The ePower Tiger 550: Hot & Quiet

Despite having well designed detachable cables, low noise at high power levels, and lots of glitz, the ePower Tiger fails to deliver when it counts. Electronically it’s no more than an ordinary Tomcat, and it’s cooled about as well as a polar bear in the Sahara. Sometimes, noise isn’t all that counts…

May 1, 2006 by Devon
Cooke

Sometimes, a name says a lot. For example, the ePower Tiger associates a power
supply with a certain feline power: A silent but deadly killer of a power supply
that holds its power in check until the last second before it strikes (perfect
for first person shooters). A more cynical person might notice that such lyrical
names are rarely associated with high end products. The Ford Focus, Toyota Echo,
and the Pontiac Sunfire may sound cool, but any car nut knows that these are
vastly out-performed by the Acura NSX, the Honda S2000, or the BMW Z3. For some
reason, high end products often have names that appear to be random
alphanumeric strings.

Of course, there are exceptions
to both rules and a product shouldn’t be judged by its name. A well
named product might be aptly described by its name, but, unfortunately,
it’s not easy to tell which ones. Will the ePower
Tiger live up to its name? There’s only one way to find out: Throw it on the
test bench and let the results do the talking.

We’ve looked at a feline product from ePower before. Our
review of the semi-passive Lion noted that the it remained silent for
a surprisingly long time, but concerns about its cooling system made us wonder
about its longevity. Naturally, we’ll be curious to see whether the Tiger suffers
from a similar problem. Hopefully, the more conventional fan-cooled design will
mean that the cooling problems have been resolved, but, as always, there will
be the question of noise.

FEATURE HIGHLIGHTS

SPECIFICATIONS

The specifications for the Tiger make it seem like an odd mongrel of a power
supply. On the one hand, it contains a -5V line, which was dropped from the
ATX12V specification more than four years ago and has been out of common use
for even longer. On the other hand, it advertises split +12V rails, which are
required by the much more recent ATX12V 2.0. In addition, the +5V line is rated
at 40A — also a throwback to times when the +5V rail was the primary source
of power. On top of that, ePower’s
web site documents the +5V rating as 48A — an unbelievable number that
would push the rating for the +5V line above what is specified for the +3.3V
and +5V rails combined.

In actual use, only the two +12V rails are likely to see even half of their
rated values, and even then only on very high powered systems. As we have documented
several times
in the past, the vast majority of systems draw well under 200W.

EXTERNAL OVERVIEW

The Tiger is slightly longer than a conventional power supply — longer
than it needs to be if the size of the internal PCB is anything to judge by.
Strategically placed open spaces at both ends suggest that the design was adapted
from a model with dual 80mm fans. The extra length may cause problems in cases
where space is tight, especially considering that the sockets for the detachable
cables also take up extra room.

Nice and shiny: Perfect for the easily distracted (or friends of the easily
distracted).

The exhaust vent uses an unusual cross-hatched design that looks at least
as open as the more popular hex design. In addition, there is also a small vent
on the right panel to provide cooling for a large MOSFET and what appears to
be a passive PFC circuit.

A small vent on the side provides some airflow for components near the inner
edge of the power supply.

The rear grill is w-i-d-e open.

One of the biggest selling points for the Tiger is the detachable cables. Although
the extra connection between the power supply and the external devices can sometimes
cause voltage drops, detachable cables are quite helpful for cable management.
Some thought has gone into making the cables user friendly. The plugs are keyed
so that they cannot be plugged into the wrong socket by accident, and the proper
connections are clearly marked and the back of the unit. There is one possible
avenue for a mistake: Some of the plugs are the same shape and size as a PCI
Express connector. Luckily, all of the cables came plugged in to the correct
sockets. The cables are also color keyed; the blue plug connects to the power
supply, while the black plug goes into the external device.

One question is why make the ATX cable detachable? There’s no situation where this cable isn’t needed.

An illustrated diagram shows which plugs go where.

INTERIOR

The distinctive black heatsinks are very similar to those in the ePower
Lion, and there is little doubt that the OEM is the same: Topower.
Topower manufacturers power supplies for several well known brands, including
OCZ and Tagan. In the past, we have found that their products are often quiet,
but also undercooled.

The heatsinks in the Tiger are smaller and thinner than the Topower-based models
we’ve seen in the past, but this is not necessarily a bad thing, as the heatsinks
were often so large that they left little room for airflow. There is more open
space in the Tiger, but the internal components are still very tightly packed.

The black heatsinks cover a lot of area but are smaller than other models
from the same OEM.

The heatsinks are situated directly beneath the fan and do not allow much airflow
to pass through them; only about a quarter of the heatsink area is open enough
to allow air through. Luckily, the fins themselves are only about half a centimeter
thick, so the air doesn’t have to go very far to flow through.

The heatsinks are slitted to allow air to flow through them. About 75% of
the area is restricted.

The fins are thin enough to allow air to pass through them.

FAN

Sleeve bearing fans are quiet, but aren’t designed for high heat environments
like a power supply.

The fan is a low speed, sleeve bearing model from Globe Fan. All of these are
good signs for noise. However, sleeve bearings are not well suited to high-heat
applications, and generally have a shorter lifespan than ball bearing fans.

CABLES AND CONNECTORS

• 19″ cable for main 20+4-pin ATX connector
• 19″ cable for auxiliary 4+4-pin 12V AUX connector
• 2 × 19″ cables for 6-pin PCIe connector with EMI shielding and
  a ferrite ring
• 2 × 26″ cables with two SATA drive connectors
• 31″ cable with two 4-pin IDE drive connectors and one floppy connector
• 2 × 25″ cable with two 4-pin IDE drive connectors
• 2 × 26″ cable with a thermally controlled Molex and a thermally
  controlled 3-PIN fan header

All of the cable sets are detachable, including the main ATX and AUX plugs.
As mentioned, they are color coded, with a blue plug for the end that plugs
into the power supply and black plugs for the peripherals. In addition, all
of the cables except for the fan headers are sleeved. Most cables use black
plastic mesh, but the two PCIe cables are sleeved in some kind of metal mesh
to reduce EMI. These two cables also come with ferrite rings as a further measure
against EMI. These measures are intended to reduce ripple voltage, but such
gimmicks are usually unnecessary for the majority of users.

Of more interest are the two fan headers, which supply a variable voltage depending
on the internal temperature of the power supply. The voltage is the same as
received by the internal cooling fan, so our testing will characterize the behavior
of these headers as well. Fans with 3-pin and 4-pin Molex headers are both compatible,
as both headers are included on the cables.

TEST RESULTS

For a fuller understanding of ATX power supplies, please read the reference
article Power Supply Fundamentals & Recommended
Units. Those who seek source materials can find Intel’s various PSU
design guides at Form
Factors.

For a complete rundown of testing equipment and procedures, please refer to
SPCR’s PSU Test Platform
V.3. The testing system 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 output load, which is exactly the way it is in a real PC environment.
But there is the added benefit of a 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 standard loads. It is, in
general, a very demanding test, as the operating ambient temperature of the
PSU often reaches >40°C 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 too many variables in PCs
and 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 pretty good overall
representation, but it is not quite the same as an extended meeting in person.

REAL SYSTEM POWER NEEDS: While our testing loads the PSU to full output
(even >600W!) in order to verify the manufacturer’s claims, real desktop
PCs simply do not require anywhere near this level of power. The most pertinent
range of DC output power is between about 65W and 250W, because it is the power
range where most systems will be working most of the time. To illustrate this
point, we conducted system tests
to measure the maximum power draw that an actual system can draw
under worst-case conditions. Our most powerful Intel 670 (P4-3.8) processor
rig with nVidia 6800GT video card drew ~214W DC from the power supply under
full load — well within the capabilities of any modern power supply. Please
follow the link provided above to see the details. It is true that very elaborate
systems with SLI could draw as much as another 100W, perhaps more, but the total
still remains well under 400W in extrapolations of our real world measurements.

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. All other noise sources
in the room were turned off while making the sound recordings.

INTERPRETING TEMPERATURE DATA

It important to keep in mind that fan speed varies with temperature,
not output load. A power supply generates more heat as output increases, but
is not the only the only factor that affects fan speed. Ambient temperature
and case airflow have almost as much effect. Our test rig represents a challenging
thermal situation for a power supply: A large portion of the heat generated
inside the case must be exhausted through the power supply, which causes a corresponding
increase in fan speed.

When examining thermal data, the most important indicator of cooling efficiency
is the difference between intake and exhaust. Because the heat
generated in the PSU loader by the output of the PSU is always the same for
a given power level, the intake temperature should be roughly the same between
different tests. The only external variable is the ambient room temperature.
The temperature of the exhaust air from the PSU is affected by several factors:

• Intake temperature (determined by ambient temperature and power output level)
• Efficiency of the PSU (how much heat it generates while producing the required
  output)
• The effectiveness of the PSU’s cooling system, which is comprised of:
  • Overall mechanical and airflow design
  • Size, shape and overall surface area of heatsinks
  • Fan(s) and fan speed control circuit

The thermal rise in the power supply is really the only indicator
we have about all of the above. This is why the intake temperature is important:
It represents the ambient temperature around the power supply itself. Subtracting
the intake temperature from the exhaust temperature gives a reasonable gauge
of the effectiveness of the power supply’s cooling system. This is the only
temperature number that is comparable between different reviews, as it is unaffected
by the ambient temperature.

On to the test results…

Ambient conditions during testing were 22°C and 20 dBA, 122V/60Hz.

ANALYSIS

1. VOLTAGE REGULATION was so-so. With the exception of the full load
test, all voltages remained within the ±5% specified by ATX12V, although
the +3.3V line was very close to being more than 5% high in the lower output
range. The +5V line was also quite high. At full load, the Tiger overheated
and was unable to regulate its voltages properly. The test was halted when the
+12V line reached 11.3V — more than 6% from nominal. The voltage was visibly
falling at a rate of roughly 0.02 volts per second at the time when we stopped
the test.

Even prior to the meltdown at full load, the fluctuation between the highest
and lowest measured voltages was quite high, changing by 3% for the +12V lines
and as much as 5% for the lower voltage lines.

2. EFFICIENCY was average through the lower output range; it managed
to peak above 80% when the output hit 250W. In general, though, efficiency was
nothing special, remaining in the 70~80% range through most of the tests. Efficiency
dropped sharply after it hit its peak, perhaps because it began to overheat.
In a better cooled system, efficiency might have remained higher for longer.

3. POWER FACTOR

The Tiger comes with passive power factor correction, so the power factor was
generally slightly higher than it would have been without it. However, many
high-end power supplies now use active power factor correction, which is usually
capable of achieving a power factor of at least 0.95.

4. TEMPERATURE & COOLING

Cooling proved to be quite good at lower output levels but inadequate under
heavy load. The thermal rise across the power supply stayed below 5°C through
most of the lower test points. Some kind of threshold was reached at 200W, as
the temperature rose sharply and the fan quickly increased in speed to keep
up. But, even with this additional cooling, the temperature continued to rise,
culminating in a thermal overload as noted above.

It should be mentioned that, while our test bed is quite realistic at normal
power levels, it is unrealistic to expect any power supply to be the primary
source of cooling in a (hypothetical) system that draws 500 watts. At higher
levels, the test bed provides a punishing thermal environment that is tougher
than any real system.

5. FAN, FAN CONTROLLER and NOISE

The residual noise level of the Tiger was not very good. At 23 dBA@1m, it
was far from loud, but certainly not as quiet as the best units we’ve seen.
Subjectively, it was very easy to notice it, as it had a distinct whine and
a low drone underneath. The resulting two-pitch harmony was far more irritating
than the noise measurement suggests.

On the other hand, it took a lot of effort to force the noise level to increase.
The fan did not increase in speed until the output reached 250W (!) and the
internal temperature had reached a toasty 37°C. Even then, it remained reasonably
quiet until the internal temperature had climbed another 5°C — well
above 300W output.

The practical result of all this is that, at high loads, the Tiger may well
be the quietest fanned power supply we’ve tested, but it is also not cooled
well enough to give it much more than a half-hearted recommendation.

CONCLUSIONS

The ePower was a very mixed bag, with some things that we liked a lot (quiet
even above 250W output) and some things that we didn’t like (thermal meltdown).

Let’s start with the goods: It’s flashy, so it will look good in a showpiece.
It has a shiny, reflective finish, and nicely sleeved cables, some of which
can cut down on EMI. It also has intelligently designed detachable cables that
are unlikely to lead to user error.

Although it is comparatively quiet at higher loads, the low noise comes at
the cost of good cooling and reliability. In addition, its good performance
under high loads needs to be put into perspective to understand how the Tiger
will perform in an actual system:

1. Very few systems can sustain an output of even 200W. Only fancy gaming systems
   with dual VGA cards and possibly dual processors require this much power.
2. Unless the system is water-cooled, there will likely be other sources of
   noise that are louder than the power supplies. In particular, hot graphics
   cards are very challenging to cool quietly, and may well be a more significant
   source of noise than any power supply

On the bad side of things, the electronics are quite pedestrian. Efficiency
and power factor are average, and voltage regulation is only so-so. But, the
real kicker is the cooling: The internal heatsinks just aren’t good enough.
While it may be quiet under heavy load, it isn’t well cooled enough to trust
it for anything mission critical. In addition, the sleeve bearing fan is unlikely
to last long in such a harsh environment.

Despite its acoustic performance, we can’t really recommend the Tiger except
in very limited circumstances. It’s best suited for use in a high-end showpiece,
where it needs to look good and sound quiet, but long-term reliability is not
an issue, either because it is frequently upgraded or because it is used solely
for gaming.

In the end, our feelings about the Tiger are much the same as those for its semi-fanless cousin, the Lion: Quiet it may be, but even low noise can’t save it from the rest of its shortcomings, especially since the low noise comes at the cost of proper cooling.

* * *

Much thanks to ePower
Technology for the opportunity to examine this power supply.

*

SPCR Articles of Related Interest:
Power Supply Fundamentals & Recommended
Units
Power Distribution within Six PCs
ePower Lion EP-450P5-L1: Semi-Fanless PSU
from ePower
Seasonic S12-430: Our current low-noise champ
Seasonic S12-500/600 Rev. A2

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