SilenX iXtrema Pro 400w Power Supply

Very quiet power supply – Tom Akita


An excellent unit provided by the great guys at SilenX

For some, overclocking just isn’t any fun if they can’t hear themselves think, and gaming is a drag when they can’t hear their opponent slinking up behind them. For these enthusiasts, the market has been inundated with new, quiet fans, video card coolers, and CPU coolers, but very few quiet, reliable power supplies have been available… until SilenX released its iXtrema line of power supplies, and SilenX’s iXtrema Pro is aimed to meet the demand of PC enthusiasts who aren’t enthusiastic when it comes to noisy computers.

First Look


Specifications (taken from the SilenX website):

  • Dimensions: 150mm x 86mm x 140mm
  • Input: 115/230V @ 50/60 Hz
  • Output: 400W
  • 3.3V – 30.0A
  • 5.0V – 32.0A
  • 12.0V – 18.0A
  • <5% Load Regulation
  • <1% Line Regulation
  • Efficiency: 75% under load
  • Over Voltage Protection: 3.3V/4V 5V/6V 12V/14V
  • Over Power Protection: 105%~150% of max load



Connectors: 6 molex, 2 floppy, 2 S-ATA, sleeved 20-pin ATX power connector, 4-pin P4 connector, and AUX connector

The iXtrema Pro’s molex connectors aren’t normal white/clear connectors. SilenX used the kind of connector that has finger tabs on the top and bottom of the connector to push against the female molex during disassembly, which is very helpful when dealing with a stubborn connection in a hard to reach place.

80mm Hypro Bearing Exhaust Fan

Hypro Bearing Fans are modified sleeve bearing fans that use a magnetic field to prevent friction between the bearing and fan hub. Compared to sleeve bearing fans, hypro bearing fans are much quieter and last longer because of the reduced friction involved when the fan spins.

Silicone Vibration Dampening Fan Mounts

SilenX’s silicone fan mounts prevent vibration noise traditionally caused by a running fan mounted on metal casing.

Is it quiet?



In fact, when we shorted pin 14 and a ground on the ATX power connector to see how loud the PSU really was, we weren’t sure whether it had turned on or not because the fan was so quiet. According to SilenX, the fan inside the iXtrema Pro emits around 6-8 dBA when it first turns on.

Once things in the case and power supply start to heat up, however, the PSU’s fan speeds up a little to produce just 14 dBA at full speed. The SilenX fan emits no air noise, mechanical noise, or vibration. Simply put, this is the quietest power supply we’ve ever heard (or barely heard), and SilenX’s rating of a peak 14 dBA is, surprisingly, very accurate.



Load testing…Working hard, or hardly working?


The iXtrema Pro went through three phases of testing:

  • Stock phase (all components running at stock settings
  • Overclocked phase (CPU, video card, memory overclocked)
  • Maximum voltage phase (all components running overclocked with maximum voltage allowed by motherboard)

The power supply underwent both idle testing and load (Far Cry, Painkiller, Halo) testing with a digital multimeter measuring voltage output through the 3.3V, 5V, and 12V rails directly from the ATX power connector during each phase. Within each phase, the PSU was tested using this procedure while one hard drive was running. Then, another hard drive was added, the PSU was tested, and then another hard drive added and the PSU tested again. At the end of each phase, the power supply had three hard drives connected to it for maximum stress on the 12V line.

Test Platform, stock testing (1st Phase)

  • ASUS A7N8X Deluxe Rev 2.0 (nForce 2 chipset, BIOS v1005)
  • AMD Athlon XP 2500+ “Barton” clocked at 1836 MHz (stock, 11×166)
  • 1GB (2×512) Mushkin PC3200 (DDR400) “222 Special” RAM at 166 MHz, 2-2-2-11 timings
  • Sapphire Radeon 9800np (stock)
  • Hard Drives:
    • 100GB 7200 RPM 2MB Cache Western Digital WD1000BB during testing with 1 HDD
    • 100GB WD1000BB and 40GB 7200 RPM 2MB Cache Western
      Digital WD400BB during testing with 2 HDDs

    • 2x100GB WD1000BB, 1x40GB WD400BB during testing with 3
  • Lian Li PC-61
  • 4 Panaflo 80mm L1A’s @ 7V, AcoustiFan 92mm @12V, Arctic Cooling VGA Silencer @ low speed
  • SilenX iXtrema Pro 400w
  • Windows XP Pro

Results (Volts)

Table 1

Test Platform, overclocked testing (2nd Phase)

Same as above with the following modifications:

  • CPU clocked at 2200 MHz (11 x 200) with 1.75 volts
  • Video Card core/memory at 412 MHz / 338 MHz with 1.5 volts
  • RAM at 200 MHz and 2-2-2-5 timings with 2.8 volts

Results (Volts)

Table 1

Test Platform, maximum voltage testing (3rd Phase)

Same as stock test platform with the following modifications:

  • CPU clocked at 2300 MHz (11.5 x 200) with 1.85 volts
  • Video Card core/memory at 412 MHz / 338 MHz with 1.7 volts
  • RAM at 200 MHz and 2-2-2-5 timings with 2.8 volts

Results (Volts)

Table 1


Testing, Analysis, Summary, and Notes

Output from this power supply is excellent, even when overclocked and at high voltages with 3 hard drives running. The iXtrema Pro only falls under specification by .01V in the very last test (Phase #3) when its 3.3V voltage reads as 3.29V in Painkiller and Far Cry.

It should be noted that during Phase #1 with 3 hard drives, the second 100 GB hard drive would stop spinning between measurement of the 5V and 12V rail outputs. The reason for this is most likely that a few wires on the ATX connector were agitated when the multimeter’s positive probe was pressed against the 5V wire for testing. We don’t think this incident had anything to do with the stability of the power supply since the rail outputs during Phase #1 were very impressive and did not fluctuate. Also of note is the increase in 12V voltage from Phase #1 to Phase #3. Apparently, such is frequently the case with power supplies.

During every phase, our test platform’s CPU temperature was about 6°C higher than it was with a Seasonic Super Tornado (Papst 120mm fan @5V) as the PSU. The iXtrema Pro’s low speed fan is positioned on the outside of the PSU as opposed to inside the case, above the CPU, and as such does increase the temperature inside the case, but affects the temperature of the CPU even more.


  • Far Cry settings: 1024 x 768, No Anti-Aliasing, all video settings highest except for “texture filter quality”
  • Painkiller settings: 1024 x 768, all video settings highest
  • Halo settings: 1024 x 768, all video settings highest


By the time this review is published, SilenX’s iXtrema Pro may already be on the retail market – good news for PC enthusiasts who need a stable and extraordinarily quiet power source. As is always the case, however, a low noise level does come at the price of increased temperatures. In the iXtrema Pro’s case, low noise also comes at the price of $114.95 for the 400w model. The iXtrema Pro isn’t silent, but it’s very, very close, and its stability and low noise level are well worth its price and more.

iXtrema Pro Product Link

Thanks to…

  • Peter at SilenX for sending us this unit for review
  • Joe C. at for hosting this review

Tom Akita

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