Test Setup

All measurements were performed using two Chroma 6314A mainframes equipped with the following electronic loads: six 63123A [350 W each], one 63102A [100 W x2], and one 63101A [200 W]. The aforementioned equipment is able to deliver 2500 W of load, and all loads are controlled by a custom-made software. We also used a Picoscope 3424 oscilloscope, a Picotech TC-08 thermocouple data logger, a Fluke 175 multimeter, and an Instek GPM-8212 power meter. We also included a wooden box, which, along with some heating elements, was used as a hot box. Finally, we had at our disposal four more oscilloscopes (Rigol 1052E and VS5042, Stingray DS1M12, a second Picoscope 3424) and a CEM DT-8852 sound level meter. In this article, you will find more details about our equipment and the review methodology we follow. Finally, we conduct all of our tests at 40 - 45°C ambient in order to simulate with higher accuracy the environment seen inside a typical system, with 40 - 45°C being derived from a standard ambient assumption of 23°C and 17 - 22°C being added for the typical temperature rise within a system.

Primary Rails Voltage Regulation

The following charts show the voltage values of the main rails, which were recorded over a range of 60W to the maximum specified load, and the deviation (in percent) for the same load range.

5VSB Regulation

The following chart shows how the 5VSB rail deals with the load we throw at it.

Hold-up Time

The hold-up time is a very important characteristic of a PSU and represents the amount of time, usually measured in milliseconds, that a PSU can maintain output regulations as defined by the ATX spec without input power. In other words, it is the amount of time that the system can continue to run without shutting down or rebooting during a power interruption. The ATX spec sets the minimum hold-up time at maximum continuous output load to 16 ms. In the following screenshot, the blue line is the mains signal and the yellow line is the "Power Good" signal. The latter is de-asserted to a low state when any of the +12V, 5V, or 3.3V output voltages fall below the undervoltage threshold, or after the mains power has been removed for a sufficiently long time to guarantee that the PSU cannot operate anymore. The Venom 850 W managed to get closer to the ATX spec than any other PSU we have tested so far, which is, of course, a good sign. It is, nevertheless, still almost a millisecond away from the limit.

Inrush Current

Inrush current, or switch-on surge, refers to the maximum, instantaneous input-current drawn by an electrical device as it is turned on. Because of the charging current of the APFC capacitor(s), PSUs produce large inrush-current right as they are turned on. Large inrush current can cause the tripping of circuit breakers and fuses and may also damage switches or relays; as a result, the lower the inrush current of a PSU right as they are turned on, the better. As you you will see, the Venom PSU registered a high inrush current for which the caps used in the APFC and the small NTC thermistor used for inrush current protection are responsible.

Voltage Regulation and Efficiency Measurements

The first set of tests revealed the stability of the voltage rails and the efficiency of the Venom 850 W. The applied load was equal to (approximately) 20%, 40%, 50%, 60%, 80%, 100% and 110% of the maximum load that the PSU can handle. In addition, we conducted two more tests. In the first test, we stressed the two minor rails (5V and 3.3V) with a high load while the load at +12V was only 2 A, and in the second test, we dialed the maximum load that the +12V rail could handle while the load on the minor rails was minimal.


Overall efficiency is not as high as other Gold PSUs with a similar capacity. Efficiency barely exceeds 87% with 20% load and 230VAC input, where efficiency is, in most cases, especially at higher loads, better than with 115VAC input. Also, the PSU failed to surpass 90% efficiency on any of our tests, something we didn't expect from a Gold unit.

As far as voltage regulation is concerned, it is, at +12V, tight enough, but gets loose on the minor rails, especially at 3.3V. Finally, the 5VSB rail was clearly the weakest link since it failed to keep its voltage within ATX voltage regulation limits during the full load test. We checked the 24 pin ATX connector for any loose pins, but none were loose: the 5VSB circuit is responsible for its poor performance. Apparently, 3 A current is too much for the 5VSB and Akasa had better lower it to 2.5 A.

Regarding the unit's output noise: the fan's max speed is restricted to 1625 RPM, which means that it, even at full speed, doesn't hum loud enough to annoy. It will, at lower ambient, work at reduced RPM, resulting in a noise level that will pass unnoticed to most ears.