Zalman ZM400B PSU

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April 14, 2004 by Mike Chin

Zalman ZM400B-APS
400W ATX 12V v1.3 power supply
Zalman Tech Co., Ltd.
Sample Supplier
Zalman USA / Sharka Corp.
Market Price

Zalman has been a major player in the Silent PC market since its inception, moving from their first unique "fan-flower" heatsinks designed for low noise, to their latest statement product, the TNN500A, an entirely fanless case that acts as a massive heatsink for all the components. They were also among the first to market a quiet 300W power supply. The ZM400B is the latest and most powerful of their PSU line, which still includes a 300W model. (ZM400A and ZM300A models are also listed on their site at this time, but these are likely to be discontinued as the newer Intel ATX12V V1.3-compliant "B" models filter through their entire inventory.)

Like so many PSU players, Zalman have upped the retail packing ante with a new snazzy look in a slightly larger box. (Personally I have no problem with a plain brown cardboard box, but I am sure the numbers-crunching profile-savvy marketing folks would laugh me out of the room as a bizarre and insignificant minority.)

The box contains a bit more than usual, with velcro cable ties and a Multi-connector to go along with the AC cord and manual. The multi-connector, first supplied with their ZM300A-APF PSU, is a clever little device that converts a spare 4-pin output connector from the PSU into two pairs of 12V and 5V outputs suitable for fans.

The goodies in the box

Clever multi-connector

Among the feature highlights of Zalman's new PSU:


Realizing a Noise-Free Computing Environment (CNPS) with Auto Control Cooling Fan

Noise Level(dB) Changes In relations to Power Supply's Internal Temperature
When the temperature inside the power supply is 55Deg C or less, the cooling fan will operate in 'Quiet' or 'Silent' mode.

It is the same basic technique used by most low noise PSUs. Zalman is more candid with their graph, tying the noise to the temperature, rather than to power output as is commonly done.

Declaring that the fan will operate in 'Quiet' or 'Silent' mode at <55°C operation only serves to tell us that 'Normal' operation is loud.

Complies with Intel ATX12V ver 1.3
This is the latest product in our power supply line-up, designed to comply with Intel ATX12V Ver. 1.3. S-ATA power connectors supporting S-ATA Ver. 1.0 compliant hard disk drives are provided as standard.

V1.3 compatibility is generally a good thing, with higher current capacity for the 12V line.

Simplifying Source Input - Free Voltage
Unlike products with Passive PFC, where you have to set the operating voltage (115VAC / 230VAC) with a manual switch, this product can be used with any normal AC input source ranging from 100VAC to 240VAC.

Probably more useful for simplified inventory than for users, who are unlikely to go back and forth between different VAC zones with a desktop PC.
Improving Power Factor & Eliminating Harmonics through Active PFC
By implementing Active PFC, the power factor (PF) is improved from 75% (Passive PFC) to 94% (at full load), while harmful harmonic frequencies are reduced below regulatory requirements.
We've commented on the environment-friendly aspects of APFC in the past. It also reduces the VA rating of the Uninterruptible Power Supply used with the system.

Supplies Stable Power to Intel Pentium 4
By including a ATX12V 2x2 (4-pin) 12V power connector and an auxiliary 5-pin power connector, this product can provide stable power to Intel Pentium 4 CPUs, which need 6A of current from each power rail.

Just about universal these days...

High Efficiency Power Supply
Designed with a high switching frequency and low power-loss circuitry, the efficiency of this product exceeds 75% (at full load).

75% is very good, but no longer outstanding. Both Enermax Noisetaker and Seasonic Super models boast higher efficiency.

Certified with Safety Approval EMC Standards - UL, C-UL, CE, TUV, CB-NEMKO, FCC

Generally, the more safety approvals the better.

Strict DC Voltage Regulation & Low Output Ripple / Noise

The actual numbers are fairly standard for a high quality PSU.

Other Specifications:

AC Input:
100VAC ~ 240VAC +-10%
Total Power
DC Line

Operating Temperature

A very positive specification on the Zalman ZM400B-APS product page, under Operating Conditions, states:

Ambient Temperature: 0~50°C

This means the unit is capable of delivering full power at up to 50°C operational temperature. This specification indicates excellent heat tolerance and component quality. As you may already know, some PSUs are only rated for maximum power at a much lower temperature, such as 25°C, which means that in real computers, they are incapable of providing the rated power. Real computers often exhibit >40°C. (Whether the Zalman PSU fan will stay quiet at such a high temperature is another thing altogether.)

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