OCZ StealthXStream 600 W Power Supply Review
By Gabriel Torres on April 4, 2008


Introduction

Hardware Secrets Golden Award

StealthXStream 600 W from OCZ has a 120 mm fan, is EPS12V-compatible, has two video card power connectors for SLI and CrossFire systems and comes with an extremely attractive price tag in the USA, costing less than USD 90. Is this a good power supply? Can it really deliver its rated power? Let’s take another look at this power supply, as we updated this article to add load tests results.

OCZ StealthXstream 600 W
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Figure 1: OCZ StealthXStream 600 W.

We liked this power supply concept: it has the same features found on high-end power supplies – 120 mm fan, active PFC and high efficiency (80% at 120 V and 83% at 230 V) – but the modular cabling system, with a an impressive low price. Of course we will see if what is inside lives up to our expectations.

Regarding efficiency, meaning less power loss – an 80% efficiency means that 80% of the power pulled from the power grid will be converted in power on the power supply outputs and only 20% will be wasted. This translates into less consumption from the power grid (as less power needs to be pulled in order to generate the same amount of power on its outputs), meaning lower electricity bills – compare to less than 70% on regular power supplies.

Active PFC (Power Factor Correction), on the other hand, provides a better usage of the power grid and allows this power supply to be comply with the European law, making OCZ able to sell it in that continent (you can read more about PFC on our Power Supply Tutorial). In Figure 1, you can see that this power supply doesn’t have an 110V/220V switch, feature available on power supplies with active PFC.

This power supply uses a very good cooling solution. Instead of having a fan on its back, its fan is located at the bottom of the unit, as you can see in Figure 1 (the power supply is upside down). A mesh replaced the back fan, as you can see. Since the fan used is bigger than fans usually used on power supply units, this unit is not only quieter than traditional power supplies, but also provides a better airflow.

This power supply comes with five peripheral power cables: two PCI Express auxiliary power cables, one peripheral power cable containing two standard peripheral power connectors and one floppy disk drive power connector, one peripheral power cable containing three standard peripheral power connectors, one Serial ATA power cable containing three SATA power connectors.

Here is where OCZ saved some bucks: other high-end 600 W power supplies have at least one more peripheral power cable with three SATA power connectors. So if you have more than three SATA devices (hard disk drives or optical drives) you will need to use an adapter to convert one of the standard peripheral power plugs into a SATA power plug.

On the aesthetic side all cables are protected with nylon sleevings that come from inside the power supply housing.

This power supply has two ATX12V connectors that together form an EPS12V connector. The main power supply connector can be used both on older 20-pin motherboards and on new 24-pin motherboards.

OCZ StealthXstream 600 W
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Figure 2: Motherboard and VGA power connectors.

All wires used on this power supply are 18 AWG, which is good enough for this power supply, and the +12 V (yellow) wires used on the motherboard connectors are 16 AWG (i.e., thicker), which is great. Cheap power supplies use 20 AWG wires or even 22 AWG, which are thinner.

Even though OCZ paid to have its own UL number, this power supply is really manufactured by FSP. FSP name was printed on the power supply printed circuit board.

OCZ StealthXstream 600 W
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Figure 3: This power supply is manufactured by FSP.

But… Wait a minute! This printed circuit board (FSP part number 3BS0110312GP) is exactly the same one used by OCZ GameXstream 700 W and Zalman ZM600-HP! Are they all the same product with a different name? Let's disasemble this unit to check this out.

A Look Inside The StealthXStream 600 W

We decided to disassemble this power supply to see what it looks like inside, how it is designed, and what components are used. Please read our Anatomy of Switching Power Supplies tutorial to understand how a power supply works inside and to compare this power supply to others.

In this page, we will have an overall look, while in the next page we will discuss in details the quality and rating of the components used.

We can point out several differences between this power supply and a low-end (a.k.a. “generic”) one: the construction quality of the printed circuit board (PCB); the use of more components on the transient filtering stage; the active PFC circuitry; the power rating of all components; the design; etcetera.

As we mentioned, this power supply is manufactured by FSP and uses the same printed circuit board as OCZ GameXstream 700 W and Zalman ZM600-HP. Thus the design of these three power supplies is identical. Whether the components used by OCZ StealthXStream 600 W are the identical to the ones used on these other two units or not is something we will analyze during our article.

OCZ StealthXstream 600 W
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Figure 4: OCZ StealthXStream 600 W.

OCZ GameXstream 700 W
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Figure 5: OCZ GameXstream 700 W.

Zalman ZM600-HP
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Figure 6: Zalman ZM600-HP.

On Figures 4, 5 and 6 you can compare the design used by these three power supplies. As you can see, visually these power supplies are identical, even though Zalman ZM600-HP uses a different heatsink design, its printed circuit board is from a different color and it has a modular cabling system.

Transient Filtering Stage

As we mentioned in other reviews and articles, the first place we look when opening a power supply for a hint about its quality, is its filtering stage. The recommended components for this stage are two ferrite coils, two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor), and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components than that, usually removing the MOV, which is essential for cutting spikes coming from the power grid, and the first coil.

Even though this power supply from OCZ has more components than the necessary – one extra X capacitor, two extra Y capacitors, one extra coil and a ferrite bead on the main power cable –, it doesn’t have a MOV, which is a sin. This power supply also features a X capacitor and a coil after the rectifiers.

OCZ StealthXstream 600 W
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Figure 7: Transient filtering stage (part 1).

OCZ StealthXstream 600 W
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Figure 8: Transient filtering stage (part 2).

A very interesting feature from this power supply is that its fuse is inside a fireproof rubber protection. So this protection will prevent the spark produced on the minute the fuse is blown from setting the power supply on fire.

All components described on this page are identical to the ones used on OCZ GameXstream 700 W and Zalman ZM600-HP.

In the next page we will have a more detailed discussion about the components used in the StealthXStream 600 W.

Primary Analysis

We were very curious to check what components were chosen for the power section of this power supply and also how they were set together, i.e., the design used. We were willing to see if the components could really deliver the power announced by OCZ.

From all the specs provided on the databook of each component, we are more interested on the maximum continuous current parameter, given in ampères or amps for short. To find the maximum theoretical power capacity of the component in watts we need just to use the formula P = V x I, where P is power in watts, V is the voltage in volts and I is the current in ampères.

We also need to know under which temperature the component manufacturer measured the component maximum current (this piece of information is also found on the component databook). The higher the temperature, the lower current semiconductors can deliver. Currents given at temperatures lower than 50° C are no good, as temperatures below that don’t reflect the power supply real working conditions.

Keep in mind that this doesn’t mean that the power supply will deliver the maximum current rated for each component as the maximum power the power supply can deliver depends on other components used – like the transformer, coils, the PCB layout, the wire gauge and even the width of the printed circuit board traces – not only on the specs of the main components we are going to analyze.

For a better understanding of what we are talking here, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses two GBU606 rectifying bridges in its primary stage, which can deliver up to 6 A each one (rated at 100° C), so the total current the rectifying section of this power supply can handle is of 12 A. These are the same components used by Zalman ZM600-HP. OCZ GameXstream 700 W uses two GBU605 bridges, but they have the same specs. This stage is clearly overspec'ed: at 115 V this unit would be able to pull up to 1,380 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 1,104 W without burning this component. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.

The active PFC circuit from this power supply uses three power MOSFET transistors (20N60C3 – the same one used by several other power supplies we took a look, like Antec Neo 550 HE, Cooler Master iGreen Power 430 W, Corsair HX620W, Thermaltake Toughpower 750 W, OCZ GameXstream 700 W and Zalman ZM600-HP), just like OCZ GameXstream 700 W and Zalman ZM600-HP. Zalman ZM600-HP, OCZ GameXstream 700 W and OCZ StealthXstream 600 W are the only power supplies we’ve seen using such design. All other high-end power supplies we’ve seen to date use only two transistors (except Enermax Galaxy 1000 W, which uses four transistors). Each 20N60C3 can handle up 300 A @ 25° C each in pulse mode (which is the case).

The active PFC transistors and the PFC diode are installed on the same heatsink.

OCZ StealthXstream 600 W
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Figure 9: Active PFC transistors and PFC diode.

In the switching section two FQPF18N50V2 power MOSFET transistors in two-transistor forward configuration are used. Each transistor has a maximum rated current of 18 A at 25° C or 12.1 A at 100° C in continuous mode (note the difference temperature makes) or 72 A at 25° C in pulsating mode, which is the mode used, as the PWM circuit feeds these transistors with a square waveform. Interesting to note that these are the same transistors used by Zalman ZM600-HP, OCZ GameXstream 700 W and Corsair HX620W power supplies.

The two rectifying bridges are installed on the same heatsink used by the switching transistors.

OCZ StealthXstream 600 W
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Figure 10: Switching transistors and rectifying bridges.

The primary section from power supply is controlled by a CM6800 integrated circuit, which is an active PFC and PWM controller combo. It is located on a small printed circuit board shown in Figure 11.

OCZ StealthXstream 600 W
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Figure 11: Active PFC and PWM controller integrated circuit.

Secondary Analysis

Like Zalman ZM600-HP and OCZ GameXstream 700 W this power supply uses eight Schottky rectifiers on its secondary, however the rectifiers are different and here lies the difference between OCZ StealthXstream 600 W and these other two power supplies. While on these other two power supplies all eight Schottky rectifiers are identical (MBRP3045N), OCZ StealthXstream 600 W uses four MBRP3045N, two for the +5 V output and two for the +3.3 V output, and four MBR2045CT for the +12 V output.

So the main difference between OCZ StealthXstream 600 W and the other two power supplies based on the same design is the +12 V output.

Each MBRP3045N rectifier can handle up to 30 A (15 A per internal diode, rated at 100° C) while each MBR2045CT rectifier can handle up to 20 A (10 A per internal diode, rated at 135° C).

The maximum theoretical current the +12 V line can deliver is given by the formula I / (1 - D), where D is the duty cycle used and I is the maximum current supported by the rectifying diode. Just as an exercise, we can assume a typical duty cycle of 30%.

This would give us a maximum theoretical current of 57 A [(10 A x 4) / (1 - 0.30)] or 686 W for the +12 V output on OCZ StealthXStream 600 W, while Zalman ZM600-HP and OCZ GameXStream 700 W have a maximum limit of 86 A [(15 A x 4) / (1 - 0.30)] or 1,029 W for the same output.

Since these three power supplies use the exact same rectifiers and design for the +5 V and +3.3 V outputs, the maximum theoretical capacity is the same: 43 A [(15 A x 2) / (1 - 0.30)] for each output, i.e., 214 W for the +5 V output and 141 W for the +3.3 V output.

The maximum power the power supply can deliver depends on other components used.

OCZ StealthXstream 600 W
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Figure 12: The eight Schottky rectifiers used on the secondary (four on each side of the heatsink).

This power supply has a thermal sensor located under the secondary heatsink, which controls the fan speed according to the power supply temperature. You can see this thermal sensor in Figure 13 (we removed the secondary heatsink to take this picture).

OCZ StealthXstream 600 W
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Figure 13: Thermal sensor.

This power supply uses Taiwanese electrolytic capacitors from Teapo, CapXon and OST. The big electrolytic capacitors from the active PFC circuit is rated 105° C like all other smaller capacitors are rated 105° C.

Power Distribution

In Figure 14, you can see StealthXstream 600 W label stating all its power specs.

OCZ StealthXstream 600 W
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Figure 14: Power supply label.

This power supply has four virtual rails, divided like this:

For a better power distribution, we think that OCZ should had put the two video card power cables on separated rails, putting the two ATX12V connectors on the same rail (but keeping them using separated wires).

Another small issue with the video card auxiliary power connectors is the way they are connected. From inside the power supply come only three +12 V wires to feed them, so it seems that this cable was originally intended for the use of just one video card auxiliary power connector and OCZ adapted this cable to add a second 6-pin connector. The first +12 V wire on the cable is connected exclusively to the plug labeled as “PCI-E1,” while the other two wires are slip into five wires distributed over the two connectors. We preferred to see each connector using individual wires coming from inside the power supply.

Now let’s see if this power supply can really deliver 600 W of power.

Load Tests

We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology.

First we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under each load. In the table below we list the load patterns we used and the results for each load.

We connected the two ATX12V connectors from this power supply to the +12VB input from our load tester. This means that this input was connected to the +12V1 and +12V2 rails from the power supply. All other plugs were connected to the +12VA input from our load tester, meaning that this input was connected to the +12V3 and +12V4 rails from the power supply.

If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (e.g., the +5 V output working at +5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. On the “Total” row we are using the real amount of power being delivered, as measured by our load tester.

Input

Test 1

Test 2

Test 3

Test 4

Test 5

+12VA

4 A (48 W)

9 A (108 W)

13 A (156 W)

17.5 A (210 W)

21.5 A (258 W)

+12VB

4 A (48 W)

9 A (108 W)

13 A (156 W)

17.5 A (210 W)

21.5 A (258 W)

+5 V

1 A (5 W)

2 A (10 W)

4 A (20 W)

6 A (30 W)

8 A (40 W)

+3.3 V

1 A (3.3 W)

2 A (6.6 W)

4 A (13.2 W)

6 A (19.8 W)

8 A (26.4 W)

+5VSB

1 A (5 W)

1 A (5 W)

1.5 A (7.5 W)

2 A (10 W)

2 A (15 W)

-12 V0.5 A (6 W)0.5 A (6 W)0.5 A (6 W)0.5 A (6 W)0.5 A (6 W)

Total

116.6 W

245.4 W

360.9 W

486.4 W

600.8 W

% Max Load

19.4%

40.9%

60.2%

81.1%

100.1%

Room Temp.

44.8° C

44.3° C

46.4° C

48.4° C

49.5° C

PSU Temp.

50.6° C

50.1° C

52.1° C

54.2° C

58.9° C

Result

Pass

Pass

Pass

Pass

Pass

Voltage Stability

Pass

Pass

Pass

Pass

Pass

Ripple and Noise

Pass

Pass

Pass

Pass

Pass

AC Power (1)

138 W

284 W

423 W

584 W

749 W

Efficiency (1)

84.9%

86.8%

85.7%

83.8%

80.8%

AC Power (2)144.8 W294.6 W435.4 W600.0 W764.0 W
Efficiency (2)80.5%83.3%82.9%81.1%78.6%
AC Voltage110.7 V109.8 V107.1 V106.8 V105.4 V
Power Factor0.9830.9930.9970.9980.998

Updated 01/22/2010: We re-tested this power supply using our new GWInsteak GPM-8212 power meter, which is a precision instrument and provides accuracy of 0.2% and thus presenting the correct readings for AC power and efficiency (results marked as "2" on the table above; results marked as "1" were measured with our previous power meter from Brand Electronics, which isn't so precise as you can see). We also added the numbers for AC voltage during our tests, an important number as efficiency is directly proportional to AC voltage (the higher AC voltage is, the higher efficiency is). Also, manufacturers usually announce efficiency at 230 V, which usually inflates efficiency numbers. We added power factor (PF) numbers as well. These numbers measure the efficiency of the power supply active PFC circuit. This number should be as close to 1 as possible.

OCZ StealthXStream 600 W can really deliver its labeled power at 49.5° C, keeping efficiency above 80% if you pull up to 80% from its labeled wattage (i.e., up to 480 W) and presenting efficiency around 83% if you pull between 40% and 60% from its labeled maximum capacity (i.e., between 240 W and 360 W). These results are good for a power supply on this price range, but of course we would like to see a higher efficiency when the power supply delivered its full 600 W to keep the great results achieved on lighter loads.

Voltage regulation during all our tests (including the overload tests we will present in the next page) was outstanding, with all outputs within 3% of their nominal voltages – ATX specification defines that all outputs must be within 5% of their nominal voltages – including -12 V, which usually doesn't like to stay within such tight tolerance.

Noise and ripple improved a lot when we got a second sample to re-test this power supply using our new precision power meter. When we were pulling 600 W from this power supply noise level at +12VA input from our load tester was at 23.8 mV (against 74 mV from the first sample), at +12VB input from our load tester was at 30.8 mV (against 64.6 mV from the first sample), at +5 V was 13.8 mV (against 25.4 mV from the first sample) and at +3.3 V was 18.6 mV (against 39.4 mV from the first sample), as you can see on the screenshots below (just to remember, the maximum allowed values are 120 mV for +12 V and 50 mV for +5 V and +3.3 V; all these values are peak-to-peak values).

OCZ StealthXStream 600 W
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Figure 15: Noise level at +12VA input from our load tester at 600 W.

OCZ StealthXStream 600 W
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 Figure 16: Noise level at +12VB input from our load tester at 600 W.

OCZ StealthXStream 600 W
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Figure 17: Noise level at +5 V with power supply delivering 600 W.

OCZ StealthXStream 600 W
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Figure 18: Noise level at +3.3 V with power supply delivering 600 W.

Now let’s see if we could pull more power from this product.

Overload Tests

We were really curious to see how much power this unit could really deliver, because by the project used we suspected it could deliver far more than what was labeled.

We tried to see not only the maximum power we could extract from this power supply with it still working inside its specs, but also if all its protections are working correctly. As you know by now, power supplies usually burn when we try pulling more than it is capable of handling if it doesn’t feature overload protection (OLP or OPP; these two acronyms mean the same thing).

The first thing we like to do is to test if over current protection (OCP) is active and at what level it is configured. Inside the power supplies all +12 V rails are connected together and the difference between them is that each group of wires uses a separated OCP circuit. We’ve seen lots of power supplies with their OCP configured with values higher than what was printed on the power supply label, or simply disabled, what transforms the power supply into a single-rail unit.

To test this feature we removed all power supply cables from our load tester leaving only the main motherboard cable. Then we increased current on +12 V until the power supply would shut down. On OCZ StealthXStream 600 W this happened when we tried to pull more than 18 A, which was a miracle: this is the first power supply we’ve seen with its OCP circuit configured with the exact value that was printed on the label. Usually on power supplies that have their OCP circuit correctly configured, the manufacturer sets this circuit at 1 or 2 amps above what is written on the label.

Then from test number five presented in the previous page, we started increasing currents to see the maximum amount of power we could extract from this power supply before it would shut down (if it implements any kind of overload protection) or burn (if it doesn’t).

We were happy to see that this power supply doesn’t turn on if you try to pull more power than it can deliver – funny enough the manufacturer doesn’t list overload protection (OPP or OLP; these two acronyms mean the same thing) as a feature for this power supply. The maximum amount of power we could pull from this unit is described below.

Input

Maximum

+12V1

27 A (324 W)

+12V2

27 A (324 W)

+5V

9 A (45 W)

+3.3 V

9 A (29.7 W)

+5VSB

3 A (15 W)

-12 V

0.5 A (6 W)

Total

736.2 W

% Max Load

122.7%

Room Temp.

48.2° C

PSU Temp.

56.7° C

AC Power (2)

986 W

Efficiency (2)

74.7%

AC Voltage101.9 V
Power Factor0.998

Under this test all outputs were within specs and noise level at +12VA input from our load tester was at 56.8 mV, at +12VB was at 60.2 mV, at +5 V was at 26.8 mV and at +3.3 V was at 20.4 mV.

Short circuit protection (SCP) worked fine for both +5 V and +12 V lines.

When the power supply fan is running slowly it is really quiet, but as soon as it starts spinning at its full speed – which happens when the power supply temperature reaches 30° C – noise level becomes somewhat high.

Main Specifications

OCZ StealthXstream 600 W power supply specs include:

* Researched at Shopping.com on the day we published this review.

Conclusions

We loved this power supply. Why? Because it has exactly the same design of two other good high-end power supplies, OCZ GameXstream 700 W and Zalman ZM600-HP, but costs a lot less – only USD 85, on average, in the USA. For the average user this is a terrific buy. This unit not only costs less than competing 600 W products, but you will be also bringing home a 735 W power supply!

The only internal difference between OCZ StealthXstream 600 W and those other two high-end models are the rectifiers used on the +12 V output, capable of delivering less current (and thus power). But it is still enough for the majority of users. The other components are exactly the same.

There are, however, some external differences that may prevent you from buying this unit. It has only three SATA power connectors (the other two power supplies have six) and five regular peripheral connectors (GameXstream 700 W has six and ZM600-HP has seven) and it does not feature a modular cabling system. So if you are thinking of installing more than three SATA devices (i.e., hard disk drives and optical units) you’d better look for a different unit, unless you don’t mind using adapters to convert standard peripheral power connectors into SATA power connectors – which isn’t a bad idea at all, due to the lower cost of this unit.

For us to consider this a “perfect” product, we’d like to see efficiency above 80% when delivering 600 W, but efficiency under other loads isn't bad at all, always between 80% and 83%.id.

Anyway, we think this is a terrific product for the average user, being a power supply with one of the best cost/benefit ratios around.

Originally at http://www.hardwaresecrets.com/article/OCZ-StealthXStream-600-W-Power-Supply-Review/451


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