Articles: Cases/PSU
 

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The PSU is parceled into a black velvety pouch with golden letters “Seasonic” to emphasize the high class of the product you’ve just bought.

Interestingly, the new PSUs of the X-Gold series have changed a little since the old X-750 even externally. The vent grid of the latter used to protrude a little above the surface of the case but now they are at the same level (the area around the grid is sunken in exactly to the same extent as the grid protrudes). This should improve the compatibility of the Seasonic PSUs with various system cases.

The overall design has remained intact, though. The PSU has a matte black case. It’s neat and lacks any decorations except for the Seasonic sticker whereas competing products can now sport colored plastic and metal details that can change a PSU’s appearance quite dramatically.

Well, I don’t think that the exterior design of a product you are likely to enjoy viewing for a maximum of half an hour (from the moment you unpack it to the moment you put it into your system case) is really important.

There are two rows of connectors for detachable cables on the back of the case. The X-Gold doesn't have fixed cables. Even the mainboard power cable is detachable. The connectors are not color-coded and are right next to each other, so you may want to connect the cables before putting the PSU into your system case, especially if the latter isn't roomy.

The design of the connectors has changed but slightly since the first version of the X series. A plastic decorative cover plate is missing and the labels are now printed on the metal rather than on a sticker above (the sticker looked rather unserious, I must confess). A 4-pin connector for a CPU cable is missing, too; there is only one 8-pin connector left.


Seasonic X-760

The interior design of the PSU has changed more (since I tested a 750W model in my earlier review, I show you a photo of its closest 760W cousin). First, the PCB is different. Although the circuit design has remained the same, some components have changed their positions inside the case. The capacitors and transformer have moved a little whereas the main PWM controller chip now resides on a small upright daughter card. These movements do not tell us much about any possible improvements in the operation of the PSU because Seasonic may have optimized the component layout for some other reasons, for example to make it easier to assemble the PSU or to utilize more affordable or available components. On the other hand, the X-760 is obviously not just a rebranded X-750 but a truly new version in its own right.


Seasonic X-760

The heatsinks are the most notable difference as they have become larger. We can see simple fins where the X-750 used to have smooth metal. And where the X-750 had simple fins, we now have a rather complex heatsink cut lengthwise and crosswise.

All of this is meant to improve the cooling of the PSU (of all of its components since every heatsink has become larger). Although I didn’t observe any overheat with the X-750, you can’t have too much cooling.


Seasonic X-560

Interestingly, the junior model of the series doesn’t differ much from its senior cousin except that it has fewer capacitors at the output. The heatsinks are the same. It must be simpler for Seasonic to order and install identical components into all the models of the series rather than to try to save on the lower-wattage ones.

Even with the changes I’ve described above, the heatsinks of the Seasonic X-Gold products look toy-like compared to many other PSUs. Those slim shiny bars that split up into "fingers" at the top (you can see them in the right part of the PSU next to a large power transformer) are installed on the input rectifier which is usually equipped with a large and massive heatsink. This is all due to the high efficiency which is itself due to the up-to-date circuit design of these PSUs. For example, they use a synchronous rectifier based on field transistors instead of a regular output rectifier based on diodes which dissipate quite a lot of power. The synchronous rectifier is more complex (the diodes work by themselves whereas the transistors have to be managed with a special chip) but also far more economical. The resistance of a modern field transistor is no higher than a hundredth of an Ohm when it's open, so it doesn't dissipate much power even when working with high currents.

There is a card with output connectors and voltage converters at the back panel of the PSU. Its component layout has also changed a little compared to the similar card installed in the X-750 although the main components have remained the same. There are two switching converters and two synchronous rectifiers on that card.

Chokes and smoothing capacitors are hidden between the card and the side panel of the case. I guess Seasonic engineers had a difficult time trying to fit all the required components into this small volume. There are polymer capacitors on the card which is especially important as they do not get any air flow from the fan, as opposed to the capacitors on the main PCB. On the other hand, these capacitors in the +5V and +3.3V rails have a much lower load in modern computer systems than the capacitors of the +12V rail.

Each of the three X-Gold models is cooled with a Sanyo Denki San Ace 120 fan (9S1212F404, 120x120x25 mm, 2200 RPM, 2-pin connection). If the fan fails or otherwise ceases to satisfy you after the warranty period, you will be able to easily find a replacement. The fan of the X-750 had a 4-pin connection, by the way.

Besides the smooth, aerodynamic shape of the impeller we can note the circle of hollows around its center. In two out of the three fans some of the hollows were filled with some brown glue-like substance. This indicates that each impeller was individually balanced by adding drops of glue to shift the center of mass as necessary. With such balancing the Sanyo Denki fans should ensure low vibration, excellent acoustic characteristics and a long life of the bearing (by reducing the stress caused by the beating of the impeller).

Each of the three models can deliver almost all of their full output power across the single +12V rail. This rail is not split up into multiple lines. The X-760 doesn't seem to be greatly different from the X-750 except that the -12V rail is weaker (0.5 instead of 1 ampere) but a modern computer has almost no consumers of that voltage (except for COM port drivers which are going to leave mainboards very soon, too). The total output power is 10 watts higher as is indicated by the model name.

Each model comes with the following cables:

  • One mainboard cable with a 20+4-pin connector (58 cm)
  • One CPU cable with a 4+4-pin connector (64 cm)
  • One CPU cable with an 8-pin connector (64 cm, for the X-760 only)
  • Two (X-660 and X-760) or one (X-650) graphics card cable with two 6+2-pin connectors (58 cm, for a total of 4 or 2 graphics card connectors, depending on the PSU model)
  • Two (X-760) or one (X-560 and X-660) cable with three PATA power connectors (55+15+15 cm)
  • One cable with two PATA power connectors (35+15 cm)
  • Two cables with three SATA power connectors on each (55+16+16 cm)
  • One cable with two SATA power connectors (35+15 cm)
  • Two adapters for two floppy-drive plugs each (15 cm)

Nothing seems to be missing here. The HDD power cables are now only 55 or 35 centimeters from the PSU case to the first connector whereas they used to be 55, 45 or 35 centimeters long to the first connector with the X-750, but the total number of connectors is the same.

The cables are packed into a cute pouch.

 
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