Corsair Power Supply Units Roundup

Today we are going to talk about four power supply units from a well-known manufacturer of computer memory – Corsair Company. We will discuss solutions targeted for different market segments and ranging from 450W up to 1kW capacity.

by Oleg Artamonov
10/10/2008 | 07:59 PM

Power supplies and computer memory seem to have little in common except that both are computer components. This common feature doesn’t sound to me like a good reason why many well-known memory makers such as OCZ, Corsair, SuperTalent have begun to produce power supplies. The trend is obvious, however.

 

Well, explaining phenomena of the computer market is not my job. Instead, I will check out how successful the manufacturers are in this kind of business diversification. This review will cover Corsair’s power supplies.

By the way, we have already tested Corsair’s products in our earlier reviews. Those were the CMPSU-620HX and CMPSU-750TX models.

Testing Methodology

Click the following link for a description of our testing methodology and the equipment we use, and a brief explanation of what the specified and tested parameters of power supplies mean. The article is called X-bit Labs Presents: Power Supply Unit Testing Methodology In-Depth. If you feel overwhelmed with the numbers and terms this article abounds in, check out an appropriate section of the mentioned article for an explanation.

You can also check our Cooling/PSU section for more reviews of power supply units. .

Corsair VX450W (CMPSU-450VX)

This 450W power supply is considered the junior model in Corsair’s line-up due to two reasons. It is the lowest-wattage model in the VX series which is the basic series from Corsair (as opposed to the enthusiast-targeted HX and TX series).

The PSU comes in a black-and-green cardboard box. The color plays an important role in model identification. With Corsair, each power supply has its own special color. On the other hand, you can hardly confuse different models because the model name is printed large and conspicuous.

Included with the PSU is a set of single-use cable straps, a sticker for the front panel of your system case, four screws, and a power cord. There is also a user manual and a fabric pouch for storing the PSU (I wonder who will ever need to store the PSU separately from both the computer and the PSU’s own box). I would exchange that pouch for more straps of different sizes. The included straps are rather short and unable to tie up a thick bunch of cables.

The PSU case is covered with black matte paint. It is somewhat rough to the touch, contrary to the fashionable glossy paint. The case measures a standard 140 millimeters of depth.

It is easy to identify the real maker of this PSU by its internal design. It is the well-known and respectable Seasonic. You can sometimes learn the manufacturer by the UL certificate number even without opening the PSU case but Corsair has obtained its own certificates.

The internal component layout of the VX450W represents a typical modern power supply. Its load-bearing semiconductor components are distributed among three heatsinks (from left to right): a heatsink with the transistors and diodes of active power factor correction (PFC), a heatsink with switching transistors, and a heatsink with output diode packs. The first two heatsinks are rather slim (2mm) black-painted aluminum bars with turned out ribs. The third heatsink consists of two such bars fastened together. You shouldn’t be surprised at this simplicity. Too massive and branchy heatsinks may even worsen the efficiency of cooling by producing more resistance to the airflow and thus reducing the speed of the latter. I have seen practical examples of this point quite a lot of times in my practice.

The PSU follows a classic circuit design with joint voltage regulation. There are two toroidal chokes next to the output cables, one of which regulates the +3.3V voltage while the other, the +5V and +12V voltages both together. It means that the voltage in the +5V rail depends on the load on the +12V rail and vice versa.

There are two chokes and noise filter’s capacitors near the exterior panel of the PSU. In the left part of the case, in between the heatsinks, there is an active PFC choke. You can see it clearly in the first photo of the PSU’s interior. The small additional card located nearby carries a chip that combines PFC and main regulator controllers. I couldn’t discern its marking as the chip was almost pressed to one of the heatsinks. The standby voltage regulator is based on an Infineon ICE2A0565Z.

KZE series electrolytic capacitors from United Chemi-Com are installed at the PSU’s output. They are rated for a temperature up to 105°C and are specifically designed for switching power supplies, besides other applications.

There is one 400V/330µF capacitor at the PSU’s input. Many reviewers note with pleasure that it is rated for a temperature of 105°C as well, but the temperature range is actually unimportant for a high-voltage capacitor and does not affect the PSU’s service life. This capacitor just doesn’t get too hot at work. Instead, I am rather surprised at its operating voltage. When the PSU is turned on, this capacitor’s voltage is 380V which is only 20 volts below the permissible maximum.

The transistors and diodes are installed in a curious way. They are all designed in compact TO-220 packages and are glued with thermal paste to aluminum bars that are somewhat larger in diameter than the package. The bars are screwed up to the heatsink via an insulating pad. This solution must be due to the low thermal conductivity of the insulating pads: the developer increased the heat dissipation area by using those aluminum bars.

The PSU is cooled with a 120x120x25mm fan (Adda AD1212MB-A71GL, 2050rpm). It uses a 2-pin connection.

About one fourth of the fan is covered with a piece of translucent celluloid film in order to achieve optimal airflows within the PSU housing. The latter has vent holes in the exterior panel only. If the fan were open fully, there would a high-pressure zone with slow airflow near the blank back panel whereas cooling efficiency depends directly on the speed of the air. When the front part of the fan is covered with the film as in this PSU, the airflow goes only into the back part of the PSU, then along the heatsinks, and out through the perforated front.

Having a total output power of 450W, the PSU can provide up to 396W (33A) across its +12V power rail. This rail is not divided into “virtual” multiple outputs, so you won’t have any problems connecting a couple of graphics cards, for example.

I want to remind you that the “virtual” division of the +12V rail is implemented for the sake of compliance with the safety regulations according to which the output power on any of user-accessible connectors of a PSU must not be higher than 240VA. When the load capacity of the +12V rail grew up beyond that mark, the developers began to install individual current limiters (set at about 18A) on the different output cables of the PSU. As a result, you could get the full output power of the PSU from all its cables combined, but only 12*18=216W from each cable taken individually. This solution can provoke some problems, for example when the PSU has two +12V output lines one of which powers the CPU and the other, the rest of the components. If the power consumption of the “rest of the components” is higher than 216W (this may happen if you have two graphics cards in SLI mode), the PSU will shut down due to the overload on the specific +12V line although it still has some reserve of wattage.

Of course, the manufacturers make use of this virtual division of the +12V power rail for marketing purposes, too. They promise that two (or more) +12V output lines ensure unprecedented wattage, stability, etc. This is wrong, of course. In a majority of PSUs there is but one +12V power rail inside. It is only at the very output pf the PSU that it is split into multiple output lines by means of current limiters.

The VX450W doesn’t have this kind of splitting. It has a single +12V power rail with a maximum current of 33A.

The PSU makes those amperes available to you through the following cables and connectors:

The cables are all sleeved. They are sufficiently enough, and there are two SATA cables for your hard and optical drives. The downside is that the PSU offers but one graphics card connector. The total output power of 450W is quite enough even for a dual-chip graphics card, let alone a GeForce 9800 GTX that has two power connectors, too. But you will have to use an adapter if you’ve got such a card.

The Molex connectors are straight whereas the SATA connectors are T-shaped (like shown in the photo above) in the middle of the cable and straight at the end. There have appeared a number of system cases where hard drives are installed crosswise. The T-shaped connector is small and proves to be handier then because you don’t have to bend the cable at an angle of 90 degrees right at the connector.

The PSU had no problems working continuously at any load from 50 to 450W.

The output voltage ripple at full load is within the norm (which is 120 millivolts for the +12V rail and 50 millivolts for the +5V and +3.3V rails) but the oscillogram shows occasional short spikes of voltage. They are not going to affect the stability of operation, though.

A cross-load diagram (see below) shows the effective values of the three main output voltages depending on the distribution of load among the different power rails of the PSU. As I wrote above, the power rails are not independent from each other in a PSU with joint voltage regulation.

The +3.3V voltage is very stable in the VX450W because it is the only one to have a dedicated regulator. The +12V voltage is good, too. What is especially nice, this voltage sags by only 2-3% when there is a high load on the +12V rail. The +5V voltage sags quickly as the load grows up and violates the permissible limits.

This is not a big problem, though. The combined load on the +5V and +3.3V rails is not higher than 40-60W in a modern PC system, and the output voltages of this PSU are all within the norm in this load range.

The PSU boasts superb efficiency in our 220V power grid. It is 79% efficient at a load of 50W and over 85% efficient at 100W and higher! The maximum is high, but I am even more pleased to see that the efficiency depends but little on the PSU load.

As I wrote above, the PSU is cooled with an Adda AD1212MB-A71GL fan. Its speed is about 865rpm at loads below 250W and then grows up steadily, reaching a maximum of 1860rpm. The PSU isn’t exceptional in terms of noisiness even as Corsair’s PSUs go, yet its result is good. The VX450W is almost silent at low loads.

Thus, the Corsair VX450W is a good and neat medium-wattage power supply that would suit perfectly a system with one graphics card. It offers a full selection of cables and connectors, delivers good electrical parameters, and works quietly at loads below 250W.

At the time of my writing this the VX450W cost about as much money as the popular ZM460B-APS from Zalman. Corsair’s product looks quite competitive to it.

Corsair VX550W (CMPSU-550VX)

The next product from Corsair to be discussed here belongs to the same inexpensive VX series but is declared to have an output power of 550W.

The personal color of this PSU is bright orange. It resembles the TX750W in the photos you can see on the Corsair website, but the latter is actually brown and far less bright.

The accessories are the same as you get with the VX450W: screws, single-use straps, a Powered by Corsair sticker, pouch, user manual, and power cord.

The VX450W and the VX550W resemble each other at first glance only, due to the same matte black paint. If you look at them closely, you can note the different position of the switch, the different shape of the case panels, and even the different way the fan grid is fastened to the case.

What is the reason for such small but obvious discrepancies between two PSUs from the same series?

Well, the interior design of the VX550W provides an immediate answer. This PSU is manufactured by Channel Well Technology (CWT) and not by Seasonic. The name of CWT should be familiar to our readers because we have tested its products under the brands of Antec (although Antec has recently switched from CWT to Seasonic), Thermaltake and many others. The above-mentioned Corsair TX750W is manufactured at Channel Well’s facilities, too.

It is, however, odd to see PSUs from two different makers in the same product series. Are these models so similar that the buyers won’t see any difference save for the extra 100W? Let’s see…

The component layout of the VX550W seems to be the same as that of the VX450W. There are three heatsinks with transistors and diode packs, one power transformer, and a PWM regulator on an individual card. Some details are just placed in somewhat different ways.

Still, it is possible to spot at least one point of dissimilarity. There are three (not two as in the VX450W) large toroidal chokes under the output cables and the nearby heatsink. You can see only one choke in the photo – the other two are hidden under the bundles of cables and the additional card. The three chokes mean that the PSU has dedicated voltage regulation: there is one choke responsible for each of the three main output lines.

That’s the only significant difference between the two PSUs, though. Like the VX450W, this model has active PFC which is based on a CM6800G controller that is located on an individual small card. This chip also serves as a controller of the PSU’s main regulator.

The heatsinks are made from aluminum bars painted black. They are about 3 millimeters thick at the top and about 5 millimeters thick at the bottom. The transistors and diode packs have large TO-247 packages. They are installed via insulating pads only – without additional plates or anything.

There are KZE series electrolytic capacitors from United Chemi-Con at the PSU’s output. The capacitors are rated for a temperature of 105°C (they do not get as hot as that, of course, but the higher temperature rating ensures a longer service life for them). A 440V/330µF Hitachi HU4 capacitor is installed at the input.

The PSU is cooled with a 120x120x25mm fan (Adda AD1212HB-A71GL, 2200rpm). The rated speed of the fan is higher than in the VX450W. Almost half of the fan is covered with a piece of celluloid film. As I wrote above, this is necessary for optimal distribution of airflows inside the PSU case. Without this film, there would be a zone with high pressure but slow airflow at the back part of the case, near the almost blank panel. It may sound paradoxical, but blocking a part of the fan’s impeller increases the efficiency of cooling!

By the way, this is a good illustration of the fact that a large fan does not necessarily cool better although many manufacturers tout 140mm fans as an indisputable advantage.

The PSU has an output power of 550W and can provide 492W across its +12V rail. In fact, the 100W addition relative to the VX450W refers to the +12V rail. That’s okay because it is the +12V rail that powers all the heavy consumers of a modern PC system such as processor, graphics card, etc.

The PSU doesn’t have “virtual” +12V output lines with current limiters. The maximum current of 41A is declared for the whole +12V rail.

The PSU is equipped with the following cables and connectors:

The selection of cables has become richer in comparison with the VX450W: there is now a second graphics card cable with a 6+2-pin connector (the 2-pin part is detachable, so this cable can go into both 6-pin and 8-pin connectors of graphics cards). Therefore you can connect either one top-end or two mainstream graphics cards to the VX550W without any adapters.

The cables and connectors have the same design as those of the VX450W: the cables are sleeved, the SATA connectors are T-shaped in the middle of a cable and straight at the end, the Molex connectors are straight but short, without rubber casings or anything.

The PSU worked normally at any load it is rated for.

The output voltage ripple on the main power rails is twice or thrice lower than the permissible limits. There are no short spikes, either.

The cross-load diagram of this PSU is perfect. None of the three voltages deflects more than 3% from their nominal values at any load distribution, and the +5V and +12V rails always keep within a 2% deflection even! Although I wrote above that the results of the VX450W are quite normal and you won’t have problems with it in a modern PC, the results of the VX550W are impressive nonetheless. With minor differences in circuit design, the senior model ensures stable operation in every mode it is supposed to support without any reservations.

The PSU is somewhat less efficient than the 450W model, especially at very low loads. The difference isn’t big, though. This model reaches an efficiency of 80% at about 100W.

The two PSUs differ more in terms of noisiness. The senior model is somewhat noisier due to the more powerful fan and different algorithm of the fan speed adjustment. The fan is rotating at 930rpm at loads up to 200W, which is somewhat higher than the fan speed of the VX450W. Anyway, this is still quiet enough.

But then the fan accelerates rapidly reaching its maximum speed at a load of 400W (150W below the maximum load). The VX450W had a fan speed of 1800rpm at such a load. Here, the fan speed is 2200rpm.

So, the VX450W and VX550W belong to the same series but have more differences than just their wattage ratings. The VX550W has two graphics card cables, which are going to come in handy for such cards as the single-chip GeForce 9800 GTX or the dual-chip GeForce 9800 GX2 and Radeon HD 3870 X2, and delivers ideally stable voltages at any loads. On the other hand, the VX450W is somewhat quieter in every mode, both at low and maximum loads, so you may want to prefer it if you are not going to assemble a particularly advanced computer configuration.

Corsair TX650W (CMPSU-650TX)

Next goes the 650W model from the TX series which is targeted at PC enthusiasts. We have tested one model from this series in our labs before (it was the CMPSU-750TX).

Pale yellow is the personal color of the TX650W. I tell you the specific shade because Corsair also produces the HX520W model which is bright yellow.

The accessories to this PSU are the same as those included with the VX series: a bunch of short cable straps, four screws, a sticker, a user manual, a power cord. The pouch for storing the PSU is black now rather than white as with the VX series (the PSU is put into the pouch in the photo above). The practical purpose of that pouch still evades me, though.

The PSU is quite ordinary on the outside. It has a dull black, somewhat rough, case made from good 0.8mm steel. The dimensions are larger now: the VX series models measured 140 millimeters of depth whereas the TX has a depth of 150 millimeters. On the other hand, it’s a trifle in comparison with some monster models measuring over 200 millimeters.

The exterior of the case is almost a copy of the VX450W model manufactured by Seasonic. This is interesting because the TX750W we tested earlier was manufactured by Channel Well. Does the TX series include models made by different manufacturers just like the VX series?

Indeed, this is a good old Seasonic M-12 without its additional fan and connectors for detachable cables at the back panel. So, junior models of both VX and TX series are manufactured by Seasonic whereas senior models of these series are manufactured by Channel Well.

The senior model of the VX series differed from the junior one with dedicated voltage regulation. In the TX series, both models have this functionality. You can notice three toroidal chokes under the right heatsink. The +3.3V, +5V and +12V voltages each have a dedicated regulator based on these chokes.

As opposed to the VX450W model, the TX650W follows a more classic design with two large heatsinks, one of which carries active PFC elements and the switching transistors of the main regulator while the other carries the diode packs of the output rectifier. The input rectifier’s bridge stands separately and is equipped with a small dedicated heatsink.

The PSU’s standby source is based on an Infineon ICE2A0565Z chip. The main regulator and the PFC device are based on a UCC28515DW controller.

KY series capacitors from United Chemi-Con are installed at the PSU’s output. They are somewhat inferior to the KZE series employed in the two previous models in their specifications. A KMQ series capacitor from the same maker is installed at the input. This 470µF capacitor is rated for a voltage of 400V and a temperature of 105°C.

The PSU is cooled with an Adda AD1212HB-A71GL fan that has a rated speed of 2200rpm. There is no celluloid film on it here.

The load capacity of the +12V rail is impressive. Having a total output power of 650W, the PSU can provide 642W across its +12V rail. Traditionally for Corsair’s PSUs, this power rail is not divided into multiple “virtual” 18A output lines. The combined load capacity of the +5V and +3.3V is high at 170W, too. Power Supply Design Guide for Desktop Platform Form Factors requires only 120W from these rails. Well, as we found out once, the real power consumption of a modern PC from these rails is often not higher than half a hundred watts.

The PSU makes all those watts available to you by means of a generous selection of cables and connectors:

That’s quite enough for most computer configurations unless you want to assemble a SLI/CrossFire system with two top-end graphics cards each of which has two power connectors. You’ll need power adapters then. The introduction of dual-chips cards from both ATI/AMD and Nvidia has reduced the demand for classic SLI/CrossFire subsystems built out of separate cards, though. Such subsystems are now limited to enthusiasts’ computers which are usually equipped with PSUs of even higher wattage.

This PSU worked without problems at any load from 50 to 650W.

The output voltage ripple is within the norm even at full load although there are accidental short spikes like we have seen with the VX450W model.

Although the PSU features dedicated voltage regulation, it cannot match the superb result of the VX550W because its +5V voltage sags suddenly when there is a high load on the +5V rail. Interestingly, the VX450W, another PSU manufactured by Seasonic, has the same problem.

This problem is not serious from a practical point of view, though. The +12V voltage, the main voltage in a modern PC, is ideal. The +3.3V voltage deflects by slightly more than 3% (while a 5% deflection is considered allowable). And even the +5V voltage remains within 3-4% from the nominal value at load distributions typical of modern PCs.

The PSU has good efficiency: 82% at a load of 100W and a peak efficiency of 87%.

It is partially due to the high efficiency and partially to the large heatsinks, but the results of the fan speed measurement shocked me somewhat: the fan speed is only 500rpm at loads up to 300W!

This is not just a record-breaking result. It is actually unique. The quietest Seasonic S-12 produced more noise even. The Enermax MODU82+ we have reviewed recently may be the only opponent to the Corsair TX650W in terms of noisiness.

Well, the fan accelerates rapidly at loads above 300-350W, making the PSU just good, rather than ideal, in this respect. Its fan is audible at a load of 500W. On the other hand, hardware components that can load the power supply at 500W are not going to be silent, either.

The odd jumps of temperature in the graph above are partially due to the weakness of the air that was flowing out of the PSU because of the low speed of the fan. The horizontal stretch at a load of 200W is obviously a measurement error.

Comparing the TX650W with the earlier-tested TX750W, these PSUs are manufactured by different companies (Seasonic and CWT, respectively) and differ from each other noticeably, even though belong to the same series. For example, the fan of the TX750W was as fast as 1100rpm even at minimum load, making that PSU not really quiet.

The Corsair TX650W is not just quiet. It is actually silent at loads up to 300-350W because you can hardly hear the sound of its fan even in a quietest room. This PSU becomes noisier at high loads but you need a serious PC configuration to achieve such loads. One CPU and one graphics card won’t be enough, for example.

Thus, the TX650W proves to be competitive to the above-discussed VX450W, at least for people who know the value of a silent PC. These two PSUs do not differ much in terms of noisiness but the TX650W costs about two times as much as the lower-wattage model.

Corsair HX1000W (CMPSU-1000HX)

I will end this roundup with the HX1000W model. As its name suggests, it has an output power of 1000 watts.

The PSU comes in an impressively large box, almost 40 centimeters long. Besides the PSU proper, the box contains a neat pouch with detachable cables and a set of traditional trifles such as single-use nylon straps, screws and a Powered by Corsair sticker.

The PSU is up to the box in its dimensions, measuring 200 millimeters of length, which is 55 millimeters longer than a standard ATX power supply. Well, I don’t think that someone will buy a 1000W power supply to install it into a compact system case.

The HX1000W is covered with black matte paint that feels somewhat rough to your fingers. The U-shaped cover is secured with eight rather than four screws as usual, although the steel of the case is thick enough to avoid any rattle.

The interior design looks familiar to me. It is the same as the design of Thermaltake’s 1200 and 1500W models. This power supply is surely developed and manufactured by CWT. And its circuit design is quite original as modern PSUs go.

The HX1000W is actually not one but two power supplies inside. The only common things between these two power supplies are the housing and the input filter. The photo shows clearly that the PSU is symmetrical inside, its left and right parts being identical: two identical active PFC chokes, two identical high-voltage capacitors, two identical transformers, and the same pairs of heatsinks.

This design is really unique. I have only met it in power supplies developed by CWT so far. Although power supplies with two power transformers are nothing new today, the two transformers in them have common circuitry for voltage control and regulation, common power transistors, diodes and other components. Here, we have not just a dual-transformer PSU but two individual 500W power supplies assembled in a single housing. In fact, you can even shut down one of them, and the other will go on working, yielding its 500 watts.

Well, the HX1000W does not offer such a half-wattage mode due to one reason. Its sub-PSUs are not exactly identical. Each of them yields two voltages, but one provides +12V and +5V whereas the other provides +12V and +3.3V. That’s why you wouldn’t be able to power your PC up using only one of these sub-PSUs.

The PWM controllers are located on small individual cards, one for each sub-PSU. They are based on the popular Champion Micro CM6800G chip that combines two controllers (for active PFC and the main regulator).

+12V is the main voltage of each sub-PSU. The +5V and +3.3V voltages are produced from +12V by means of rather low-power individual switching converters located on small individual cards. Each such converter is in fact a miniature power supply, but without an input rectifier. It has direct current at the input. The card carries a controller chip, power transistors of the converter and synchronous rectifier, a choke and smoothing capacitors. Thanks to the high operating frequency, the use of synchronous rectifiers and the rather low permissible load, these mini-converters do not require any additional cooling. This design is original but not exactly new. I have seen such regulators in some expensive PSUs. According to the developers, they ensure a quicker and more accurate reaction to changes in the load than what can be achieved with cheaper auxiliary regulators based on saturated-core chokes that are traditionally used in PSUs with dedicated voltage regulation.

The PSU is cooled with one 120mm fan running on ball bearings (Yate Loon D14BH-12, 2800rpm).

The PSU provide an output power of 1000W but it is distributed in a specific way. In an ordinary PSU, there is combined output power of the +5V and +3.3V rails and combined output power of the +12V lines, but the HX1000W is different due to the internal division into two sub-PSUs. Each sub-PSU can provide up to 500W of output power, but this number is the total of the loads on the +12V (1) and +5V rails of the first sub-PSUs and the total of the loads on the +12V (2) and +3.3V of the second sub-PSU. Thus, the HX1000W is one of the few PSUs available in which the two +12V power rails are indeed separate and independent from each other.

Both +12V rails were loaded identically during my tests. Our testbed has two independent 12V load blocks. Such parameters as voltage and pulsation were recorded for the first +12V rail only. The PSU being symmetrical inside, these parameters should be identical for both +12V lines.

The +5V standby source is implemented on yet another individual card. Unfortunately, its location isn’t quite good. The card is covered with an insulating plate (I removed it to take the photo) which blocks some of the vent holes in the exterior panel of the PSU.

The HX1000W has a modular design with four fixed cables and ten connectors for detachable cables. The label below the connectors explains which +12V line goes where. As for the fixed cables, neither the label nor the user manual gives you any clue about them. Well, it is easy to find this out even without taking the PSU apart. The different lines go from the different sub-PSUs, so the voltages should also differ slightly in them. The fixed cables for the mainboard and processor power supply were connected to the first 12V1 line, while the fixed cables for graphcis cards power supply - to the second 12V2 line.

The PSU is equipped with the following cables and connectors:

Included with the PSU are:

This set of connectors will suit every PC system. You can easily power up three top-end graphics cards and about ten hard and optical drives. It is good the PSU offers cables for drives of different lengths and with a different number of connectors. You can choose what suits your system case best.

Take note of the design of the cables. The fixed cables are ordinary enough while the detachable cables use a ribbon design in which adjacent wires are connected to each other along the entire length of the cable. This cable doesn’t need a nylon sleeve. It is rather soft and can bend at small angles, thus being handier when you try to lay it out in your system case. I have seen such cables before in PSUs from Ultra Products.

The detachable cables for graphics cards have additional ferrite rings that must suppress high-frequency pulsations of the supply voltage. The detachable cables don’t have such rings.

The PSU worked normally at its full load of 1000W. Unfortunately, it couldn’t work with my UPS (APC SmartUPS SC 620): at a load of only 300W there was a characteristic bubbling noise from the UPS and it would shut down in 20-30 seconds, reporting overload.

The high-frequency pulsation of the output voltage is normal on the +5V and +3.3V rails. Its peaks match the permissible maximum of 50 millivolts.

There were no low-frequency output pulsations as well, except the situation when the outputs of two different sources – 12V1 and 12V2 – are closed with one another. However, this is impossible in an actual computer system, because different graphics card power connectors are not directly connected to each other but to a special circuitry that allows balancing the load to ensure that none of the connectors will get overloaded.

The voltages are not very stable, either. Such results could be expected because the 1200 and 1500W models from Thermaltake based on the same platform hadn’t been any better.

The +12V voltage is good, deflecting by no more than 3%, but the +3.3V voltage violates the 5% limit at high loads. As a result, you cannot get the full 1000 watts from this PSU while staying within the voltage limits defined by the industry standard.

Although a modern computer doesn’t make much use of the +3.3V voltage (most of the components are powered by the +12V rail), that’s not a good thing. On one hand, a computer will work with the HX1000W, especially as it is not so easy to create a load of 1000 watts. Even a system with two Radeon HD 4870 X2 cards and a top-end CPU will consume much less. On the other hand, I have seen a lot of 1000W power supplies that delivered stable voltages. And the HX1000W doesn’t offer any advantages that would make up for this problem.

The PSU is 85% efficient at the maximum but its efficiency lowers to 80% at full load. This is a normal result. The power factor is rather odd (it usually grows up along with the load) but higher than 0.9 overall.

Noise is a most important factor for a 1000W power supply. As you may know from our reviews, early 1000K models were not quiet even under low loads.

The HX1000W is better in this respect. Its fan is rotating at about 1000rpm at loads up to 350W, making the PSU comfortable if not silent. Then the fan accelerates, reaching a speed of 2050rpm. The airflow is audible but acceptable, especially if you imagine how noisy the coolers of CPUs and graphics cards that consume so much power would be. Thus, the HX1000W is a rather quiet PSU as 1000K models go and average in terms of noisiness if compared with PSUs of other wattages.

Although the Corsair HX1000W has better results in my tests that Thermaltake’s PSUs based on the same platform that I tested earlier, I cannot call the results satisfactory. The poor stability of the +3.3V rail prevents this power supply from delivering its full declared output power. Moreover, the PSU could not work normally with my UPS. This is all rather disappointing because the HX1000W might claim to be among the best 1000K power supplies in its other parameters such as the selection of connectors, quality of manufacture, noisiness. Hopefully, the manufacturer is working upon this platform to get rid of its drawbacks.

Conclusion

I guess the most interesting thing I have found in this test session is that there are models from different developers in the same PSU series offered by Corsair. The junior models of both VX and TX series are manufactured by Seasonic while the senior models come from Channel Well.

There is no fundamental difference between the VX450W and VX550W models of the VX series. The former is somewhat better in terms of noisiness and the latter, in terms of electrical parameters. Both models are good, so your choice should be based on personal preferences.

The difference between the TX650W and the TX750W is big, however. The latter is average in terms of noisiness while the TX650W tested today is virtually silent at loads up to 50% from the maximum. It will be a perfect choice for people who want to assemble an advanced PC configuration as well as for everyone who loves silence. Of course, this PSU is more expensive than others of its class. By the way, paying extra for the TX750W doesn’t make sense because it is noisier.

The highest-wattage model was a bit of disappointment. Like Thermaltake’s power supplies based on the same platform, the HX1000W could not deliver stable output voltages. As a result, it could not deliver the promised 1000 watts of output power, either.