Clever Power SPS-400

It’s unique in two ways: A 15cm blower fan… which provides enough space on the back panel for four convenience AC outlets! The 400W ATX12V v1.3 compliant Clever Power SPS-400 is also claimed to have a noise level of only 18~25 dB. Our review lays a sample of this unusual PSU on the examining table.

February 7, 2005 by Devon
Cooke with Mike
Chin

Ever heard of Clever Power? Neither had we. A quick trip to the Clever Power website
reveals that they’re a Taiwan-based company that sells two products: A notebook
pad, and three variants of the power supply you see below, the others being 300W and 500W models. Mike shook his head and muttered that he had seen this PSU when it was called something else, but he couldn’t remember what. It was not until we’d got inside and pulled out the fan that he remembered. The Just Cooler logo on the fan got him to the nearest keyboard, Google-searching away.

It turns out that Just Cooler is the brand of another company called Orbitron International that makes the Clever Power products, and a few other things. Mike recalled unsuccessfully requesting review samples from Orbitron a couple of years ago. We’re guessing that Clever Power probably has the distribution rights for the U.S. But that’s enough genealogy; do we really care?

There’s been some thought put into distinguishing this power
supply from the dozens of other metal boxes with fans out there. A quick visual
inspection reveals two unusual features of this power supply:

• Built-in AC outlets
• An exhaust vent that is tiny by modern standards. The reason for the small vent
  is not apparent until the casing is opened up to reveal a proprietary 15cm blower-style
  fan.

The question of interest to SPCR readers will be whether the Clever Power can
live up to the 18-25 dB (not dBA) sound level that is claimed on the product
page. As is often the case for a SPL claim in product marketing, no distance
is given, so we will assume that a distance of 1 meter for our testing. Also
claimed is 70% efficiency — or 74% depending on which document you look at.

No exactly a slick point of sale package; it contains the PSU, a power cable, and
a four page manual.

A power strip is a nice idea, but
what will it do to airflow? That grill looks pretty small.

The intake vent is also smaller than usual, but given the size of the
exhaust it’ may not be an issue.

PHYSICAL DETAILS

The Clever Power is an interesting mix of past and present styles. The glowing
orange power switch is a throwback to the time when the home computer industry
was dominated by electronics geeks and computers were bought in kits at hobby
shops. The AC pass-through is also an old idea; power supplies for computer
terminals often included an outlet for the monitor. On the other hand, the polished
chrome finish is strictly a fashion statement, which dates this PSU to our modern
era in which power supplies can make fashion statements. Of course, the most
interesting parts of the power supply are under the casing. Let’s take a look…

The blower on the right is the reason why the vents can be so small without
compromising airflow. (NOTE: The red wire running out the exhaust vent was added by
us for testing purposes — fan voltage monitoring.)

The positioning of the intake grill against the heatsinks is
an attempt to manage airflow within the power supply.

The size and location of the vent holes on the Clever Power are
unusual enough to warrant a second look. Clever Power appears to be trying
to direct airflow rather than just force as much air as possible through
the case. To this end, there are three possible sources of airflow: The main
intake through the back and two small intakes near the bottom middle of each
side. This arrangement guarantees a direct airflow path across the heatsinks,
with auxiliary cooling provided by the two side vents.

Clever Power’s patented blower-style fan.

Unlike most power supplies, the Clever Power uses negative pressure airflow
to suck air through the unit rather than blow it
into the power supply.

The result is that the exhaust air is focused, meaning that the exhaust
vent need only be as large as the mouth of the fan.

The focused airflow that Clever Power utilizes is made possible
by the use of a fan that sucks air through the power supply along specific paths
rather than simply blowing it in and letting it find its own exhaust route.
This means that the components that are directly in the path of the airflow
will be better cooled than usual, while the rest of the power supply will have
less airflow overall. Hopefully the design engineers have paid enough attention
to design to place the hottest components in the airflow. Ultimately, the best
test of this will be how stable the unit is under a high power (and thus high
heat) stress test.

CABLES AND CONNECTORS

There are a total of six cable sets.

• 16″ sleeved cable for main 20-pin ATX connector
• 16″ 4-pin auxiliary 12V connector for processors that require it
• 16″ 6-pin auxiliary connector for older Pentium 4
  motherboards
• 2 x 32″ cable with two 4-pin peripheral connectors
  and one SATA connector
• 32″ cable with two 4-pin peripheral connectors and
  one floppy connector

Only the cable for the ATX connector has a sleeve.

With the exception of the main ATX header, the cables are both
unsleeved and untwisted. This allows the individual wires to become tangled
quite easily; not good for cable management.

The individual wires are tangled even as they leave the housing of the
power supply.

Another issue related to cables is that no 20-24 pin adaptor is included, so some of the latest motherboards will not be fully supported by the Clever Power. There is also no 6-pin auxiliary cable or any support for PCI Express. Because the Clever Power conforms to an older version (1.3) of the ATX12V standard, it is designed for higher on the 5V and 3.3V lines than is normal for the most recent motherboards.

The practical consequence of this is that the Clever Power is well suited for use in a system in which the processor draws primarily off the 5V line, such as an Athlon XP. The 12V line capacity of 20A is quite good, however, and it should also do well with more modern processors such as the Pentium 4 and the Athlon 64.

TESTING

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
article
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.

One very important point is that the 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, consider the power consumption of the systems described below. They were tested with the same equipment used to test power supplies.

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.

TEST RESULTS

Ambient conditions during testing were 21°C and 20 dBA, with input of 120 VAC
/ 60 Hz measured at the AC outlet.

ANALYSIS

Any new or unusual way of doing things always has some element of risk. The
test bench will determine whether the fancy airflow and blower fan actually
have any practical benefit for quiet computing.

1. VOLTAGE REGULATION was excellent, within ±2% on all lines
at every load. The 12V was consistently low, but only by 0.1~0.2 V.

• +12V: 11.8 to 11.9
• +5V: 4.9 to 5.0
• +3.3V: 3.3

2. EFFICIENCY was fairly average by today’s standards, staying in the 78-80% range for the
crucial 150-250W range. When this PSU was released a year ago these numbers
would have been excellent, but the competition in this area has stiffened a
lot in the past year.

3. POWER FACTOR was quite good, ranging between 0.65 and 0.73. While
it’s obviously not an active PFC unit, we’ve seen much worse numbers from
more expensive power supplies.

4. FAN, FAN CONTROLLER and NOISE: The Clever Power starts up with a
quick 12V burst to make sure the fan starts and immediately drops to the lowest
voltage required to keep it spinning, around 4.3V. At this voltage, the fan
is practically inaudible from 1 meter. The noise it produced
was close to our ambient noise level of ~20 dBA. Could it be that Clever Power’s
claim of 18-25 dB be accurate?

Of course, if you’ve been reading carefully, you will have noticed that our
voltage table starts at 6.4V. Why not 4.3V? The 4.3V reading that we measured
was obtained in open air while the PSU was cold. Installing the Clever Power
in our test setup had the immediate effect of boosting the fan voltage (and
noise). The noise level of 31 dBA/1m at 65W would not be acceptable in a quiet computer;
if the PSU is mounted in an actual case, the bass hum of the fan will never totally
disappear.

Moving to a higher load has an immediate and audible effect on the Clever Power.
The transitions between voltages are not very smooth, and changes in fan speed
are clearly audible. The thermal sensor is sensitive enough that it responds
audibly when the exhaust path is blocked.

The fan controller appears to be very conservatively tuned, and responds linearly to increases in load / heat. Almost all of the
adjustment range is used below 150W, which means that in a high powered system, the PSU fan may never run below ~9V. This is too high a voltage to produce acceptable
noise levels. The designers of this PSU would do well to examine the more “stepped” or exponential fan speed-to-heat response curves of the best quiet PSU fan controllers.

CONCLUSIONS

There was a considerable amount of thought put into designing the
Clever Power SPS-400. A negative pressure airflow system and a built-in power
strip are not common features for a power supplies. Unfortunately, it seems that not enough time was spent on the test bench; tampering with the internal airflow does not seem to have produced any tangible benefits. It is true that the AC outlets are indirectly made possible by the use of a blower-style fan that does not require the whole back to be used as an exhaust vent. However, the fan controller that the blower is paired with makes it difficult to consider this power supply for use in even a moderately quiet system. A system
with a fresh air intake duct for the PSU might prevent the blower fan
from ramping up in speed.

The extra AC outlets could be quite useful depending on
how your system is set up. For people who want to centralize their cable management
(and don’t mind adding even more cables to the tangle behind their case), this
could be quite a welcome addition. The 2A maximum current may be too low for
some applications though. In North America, larger CRT monitors and laser printers
routinely draw more than 2A. For countries that have 240V power systems this
will be less of an issue because the higher line voltage effectively halves
the current draw of all electrical appliances.

For $45, the Clever Power is cheap enough that it might be worth integrating
it into a system that is specially designed for it. We had no issues about
either its stability or its efficiency. However, anyone looking for a cheap
quiet power supply to drop into their existing system would be best advised to look
elsewhere. Just about any PSU in our Recommended table will be quieter. This power supply will be a significant source of noise in any situation
in which it is expected to exhaust warmed air from a case.

* * *

Much thanks to Clever
Power for the opportunity to examine this power supply.

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