Vantec's "Stealth" 420W Power Supply

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October 6, 2002 -- by Mike Chin

Product Vantec Stealth VAN-420A Power Supply Unit
Manufacturer Vantec Thermal Technologies, Inc.
Supplier Vantec Thermal Technologies, Inc.

Vantec Stealth PSU has 3 fansVantec is a name that has been associated for years with CPU heatsinks; that is, until they launched a line of power supply units (PSU) called the Stealth series several weeks ago. Stealth is the moniker Vantec have been using for a line of quiet fans they introduced earlier this year. One assumes these PSUs are also intended to be quiet. Three models are offered: VAN-420A, VAN-470A and VAN-520A. The model number denotes the power rating. Given that Vantec has no previous history with PSUs, these are probably built to Vantec specifications by an OEM supplier in China.


  • 3-Speed Thermal Fan Control Switch
  • 3 Temperature Controlled Dual Ball Bearing Fans (The mirror in the photo is there to show you all three fans at once.)
  • Universal Connector Fits Most of Branded Mainboards
  • Additional AC Output For Peripherals
  • Lightweight Black Aluminum Casing
  • Electric-Shock-Free Protection
  • Over Voltage Protection
  • Over Current Protection
  • Short Circuit Protection
  • ATX 12 V
  • Low Noise Level


The steathy retail boxLike the Vantec Stealth fans, the VAN-420A PSU comes in a snazzy retail box with outline drawings of the US Stealth bomber plane.

Inside the box, the PSU, AC cable, 4 mounting screws and 4 plastic zap-straps or wire ties for tidying up cables are conveniently provided. The wire ties will probably be useful, as the DC power leads are about the longest ever encountered. In most cases, they are really too long, but the length will be handy if you have a case taller and/or deeper than 24" .

The PSU itself has an all-black aluminum-case with silver wire grills over the three 80mm fans and looks kind of sexy in a Darth Vader kind of way. Presumably a large enough case window might show off a bit of this posh panache, but one wonders. Although Vantec promotional material claims the case material as a benefit, it's difficult to attribute any special advantage to aluminum.

Vantec PSU with included  parts

Long, long cables; many connectors

One curiosity is the main ATX connector, which is a 24-pin connector for server motherboards. A 24-pin to 20-pin adapter with about 5 inches of cable is supplied. While this features makes the PSU adaptable for a wide range of server motherboards, the adapter is necessary for use with all desktop motherboards. The addition of another 2 sets of contacts, often the cause of voltage drops between PSU and motherboard, is not ideal.

24-pin ti 20-pin ATX adaptor

Another unusual connector is an 8-pin version of the 4-pin 12V plug for use with P4 motherboards. It is precisely that: a double 12V plug that certain server motherboards utilize. A folder of laser printed sheets provided details on six different types of motherboard connection combinations; this information is available as PDF downloads on the Vantec USA web site.

4-pin and 8-pin 12V feeder

When all of these connector details are considered along with the high power rating of the Vantec PSUs, the intended market appears not to be the enthusiast desktop sector suggested by the slick packaging and name. Instead, it looks set up for use in server machines.


Normally there not much on the back panel of a PSU, but in this case, it really can be described as a control panel. Besides the usual power switch and IEC AC jack, there is a 3-position switch (marked A, M and L - presumably for Auto, Medium or Manual, and Low) that sets fan operation, a 110/220 VAC selector, and a convenience outlet for another component such as a monitor. The red slider switch selects low, medium or high fan speed ranges, but a thermistor is also tied into the circuit; high internal temperature will make the fans speed up at any of the 3 settings.

Back panel

The convenience outlet is a nice touch. No current rating is specified for this outlet, but as the AC cable/plug supplied is ordinary 18AWG wire (nominally rated for ~10A @ 120V), caution should be exercised about any devices that might draw significant amounts of power, especially in an application where the full power of the PSU is actually utilized. Most monitor should be fine, though.

Finally, the label: note the large number of approvals; generally, A Good Thing...

The specs label

...which brings us to...


PSU Type: ATX / ATX12V

AC Input
100~120 VAC / 200~240 VAC, 10 / 6A, 60 / 50Hz
DC Output
Load Regulation
Max Current
Max Power

There is mention of an Active Power Factor Correction (PFC) option with automatic AC input voltage selection in the spec sheet (downloaded as a PDF file from the Vantec USA website). As this unit has an AC selector switch, it does not appear to feature PFC.

Efficiency is not specified. As efficiency indicates how much heat is generated while the PSU is delivering a given power, it is a very important consideration for anyone concerned with thermal and cooling issues. Its absence is surprising.


The printed materials that came with the review samples provides a sketchy, confusingly worded explanation of their fan control system. Here's a summary of the points that did seem clear:

  • Vantec claims that when running multiple fans in a PSU, the one blowing out should have higher airflow than the others. So presumably this is the way the fans in the 420A are set up.
  • A thermistor is used to keep control the fan speed to keep airflow appropriate to the PSU temperature.
  • The 3-position fan speed switch also changes the speed of the fans.
  • The 2 inside fans suck air into the PSU while the back panel fan blows it out.

How the thermistor and the 3-position fan speed control combine is completely unexplained. The chart below shows fan speed as a function of temperature -- thermistor temperature, presumably. However, as the outside fan is spinning faster than the inside ones, this chart can only represent one of the two fan types used. The maximum speed of 2500 RPM correlates to the specs for the slower inside fans.

fan rpm vs. thermistor temperature

The fan speed curve suggests that the relationship between thermistor temperature and fan speed is virtually linear. The steepest part of the curve is in the temperature range 20-40° C, after which the fan increases speed more slowly. The curve is almost exactly opposite of that for the Seasonic and Zalman PSUs, which look exponential.

In previous reviews using a quiet, low airflow system, the internal temperature of all the PSUs move into the 30° C range almost immediately after turn on and hover around 40° C in normal operation. This suggests that the fans in the VAN-420A will changes speed easily and quickly in normal use. This does not bode well, as changes in noise level are usually perceived as more noticeable and annoying. On the other hand, the increased airflow from 3 fans may keep the PSU cooler, and thus keep the fans running at lower speeds.


The VAN-420A is chock-full inside, as the next two photos show. The heatsinks are only of moderate size for the rated power, but perhaps with the airflow of 3 fans, they don't have to be any bigger. In the lower photo below, the red and black leads from the inside fan can be seen coming over and touching one of the heatsinks. There was no way to reposition it to prevent contact. This is a minor detail, such close contact does not seem wise, especially over time in a hot computer.

Internal view,  from right

Internal view,  from left

The fans are Globe Fan units: 1 model B01138812H (80 x 25 mm) and 2 model B080152M (80 x 15 mm). They are 12 VDC, dual ball bearing fans with clear plastic blades, with small 2-pin connectors. Globe Fan's specifications:

Fan Model
Air Flow
0.23 A
39.80 CFM
32.6 dBA
0.13 A
25.17 CFM
28.3 dBA

The two lower-speed fans are moderately loud on their own at 12V, and become quiet at 5V. Not as quiet as our reference Panaflo 80mm L, but fairly quiet. The H (high speed) model, which is found on many other PSU brands, including Enermax and SuperPower or SH, is quite noisy at 12V and not that quiet at 5V. These comments are based on removing the fans from the PSU and listening to them while held in the hands. They were powered by a fanless PSU.

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