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OCZ ModStream OCZ-520 12U Power Supply

December 24, 2004 by Devon
with Mike

Technology ModStream OCZ-520 12U

520W ATX/BTX power supply

Market Price


Devon Cooke is a new Vancouver-area editorial volunteer. A fourth-year philosophy major at the University
of British Columbia and and a regular reader of the site for more
than two years, Devon spends his spare time making short films and poking
around in the SPCR forums under the handle Devonavar. This is his first

-- Mike Chin, Editor / Publisher, SPCR

The OCZ ModStream OCZ-520 12U PSU is marketed as a high-power, low-noise unit.
With a handsome chrome finish and a 120mm blue LED fan, it is obviously aimed
at those who appreciate style in their computers as well as well regulated power
or, in the case of most SPCR fans, quiet power. One of the main selling
points of this PSU is the OCZ EZMod advanced cable management system, a fancy
name for detachable cables (with blue plugs!). Its cables are all shielded for
superior power regulation. They also glow under UV light.

The OCZ ModStream line of power supplies is a new alternative to the
OCZ PowerStream line, a sample of which was reviewed
in June. A lower powered 450W
version is also available. Both models are listed on the same page of the OCZ
; the
only relevant differences between them on the spec
for the ModStream line appears to be the different current available on the +5V and +12V lines.

A big retail box, full color and covered with marketing blurbs.

The contents of the box: power supply, EMI shielded power cable, installation
guide, and an accessory box.

Inside the accessory box: assorted detachable cables covered
in stiff clear plastic and a package of zap straps and Velcro straps.

as in the previous photo, the EMI shielded power cable is shown.

Feature Highlights of the OCZ Technology ModStream
OCZ-520 12U


OCZ PowerWhisper Technology with 120mm fan

Presumably their name for a temperature-regulated fan.

OCZ PowerShield PCI-Express lead

Support for
the latest graphics cards.

OCZ EZMod advanced cable management system

cables + velcro straps = cable management system.

Supports ATX/BTX/PCI Express/SATA

All the latest
technologies are supported.
Active PFC**

This is somewhat
misleading. Active PFC is ONLY available on the international version. Our
version was passive PFC.

3 Year warranty with OCZ’s exclusive PowerSwap replacement

Not bad, but
their PowerStream line has a 5 year warranty.
Over-Voltage / Short-Circuit
I would hope

SPECIFICATIONS: OCZ Technology ModStream OCZ-520 12U

AC Input

95~132VAC/190~264VAC 10/6A 60/50Hz

DC Output







Maximum Output Current







Maximum Combined









Although advertised as having an active PFC, this feature is only available on
the international version, model OCZ-520 12U EU. The unit we tested
had a passive PFC, and had the usual red 115/230 VAC selector on the


The ModStream OCZ-520 12U is visually striking, especially when powered
up. With a chrome finish, cables that glow under UV light and a Blue LED fan,
this power supply should provoke the envy of even jaded LAN partiers.
On a more serious note, this power supply is about 2cm longer
than normal, making it a less than ideal choice if space inside your case is

Part of OCZ's "Advanced Cable Management System". Note that
only the 4-pin Molex connectors and the 6-pin PCI Express/SATA connectors are
detachable; the 20/24-pin ATX power cable and the additional 4-pin 12V cables
are hardwired and not detachable.

The underside of the unit. The wire fan grill should not restrict airflow
much at all.

This is the most open PSU exhaust grill we've seen. There might be some
question as to how well it can contain EMI. Still, the unit passed the requirements of seven different
standards organizations. Note the 115/230V
selector. This gives away the fact that our review sample is the North American
version, without active PFC.

The fan is made of transparent plastic, which feels a bit brittle. This may not be the wisest
choice acoustically.

On close examination, it turns out to be a Yate Loon. Their 120mm fans have been featured in the quietest PSUs we've reviewed.

This one is definitely not so good. The
BH designation stands for Ball bearing and High speed.

Capacitors nestled under extended heatsink fins.

The extra length and the dead space on the right suggests that this power supply may have been
adapted from OCZ's dual-80mm fan design.

There are three fan headers, only one of which is used. The header (if not the whole PSU) was probably
adapted from a three fan model.


There are a total of six cable sets. As mentioned above, the ATX connector
and the 4-pin +12V cable are not detachable.

  • 15" sleeved cable for main 20/24-pin ATX connector(more
    on this in a moment)
  • 18" auxiliary 12V connector for processors that require it
  • 25" cable with two 4-pin IDE drive connectors and
    one floppy drive power connector
  • 2 x 25" cable with three 4-pin IDE drive connectors
  • 25" cable with two SATA drive connectors
  • 16" 6-pin auxiliary power connector for PCI Express

The cable lengths are pretty standard.

The 4-pin Auxiliary 12V connector on left.

The 20-pin motherboard header in center, and a 4-pin
adapter that slides on to the 20-pin header... produce a 24-pin header.

The detachable cables for the OCZ-520 may well be the primary reason for
the existence of this power supply. Unlike the recently reviewed Ultra
X-Connect 500
, only the peripheral power cables are detachable; the motherboard
header, its 20/24-pin adapter, and the 4-pin auxiliary 12V power cable are not
removable. In this regard, it more resembles the Antec NeoPower PSU. This should not be an issue for most systems (unless you plan on
running a case without a motherboard!).

noted in the pictures above, the 20/24-pin motherboard adapter is unique in
that it is simply an extra 4-pin header (with its own separate cable) that clips on to ordinary 20-pin header.
Very neat. But as most current motherboards do not require a 24-pin header, this cable / connector will have to be tucked away somewhere instead of removed.

All cables are EMI shielded and should not cause or receive much
significant interference. OCZ
says that the shielding is copper, but its distinctly silver color suggests
that it is some other material, perhaps a copper alloy. The cables are also
insulated with sleeves made of 1/8" clear plastic. Unfortunately, this
makes them extremely stiff and difficult to bend, makes routing cables
quite difficult.

The main attached cables are also quite short for a power supply in this price
range. The motherboard and 12V cables in particular are only 15 inches long,
and you may have difficulty reaching the motherboard header in larger cases or cases
where the motherboard is mounted upside down. Because of the
unique setup of our PSU
testing system
, we had to use a cable extension for the 12V cable in order
to reach the PSU tester. However, most systems should be fine.

All in all, the features of the supplied cables are somewhat of
a mixed bag. The detachable cables and the unique 20/24-pin adapter are well
thought out improvements, and EMI shielding is nice to have. However, the combination
of the inflexibility and the short length of the main cables may nullify some of the
advantages that detachability provides.


For a fuller understanding of ATX power supplies, please read our article Power Supply Fundamentals & Recommended Units. Those who seek source materials can find Intel's various PSU design guides, closely followed by PSU manufacturers, at Form Factors.

For a complete rundown of testing equipment and procedures, please refer to the
SPCR's Revised PSU Testing System
. It is a close simulation of a
moderate airflow mid-tower PC optimized for low noise.

In the test rig, the ambient temperature of the PSU varies proportionately with
its actual output load, which is exactly the way it is in a real PC
environment. But there is the added benefit of a precise high power load tester
which allows incremental load testing all the way to full power for any
non-industrial PC power supply. Both fan noise and voltage are measured at
various loads. It is, in general, a very demanding test, as the operating
ambient temperature of the PSU often reaches 40°C or more at full power.
This is impossible to achieve with an open test bench setup.

Great effort has been made to devise as realistic an operating environment for the PSU as possible, but the thermal and noise results obtained here still cannot be considered absolute. There are far to many variables in PCs and far too many possible combinations of components for any single test environment to provide infallible results. And there is always the bugaboo of sample variance. These results are akin to a resume, a few detailed photographs, and some short sound bites of someone you've never met. You'll probably get a reasonably good overall impression of that person, but it is not quite the same as an extended meeting in person.

SPCR's high fidelity sound recording system was used to create MP3 sound files of this PSU. As with the setup for recording fans, the position of the mic was 3" from the exhaust vent at a 45° angle, outside the airflow turbulence area. The photo below shows the setup. All other noise sources in the room were turned off while making the sound recordings.

Ambient conditions during testing were 20°C and 18 dBA, with input of 120 VAC
/ 60 Hz measured at the AC outlet.

DC Output (W)
AC Input (W)
Intake Temp (°C)
PSU Exhaust (°C)
Fan Voltage
Noise (dBA/1m)
Power Factor

NOTE: The ambient room temperature during testing
varies a few degrees from review to review. Please take this into account
when comparing PSU test data.


We did not test the output capabilities of this power supply up to its maximum
rated capacity of 528W, nor did we test its rated peak load (60s.) of 620W.
The maximum noise characteristics were reached just above 400W output, and it is difficult
to imagine that someone interested in silent computing would be using a system
that draws even half of this power.

1. VOLTAGE REGULATION was excellent, within -/+2% on all lines in any combination of loads. The low and high voltage seen on each of the main lines is shown:

  • +12V: 12.24 to 12.35
  • +5V: 4.85 to 5.02
  • +3.3V: 3.15 to 3.31

2. EFFICIENCY was very good. The efficiency / power output ratio curve is quite
flat, and efficiency did not start to drop until above 300W - above the
highest wattage draw in most systems. For most of the range in which this power
supply is likely to be used, efficiency remained between 77~78%. Although there are a few
power supplies with efficiency in the low to mid-eighties, these tend to be at 60~80% of rated power, where few system ever reach. In the realistic power draw range, this
power supply is close to the best we've measured.

3. POWER FACTOR was typical for a unit with a passive PFC, with a range
between 0.62~0.69, increasing with power draw.

4. FAN, FAN CONTROLLER and NOISE: The test environment is live, so
readings are higher than would be obtained in an anechoic chamber readings, due to reflections and reinforcement of sound waves off the walls, ceiling and floor.

Despite the modest start SPL of 26 dBA/1m, the fan in the OCZ-520 would not be considered really quiet by most silent computing
enthusiasts. Even at 4.6 volts, this fan produces bearing noise in a distinct
rhythmic chatter. The problem may be exacerbated by the brittle clear
plastic frame. Motor noise is fairly good, representing a low hum that is noticeable
mainly at lower speeds when it is not overpowered by air turbulence. At higher voltages, the rhythm of the bearing chatter increases in speed
and volume, and air turbulence begins to overpower the hum of the motor noise.

The fan controller of the OCZ-520 is very
good from a low noise point of view. The start voltage was 4.6V, and it did not increase substantially until the
intake air reached 32° C at around 300W output. At idle, most systems may
not produce enough heat to cause the fan to rev up. Even at full capacity, low
to medium powered systems with good airflow may not produce enough heat to cause the fan voltage
to rise above 5V. At around 300W output, the OCZ-520 begins to produce
enough internal heat to cause the controller to rise to 7V. The noise produced
at this level is not much different qualitatively from that at 4.6V, although
it is slightly louder. Above 300W, however, the fan voltage ramps up to full
power, just above 11.3 volts. The noise at this level is still dominated by
bearing chatter, and, in the quiet SPCR lab, the noise began to reverberate
around the room. At this level, the OCZ-520 is decidedly noisy, but it is difficult
to imagine what system would draw above 300W consistently.

Overall, the fan controller buffered the changes in voltage quite well. The
transitions between the voltage levels were gradual enough that it not possible to detect a specific change in noise level. The transition between 7V and
10.5V was drawn out over a period of about five minutes. In a working environment,
the lack of sudden shifts in fan speed would make the changes in noise level
reasonably benign.

MP3 Sound Recordings of OCZ Technology OCZ-520 12U

Technology ModStream OCZ-520 12U @

OCZ Technology ModStream OCZ-520 12U @ 300W (34 dBA/1m)

There was no need to make recordings at higher power levels; it's simply too loud.

Sound Recordings of PSU Comparatives

Seasonic Tornado 400 @ 65W (19 dBA/1m)

Nexus NX4090 at @150W (24 dBA/1m)

Seasonic Tornado 400 @ 200W (24 dBA/1m)

Nexus 92mm case fan @ 5V (17 dBA/1m)


These recordings were made with a high
resolution studio quality digital recording system. The microphone was 3" from
the edge of the fan frame at a 45° angle, facing the intake side of the fan to
avoid direct wind noise. The ambient noise during all recordings was 18 dBA or

To set the volume to a realistic level (similar to the original), try playing the Nexus 92 fan reference recording and setting the volume so that it is barely audible. Then don't reset the volume and play the other sound files. Of course, tone controls or other effects should all be turned off or set to neutral. For full details on how to calibrate your sound system to get the most
valid listening comparison, please see the yellow text box entitled Listen to
the Fans
on page four of the article
SPCR's Test / Sound Lab: A Short Tour.


The OCZ Technology ModStream OCZ-520 12U is a capable high power
unit packaged cleverly to appeal to the fashion conscious "power" geek. From the perspective
of a PC silencer, its best features are the fan controller, which stayed at
a low voltage until the output reached a very high 250W, and its detachable cables,
which help improve cable management and airflow.

Unfortunately, the benefit
conferred by the fan controller is reduced by the clicky fan. Additionally, the advantage of removable cables
is countered by their stiffness and short lengths.
The cables are not unworkable; users of other stiff-sleeved cables have reported good results using a hot hair dryer to bend the cables in place. The fan is not really loud at typical power levels, but its acoustic character will become annoying in a quiet PC. The fan could be replaced with a smoother, quieter one. In combination with that benign fan voltage controller, this could make for a very quiet and stylish PSU.

At this price level,
however, a PSU that needs modding right out of the box seems
a bit much. Especially when that's bound to void the 3-year warranty. For the likely target market -- gamers, overclockers, case modders -- there is no need for modding. It looks good, has snazzy features, tons of power and is certainly quieter than your average high power flashy PSU.

The SPCR audience is more demanding, acoustically. Ultimately, it's the choice of fan in this PSU that makes it less than ideal for use in a quiet or silent system. We'd like to see a special quiet fan version. Combined with the slow-ramping voltage behavior of the thermal fan controller, a quieter fan could make this is a very nice quiet high power PSU.

* * *

Much thanks to OCZ
for the opportunity to examine this power supply.

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