Nexus NX-3000 PSU

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October 6, 2002 -- by Mike Chin

Product Nexus NX-3000 PSU
Manufacturer Nexus
Supplier Silent PC NL / CG Consultant BV
MSP ~US$75

From the people who brought you Q-Technology comes a new PSU called the Nexus NX-3000. The new model is claimed to be 5 dBA quieter than the quietest fan-equipped ATX/PS2 power supplies. Yet with high efficiency and fan intelligence, it stays cool with good airflow under high loads.

A report based on acoustic tests conducted in an anechoic chamber was provided. Unfortunately, they insisted I not publish the report; but I am allowed to tell you about it. I believe the reason for this is that the Nexus is tested along with the Q-Technology QT-02300, which does not fare well in the comparison.

In any case, the acoustics report indicates that in an ambient of 30C (not clearly defined whether this is room temperature or intake air temperature), the Nexus 3000 remains at 22-23 dBA @ 1 meter up to ~100W output. Even at 150W, the noise is only ~26 dBA. The graph below from the acoustics report, digitally edited to show only the Nexus information, provides noise performance through its entire power range.

It is an impressive set of data.

The Nexus bears a strong resemblance to the Zalman ZM300A-APF as well as some of the PC Power and Cooling units. The stamped-put grill for the fan is an obvious difference, but the case, intake ventilation slots and the extra mounting flange are all very familiar.

Things are a bit different under the hood. One of the heatsinks is half the size of the other. This is to make room for the transformer mounted off the side of the cover, just behind the fan. One would think this is a hefty bit of airflow impedance. A brief examination of the unit tells me little. It does not look much different from most PSUs. For the record, here's a better internal photo. The small PCB with traces facing up appears to be the main fan control circuit. The fan leads are soldered directly to this PCB.

The fan is familiar, too. It is identical to the one used in the Zalman ZM300A: MGA8012HB by Protechnic Electric. As mentioned in the Zalman review, it is a 0.24A unit, similar in rating to most PSU fans. A web search finally netted some information about this fan. Protechnic Electric appears to be a Chinese subsidiary or partner of a Korean company called Sechang Semicon. Protechnic's fan catalog was downloaded from this site.

The basics of this 12VDC Dual-Ball Bearing fan:

3,000 RPM
38 CFM
29 dBA

The 29 dBA rating is lower than most similar fans. Listening with the PSU on idle, I can say that airflow noise is present, but bearing noise is virtually absent. It has a smooth, even sound.


  • Real silent power supply, only 22.2 dB(A) in idle mode
  • Below 26 dB(A) at an average PC power consumption
  • High efficiency, Excellent air flow
  • Output over voltage protection
  • Short circuit protection on all output
  • Reset Table power shut down
  • Approved by:: T√úV, CSA, UL, NEMKO, FCC, CE
  • Internal 12 VDE fan
  • 100% burn-in under high ambient temperature (50C)
  • Vacuum-impregnated transformer
  • MTBF: 100K hours at 25C
  • 100% Hi-pot tested
  • Line input fuse protection


  • Remote ON/OFF Control: The power supply shall accept a logic open collector level which will disable / enable all out put voltage (excluding +5V standby)
  • Passive PFC
  • Temperature range:
    • operating 0C~50C
    • storage -20C~+65C
  • Temperature coefficient: 0.01% / C
  • Transient response: output voltage recovers in less than 1ms max. following a 25% load change
  • Dielectric withstand: input / output 1800VAC for 1 second, input to frame ground 1800 for 1 second
  • Humidity: 5~95% RH
  • Efficiency: 65% min. 70% typical, at full load
  • Power good signal: turn-on delay 100ms to 500ms
  • Overload protection: 150% max.
  • Inrush current: 60A cold, 80A warm at 264 VAC
  • Over voltage protection:
    • +5V : 6.5V(max.)
    • +3.3V : 4.6V(max.)
    • +12V : 15.5V(max.)


AC Input
100~120 VAC / 200~240 VAC, 10 / 6A, 60 / 50Hz
DC Output
Load Regulation
Line Regulation
Ripple + Noise
50mV P-P
50mV P-P
120mV P-P
120mV P-P
100mV P-P
50mV P-P
Min Current
Normal Current
Max Current
Max Power


There are five 4-pin Molex connectors and two floppy drive power connectors on three sets of 16" wires. Both the length and the number of connectors are modest, compared to many high end PSUs, which tend to provide to much length and number, forcing extra cabling and connectors to be bundled up and tucked away somehow in the typical desktop / tower PC. The main ATX and 12V connectors are on 20" wire sets. Plus there is the useless (for most) 6-pin 5 + 3.3V connector on another 20" wire set.

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