Bitfenix Whisper Series 550W PSU Review

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Load Regulation, Hold-Up Time, And Inrush Current

To learn more about our PSU tests and methodology, please check out How We Test Power Supply Units. 

Primary Rails And 5VSB Load Regulation

Load Regulation testing is detailed here.

Hold-Up Time

Our hold-up time tests are described in detail here.

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As expected, the hold-up time we measured is lower than 17ms. Thankfully the power-good signal is accurate, and it doesn't last longer than the unit's actual hold-up time.

The difference between the hold-up time and the moment the power-good signal is deasserted should be at least 1ms. As you can see, in this case it's only 0.62ms. 

Inrush Current

For details on our inrush current testing, please click here.

The inrush current with both 115V and 230V is a little higher than the average in this wattage category. An NTC thermistor with increased resistance should be used instead of the only that's installed.

Load Regulation And Efficiency Measurements

The first set of tests reveals the stability of the voltage rails and the PSU's efficiency. The applied load equals (approximately) 10 to 110 percent of the maximum load the supply can handle, in increments of 10 percentage points.

We conducted two additional tests. During the first, we stressed the two minor rails (5V and 3.3V) with a high load, while the load at +12V was only 0.1A. This test reveals whether a PSU is Haswell-ready or not. In the second test, we determined the maximum load the +12V rail could handle with minimal load on the minor rails. 

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Test # 12V 5V 3.3V 5VSB DC/AC (Watts) Efficiency Fan Speed Fan Noise Temps (In/Out) PF/AC Volts
1 2.753A 1.973A 1.975A 0.985A 54.75 85.96% 400 RPM 21.3 dB(A) 38.16°C 0.944
12.054V 5.058V 3.338V 5.070V 63.69 40.99°C 115.1V
2 6.552A 2.960A 2.967A 1.182A 109.74 89.76% 400 RPM 21.3 dB(A) 39.16°C 0.974
12.043V 5.052V 3.334V 5.064V 122.26 42.58°C 115.1V
3 10.702A 3.465A 3.482A 1.380A 164.83 90.90% 400 RPM 21.3 dB(A) 40.14°C 0.982
12.032V 5.047V 3.329V 5.059V 181.34 44.13°C 115.1V
4 14.857A 3.962A 3.968A 1.580A 219.76 91.22% 400 RPM 21.3 dB(A) 41.00°C 0.985
12.022V 5.042V 3.323V 5.054V 240.92 45.84°C 115.1V
5 18.670A 4.967A 4.969A 1.781A 274.74 91.00% 400 RPM 21.3 dB(A) 41.60°C 0.986
12.011V 5.036V 3.319V 5.047V 301.91 47.51°C 115.1V
6 22.493A 5.961A 5.972A 1.980A 329.68 90.18% 400 RPM 21.3 dB(A) 42.91°C 0.987
12.000V 5.031V 3.314V 5.040V 365.59 50.75°C 115.1V
7 26.322A 6.968A 6.979A 2.182A 384.67 89.64% 650 RPM 26.5 dB(A) 43.19°C 0.986
11.989V 5.025V 3.309V 5.034V 429.15 51.41°C 115.1V
8 30.161A 7.969A 7.990A 2.385A 439.62 89.04% 830 RPM 31.6 dB(A) 44.10°C 0.985
11.977V 5.019V 3.303V 5.027V 493.75 52.97°C 115.1V
9 34.439A 8.476A 8.518A 2.385A 494.69 88.45% 1260 RPM 41.0 dB(A) 45.28°C 0.986
11.966V 5.015V 3.299V 5.025V 559.29 54.80°C 115.1V
10 38.676A 8.987A 9.016A 2.488A 549.54 87.90% 1400 RPM 42.7 dB(A) 45.94°C 0.987
11.954V 5.009V 3.294V 5.020V 625.18 53.35°C 115.1V
11 43.323A 8.996A 9.022A 2.489A 604.57 87.00% 1400 RPM 42.7 dB(A) 45.99°C 0.988
11.942V 5.005V 3.291V 5.018V 694.89 54.19°C 115.1V
CL1 0.100A 12.010A 12.005A 0.003A 101.51 84.47% 400 RPM 21.3 dB(A) 43.07°C 0.974
12.037V 5.033V 3.319V 5.090V 120.18 52.80°C 115.1V
CL2 45.784A 1.002A 1.003A 1.002A 560.96 88.35% 1400 RPM 42.7 dB(A) 44.47°C 0.987
11.959V 5.029V 3.312V 5.058V 634.91 51.75°C 115.1V

Load regulation is fairly tight on all rails, and the PSU easily meets the 80 PLUS Gold requirements, even under high ambient temperatures.

Output noise remains low thanks to a conservative fan profile and low-speed fan. We have to push the PSU hard in order to make the fan spin higher than 1000 RPM. The transition to higher speeds could be smoother, since the difference between the 80% and 90% load tests is huge.

In any case, the PSU performs well. It doesn't seem to have any problem running in unforgiving environments as it delivers full load for prolonged periods.

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Aris Mpitziopoulos
Contributing Editor

Aris Mpitziopoulos is a contributing editor at Tom's Hardware, covering PSUs.

  • turkey3_scratch
    Bitfenix did the right thing pairing with CWT here. This is a great unit!
    Reply
  • Aris_Mp
    Indeed, its performance was a nice surprise for me as well. It's good to see some new competition in this market.
    Reply
  • Nuckles_56
    Damn, I wonder what Australian pricing will be like for this unit, as I'd be almost tempted to replace my current PSU with a quieter one like this if it is priced well
    Reply
  • MarekRMac
    Hi, please give me quick advice: Bitfenix Whisper M 550W or Corsair RM550x ?
    Reply
  • Aris_Mp
    19083753 said:
    Hi, please give me quick advice: Bitfenix Whisper M 550W or Corsair RM550x ?

    Which ever you can find at a lower price. Performance wise they are very close.

    Reply
  • jonnyguru
    One noticeable difference between the RMx and the Whisper is that the RMx uses an MCU for the fan controller instead of the standard thermistor/transistor circuit in the BitFenix product.
    Reply