The SilverStone NightJar NJ700 Passive PSU Review: Silent Excellence

One particularly annoying drawback of nearly all powerful electronics is the noise generated from their required coolers. Although PC components are getting more and more efficient, the general rule still holds: a powerful PC will come with significant cooling requirements.

This typically is not a concern for gamers, as the noise generated by the PC is often overshadowed by the speakers or headphones. For users who want to build a high-performance entertainment center, however, noise can be a significant issue. When a PC is installed in the living room, it needs to be powerful enough for games, but still quiet while playing/streaming media. The same goes for users who combine their professional and gaming needs into one system or, for whatever reason, they require abundant processing power to perform their profession.

One of the major noise sources inside a PC is the power supply unit (PSU). Low-cost PSUs tend to be less efficient – losing a larger portion of their input power to waste heat – and as a result they rely on a strong flow of air rather than heatsink surface area alone in order to dissipate heat, which makes them quite loud when power requirements are high. Thankfully, improvements in PSU efficiency have been driving down the amount of waste heat (and thus noise) over the years – at least for the higher-end models. As a result, what we often find is that the higher quality (higher priced) a PSU is, the quieter it operates.

In today’s review, we are having a look at a PSU from SilverStone that puts that rule to the test: the Nightjar NJ700, a 700 Watt ATX PSU that is so efficient and well-designed so as to require no active air cooling at all. Although passively cooled PSU are as rare as hen’s teeth, we have seen several passively cooled PSUs in the past, including our recent review of SilverStone’s own Nightjar NJ450-SXL. The unique aspect of the Nightjar NJ700 is the high power output of 700 Watts, which requires an amazingly efficient design to be able to cope with the thermal losses without any active cooling.

Power specifications ( Rated @ 50 °C )
AC INPUT 100 – 240 VAC, 50 – 60 Hz
RAIL +3.3V +5V +12V +5Vsb -12V
MAX OUTPUT 20A 20A 58A 2.5A 0.3A
100W 696W 12.5W 3.6W
TOTAL 700W
 

We received the SilverStone NJ700 in an aesthetically simple but practical cardboard box. The artwork is simplistic, with a blue/gold color theme and based around a picture of the PSU itself. On the other hand, the box is sizable and with very thick exterior walls, providing ample shipping protection.

SilverStone usually goes with the bare minimum number of bundled items, but the NJ700 seems to be an exception. Inside the box, we find the mounting screws, the required AC power cable, a thorough manual, numerous cable ties, and five high-quality black/white cable straps.

The SilverStone Nightjar NJ700 is a fully modular PSU and every cable, including the 24-pin ATX cable, can be detached. With the exception of the 24-pin ATX cable, the rest of the cables are ribbon-like, “flat” type. The main 24-pin ATX cable is made of all-black wires too but they are bundled and held inside a black nylon sleeve.

SilverStone Nightjar NJ700
Connector type Hardwired Modular
ATX 24 Pin 1
EPS 4+4 Pin 1
EPS 8 Pin
PCI-E 6+2 Pin 4
PCI-E 8 Pin
SATA 12
Molex 6
Floppy 1

External Appearance

The SilverStone Nightjar NJ700 definitely is an irregular design, with all surfaces except its bottom perforated to allow for the maximum possible passive airflow. The perforation pattern alone is enough to hint the OEM behind this PSU’s creation to a seasoned expert.

 

Its chassis is dimensionally close to that of an ATX unit but the NJ700 is 170 mm long, making it a bit longer than what the ATX standard dictates. Still, there should not be any clearance issues with any but the most restrictive of PC cases. Due to its thermal design, however, we would not recommend installing it inside a case with a tight PSU cover because it would essentially block any heat transfer from the unit. The NJ700 is designed so as to be installed with the vents facing upwards, letting the hot air rise and ultimately exit the case via other fans or vents.

In order to leave the heatsinks unobstructed, the designer moved the sticker with the unit’s electrical specifications and certifications to the bottom side of the unit. Even there, the sticker was limited to less than half the surface area, as small vents have been placed under critical components.

 

At the rear side of the PSU, we find the typical on/off switch and the AC cable receptacle. The interesting thing here is that SilverStone’s engineers placed two mounting hole patterns, allowing the mounting of the PSU to face upwards or downwards. Depending on the case that the PSU will be installed in, the user has to make an educated guess in order to ascertain the optimal orientation for effective passive air cooling. The front side hosts the connectors for the modular cables, all of which are black but are keyed and it is not possible to mix-up the connectors while attaching the cables. A basic legend is sprayed directly on the PSU’s chassis.

Internal Design

With no fan to talk about inside the SilverStone NJ700, we jump right away to the OEM of the platform, who is none other than SeaSonic. As we mentioned above, this is obvious to an experienced PC builder, as the external design of the PSU is, with the exception of the company’s logos, practically identical to that of the SeaSonic Prime Fanless. SilverStone usually employs Enhance for their fanless PSUs but, apparently, Enhance does not yet have a platform that can deliver this high a power output without any active cooling.

 

As expected from SeaSonic and for the nature of this particular design, the platform that the NJ700 is based upon is pretty much the best it could possibly be without employing cutting-edge digital electronics. That their engineers managed to squeeze 80Plus Titanium efficiency levels out of an analog design is quite a feat on its own. SeaSonic probably sticks with such designs due to their extremely high reliability and proven track record from decades of use.

The insides of the SilverStone Nightjar NJ700 do not look much different than any other high quality 700W PSU. Even the heatsinks, though sizable, are not as substantial as one would expect from a passively cooled unit. Only the heatsink placed directly on the main transformer stands out compared to typical ATX products.

A generous filtering stage begins at the back of the AC receptacle, under a shield, with six Y capacitors, three X capacitors, and two filtering coils. There are two powerful rectifying bridges, with a sizable heatsink sandwiched in between them. There are two APFC capacitors, both made by Nippon Chemi-Con and rated at 400v/470μF each.

The primary side of the PSU is a standard full-bridge configuration with an LLC resonant converter. On the secondary side, four MOSFETs generate a single 12V line, with additional DC-DC converters present to generate the 5V and 3.3V lines from that. The difference is that both the four inverting transistors on the primary side and the four converting MOSFETs on the secondary side are top-tier products with extremely low drain-source resistance and gate charge, making them remarkably efficient.

Most of the secondary capacitors in the SilverStone NJ700 are polymer products made by FPCAP. A lot of them are placed on the secondary PCB that holds the connectors for the power cables for the final filtering of the DC power lines. Nevertheless, there are a few electrolytic capacitors present, one made by Rubycon and the rest by Nippon Chemi-Con, making the Nightjar NJ700 an all-Japanese affair.

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.

Due to the unique thermal design of the Nightjar NJ700, we had to change our testing methodology quite a bit. As there is no airflow to assess, we placed a sensor on the bottom side of the chassis and measure its surface temperature instead. Note that these thermal results are not directly comparable with those obtained by testing regular air-cooled products.

As expected from a fanless PSU with this kind of power output, its efficiency is extremely high. Our measurements indicate that the SilverStone NJ700 surpasses the 80Plus Titanium requirements regardless of its input voltage. It has an amazing 95% average efficiency across the entire nominal load range when powered by an 230V AC source, which drops down by just 0.6% when the input is lowered to 115V AC. The efficiency at just 5% load is above 86% and the peak efficiency is above 96%.

As expected from any well-designed PSU without active cooling, the surface temperature increases almost linearly and in near-perfect alignment with the unit’s thermal losses. The surface temperature does reach over 38 °C, which is to be expected, as the body of the PSU itself partially acts as a heatsink. The heatsinks of the PSU do reach temperatures over 50°C when the power supply is heavily loaded but that is a perfectly safe figure for an advanced PSU. The primary side is getting a little bit hotter than the secondary side. 

The energy conversion efficiency of the SilverStone Nightjar NJ700 was almost entirely unaffected by the high ambient temperature of our hotbox, with the efficiency dropping a mere 0.25% average across the entire load range. This, in conjunction with the lack of any active cooling, suggests that the active components are both oversized and designed so as to greatly resist thermal stress.

Under these operating conditions, the surface temperature of the SilverStone NJ700 reaches levels that would be painful for most people to touch. Nevertheless, the internal temperature of the unit does not get high at all. As a matter of fact, both the primary and secondary side heatsinks stayed a bit cooler than what actively cooled PSUs with such a power output can attain at maximum load.

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

Main Output
Load (Watts) 141.38 W 352.97 W 528.19 W 703.06 W
Load (Percent) 20.2% 50.42% 75.46% 100.44%
  Amperes Volts Amperes Volts Amperes Volts Amperes Volts
3.3 V 1.8 3.41 4.49 3.41 6.74 3.4 8.99 3.39
5 V 1.8 5.09 4.49 5.09 6.74 5.08 8.99 5.07
12 V 10.42 12.1 26.06 12.08 39.09 12.05 52.12 12.03
Line Regulation
(20% to 100% load)
Voltage Ripple (mV)
20% Load 50% Load 75% Load 100% Load CL1
12V
CL2
3.3V + 5V
3.3V 0.75% 12 12 14 16 14 12
5V 0.5% 8 8 10 16 8 12
12V 0.6% 6 8 8 12 8 12

The power quality figures that we received while testing the SilverStone NJ700 inside our hotbox were astounding. We recorded a maximum voltage ripple of 12 mV on the 12V line at 100% load, an incredible power quality figure by any comparison. Voltage regulation also is very tight on the 12V line, staying lower than 0.6% across the nominal output range. The secondary 3.3V and 5V rails are a bit less well filtered, with the voltage ripple reaching 16 mV on both rails under maximum load. Otherwise, the secondary lines are just as tightly regulated, at around 0.5% for both the 3.3V and 5V rails.

SilverStone is greatly focused on the development of high-performance living room entertainment PCs, which goes in tandem with the marketing of ultra-quiet PSUs. The Nightjar NJ700 is a statement product designed both to lure in enthusiasts that will not mind the hefty price tag and to outdo the company’s main competitors.

The OEM behind the Nightjar NJ700 is SeaSonic, perhaps the most reputable top-tier PC PSU OEM. On top of that, the NJ700 is based on what is currently SeaSonic’s best platform. We found only top-tier components inside the Nightjar NJ700, ranging from critical parts down to insignificant filtering capacitors. The developer of this PSU spared no expense and that showed during our testing, when the Nightjar NJ700, a PSU that lacks any form of active cooling, was operating unaffected inside our hotbox and with virtually no change in its performance. SilverStone covers the Nightjar NJ700 with a five-year warranty, which is sufficient, yet strange when the OEM markets the same platform with a 12-year warranty.

Although the platform that the Nightjar NJ700 is analog and relatively basic by today’s standards, the designer of this PSU managed to get ridiculous performance figures out of it. The Nightjar NJ700 comes with an 80Plus Titanium certification tag and it honors it, delivering exceptionally high energy conversion efficiency even when the load is very low. Efficiency is not the only thing that the NJ700 excels on, as its power quality figures also are astounding. Despite its lack of active cooling, heat has practically no effect on the unit’s electrical performance either. All in all, the overall performance of the Nightjar NJ700 is world-class.

With all of that said, when using a passively cooled PSU, there are certain implications that need to be considered. The major point that is the fact that the thermal losses of the PSU will be released inside the system itself, whereas typical, active-cooled PSUs would exhaust most of that thermal energy to the outside of the case. This means that the system itself will get hotter and may require better cooling in order to sustain its overall performance. In this case, the high power output of the NJ700 translates to significant thermal losses when the unit is heavily loaded – regardless of its very high efficiency, there will be more than 35 Watts of thermal energy released to the environment. This will probably not be a problem with modern systems that are built with efficiency in mind, but the specifics of this must be considered and weighted by the system’s builder. After all, it would not make any sense to use a passively cooled PSU only to replace it by another noise source, such as additional case fans.

SilverStone’s choice to market the Nightjar NJ700 could not have been easy. On one hand, the nature of the product aligns with the company profile and their efforts to develop top-performance living room gaming systems. On the other hand, SilverStone has to compete with the OEM of the NJ700, the legendary SeaSonic, as they also market the same platform under their own brand. Practically no other company offers direct competition to the passively cooled NJ700 right now, meaning that its success largely depends on how well its $308 retail price and overall availability fare in comparison to SeaSonic’s Prime Fanless TX-700. That, in conjunction with the strangely significantly shorter warranty length, can be a very complicated subject for SilverStone’s marketing department.