A ways back we reviewed the Zalman ST300BLP which was very quiet, but lacked sufficient air vents in our opinion. While this may by a totally subjective standpoint to take, the ZM300A certainly has proven that Zalman have improved on the design of old.

The ZM300A-APF is pictured on the top in both of these photos. Compared to the older model the ZM300A offers a few immediate upgrades . First and foremost, the use of a wire grill reduces noise when faster fans are used so cooling levels can be increased without creating more turbulence, and hence noise. Secondly, since the ZM300A is an Active Power Factor Correction power supply the little red switch which sets the PSU to 115VAC or 230VAC is no longer necessary.

Where the older power supply was just a solid piece of metal (right), the newer ZM300A-APF has been filled with much needed vents. We actually took a saw to the old ST300BLP and hacked out a vent of our own to improve case air flow. You can see the end result of the power supply mod job for yourself right here.

The rear of the 300W ZM300A-APF on the left again has also benefitted from a healthy dose of venting. In our previous review we were concerned that the ST300BLP might not offer a level of case venting that it should because of the limited amount of internal vents. The new ZM300A has taken the internal hestsink to the next level as well, using a slightly improved model to cool the electronics.

Power tests:

For testing, we took a peek at the voltages with the system under load. This is not the most exact way of measuring a power supplies' electrical tolerances, but it does give a bit of insight into the degree of DC voltage jitter. The results are shown in the table below.

Listed Voltages	AMP	Lower Voltage	Upper Voltage	Jitter
3.3v	28A	- 3.26v	- 3.29v	0.03v
+5.0v	40A	- 5.02v	- 5.02v	0.00v
+12v	15A	- 11.67v	- 11.73v	0.06v
-12v	0.8A	- 11.78v	- 11.86v	0.08v
-5.0	0.3A	- 4.84v	- 4.84v	0.00v
+5.0sb	2.0A	- 4.99v	- 4.99v	0.00v

The Zalman PSU offers quiet performance and 300W of power which is an excellent combination on any scale. As temperatures within the power supply increase, the speed of the rear exhaust fan is dynamically adjusted to compensate. The user doesn't have to turn a dial, or set the fans speed themselves.

The key here of course is the very low noise level the power supply falls under. That can be a great benefit to users assembling systems optimized for lower noise signatures (the ZM300A measured around 36db from about 16" off the rear in our tests), and yet still need something with the wattage to support multiple drives and the Pentium 4 platform.

Without unnecessary flash, the Zalman ZM300A-APF offers itself up as a good low noise power supply that will ensure there is one less thing to hear when you hit that power button.

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