Final Thoughts and Conclusions
The obvious advantage of the SFX small form factor power supply is its relatively small size, especially when compared to a full size ATX PSU. However, the small size is also a disadvantage as it only leaves room for an 80mm cooling fan, not to mention a cramped space for component layout. SilverStone has addressed this issue by creating the SFX-L Series power supply, which features a chassis that is 30mm (1.2”) longer; just enough room to spread out components for better airflow and to mount a 120mm cooling fan.
SilverStone’s new SX500-LG SFX-L Series PSU brings 500 watts of combined DC output to the small form factor market in an extended chassis. Its most obvious feature is its small size, but the PSU also incorporates many of the features found in enthusiast-grade ATX power supplies (good voltage regulation, high efficiency, and modular flat ribbon style cables).
The SX500-LG power supply delivered 500W of combined DC load with good voltage regulation and high efficiency (80 Plus Gold certified) during our tests. AC ripple and noise suppression fell well within the ATX guidelines. The build quality and component selection was very good. The power supply features an “intelligent semi-fanless” fan speed control circuit, which turns the fan off at low power for silent operation. At low power the SX500-LG is silent and at mid-power it remains very quiet.
The SX500-LG SFX-L power supply is fully modular and comes with five relatively short ribbon style cables intended for use in small form factor cases. If you find one or more cables are too short for your particular build (especially if you are installing the SX600-G in a larger ATX enclosure) SilverStone offers a complete line of full-size modular cables that can be purchased separately. All of the sleeved cables in the PP06 and PP07 Series will work with the SX600-G SFX power supply.
SilverStone offers a 5-year warranty on some of their premium PSUs but unfortunately the SX500-LG comes with only a 3-year warranty. The MSRP for the SilverStone SX500-LG SFX-L V1.1 power supply is $99.99 USD.
Even though the SX500-LG was designed for use in small form factor cases, it can also be used instead of a larger ATX power supply via the included ATX adapter bracket. This can be a big advantage when working inside a relatively cramped enclosure packed with components, cables and hoses. As you can see in the photo above (CM Elite 110 mini-ITX case), using one of SilverStones SFX PSUs instead of a standard ATX power supply left enough room to incorporate a water cooling system into the build (no way would it fit with a full-sized ATX PSU installed).
Strengths:
• 500W Continuous DC output in an extended SFX form-factor housing
• Can be used in place of a standard ATX PSU (adapter included)
• Quiet 120mm cooling fan with semi-fanless operation
• 80Plus Gold efficiency
• Good voltage regulation (±3%)
• All modular cables, flat ribbon style
• Single +12V output can deliver up to 40A/480W
• Two PCI-E connectors (6+2 pin)
• Active PFC with universal AC input
• Compatible with SilverStone custom PP06 and PP07 sleeved cables
Minor Weaknesses:
• 3-Year warranty
• Relatively high price for a 500W PSU
• Sleeve bearing fan
SilverStone SX500-LG SFX-L Series Power Supply
Our thanks to SilverStone for sending us the SX500-LG PSU to review!
An important thing to note
An important thing to note about the ‘fanless’ mode: The entirety of the fan control system is composed of a thermistor attached to the internal heatsink that controls fan voltage, and Silverstone using a fan which happened to have a startup voltage that worked well with the voltage produced by the thermistor and desired startup temperature. The problem being that it is an entirely dumb control system, with only the thermal load of the heatsink (or rather, the thermistor strapped to the heatsing with a short length of heat-shrink tubing) providing any hysterisis.
The upshot being that under idle/low-load conditions, the fan will tend to hover just at the startup voltage. Unfortunately, the fan will also make a lot of noise in this regime, with clicks coming from startup/shutdown and buzzing just below startup as energy is dissipated into the rotor sufficiently to produce audible vibration but insufficient to overcome static friction and start the rotor moving.
Sadly, this makes the PSU in practice a lot noisier than it should be. Infuriatingly, without the ‘fanless mode’ the PSU would be really quite silent. Silverstone (via Tony Ou on the HardOCP forums) even tried their own slim 120mm fan, [url=http://hardforum.com/showpost.php?p=1041479391&postcount=596]and rejected it doe to not spinning down[/url], meaning the PSU is semi-fanless at the expense of actual low-noise operation!
There are quite a few other PSU sellers using the same Sirfa platform that Silverstone are using here, and with different fans, so if they avoid the ‘semi-fanless’ mode those should in practice be quieter. Or the SX500-LG could be modified with Silverstone’s own fan if you’re willing to void the warranty (the fan is soldered to the PSU PCB). Option 3 would be to strap a thick 120mm fan to the outside to keep the PSU cool enough that the thermistor never gets hot enough for the fan to approach the startup voltage in the first place.
I’ve replaced the stock fan
I’ve replaced the stock fan in my SX500LG with the Silverstone FW121 that Tony Ou used. It’s not perfect as the fan still has a quiet buzzing/chatter while spinning, but it’s a good improvement over stock.
Also the stock Globefan was not soldered down. It used a 2 pin fan plug+socket, with some sort of glue on top (not engulfing) to secure it.
My next plan is to swap the FW121 for a Scythe Slip Stream SY1225SL12M as it has a very low starting voltage, although this is a full thickness fan that will need to be mounted to the outside.
I recently purchased this
I recently purchased this power supply and it’s installed in my Xigmatek Nebula ITX case with Z97 mobo, 4690k, GTX970 ITX and even while gaming (Shadow of Mordor – high/ultra settings for example) the fan on the psu still doesn’t spin up. I figured out that because my case has negative air pressure, air is being drawn in from the rear of the power supply keeping it cool enough so it never gets to the target temperature for the fan to kick in – making it passively cooled. Fantastic power supply – I’d just rather it didn’t use semi fanless mode as the Nebula case is designed so that the psu aides the removal of warm air. My case, GPS and cpu temps are all fine, I just think they’d be a little lower with the extra exhaust provided by a spinning psu fan.