Seasonic S12-330 PSU, new sleeved version

The Seasonic S12 power supplies need no introduction. It’s been a favorite on SPCR since its introduction a year ago. Now, it has been updated with longer, sleeved cables and lower capacity models boast a PCI Express connector. This time around we look at the baby of the bunch.

April 27, 2006 by Devon
Cooke

Since it was introduced in early 2005, Seasonic’s S12 series has been recommended
on SPCR more than any other power supply. We consider it a quiet reference,
against which other power supplies can be measured. Even so, the S12 is not
perfect — there are too many variations in individual circumstances for
one power supply to work for all users. For example, many potential users have
been disappointed to learn that the lower capacity S12’s did not come with a
PCI Express connector — despite the fact that they are more than capable
of supplying enough power.

The special status of the S12 warrants a little bit of special attention. We’ve
looked at three S12 models previously, the
430 watt model and the
500 and 600 watt models, but a new revision that addresses the lack
of PCIe connector makes the S12 worth another look. This time, we’re looking
at the baby of the bunch: The S12-330. 330 watts is enough power for almost
any desktop machine with the exception of dual-video card gaming rigs, but there may be differences in addition to capacity.

Unlike the changes made in the last revision, the new changes are concerned
with cosmetics and usability, not the internal design. This means that the newly revised S12’s are quite easy to identify, not least because they sport a new,
more colorful and slightly smaller retail box. At the same time, some changes
have been made to the accessories bundled with the S12:

• Dr. Cable (a system for cable management) has been dropped in favor of simple
  cable sleeving.
• The IDE to 5 volt / 12 volt fan-header adapter is no longer included
• A new IDE to 2 x Floppy adapter is included, as there are no longer any floppy
  connectors on the base cables

The new box on the right is smaller but brighter and more visible.

Some other changes were summarized quite succinctly by forum user dhanson865:

• 6 HDD connectors (previously 5) – 330 & 380W models
• 6 HDD connectors (no change) – 430W model
• 9 HDD connectors (previously 6) – 500 & 600W models

• 4 SATA connectors (previously 2) – 330, 380 & 430W models
• 6 SATA connectors (previously 2 or 3 depending on US version or not) – 500W
  model
• 6 SATA connectors (previously 4) – 600W model

• 1 PCIe power connector (previously 0) – 330, 380 & 430W models
• Longer (black) sleeved cables – All
• RoHS compliant – All

One final change is that the Fan RPM monitor cable has been removed. It is
no longer possible to monitor the speed of the internal fan. Most likely, it
was dropped because so many motherboards have trouble detecting an RPM signal
at the slow speed that the fan spins.

OVERVIEW

The exterior casing has not changed between revisions; so the spec label and
the cables are the only visual means of identifying the new version.

One concern with the original casing is that there are many vents that exhaust
heat into the system rather than out the back panel. This is still an issue
with the latest revision. That said, these vents are partially responsible for
the excellent cooling in the S12 line, so the tradeoff may be worth it for the
reduction in noise that it makes possible.

Heatsinks are smaller in the low end 330 watt model…

Under the hood, things look sparser than the models we’ve looked at previously.
However, this can probably be attributed to the lower capacity of our sample,
not to the different revision. The extra room comes from the smaller heatsinks
that are used in the 330 watt model. The heatsinks use the same basic design
as the S12-430, but the individual fins are shorter and there are no “split-level”
heatsinks that double the number of fins.

…but the basic circuit hasn’t changed.

The fan controller no longer supports an RPM sensing signal.

For comparison: The 430 watt version has larger, more effective heatsinks.

FAN

The fan hasn’t changed.

The most important parts of the fan haven’t changed: It is still a low noise,
low speed, ball bearing fan from Adda. The only difference is the lack of RPM
monitoring in the new revision, shown by the “1” in the suffix of
the model
number. Unless the fan controller is substantially different, we can
expect that the quality of noise hasn’t changed.

CABLES AND CONNECTORS

As mentioned, all of the cables are now sleeved and tend to be longer than
in previous versions. The cables are no longer twisted, which may be how Seasonic
could afford to extend them. A small amount of protection against EMI may have
been lost, but few users are likely to notice the difference, since EMI is rarely
a significant problem.

• 21″ cable for main 20+4-pin ATX connector
• 23″ cable for auxiliary 4-pin 12V AUX connector
• 22″ cable for 6-pin PCIe connector
• 23″ cable with two SATA drive connectors
• 20″ cable with two SATA drive connectors
• 28″ cable with three 4-pin IDE drive connectors with squeeze grips
• 21″ cable with three 4-pin IDE drive connectors with squeeze grips
• 5″ splitter from Molex to 2 × Floppy connectors

The additional connectors and increased cable length will be most appreciated
by power users who actually need four SATA connectors or six IDE connectors.
Unfortunately, the need to accommodate this limited market sector means that
there are more cables that need to be neatly tucked out of the way in the minimalist
systems preferred by silencers. The one exception is the PCIe cable, which will
be greatly appreciated by gamers whose favorite 3D accelerator requires it,
although such cards are often too hot to cool quietly.

The extra length is a less of a mixed blessing, since it will help solve compatibility
issues with larger cases — like the Antec P180.

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. The photo below shows
the setup (a different PSU is being recorded). 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 21°C and 20 dBA, 122V/60Hz.

ANALYSIS

1. VOLTAGE REGULATION was good, within ±3% of the nominal values
throughout the test. Both the +12V and +3.3V lines were slightly lower than
nominal throughout the test, which is fairly unusual; most power supplies are
slightly high.

2. EFFICIENCY was almost identical to the Rev. A1 S12-430 that we tested,
which is to say that it is among the select (but growing) number of power supplies
that reaches above 80%. It didn’t do quite as well at the very low end of its
output range, but even then the difference was rarely more than a watt or two.
At 150W and above, any differences were typically less than half a percentage
point and could easily be put down to sample variance.

3. POWER FACTOR was excellent thanks to the active power factor correction
circuit. A couple of times, it was so close to the ideal value of 1.0 that no
difference could be measured. And, unlike some other active PFC circuits, the
power factor remained above 0.99 even at the very low end.

4. TEMPERATURE & COOLING

Temperature was not an issue, and the temperature rise remained below 10°C
even at full load, so there is no reason to believe that the smaller heatsinks
are inadequate for the 330 watt capacity. The only indication that they are
not quite as effective as the ones in the S12-430 is the fact that the fan reached
full speed even before full load was reached.

5. FAN, FAN CONTROLLER and NOISE

As mentioned, the fan did not change with the new revision, so the noise character
tended to be very similar to the previous S12’s, especially the 430 watt version
(higher capacity models use a faster fan). Our latest sample produced a more
pronounced buzz than the models we’ve heard previously, although the difference
was quite subtle and the volume was not loud.

Of more concern was the fact that the fan ramped up much more quickly than
in the previous tests. The fan remained very quiet until just above 150W load,
but it jumped up very quickly after that. This was probably caused by the smaller
heatsinks that could not cope as well with heavy loads. The end result is that
the S12-430 is a better choice for a quiet mainstream or high powered system,
since these often peak between 150W and 200W under load. Systems with lower
power consumption are less likely to see a difference between the two models.

CONCLUSIONS

The newest version of the S12 brings some much requested features to the table,
mostly to do with cable selection and management. Those who were requesting
the features will no doubt be thrilled, but we can’t help but notice that none
of the improvements really cater to the low-noise crowd. Longer cables and more
connectors are all very well if they are needed, but the extra wiring does need
to be hidden if it’s not used. Considering the minimalist preferences of the
silencing crowd, the changes in cabling seem like much ado about very little.
We also miss the 5V fan headers that used to be included.

Overall, our favorite change has very little to do with the technical details
at all but with the way the power supplies are manufactured: We are pleased
so see that the S12 is now RoHS compliant and lead-free. No doubt many users
in the EU will agree, since it means that S12’s will continue to be available
in Europe.

The different revision aside, our inspection of the low capacity S12 was a
bit of a let-down from an acoustic viewpoint. The S12-430, 500 and 600 models’ biggest strength has been their ability to
remain quiet even in the 150~250W output range, but the smaller heatsinks mean
that the S12-330 ramps up comparatively early. The end result is a power supply
that is not the best in its class but is one of several quiet power supplies that become noisier when they are heavily stressed in a medium-to-high powered system.

The S12-330 is still very efficient, stable and well cooled. However, our ultimate concern is noise, and the higher capacity S12s beat the S12-330 at >150W loads. The S12-330 is a good choice for a lower-powered system, and it does have a price advantage over the other models.

It has to be said that the >150W fan rampup is probably a much smaller issue than it might have been even a few months ago. Most silent PC builders tend to choose lower power components, and today, with Athlon 64 and 64X2 processors running as cool as they are already, the Intel Core Solo and Duo components starting to come into the market, keeping even a highly capable computer under 150W DC maximum load is not at all difficult to do.

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Much thanks to Seasonic
USA for the opportunity to examine this power supply.

*

SPCR Articles of Related Interest:
Power Supply Fundamentals & Recommended
Units
Power Distribution within Six PCs
Seasonic S12-430
Seasonic S12-500/600 Rev. A2

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