Enermax Noisetaker II (Rev. 2.2): A New Rev of an Old Fave

Power
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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 22°C and 19 dBA, 121V/60Hz.

OUTPUT & EFFICIENCY: Enermax NoiseTaker II (Revision 2.2)
DC Output Voltage (V) + Current (A)
Total DC Output
AC Input
Calculated Efficiency
+12V1
+12V2
+5V
+3.3V
-12V
+5VSB
12.19
0.99
12.17
1.74
5.16
1.00
3.43
0.98
0.0
0.2
42.8
65
66.0%
12.15
1.91
12.14
1.74
5.16
2.00
3.42
1.91
0.1
0.3
63.9
92
69.4%
12.14
1.91
12.12
3.31
5.16
2.00
3.42
3.84
0.1
0.5
90.5
123
73.8%
12.13
3.85
12.10
5.00
5.15
4.82
3.46
3.80
0.2
0.8
151.6
192
78.9%
12.10
5.70
12.06
6.50
5.15
4.71
3.45
5.55
0.2
1.0
198.2
247
80.2%
12.10
6.69
12.06
8.11
5.15
7.41
3.40
6.65
0.3
1.3
249.7
310
80.5%
12.10
7.84
12.05
9.67
5.14
9.23
3.40
8.65
0.3
1.5
299.3
373
80.3%
12.06
11.56
12.00
12.68
5.11
11.02
3.38
11.20
0.4
2.0
400.5
508
78.8%
12.03
15.28
11.98
14.24
5.10
15.10
3.37
14.47
0.5
2.5
498.7
652
76.5%
12.00
17.93
11.93
17.27
5.09
18.30
3.35
18.40
0.6
3.0
598.2
813
73.6%
NOTE: The current and voltage for -12V and +5VSB lines is not measured but based on switch settings of the DBS-2100 PS Loader. It is a tiny portion of the total, and potential errors arising from inaccuracies on these lines is <1W.

OTHER DATA SUMMARY: Enermax NoiseTaker II (Revision 2.2)
DC Output (W)
42.8
63.9
90.5
150.6
198.2
249.7
299.3
400.5
498.7
598.2
Intake Temp (°C)
23
25
30
34
35
39
42
48
50
53
Exhaust Temp (°C)
26
28
31
36
40
43
45
51
54
58
Temp Rise (°C)
3
3
1
2
5
4
3
3
4
5
Fan Voltage (V)
3.6~5.1
3.6~5.5
3.6~6.1
4.2~7.5
6.0~9.2
7.4~10.2
8.7~11.4
11.2~11.6
11.6
11.6
SPL (dBA@1m)
24~30
24~32
24~32
26~38
33~42
37~44
40~44
44
44
44
Power Factor
0.97
0.99
0.99
1.00
0.99
0.99
0.99
0.99
0.99
0.99
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.

ANALYSIS

1. LOW LOAD PERFORMANCE

Power consumption in standby mode was quite low, coming in at ~0.5W and a power factor of 0.11. However, the power supply would not start properly with no load applied. In fact, there were problems starting (and staying on) even with substantial loads on the main voltage lines.

The problem was traced to the two minor voltage rails: -12V and +5VSB. Applying a small 0.1A load to either of these lines would allow the NoiseTaker II to function normally. However, removing the load from these lines even for a split second was a recipe for trouble, as the power supply would either turn off entirely or rapidly cycle between on and off. We were happy that the power supply was connected to our test bench, not an actual system when this happened.

2. VOLTAGE REGULATION was quite good; none of the voltages fluctuated by more than ±3%. However, all of the voltages were slightly high, especially the +3.3V line which was typically about 4% above the nominal voltage.

3. EFFICIENCY was about average for a high end power supply. The peak just barely cracked 80% at the relatively high output load of 250W. This is an improvement over the earlier version, which peaked at 78.5%. At lower loads, efficiency was actually quite poor, staying below 70% until ~65W output. Most systems require less power than this at idle and tend to spend much of their time idling. For this reason, the NoiseTaker II would actually be relatively inefficient under real world circumstances.

4. POWER FACTOR was excellent thanks to the active power factor correction circuit. Power factor stayed above 0.97 throughout the testing, which is very close to the theoretical maximum of 1.0.

5. TEMPERATURE & COOLING

Cooling in the Noisetaker II was not a cause for concern. The internal temperature rise never rose above 5°C — a very good result. However, the temperature got quite high in absolute terms. The 53°C intake temperature reached at the end of the test is well above the 40°C ambient temperature specified as the maximum operating temperature.

It is a bit difficult to know what to make of the thermal results. There is only one difference in the cooling system compared to the last version: The internal vent has been cut down to about half the previous size. Yet, the thermal results of the two units were quite different. The earlier version that we tested had a higher temperature rise, which suggests that the change in airflow was beneficial. On the other hand, the intake temperature, which should not change significantly between tests, jumped up by as much as 10°C.

The implication is that while airflow within the PSU is perfectly adequate for self-cooling, the PSU's contribution to overall case cooling is lower than before. It suggests that an exhaust fan for the case is very important when using this PSU. This is ironic, considering that Enermax lists its 2-fan system among the features as the best cooling method for a PC.

6. FAN, FAN CONTROLLER and NOISE

The quality of noise in the NoiseTaker series has never been that good, and it was an issue once again in the latest revision. There are two major issues:

  1. The fans themselves sound bad, even when running at the minimum speed of 3.6V.
  2. The individual fans interact acoustically (intermodulate), creating a dissonant motor noise.

The baseline noise level was about 24 dBA@1m. It is quiet, but there are numerous other power supplies that are quieter. The noise was primarily a two-tone hum that was the result of the two fans spinning together. A distinct buzz could also be heard, especially from closer distances.

As the fans speeded up, the two-tone hum quickly became irritating and more dissonant. The noise had the quality of a train whistle that uses two dissonant pitches to get attention; unfortunately, attention is exactly what a low noise power supply needs to avoid.

The fan controller has fallen a bit behind the times. At one time, simply staying at the baseline level for a while was enough to gain our recommendation, but times have changed, and there are now much better options available. The fan began to increase in speed quite early, when the intake temperature was about 34°C. The corresponded to ~150W output — a level that can easily be exceeded in a system with a hot graphics card.

Those who are inclined to tinker may be interested to hear that the fan control knob on the back panel allowed about twice the adjustment range as the previous version. Unfortunately, even the lowest setting was less than satisfactory for our standards.

Given that the NoiseTaker II is targeted at Dual CPU / Dual VGA systems, it is hard to imagine that it would be quiet when used as intended.



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