SilverStone 400W ST40EF

Date: October 31, 2006 - Author: Matthew Harris - Editor: Rob Williams

With power supplies pushing the stratosphere of over 1000 watts we lose sight of the needs of the basic user. If your system isn't bleeding edge with terabytes of storage, SLI or Crossfire and a pair of power hungry processors you really don't need tons of juice. If you're like the majority of users out there with a couple of hard drives, a burner or two, a single video card and a dual-core processor you just need a simple, reliable power supply.

Introduction

Often overlooked are the lower range of power supplies, I say lower range because we're talking sub-500W. For years and today still most PC builders use power supplies in the neighborhood of 250W or less. The huge PSU club is generally reserved for servers and high-end workstations in the OEM world. Why then are all the enthusiasts jumping on the monster PSU bandwagon? It's hard to say. Some of it has to do with hype, fear that something will come along and render their dear old PSU useless but fear not, if you're not running an extreme machine you could get by with a power supply that doesn't cost an arm and a leg and still have great results.

Today we'll take a look at a product that fills that niche, the Silverstone SST-ST40EF. The ST40EF is a 400 watt PSU that's not only priced right but is quiet and efficient. The ST40EF is a member of the 80 Plus club, this means that it's certified to put out 80% of what it's using from the wall. If it's drawing 100W from the wall it's putting out 80W to the PC. The better the efficiency your PSU has the less wasted energy in heat and the lower the power consumption per hour your PC is on.

Let's take a quick look at what Silverstone has to say about this little gem.

Equipped with a new generation of design and components, the Element ST40EF continues SilverStone’s stride toward more efficient power supplies. With higher than 80% efficiency across all loading conditions (from 20% to 100%), the ST40EF produces less wasted heat than typical power supplies and allows the included 120mm fan to operate at minimal speeds, ensuring silent operation for nearly all applications. This stable output and efficient characteristics are packed inside an environmentally-friendly casing that is compatible with nearly any ATX enclosures on the market. If strong and silence are the main priorities, the Element ST40EF is for you.

Special Features:

Efficiency over 80% across all loading conditions (20% to 100%)
Dual +12V rails for advanced systems
Dual PCI-E connectors (Multi-GPU ready)
Industry-leading silent running 120mm fan
Support for ATX 12V 2.2
Active PFC

Specifications:

Now that that's out of the way let me set the record straight, they goofed up. The ST40EF does not have dual PCI-e connectors as it says in the special features section. No, it's only capable of running one PCI-e card as it sits out of the package although I wouldn't hesitate to run a pair of 7600GS's or lower on it in SLI since they don't need an external power source. I'm sure that a single 7900GT probably draws as much power as a pair of 7600GS's would need so it's a no brainer. "But Matt," you're saying to yourself, "For SLI'd 7600GS's you'd need a PSU with 28A on the 12V rail." Yes you would and you have that with this baby. but I'm getting ahead of myself. Let's look at some pictures shall we?

The ST40EF comes in an unassuming box, the box art explains about the 80 Plus and how it benefits you, the user and also lists the features of the PSU. Inside the box is the PSU, manual, 24 pin to 20 pin adaptor and some screws. That's it.

Inside the PSU we find that the layout is clean and simple. It's cooled by an ADDA 120mm fan and has notched and bent heatsinks similar to the swaged heatsinks used in the Toughpower 750 I reviewed recently. I've got to say that while these types of heatsinks might look cheesy they're actually very well thought out. They allow the air to pass through the "fingers" of the heatsink thereby giving the best heat exchange.

Closer Look

On electronics heat equals resistance to electron flow which lowers efficiency. Are you starting to see the pattern here? You'll also note that the majority of he cables are not sleeved. Just the main ATX, 4 pin ATX 12V and PCI-e cables are sleeved. Yes, I know it's not pretty but you pay for those additions so in the end it balances out. This PSU retails for around $85, while it's pricey it's till not as pricey as a 750 modular with fully sleeved cables. If sleeving is your thing you can pick up a kit and do it yourself in the color of your choice so there is that option and if you're the type that would re-sleeve a PSU in the color of your choosing this saves time in not having as much to remove.

The PFC circuitry uses nice fat torroid transformers while the secondary side uses a mix of torroids and iron core transformers. The caps are by Teapo and while Teapo has a bad rep it's only if they're abused. If a Teapo cap is used in a properly cooled device they last just fine, they just don't do well in marginal environments. Nothing to fear here.

A look at the label shows the ratings per rail and a surprising note, the name of the OEM for this particular model. This particular model is made by Enhance Electronics. While this might not mean much to most rest assured that Enhance makes very nice PSU's.

Looking at the rear of the ST40EF shows a nice open honeycomb grid pattern that will ensure that the unit gets great air flow. That coupled with the 120mm fan under the black wire grill helps to make sure that the ST40EF keeps it's composure under the most grueling conditions. Here's a better look at the cabling of the unit, there are 6 SATA, 6 IDE (molex), 2-4 pin floppy connectors, 1 PCI-e connector, the 12V ATX 4 pin connector and the 24 pin main ATX connector. Be advised that you don't want to hook a dozen drives up to this unit along with a high-end PCI-e card. It could lead to problems. Personally I'd suggest using 6 drives max.

My testing methods have changed, no more slapping a PSU into my PC and seeing how it holds up, now I'm using a SunMoon SM-268+ active load tester to load the PSU. I'm also using an oscilloscope to measure the ripple on the rails. I'll also report the efficiency of the unit at each stage of testing along with the PF (power factor).

The ripple on the 3.3V and 5.0V rails never exceeded +/- 10mV and the ripple on the 12V rails was likewise clean at +/- 30mV. Very impressive especially considering that test five pushed the unit 11 watts past the rating of the unit. During testing I never noticed the fan approaching an audible level above the fan in the SM-268+. The fan in the tester is pretty loud but in the time I've been using it I have seen more than a few units heat up to the point that the fan(s) drowned out the fan in the tester. The air coming from the exhaust on the ST40EF never got above lukewarm under load, even at the highest setting in test 5 and I kept the load on it for well over 20 minutes.

Overall I'm impressed with how well a "lowly" 400 watt power supply has performed. The rails stayed firm under full load, the efficiency is simply great and the ripple was phenomenal. This is a very clean and well regulated power supply. While the ST40EF might not be the prettiest belle at the ball it's a very solid performer and should be more than up to the task of powering a good mid-range PC. That said I'm awarding the Silverstone ST40EF an 9/10 and our Editor's Choice award.

If you have a comment you wish to make on this review, feel free to head on into our forums! There is no need to register in order to reply to such threads.