Nexus RX-8500 850W Power Supply

Power
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8. NOISE and FAN CONTROL

The noise level at startup was a very low 14 dBA@1m and the quality of the sound was benign. However, this noise level was maintained only up to 150W load, by which point, the fan began speeding up in response to increasing heat.


The audio spectrum looks benign and very low in amplitude at up to 150W load
.


By 200~250W, the fan noise rose to 20 dBA.

By 200W load, SPL rose to 18 dBA@1m (and it was probably still climbing when the power level was shifted up — hence the screen capture above). The overall noise character was still smooth, mostly broadband. The fan speed continued to rise almost linearly in response to load (and temperature): 24 dBA at 250W, 28 dBA at 300W, and to the maximum of 32~33 dBA@1m reached at 400W. The PSU did not get significantly louder even with much higher load; the fan already seemed to be at full speed.

The voltage across the fan leads could not be monitored; it showed up as 12V at all times. This suggests some type of PWM circuit is used to control the fan speed. The main advantage of such a fan controller is that it draw slightly less power and allows most fans to run at lower speed than with a voltage controller. The fan speed could not be monitored for lack of a speed monitoring device or signal cable. However, the SPL is the essence of the fan data, and that is clearly shown in the second table above (OTHER DATA).

9. COOLING

The RX-8500 kept itself cool enough up to around 500W load, but internal temperature seemed to rise faster than normal above that point. At maximum load, the exhaust air temperature exceed 70¬įC, which suggests the unit should not be pushed so hard for long. Aside from the usual smell of electronic burning as full load was approached, there was no evidence of misbehavior associated with overheating. That power efficiency dropped a few point at full load is no surprise.



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