Enermax NoiseTaker 475 PSU

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For a complete rundown of testing equipment and procedures, please refer to the article SPCR's Revised PSU Testing System.

Measure temperature of ambient air, case, and PSU exhaust
Digital readout thermometer. There are several in the lab that are used. (Like DigiDoc.) They measure within ~1°C of each other, which is good enough for our purposes. Powered by the PSU being tested. (1~2W power draw.)
Measure voltages across fans and DC output line
Heath / Zenith SM-2320 multimeter. This is an ordinary multimeter. It has been compared against a much more expensive lab instrument and comes very close (within 2%) on readings of 0~20VDC.
Load PSU to specific DC output power loads for each voltage line

Click for larger imageDBS-2100 PSU load tester. Made specifically for testing computer power supplies, it consists of a large bank of high power precision resistors along with an extensive selection of switches on the front panel calibrated in Amps (current) and grouped into 6 voltage lines: +5, +12, -12V, +3.3, -5, +5SR. Leads from the PSU plug into the front panel, and there are taps for taking voltage readings for the 3.3V, 5V and 12V lines.

Measure AC power, power factor (PF), VA, AC line voltage
Kill-A-Watt Power Meter. An inexpensive consumer power meter with very good accuracy and a host of useful functions.
Measure noise in dBA from 1 meter distance B&K model 2204 sound level meter. This professional caliber SLM dates back to 1978, weighs over 10 pounds, and is completely analog in design. It has a dynamic range that spans over 140 dB. The unit's absolute sensitivity reaches below 0 dBA. A quiet environment is a prerequisite to low noise testing; the lab has been measured down to ~17 dBA at night, and a 12 dBA adjacent room is also available for any PSUs that are quieter.
Thermal environment directly related to the power delivered. Custom Thermal Simulation Box. A NEW ADDITION to the lab, it ensures that the heat generated by the PSU creates the thermal ambient of its working environment. Please see SPCR's Revised PSU Testing System for full details!

The testing was conducted in the main lab, a converted 10' x 10' kitchen with a ceiling about 8.5' high. It's a room that's bare except for electronics, PC gear and instruments with a tiled linoleum floor. Acoustics are lively and reflective. Ambient during testing: 22°C and 17 dBA.

An Important Note about the new thermal simulation box is that it has NO exhaust ventilation other than the PSU fans. The box is not perfectly sealed, and around the hole where the cables exit, a fair amount of air can be felt blowing out. Normal PC cases have at least one or two ventilation fans other than the PSU fan. It probably means that the simulation is tougher than real systems in some ways.

On the other hand, the heat in a system is concentrated very close to the PSU -- both the CPU and the VGA card, which together can generate nearly well over 150W of heat, are situated directly beneath the PSU in a mid tower. In my thermal simulation box, the heat source is much farther away, and there are four 0.25A 80mm fans flowing cool air across the hot resistors. Of course, the heated air exhaust from the hot resistors is what fills the box, so perhaps its six of one or half a dozen of the other for either argument.

For the record, here's a photo of the Enermax NoiseTaker 475 in the PSU test rig. The unit had to be held down with masking tape to make sure the tension of the ATX cable would not pull it out. That cable was stretched as far as it could go.

Enermax NoiseTaker 475
DC Output (W)
AC Input (W)
Case Temp (°C)
PSU Exhaust (°C)
Fan Voltage (min/max)
Noise, min (dBA/1m)

1. VOLTAGE REGULATION is very good, within -/+2% on all lines in any nominal combination of loads. The low and high voltage seen on each of the main lines is shown:

  • +12V: 11.8 to 12.3
  • +5V: 4.8 to 5.3
  • +3.3V: 3.3 to 3.5

We have no way of testing line regulation; AC conditions are steady-state, not dynamic as it would be (potentially) in a real PC. The AC line in the test lab as measured by Kill-a-Watt is usually very stable, within a couple of volts of 120V.

2. EFFICIENCY is the highest of any PSU tested by SPCR so far. No other unit has ever reached 80% in the SPCR lab. The Enermax NoiseTaker 475 actually hit 82%! The closest runner-ups are the Seasonic Super series PSUs, which reach 78-79% at max efficiency. This performance is all the more amazing when you consider that neither the Enermax spec sheet nor their promotional marketing materials even mentions efficiency.

In fact, the efficiency is so high that after the first run of tests, I ran them all through again, sure that I had made an error -- and got the same results. The small difference between case and exhaust temperatures is one practical indication of this efficiency: The PSU adds little additional heat to the air going through it under all but the highest loads.

3. POWER OUTPUT: The unit had no trouble at all in the test environment, and ran with great stability at all the lower output levels. Even at 400W output, it ran for a full 5 minutes without any sign of overheating or overload.

After about 3.5 minutes at 470W, however, protection circuitry kicked in and the unit simply shut down. The fans stayed running at least 3 mninutes after the PSU had shut down, as advertised. In this case, this feature seemed like a good thing. After the fans stopped, I reduced the load and turned the power switch off and on. It came right back on without any problems, and no apparent damage.

It is not clear why the unit shut down. There are several protective features that can shut this PSU down:

  • Over Voltage Protection - unlikely; none of the output voltages were misbehaving
  • Over Load Protection - unlikely; the load was exactly at maximum
  • Over Current Protection - maybe: very clear limits are specified, and in setting the load for 470W, I may have exceeded the limit on one of the voltage lines.
  • Over Temperature Protection - possible: 40°C is the specified maximum operating temperature, and the case temperature was recorded at 39°C, with exhaust at 44°C. How one defines or where one measures the temperature becomes very difficult. If the Over Temperature Protection function shut the unit down, it is very probable that the operating temperature (as Enermax defines it) was exceeded. As it is so unlikely for any system to reach steady 470W output for any length of time, never mind 3.5 minutes, I have no quibble with the shutdown. It is a very extreme and unrealistic test. In fact, I am pleased that the protection circuitry worked well.

4. POWER FACTOR is as expected for a passive or non-PFC unit (not specified in the specs), staying at around 0.65 throughout the testing. An Active PFC version appears to be available or at least in the works, according to the Enermax web site.

5. FAN VOLTAGE: As noted earlier, only the 92mm fan voltage was monitored. It is not certain whether the 80mm fan receives the same voltage. The 92mm fan gets full voltage (11.5V) for a couple of seconds upon startup to ensure that it always starts. The default voltage just after a cool start is ~3V. In the thermal simulation case, the first significant change comes at the 250W output level. The fan voltage jumps from 3.1V at 200W to 5.8V at 250W. At 400W and up, the fan voltage is pegged at 11.5V. Upon shutdown, the fans continue blowing at minimum or a bit higher (depending on temperature when shut down) for at least 2 minutes.

6. NOISE was measured at 1 meter from the exhaust grill with the manual fan speed knob always at minimum. The test environment is live, so readings may be higher than would be obtained in an anechoic chamber.

Subjectively, the Enermax NoiseTaker 475 is very quiet from idle all the to 200W output: There was no change in noise from 65W load to 200W. But between 200W and 250W output, there is a major step in fan speed and noise, and hits 32dBA at 250W. All the noise levels at the 250W mark and beyond are too high to be of real interest to PC Silencers.

The quality of the fan noise is not particularly smooth, however. Even at the lowest speed, there is a kind of rattling-chugging sound. This noise actually dissipates as the fans spin up, and at higher speeds, the whooshing of fan turbulence dominates. There are no high frequency sounds that can be detected, not from the fans or from the electronics. Coil noise is often the result of interactions between components, however, so the absence of this noise in the lab does not guarantee its absence with PC components.

The minimum noise is not better than the quietest PSUs tested, especially when the quality of the noise is considered, but the ramp-up step of fan speed at over ~200W output is at considerably a higher point than seen before. This may give the Enermax NoiseTaker a very practical real-world advantage when used in high power systems.

A CAUTION: The noise-to-power performance achieved here is specific to prevailing temperatures. In other words, if your ambient temperature is 35°C and your case temperature measures 40°C, you can expect much higher noise, regardless of the electrical load. Similar, in fact, to that obtained here at 400W and above: Loud.


The Enermax NoiseTaker 475 frankly surprised me. I was not expecting anything special from this model, jaded as I am with marketing hokum from any source; Enermax spreads its share of such hokum. I certainly was not expecting 82% maximum efficiency, nor low-noise operation to 200W and beyond. Both of these qualities are enough to immediately put this model among the Recommended PSUs. Add the high stability and high power capability, and it really starts to look like... something special?

It's true that the ATX12V V1.3 PSU Guideline calls for higher efficiency than before, but the numbers ° 70% at full load, 60% at typical load and 50% at light load ° are nowhere near what Enermax has achieved here.

The protection circuitry works well. In truth, it would be amazingly difficult to build a desktop system that could demand 470W from the PSU for any length of time. Thus far, the highest power draw I've seen is with an ARM Systems P4-3.2 dual SATA drive PC, which only demanded 235W max in AC power. This NoiseTaker was drawing 600W in AC voltage before the protection circuits shut it down.

This is not to say the unit has no flaws.

The bunched cables may be tidy and nice looking but ye gads, get those girdles off! They could be a real struggle to manage in a real system. Even Ralf Hutter's cabling skills may not be enough here.

Then there are the fans that clatter at low speed; they really can and should be improved. Yes, the usual swaps with quieter fans will make real improvements here, if you can negotiate the tangle of wires inside and are willing to void that 3-year warranty. (The full voltage startup surge should help most fan get started and 3V may be be enough to keep most of them running once they're started).

Sorry to be addressing just the modders and diehards.

Even without any modifications, the Enermax NoiseTaker 475 will be useful and important for people who want to build high power systems that still run quietly. It may not be the quietest PSU at idle, but at 200W output and still just in the low-20s dBA @ 1 meter, it is tough to beat!

It would certainly be interesting to look at the other models in the NoiseTaker line. If that >200W fan speed ramp up point remains unchanged, the lower power NoiseTakermodels would be of great interest to SPCR enthusiasts.

Much thanks to Maxpoint for the Enermax NoiseTaker 475 review sample and for their kind support.

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POSTSCRIPT: Tests Repeated after Changes to PSU Test Platform! See Page 4!

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