Part 2: Four Cheap 80 PLUS Bronze Power Supplies, Reviewed

Part 2: Which One Of These PSUs Is Right For You?

In yesterday's half of this round-up, we suggested that it is possible to find a well-built, efficient power supply at a value-oriented price. But don't be duped by cheap PSUs. An 80 PLUS Bronze logo is not a promise of quality. In fact, Cougar's A350 is advertised with the Bronze rating and can't even achieve the necessary efficiency levels to justify that badge. Fortunately, all of the power supplies in part two at least satisfied the efficiency specifications they advertise. Nevertheless, our testing still uncovers a handful of weaknesses spread through the field.

We'll start with a power supply that appears free of any serious issues: Cooler Master's Silent Pro M2 520. Modular cable management helps it stand apart from the crowd, and its workmanship is darned near perfect. For all of that, however, you'll need to pay a price at the upper end of our budget range. The Silent Pro M2's hold-up time and sound level results are both commendable. If you want above-average power and are thinking of building a more graphics-heavy system, you should consider this PSU, though remember it's not available in the U.S. yet, so you may find yourself shopping for the 550 or 650 W versions instead.

Corsair's CX500 is rated for 20 W less, but at a retail price of $60, it is also less expensive. Apart from its lower maximum output, the CX500 loses modular cable management compared to Cooler Master's offering. And ready availability in the U.S. means we'd be more inclined to favor Corsair's offering. After all, you still get a pair of auxiliary PCI Express power connectors, along with quality that leaves almost nothing to be desired. Workmanship, interior construction, sound level, and efficiency are all good. The CX500 would be close to perfect, actually, if there wasn't an issue with its short hold-up time. All in all, this is decent budget-oriented PSU.

Too-few connectors and relatively low power output are the two biggest detractors from Gigabyte's Greenmax 450 Plus. It also doesn't help that we're not finding it for sale in the U.S., making it impossible to judge its value proposition. Should it show up soon, know that its electrical quality is impressive, aside from high inrush current. On the plus side, its hold-up time is very long. We do take issue with the power supply's acoustic output. Gigabyte's submission is the loudest of the PSUs we tested, and that applies to both load profiles. A sound level above 35 dB(A) cannot qualify as quiet. Sorry.

Maxing out at just 360 W, Seasonic's SSR-360GP seems pretty puny compared to the other power supplies in our round-up. However, it's also the only PSU bearing an 80 PLUS Gold rating for a scant $60. It delivers on that promise, too. Its outstanding efficiency runs rings around the other test candidates. Unfortunately, it doesn't give you many connectors. Great efficiency translates to less waste heat. As a result, the SSR-360GP's fan doesn't have to spin very fast. We measured just a tad over 30 dB(A), which is very quiet indeed.

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    Top Comments
  • Deemo13
    You guys aught to make a power supply hierarchy chart.
    25
  • Other Comments
  • Deemo13
    You guys aught to make a power supply hierarchy chart.
    25
  • pepsimtl
    Please, if you could say , if the power supply is compatible with Haswell .I think this is very important .
    1
  • benedict78
    I second that request. Does ANY of those PSUs support the new Haswell C7 state?
    -2
  • ojas
    There's also a CX500M...
    5
  • jeffunit
    I am not sure why you think that a 40w bulb is purely resistive. Almost all bulb filaments are coiled, which makes them inductive. For example, http://www.donsbulbs.com/cgi-bin/r/b.pl/h4652|12.8v|40w|60w~usa.html shows a 12v 40w bulb filament, which is coiled.

    Perhaps you should measure the inductance of your bulbs, rather than just stating they are purely resistive.
    0
  • vertexx
    A couple different PSUs for different applications. I use the Corsair CX 430 & 500 for budget gaming builds, and just this week I ordered the Seasonic for the first time for a home server build. Nice to see those choices validated.

    Thanks guys, nice article!
    0
  • Someone Somewhere
    Quote:
    In spite of its low price, no important components fall victim to cost cutting.


    In the CX500. I think Samxon caps count as cost cutting.
    6
  • flong777
    I have recommended the CX500 many times to budget builders and now I feel better about it. It is the clear winner. Funny TH says it is loud but it was nearly identical to the CM 520 on their chart in DB noise.

    On sale you can pick up the CX500 for $40 which is about as cheap as you will ever find any PSU. If you compare how well that Corsair backs its products, there really is no comparison - Corsair is the only choice.

    As far as the Seasonic 360, why on earth would you buy a 360W PSU? I just don't see the point. While I can justify a 500W PSU to a budget builder, I really cannot comprehend recommending a 360W PSU to anyone. I feel cautious with a low wattage 500W PSU. All of these PSUs will run hot and loud if they are stressed and so moving up to a 650W or even an 850W PSU really is not that more expensive.

    I got the gold rated 850W Corsair HX 850 for $144.00 on sale. I can not even begin to describe how excellent this PSU is. It runs as something around 92% efficiency under load and I have never hear the fan even come on (it may be that low fan is inaudible). It comes with a 7-year warranty and is modular.

    If you are not strapped with a low budget, moving up is the only way to go. If you are, the CX 500 is a good choice.
    -10
  • vertexx
    Anonymous said:
    As far as the Seasonic 360, why on earth would you buy a 360W PSU? I just don't see the point. While I can justify a 500W PSU to a budget builder, I really cannot comprehend recommending a 360W PSU to anyone.

    I just ordered the Seasonic for a home server build. The higher efficiency is a plus since it will be running 24x7. Plus, the system really doesn't need the extra wattage.

    PSUs run more efficiently under load. IMO, the trend has been to overkill on the PSU when it's not really needed. In reality, when you actually add up the max loads of all components a 350-450W PSU is more than enough to run most single GPU gaming builds.
    3
  • vertexx
    Anonymous said:
    I am not sure why you think that a 40w bulb is purely resistive. Almost all bulb filaments are coiled, which makes them inductive. For example, http://www.donsbulbs.com/cgi-bin/r/b.pl/h4652|12.8v|40w|60w~usa.html shows a 12v 40w bulb filament, which is coiled.

    Perhaps you should measure the inductance of your bulbs, rather than just stating they are purely resistive.

    It's been a while since I've been involved in DC power calculations, but these bulbs are DC bulbs. At DC steady state, what role does inductance play?
    1
  • JimmiG
    Anonymous said:
    Please, if you could say , if the power supply is compatible with Haswell .I think this is very important .


    All PSUs are compatible with Haswell. It's only the C6/C7 idle states that *may* cause problems.

    Any PSU that uses DC to DC for the non-primary rails will support these idle states. Most other PSUs will be just fine as well. Remember that even if the CPU is drawing almost no power, you usually have some fan, hard drive etc. that's active on the 12V rail. I've never had any problems with my 5 years old Corsair VX 450W and my 4770K with C6/C7 enabled.

    Even if you end up having to disable C6/C7 sleep, it will only increase power consumption by 3W at idle. This may make a difference with laptops, but it's hardly an issue with desktops.

    Anonymous said:
    PSUs run more efficiently under load. IMO, the trend has been to overkill on the PSU when it's not really needed. In reality, when you actually add up the max loads of all components a 350-450W PSU is more than enough to run most single GPU gaming builds.


    True. PSUs only reach peak efficiency under a certain load. With an overpowered PSU, you may never load it enough for it to reach peak efficiency. A smaller PSU might end up being more efficient.

    My 4770K overclocked to 4.5 GHz and a factory overclocked GTX 670 reaches 405W at the wall when stress-testing the GPU and CPU simultaneously. In games, it's at 250 - 310W depending on the game.
    5
  • Someone Somewhere
    None at all...

    Inductors react to change in current and attempt to counter it. On a constant voltage with a constant resistance, current is also constant.
    0
  • vertexx
    Looking at those voltage spikes, I'm wondering if the DC bulbs could be the cause of that.

    A couple of other guys have commented on the inductance of the light bulbs. While I don't think inductance has anything to do with DC loading at steady state, it certainly can play a role with fluctuations in DC loading (i.e. startup, shutdown, and fluctuations).

    Those spikes occur at relative minimums and maximum voltages within the minor fluctuations of each PSU. If I remember correctly, that would indicate points where current is changing. Since inductance resists changes in current flow, that could cause a spike in voltage.

    Interested in your thoughts on that.
    0
  • Someone Somewhere
    Retest with a lot of NiChrome wire in a bucket?
    -1
  • InvalidError
    Anonymous said:
    Looking at those voltage spikes, I'm wondering if the DC bulbs could be the cause of that.

    Unless lightbulbs which are passive devices have something in them that can generate glitch energy at over 10MHz, no.

    The spikes are caused by impulse noise that occurs during the brief cross-conduction when switching elements inside the PSU toggle from forward rectifiers to free-wheeling rectifiers. For the few nanoseconds it takes for one device to turn on and the other to turn off, both will be conducting at the same time and this will momentarily short out the transformer's output. Although this cross-conduction is generally undesirable, some of it is necessary since without it, EMF from output inductors could destroy synchronous rectifiers.

    In a real-world application, the PSU would have over 10 000uF worth of extra capacitance from the motherboard which should considerably reduce if not eliminate most of the (very-)high-frequency noise from the PSU visible from the motherboard's point of view.
    0
  • vertexx
    Anonymous said:

    Unless lightbulbs which are passive devices have something in them that can generate glitch energy at over 10MHz, no.

    I'm not saying this is definitely the reason, but a passive inductive load absolutely can cause a voltage spike with a fluctuation in current. Although your answer sounds a lot more smarter than mine.

    But the theory is sound - more detailed explanation here:
    http://www.daycounter.com/Articles/Inductive-Voltage-Spike.phtml
    0
  • Onus
    Over at HardwareSecrets, there's a guy named c.hegge who is an Australian PSU reviewer. He has documented how bad the Samxon "GF" capacitors are. They don't like heat, and tend to fail. He has recapped Corsair "CX" PSUs with capacitor problems. This is also described on the badcaps.org forums. The Corsair CX reviews well, and looks great when new, but I won't buy or recommend them, especially in gaming PCs that tend to run warm.
    Of this batch of PSUs, I'd take the Seasonic every time. As Vertexx points out, it offers sufficient wattage for most PCs with a single graphics card using just one PCIe power connector.
    7
  • InvalidError
    Anonymous said:
    I'm not saying this is definitely the reason, but a passive inductive load absolutely can cause a voltage spike with a fluctuation in current.

    Not if the voltage spike is too short for the inductor's current to change by a significant amount.

    Also, a passive load being excited at 200-500kHz by the PSU's ripple voltage would not mysteriously generate noise at over 10MHz no matter how capacitive or inductive it might be unless you make/break contact but then it wouldn't be quite a passive load anymore since it is being actively switched on/off.

    Additionally, the back-EMF spike only applies when you are attempting to disconnect an inductive load before its current drops to zero. Here, the light bulbs remain connected to the PSU so there would be no make/break spikes from whatever inductance those bulbs might have as described in your link.
    0
  • Maxx_Power
    For those who worry about the inductance of the light bulb, remember that the inductance is proportional to the amount of electrons in the conductor, and therefore, for a length of wire, is proportional to the length and diameter of the wire, as well as the conductance of the wire.

    To put it in perspective, the wire in a coiled incandescent light bulb (there are non-coiled ones) is very very thin (sub-milimeter), and about 60 cm long (2 feet). Therefore, the max inductance of the wire is about the same as a single strand of a stranded wire in the PSU wiring or the bench-test box wiring, and thus, much much less than the total inductance of the system, just due to wiring alone. In this way, Toms correctly considered the inductance of the light bulbs to be negligible, when compared to the principal resistance of the light bulb (the resistance of the bulb-wire is high, particularly when it is heated up).
    0
  • rolli59
    Great to see PSU reviews again at Toms. After these two I am glad I vent with the Antec HCG400 when I needed a spare last year.
    2