You are here

Enermax Noisetaker EG701AX-VE SFMA 2.0: 600 Watts!

February 16, 2005 by Mike Chin and Devon Cooke

*POSTSCRIPT added Oct. 22, 2005*

Noisetaker EG701AX-VE SFMA 2.0

600W ATX12V 2.01 Power Supply

Market Price

~US$170 ($180 with SLI capability)

Over the past 18 months, power supply manufacturers have pushed
the maximum output ratings for their top ATX products well beyond the 400W
range. Enermax's Noisetaker line is a perfect example of this trend; the current top model is rated for a whopping 600W! This is considerably higher
than the 470W Noisetaker that we reviewed
last March

The incentive to introduce such high powered PSUs is perceived need and real market demand among PC enthusiasts and gamers. Gamers, especially, love to tell each other that ever more power is needed for fast processors and video cards, especially with the dual VGA cards used in SLI. There is, indeed, increased power need, but just how much is open to debate; we question the prevailing wisdom in another
. Gamers tell each other that overclocking a powerful system requires even more power, or else instability will result -- which may be true, except they underestimate the role of the power components in a motherboard that get overstressed in overclocking. In any case, there is no substitute, they say, for ever more power. Bigger-&-more-is-better advocates have found eagerly willing acolytes among PC enthusiast / gaming geeks. The power supply companies agree gleefully as they churn out models with increasingly higher ratings and prices. One can't help but see a parallel with the monster gas guzzling SUVs and so-called "mini"vans that choke North American roadways.

So we come to our new top of the line 600W Noisetaker from Enermax, with the unintuitive model number EG701AX-VE (W) SFMA. (Is this a deliberate effort to suggest an even higher power rating that it actually has? Or are we getting too jaded and cynical for our own good?) Our sample is a Noisetaker version 2. The main
difference between the Noisetaker revisions appears to be adherence to the newer v2.01
rather than v1.3 of the ATX12V PSU Design Guide. The actual specifications have not changed
much for comparable models; according to Enermax's spec
, the only differences are a slightly higher rating for one of
the 12V rails and the disappearance of a combined maximum wattage for the 3.3V
and 5V rails.

The absence of a combined wattage spec for the lower voltage rails suggests that
they are now independently
regulated. In most power supplies, power for the 3.3V rail is taken from the
same source as the 5V rail. This means that the maximum power available on each
of these rails is limited by the amount of power being delivered on the other. The
practical consequence is a combined maximum rating. A quick e-mail to Enermax
confirmed that the 3.3V and 5V lines are now fully independent of each other.

At the time it was reviewed, the 475W Noisetaker had a record-breaking peak
efficiency of 82%. While this mark has since been surpassed (the high water
mark as of February 2005 is 88%), the original 475W Noisetaker is still an exceptionally
efficient power supply. We would expect our new 600W version to at least equal
this mark.

Like its predecessor, this Noisetaker comes in an exceptionally colorful, exceptionally
LARGE retail box.

All the usual fixings, including a large, detailed manual.

Feature Highlights of the Enermax Noisetaker EG701AX-VE (W) SFMA


Supports nVIDIA SLI Technology

Only available as a separate 600W model. We reviewed the non-SLI version.

ATX 12V V2.01 Compliant

Not only
that, it's on the Intel-Approved Tested
Power Supply List

Dual, Smart Fans

They're thermally
controlled, manually controlled, and stay running for 2 minutes after shutdown.
They'll be factoring polynomials next...

Manual and automatic fan speed control

The "and"
is important; you can't choose one or the other.
and Well-Protected
from over-current, over-voltage, over-load, over-temperature, under-voltage
and short circuits. And that's a lot of protection folks.

Ring Core

Works with
PFC to prevent changes in the power supply from affecting the external AC
Active PFC
Expected of
a top-of-the-line model.
Fan Monitor
Fan header
allows the motherboard to read (but not adjust) the PSU fan speed.
Silence That's right,
silence is a "feature" of this model. Call me skeptical, but...

SPECIFICATIONS: Enermax Noisetaker EG701AX-VE (W) SFMA

AC Input

90~265V (Adjusted Automatically), 47~63 Hz
Max AC current draw
4~9.5A (Varies with input voltage. Typical in North
America is ~8A, Europe is ~4A)

DC Line







DC Output (Min/Max)







Total DC Output



Maximum +12V Current: 35A

Inrush Current Limiting: 80A /230V and 40A/115V max during cold

Hold up Time: 17ms at 115VAC or 230VAC, full load

Operating Temperature: 0°C ~ 40°C

Mean Time Between Failure: >100k hours at 70% of full rated
load; 230 VAC / 50Hz input; 25°C ambient

Safety: UL (Level 3), cUL (Level 3), VDE, CB, NEMKO, SEMKO, DEMKO,

Dimensions: W150 * H86 * D140 (mm)


The Noisetaker 701 employs the thermally regulated dual fan cooling system they introduced many years ago: An 80mm exhaust fan
on the rear of the PSU, and a 92mm intake on the bottom. It also includes a
manually adjustable fan speed dial that works in conjunction with the automatic
thermal regulation to bias the speed of the fans towards low noise or low temperatures.

One new feature of the Noisetaker V2 series is the introduction of what Enermax calls
a Ring Core. This consists of a gasket that fits around all of
the output wires as they exit the casing of the PSU that is designed to suppress
EMI. We do not have the equipment to test the actual effectiveness
of this feature.

Externally, the Noisetaker 2.0 revision looks identical to the earlier
version. The darker shade of blue indicates that our model has an active PFC.
A lighter blue version is available without active PFC.

There is a passive intake vent on the front that allows air to flow across
the internal components that are farthest from the fans. The "Ring Core"
that Enermax advertises can be seen around the cables as they exit the casing.

The internal PCB is neat and well laid out.

Loose spacing between the components means less airflow is needed for
adequate cooling.

Back exhaust fan at left; bottom intake fan on right. The larger intake fan
is rated for higher current, which means it moves more air than the exhaust fan. Why? Perhaps to
accommodate different pressure loads so that the inflow, after going through
the PSU (and some of it betting lost in back pressure), is equal to the exhaust

Cables and Connectors

There are eight cable sets, as well as fan header that transmits a fan RPM
signal to the motherboard.

  • 21" sleeved cable for main 20/24-pin ATX connector
  • 21" cable for 4-pin auxiliary 12V connector
  • 21" cable for 6-pin PCI-Express connector
  • 2 x 26" cables with two 4-pin IDE drive connectors and one floppy drive
    power connector
  • 34" cable with three 4-pin IDE drive connectors
  • 2 x 24" cables with two SATA drive connectors
  • 24" cable for PSU Fan RPM sensor

Aftermarket PCI-e adapter cable

It is in the number and type of cables that we expect to see the most
obvious differences between this Noisetaker V2 and the older version. In compliance with ATX12V 2.01, the main header now supports 24-pin
motherboards. Like the recently reviewed OCZ
, the header is convertible between 20 pins and 24 pins as
needed via an extra 4-pin plug that clips on the basic 20-pin connector.

Aside from the changes to the main ATX header, a PCI-Express connector
has been added, as well as two additional SATA power connectors. An additional
PCI-Express connector for SLI systems is available in the SLI model for $10 more. It has to be noted, however, that this PCI-e connector carries only 12V and ground lines; inexpensive adapters to convert two standard 4-pin Molex power connectors into a PCI-e connector are already available.

Flexible woven sleeves divide the cables into three bundles for improved management. This is a welcome improvement. The previous Noisetaker we reviewed had very stiff plastic
sleeves that made cable management ridiculously difficult.


  • 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.

REAL SYSTEM POWER NEEDS: 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, we recently conducted system
tests to measure the maximum power draw that an actual system
can draw under worst-case conditions.
Our most powerful P4-3.2 Gaming rig drew ~180W 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 150W, but the total still remains well under 400W in extrapolations of our real world measurements.

Ambient conditions during testing were 21°C and 19dBA, with input of 120 VAC
/ 60 Hz measured at the AC outlet. Fan voltage and noise levels were measured
with the manual fan controller at its highest and lowest points, although we
consider only the lowest points relevant in our analysis.

Enermax Noisetaker EG701AX-VE (W) SFMA Test Results
DC Output (W)
AC Input (W)
Intake Temp (°C)
PSU Exhaust (°C)
Fan Voltage (V, min-max)*
Noise (dBA/1m)
Power Factor

* min-max is the voltage range afforded by the manual fan speed control.

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


1. VOLTAGE REGULATION was excellent, within ±4% on all lines
in any combination of loads. As noted in the introduction, the 3.3V and 5V rails
are now regulated independently, meaning that their relative stability are
not as closely linked as in an ordinary power supply. Greater
fluctuations may be apparent when the Noisetaker is places in a real system.

  • +12V: 12.28 to 12.35
  • +5V: 5.02 to 5.18
  • +3.3V: 3.31 to 3.38

2. EFFICIENCY was very good, although it does not appear to have improved
appreciably since the last version. There are now a number of top-of-the line
power supplies that can achieve similar levels of efficiency. Regardless of
what the competition is doing, however, any power supply that can achieve efficiency
above 80% is worthy of special mention. This is a spec worth paying for
because it has a significant impact on the amount of heat produced within the
power supply, and thus how difficult it is too cool it quietly.

Compared to the previously reviewed 475 Noisetaker, our 600W version was less
efficient at the lower end of its output range. However, its peak efficiency was
reached at roughly the same point, around 300W, and sustained to a much higher power draw. The differences that we measured
between the two models probably stem from the the differences in power rating, not changes in basic efficiency between V1 and V2 Noisetakers

Against other top performers, the 71~77% efficiency of this PSU between 65 and 150W is almost poor. A number of recently reviewed PSUs manage ~78% efficiency from the starting low power test of 65W and continue up from there. Since so many PC systems in the real world remain at or close to idle much of the time, the poorer power efficiency at low power is at least somewhat significant. The efficiency of this PSU does seem optimized for systems with higher idle or minimum power draw.

3. POWER FACTOR was typical for active power factor correction unit,
staying very close to the theoretical best value of 1.0. You can't do much better
than that.

4. FAN, FAN CONTROLLER and NOISE: The test environment is live, so
readings are higher than would be obtained in an anechoic chamber readings.

The fans have not changed since the earlier version
Noisetaker. The acoustic signature of
2.0 revision is largely the same: The fans start quiet but not silent. However, the starting voltage is not
as low as the Noisetaker 475 tested previously. The extra 0.3V is enough to make an audible
difference as it represents a 10% difference in voltage, and results in a 2 dBA increase in the minimum noise level. The reason for the increased fan speed may be the assumption (by Enermax engineers) that the minimum power demand will be higher because this PSU will usually be used in more power hungry systems. Hence, a little more airflow to help with cooling right from the start.

At start, the fans produce a low-pitched
background hum that is quite easy to tune out. As the voltage increases,
this hum increases in volume but changes little in character. Once the
fan voltage reaches about 5V (around the 200W level on our test bench)
the hum is no longer quiet enough to tune out easily. The increase in fan voltage appears to coincide with a sudden spike
in the exhaust temperature at the 200W level, suggesting that fan controller
increases the output voltage precisely when additional cooling
is required. These fans are not the
quietest out there, but they are acceptable at the low voltage that is
supplied when the Noisetaker is under low load.

Shutting down a system connected to the
Noisetaker does not immediately turn off the internal fans. As a safety measure,
the fans continue spinning for a couple of minutes after shutdown in order to
cool the PSU and perhaps exhaust the hot air in the case. It may save a bit on product longevity; it could also be a minor issue in noise-critical
applications like audio recording.

The manual fan controller is a strange feature. We have difficulty
believing that anybody interested in a low noise PC would use
this PSU at anything except with the fan control at minimum. The full adjustment range of the controller is
only about 1.5V, and it has a tremendous amount of hysteresis. Typically, we had to wait 10-15
seconds after adjusting the knob before any change in fan voltage was observed.
The adjustment range is roughly half of
what it was in the previous Noisetaker.

Our quibbles with the manual fan controller aside, it is the automatic fan
controller that makes this power supply still worth considering in a quiet
system. As with the original version, the fan controller stays at minimum voltage
until almost 200W output, at which point it gradually increases as the internal
temperature increases.


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

Noisetaker 600W (2.0) @ 90W (23 dBA/1m)

Enermax Noisetaker
600W (2.0) @ 150W (27 dBA/1m)

Enermax Noisetaker
600W (2.0) @ 200W (30 dBA/1m)

Enermax Noisetaker
600W (2.0) @ 300W (35 dBA/1m)

Reference Files:

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

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

Tornado 400 @ 200W (24 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 lower.

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.


Our verdict on the Enermax
Noisetaker EG701AX-VE SFMA 2.0
is similar to that reached for the Noisetaker 475. The combination of high
efficiency and a well designed fan-controller are strong points. The small improvements made for this new revision are welcome additions
and, for the most part, do not interfere with most of the traits that made the Noisetaker
475 a successful product. The EMI-reducing Ring Core may be a good thing. The newly independent 3.3V and 5V rails should
contribute to overall stability, especially in a newer
system in which the load across the various lines can be quite unbalanced.

Overall, the Noisetaker 701 is fairly quiet, but no PSU designed to deliver this much power has low noise as a primary goal. There are other models on the market that
can compete quite capably with the Noisetaker in terms of both efficiency and
quality of fan controller. The Noisetaker 701 is
a very good PSU choice for low noise, and if you really need — or want, more likely — this kind of power level, then it's probably about as quiet as you can expect. We have yet to test any other PSUs that can deliver 600W.

Much thanks to Maxpoint
for this Noisetaker EG701AX-VE SFMA 2.0 sample!

POSTCRIPT: Efficiency Correction

October 22, 2005

Recently, we discovered that our power supply testing equipment and methodology were providing erroneously high efficiency results. In general, the biggest errors occurred at higher
output load points above 300W. At lower output levels, the efficiency error
was often no more than one or two percentage points. No other tested parameters were significantly affected.

Through a fairly arduous process of discovery, analysis and old fashioned problem solving, we modified our testing equipment and methodology to improve the accuracy of the efficiency results and described it all in the article SPCR's PSU Test Platform V.3. As part of this revision, we re-tested most of the power supplies on our Recommended PSU List. In most cases, the same sample was used in the second test.

The corrected and original efficiency results for all the re-tested PSUs are shown in in the article, Corrected Efficiency Results for Recommended Power Supplies. The relative efficiency of the tested power supplies has not changed.
If the tested PSUs are ranked by efficiency, the rankings remain the same whether we use the original results or the new results.

data is also being added to relevant reviews as postscripts like this one.

Noisetaker EG701AX-VE SFMA 2.0

Target Output








Actual Output




In this case, our original efficiency calculations were essentially correct through to about 150W output. Above that, the original results were too high, and the error kept increasing with rising output power till it reached over 5 percentage points off at maximum load. The new figures put the efficiency at below 80%. High, but not exceptionally so, about the same as the Seasonic Super Series, the first high efficiency PC PSU models to hit the retail market

* * *

Discuss this article in the SPCR Forums.



www SPCR