StealthPC Foundation Kit by ARM Systems

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March 17, 2004 by Mike Chin

StealthPC Foundation Kits
ARM Systems

The ARM Systems StealthPC P4-3.2 Powerhouse was reviewed here January, to much kudos from SPCR enthusiasts. There was a great deal of interest expressed in the case ARM Systems uses for their PCs. In response to the expressed interest, Roy Manalastas and Steve Collins of ARM Systems have begun offering StealthPC Foundation Kits for Do-It-Yourselfers. The Foundation kits consist of their noise-optimized mid-tower case with top quality damping fully applied, an ultra-silent modified Zalman power supply, and various noise and vibration reduction devices.

StealthPC Foundation Base Kit Contents

ARM Systems are flexible about the exact configuration of the kit, and can adjust contents and price based on customer requirements. Their PDF promo / price sheet provides information on three kit options. Please note that all prices quoted here are valid at time of posting but subject to change without notice.

1) The base US$249 CA-ST-KIT-4252-1 kit consists of the following:

  • 1 - Evercase 4252 mid-tower case w/120mm rear exhaust vent and one detachable dual-HDD cage equipped with EAR hard drive grommets and matching screws
  • 1 - RamAIR Cold Air Induction CPU Duct System
  • 2 - Quiet 120mm ARM System brand fans, premounted on exhaust and intake vents with EAR grommeted screws
  • AcoustiPack damping materials treatment of all interior case panels
  • 1 - Zalman ZM300B power supply, ATX12V v1.3 compliant with ultra quiet Panaflo fan modification.
  • 2 - Zalman Fanmate1 fan voltage controller

2) The US$299 CA-ST-KIT-4252-2 kit provides an upgrade to the higher power Zalman ZM400B PSU, also Panaflo-modded.

3) Their $499 CA-ST-KIT-865-28 addition is sold only with either of the above kits, and turns them into almost complete prebuilt systems. Only memory, VGA card, drives and preinstalled OS are missing:

  • Intel D865GBFL or D865PERLX motherboard (Specify at time of order)
  • Intel P4-2.8Ghz 800 FSB 512K Cache Processor, installed
  • SLK947U (Thermalright) CPU Cooler w/ 92MM Quiet fan / Fanmate, installed on motherboard w/ Arctic Silver 5 High Performance Thermal Compound
  • Fan adjusted to optimal setting for cooling and noise reduction.
  • Motherboard is installed in case / tested and BIOS updated prior to shipping.
  • Also included in kit: ATA Cable, HD Cable, (2) SATA HD Cable, cable ties.
  • Depot Parts warranty - Motherboard and CPU (3 years)**


Recently, ARM Systems shipped over a review sample of a new prototype version of the CA-ST-KIT-4252-2 kit with the 400W PSU. This kit will be available very shortly.

By now, SPCR readers are familiar with the Evercase 4252 that ARM Systems uses in the StealthPC line. There are numerous photos in the previous StealthPC P4-3.2 Powerhouse review. Here is a look at this new prototype:

Perhaps the difference is not immediately apparent, because it is difficult to capture details in the black. Here are a couple of looks at the interior. Note power cord and other goodies in the plastic bag.

By now, you will have noticed that the Zalman PSU looks a bit too long. A closer look:

Yes, there is an extension to the back of the PSU, a little black box that looks completely closed... except for this vent at the top of the case. The green arrow is there just to make sure you see it.

The grid of holes on the top do not function like a conventional "blowhole"; it is an intake vent. The little box on the PSU is actually a duct which forces the PSU fan to draw in air only through the top vent holes.

ARM Systems have created the first commercial implementation of a case cooling / quieting feature I've been espousing in SPCR for over a year. However, their version does not rob the case of any external optical drive bays.* It is...


The duct is a small 4-sided box made of a high temperature, flameproof, no-melt mylar. It feels like very smooth heavy card stock ¬ó business cards, I mean. The two open sides face the top, where the vent holes are, and the intake side of the PSU. The mylar duct is attached to the PSU and the inside of the top case panel with what appears to be black electrical tape.

The holes on top have obviously been done manually, judging by the uneven pattern. Roy Manalastas of ARM says not to be too concerned about how this prototype looks. They have arranged for Evercase to custom manufacture ventilated versions of this top panel. ARM Systems have exclusive rights to Evercase 4252 cases outfitted with this top panel vent.

All StealthPCs and Foundation Kits with 400W PSUs (or larger) will be equipped with the PSU fresh air duct. There is also consideration of offering just the top panel as a retrofit mod for all the thousands of customers who have purchased ARM System PCs built in this chassis. The top panel is easily removed by accessing two locking screws hidden under the front bezel. This would allow older systems to be cooler, quieter, and/or allow better upgradeability with hotter components.

The benefits of the PSU fresh air duct are simple:

1) The PSU always gets the benefit of cooler ambient air rather than the preheated air from within the case, and from the CPU. The temperature advantage can be over 20°C.

Much of the hot air rises and tends to pool at the top of the case where it gets sucked into the PSU. Actually, this is a defined design function of the PSU within the ATX specification. However, the ATX specification was created nearly a decade ago when systems barely created 100W of heat in a case. Today, the CPU alone can create this much heat! Using the PSU as an exhaust fan has the great detriment of channeling a huge amount of heat through an electronic device that already runs hot.

2) With cooler air, the thermally controlled PSU fan tends to run at minimum speed and rarely ramps up. Because the PSU sees so much less heat, it runs cooler, and the fan only has to evacuate only the heat that is generated by the PSU. This is typically 25~35% of the total AC power drawn by the system. This means that the internal thermistor which controls the fan speed in a modern PSU rarely sees temperatures high enough to increase the voltage to the fan. Normally, if the PSU shares the job of evacuating the hot case air with a case fan on the back panel, it is dealing with at least ~50% of the total heat in the system.

3) Acoustically, the end results are lower PSU noise, and less variability in PSU noise. The latter aspect is as important as the former: Even at low volume, small changes in noise are easily heard as annoyances, especially if they are frequent. In my own DIY implementations of PSU fresh air intake venting, I've been able to run up to a 170W (max total heat) system with a Seasonic or Zalman 400W PSU with virtually no speed up of the PSU fan in normal use.

There is only one or two potential downside:

The task of evacuating the hot air from the case falls entirely to the back panel case fan. Because the PSU fan is no longer pulling the hot air out at the top, the back case fan now must evacuate 65~75% of the total heat in the system. In the ARM Systems case, the 120mm fan should be able to handle this fine on its own, at least up to hottest current desktop CPUs (~100W).

With really hot components and/or inadequate case airflow, the PSU fan may still end up running faster. This is because the CPU is located just directly below the PSU, and only a thin steel wall insulates the PSU from the CPU heat. Still, even if it did occur, it would occur less with the duct.

(* The first appearance of the PSU fresh air duct idea was in Leo Quan's Dual MP System article. I'd suggested it might cool his beast more quietly. The most complete documentation of a PSU duct implementation was by Lilla in the SPCR Forum thread Building a PSU intake duct/vent: In this thread is a link to a personal website by Lilla featuring details of a system that incorporates a very nicely made DIY PSU duct.)

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