the PSU, for example a 500RPM model from Scythe. Equipped with such a fan, the PSU could be installed in any position. It would still be very quiet at any load and would be protected against overheat.

Circuit Design

This model differs from its X series cousins in the ratings of some components (for example, there is only one high-voltage capacitor in the input circuitry whereas the higher-wattage models have two capacitors there) and in the size of the heatsinks. It looks like Seasonic didn’t have to revise the circuit design much to release this fanless model.

Thus, the X-400 Fanless implements everything I described in my X-750 review. It is a cutting-edge product with all economically justifiable technologies available today: a resonance converter, synchronous rectifiers based on field-effect transistors, a main regulator for one voltage (+12 V), additional DC-DC converters for +5 and +3.3 volts, and polymer capacitors. All of this is meant achieve as high efficiency as possible.

The developers even installed an electromagnetic relay that closes the input thermistor which limits the inrush current. When the computer is turned on, this resistor has a high resistance of a few Ohms (that’s actually how it limits the current the PSU consumes from the wall outlet in the first few milliseconds). In a few seconds the resistor warms up, lowering its resistance to 0.1-0.2 Ohms, so its heat dissipation is no higher than 1 watt. However, the developers made sure to avoid even this seemingly negligible loss of power!

Cables and Connectors

The PSU is equipped with the following connectors:

Included with the PSU are:

Well, that’s a nice selection of connectors for a 400W model, especially considering its modular design (by the way, this is most valuable for a fanless PSU because you can only attach the cables you really need and prevent unnecessary cables from obstructing the airflow). The CPU cable is long at 65 centimeters, which should be enough for any system case with bottom PSU bay. It is also good that the PSU offers HDD cables of two different lengths.

Specifications

The X-400 Fanless can yield up to 400 watts of power, but the manufacturer doesn’t specify the maximum allowable air temperature. The +12V rail is solid and rated for up to 396 watts.

Temperature and Noise

Seasonic products are sometimes criticized for having hissing chokes, but my sample didn’t produce any unwanted sounds.

I cannot give you any temperature results because the PSU has no external heatsinks whereas the internal ones differ in temperature. Moreover, the exact temperature depended on what point of the heatsink I could reach with the sensor. Such measurements wouldn’t be reliable.

However, I can tell you that the PSU did not show any sign of overheat after working for 1.5 hours at a load of 400 watts. The top panel was warm but not hot then. There was no smell of overheating plastic, either.

UPS Compatibility

The PSU worked with my uninterruptible power supply (APC SmartUPS SC 620) at loads up to 392 and 330 watts when powered by the mains and batteries, respectively. They had no problems switching to the UPS’s batteries and the UPS was perfectly stable.

Output Voltage Stability

The three main voltages deflect no more than 3% from their nominal values irrespective of load. This is a very good result.

Output Voltage Ripple

There is some occasional pulsation on the +5V rail. The other two rails do not have even that.

There is some low-frequency pulsation of about 15 millivolts on the +12V rail. This is far below the allowable maximum of 120 millivolts, though.

Efficiency and Power Factor

After examining the circuit design of this PSU, we can expect only best results in this test! Indeed, the X-400 Fanless is 90% efficient at a load of 75 watts whereas its maximum efficiency is as high as 92.7%! The efficiency is never lower than 86% throughout the graph which stretches from a load of 50 watts to full load.

+5Vsb Standby Source

The standby source is rated for 2.5 amperes and copes with its job. Its voltage sags to 4.86 volts only, the allowable minimum being 4.75 volts.

Summary

The Seasonic X-400 Fanless looks more like a regular PSU the manufacturer has forgotten to install a cooling fan into rather than like a model capable of delivering up to 400 watts of power without that fan. However, it is quite capable of doing that. Moreover, the X-400 Fanless boasts excellent electric characteristics and features a modular design.

A computer enthusiast may want to install a low-speed fan on its meshed top panel to get a very quite PSU with active cooling. That’s not as odd a solution as it sounds, actually. There are too few low-wattage PSUs that can be called really quiet. As for fanless models, many users do not feel sure that their cooling is sufficient and that their service life will be long. Installing a 500RPM fan would guarantee proper cooling (an active fan is always better than natural convection) at minimum noise. As for wattage, this model offers enough of power not only for an HTPC but even for a midrange gaming machine!

Conclusion

Both power supplies I’ve tested today are good. Indeed, I have got not a single serious complaint about the SilverStone Nightjar SST-ST45NF or the Seasonic X-400 Fanless SS-400FL. Both are going to be a good choice for building a quiet home computer.

Between the two, the Seasonic is the better option. It represents the company’s new platform that features nearly all economically justifiable technologies and solutions available today. This platform proves to be suitable for designing fanless PSUs as well. By achieving high efficiency and placing hot components apart from each other on the PCB, the developer made heavy and bulky heatsinks unnecessary while cooling the PSU through convection only.

In conclusion we would like to award Seasonic X-400 Fanless SS-400FL with our Editor's Choice title:

SilverStone Nightjar SST-ST45NF recieved our Ultimate Innovation award:

Still, I have to remind you that building computers with fanless PSUs requires some experience. You shouldn’t try to remove all the fans from your system case because they cool not only the components they are actually attached to, but also other things, like the power transistors of your mainboard. Graphics cards with passive cooling get very hot, and may even overheat altogether, if there is no airflow along their heatsinks. Therefore, the reasonable solution would be to install one or two low-speed fans (500-700 RPM) which would ensure a weak, yet constant, intake of fresh air into the system case without producing any noticeable noise.