Corsair RM650x (2021) power supply review

PSU - Power Supply Units 106 Page 7 of 8 Published by


Stability Testing The PSU


Stability Testing The PSU

During our tests, we also monitor the voltage fluctuations as shown below in both IDLE and LOAD states of the PC. We write down the lowest and highest values we see within a certain PC state. The difference are the fluctuations. If a PSU is unstable we'd see a lot of fluctuation, differences, and discrepancies which can result in instability.


This is the old-fashioned Digital MultiMeter work tapping voltage measurement spots on the mobo as well as the power connectors. Once we've gathered all voltage results we can place them in an easy to understand chart. Look at the chart, the two lines show both the idle and load state of a specific voltage rail, the dark blue one the lowest voltage dip measured, the dark blue one the highest fluctuation. That's your baseline. The ATX specification requires that the PSU needs to stay within a 5% fluctuation; for example, each +12 Volt rail should remain between 11.4 - 12.6 Volts. All results remain far within specification and tolerance thresholds. As you can see, the PSU when utilized stays consistent as you can hardly even see the blue line, meaning that the PSU is functioning within ATX specified limits.

Sound levels (dBA)

As usual, we grabbed our dBA meter. The human hearing system has different sensitivities at different frequencies. This means that the perception of noise is not at all equal at every frequency. Noise with significant measured levels (in dB) at high or low frequencies will not be as annoying as it would be when its energy is concentrated in the middle frequencies. In other words, the measured noise levels in dB will not reflect the actual human perception of the loudness of the noise. That's why we measure the dBA level. A specific circuit is added to the sound level meter to correct its reading in regard to this concept. This reading is the noise level in dBA. The letter A is added to indicate the correction that was made in the measurement.


As always we measure 75 CM away from the product (usually the distance between you and a desktop computer). This is a subjective test though.

  • At ~ 20% idle you cannot hear the PSU
  • At ~ 60% load you cannot hear the PSU
  • At ~ 50% load you can barely hear the fan, it remains virtually silent.
  • At ~ 80% load you are hard-pressed to hear the fan. 

All in all the conclusion here is simple, the PSU simply remains silent under normal load conditions. Everything under 38 dBA you can't really hear unless you put your ear next to the device. Below a chart, as compiled by Corsair to better demonstrate the fan RPM behavior up to 650 Watt (fan curve). Historically speaking I can report that ML fans can't be heard until they pass the 600 RPM marker. below a plot from Corsair on RPM behavior. 


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