The new series of power supplies recently released by Zalman ha a “RS” suffix in its name which stands for “Resonant Switching”. Compared to Two-Forward Switching, the more advanced Resonant Switching minimizes “switching loss” reduces heat generation, and operates more efficiently by eliminating the need for an output inductor leading to outstanding stability and reliability.

With the use of “Resonant Switching” it is possible to use smaller components which don't generate as much heat. Thus, it's possible to use o less noisy cooling solution. As the RS technology minimizes the loss of power in the conversion, this can be considered a very “green” and energy saving product.
OK, so let's have a look at the specifications:

Zalman ZM500-RS
Power 500W
Efficiency 87% maximum. “80+BRONZE”
Fixed wiring ATX 20+4 pin connector
6 PCI-E pin connector
6+2 PCI-E pin connector
4+4 ATX 12V pin connector
4 SATA connectors
4 molex connectors
1 FDD connector
PFC 99% maximum
Cooling solution 120mm fan
Electrical protections OVP, OCP, SCP, OTP, UVP
Dimensions 140 x 150 x 86 mm
Power in 100V/240V
Power out +3.3V 24A (tip of 30A)

+5V 24A (tip of 30A)

+12V1 18A (tip of 22A)

+12V2 18A (tip of 22A)

-12V 0,5A

+5VSB 3A (tip of 3,5A)
Combined power maximum +3.3V, +5V 130W

+12V 432W

-12V, +5VSB 21W

+3.3V, +5V, +12V, +5VSB 500W

The RS-series also includes a 600W model perhaps more adapted to high end components. The RS-series will without a doubt be very appreciated by builders of compact systems, the only thing I miss is a modular design for the wiring.


The unit comes in a nice looking cardboard box with a lot of printing on it which emphasizes the most important characteristics of the power supply.

In the back side of the box, Zalman has put some images of details such as the wiring and used components. They have also placed summaries in different languages of the most important specifications.

In the box I found the power supply (perfectly protected); a power cable; some plastic bridles; screws and the manual.


One of the first things that I noticed about the Zalman ZM500-RS is that it's smaller than normal PSUs. Of course it still follows the ATX standard in terms of where the screws are placed and everything else. It's just not as bulky as what I am used to, which makes it ideal for smaller dimensions cases.

The side with the power cord connector and the on/off switch has a metallic grid to increase the air flow. The right side has the Zalman logo engraved in it. The opposite side holds a big tag with all the specifications of the power supply.

The cooling solution consists of a 120mm fan which runs at a constant speed (not heat regulated). Of course I had to take the top cover off and take a look. I found out that this PSU is actually assembled by POWER LOGIC which is a well know builder of PSUs, used by other players like Xigmatek and Asus.

The wiring of the Zalman ZM500-RS is contained by strong acrylic plastic which holds it firmly in place. The length of the wiring is sufficient for an average tower case but I wouldn't recommend using it with full tower cases.


This will be one of the last reviews I do with my usual test system setup, never the less, here are the specifications:

Test equipment
Processor AMD Phenom II 920
Fan Cooler Master Hyper N520
Motherboard Sapphire PC-AM2RD790 – CrossFireX PUREE
Graphics card Sapphire Radeon HD 2900XT
Soundcard Auzen X-Fi Forte 7.1
Memory Kingston HyperX DDR2 1066 2×2GB T1 Series
Hard disk Samsung SP2504C (SATA II, 7200rmp, 8MB)
Power supply Zalman ZM500-RS
Case Antec Skeleton

To realize the test I used OCCT 3.1 to load the system to the max. In order to measure the voltages I used an ordinary digital multimeter and the power usage was measured with the ZM-MFC3 which I reviewed last week. The results can be viewed in the graph below:

As you can see from the graphs, the numbers the Zalman ZM500-RS produced are excellent. The voltages are tremendously stable; the PSU remains totally capable of delivering the power as it should even at full system load. The total consumption at full system load is the lowest I have measured with my system, which surely is a result of the Resonant Switching technology.

The noise emitted by this PSU is almost not possible to hear, that is just how quiet the fan is and because the fan turns at a constant speed the load doesn't affect the noise emission.


Doubtless the Zalman ZM500-RS is a high quality power supply with many interesting characteristics. I love that it's small which makes it perfect to put in a small HTPC case or any other smaller PC case. However, the wiring is rather short so if you are building a PC system in a full tower case you will probably not be able to use this PSU without any extension cables.

The performance is absolutely fantastic, it is in fact the most energy efficient PSU I have tested so far. The energy efficiency is of ever increasing importance and it's nice to know that your system is using up the minimum amount of power, which will in the end mean minimal cost. The PSU is ultra quiet and the voltages are stable no matter what you throw at it.

Zalman has done a great work with this product; the RS technology is a smart innovation that will save you money in the long run. The price of the ZM500-RS goes up to around 90EUR which is a lot of money for a PSU. It is clearly aimed towards PC builders with a bigger budget or anyone interested in its power saving or low noise features.


Source by Fredrik Marshall