Efficiency

Using the efficiency results from the previous page, we plotted a chart showing efficiency of the AGD-750 at low loads and at loads equal to 20-110% of the PSU's maximum-rated load.



This unit wins the low loads category and only loses to Corsair's digital unit with normal loads. This is an outstandingly efficient PSU and High Power deserves to be congratulated for achieving such a high performance in this area without going fully digital.

Efficiency at Low Loads

In the next tests, we measured the efficiency of the AGD-750 at loads much lower than 20% of its maximum rated load (the lowest load that the 80 Plus Standard measures). The loads that we dialed were 40-, 60-, 80-, and 100 W (for PSUs with over 500 W of capacity). This is important for settings where the PC is in idle mode with power saving turned on.


Efficiency at low loads is out of this world. The Astro GD-750 is the most efficient unit we have reviewed at this load range. The fan also didn't spin up at all during these tests, which made the PSU completely silent.

5VSB Efficiency

The ATX spec states that the 5VSB standby supply's efficiency should be as high as possible and recommends 50% or higher efficiency with 100 mA of load, 60% or higher with 250 mA of load, and 70% or higher with 1 A or more of load.

We will take four measurements: one at 100, 250, and 1000 mA each, and one with the full load the 5VSB rail can handle.


The 5VSB rail registered very good performance. In the final test, efficiency even surpassed the 80% mark, which is not easily achieved on this rail. We are very satisfied about the 5VSB circuit's performance being in line with the unit's overall performance.

Power Consumption in Idle & Standby

In the table below, you will find the power consumption and the voltage values of all rails (except -12V) when the PSU is in idle mode (powered on but without any load on its rails) and the power consumption when the PSU is in standby mode (without any load at 5VSB).


Vampire power is dead low, being close to one third of the threshold the ErP Lot 6 2013 directive sets.

Fan RPM, Delta Temperature and Output Noise

The cooling fan's speed (RPMs) and the delta difference between input and output temperature are illustrated in the following chart. The following results were obtained at 40-46°C ambient.



A chart that shows the cooling fan's speed (RPMs) and the output noise follows. We measure the fan's noise from 1 meter away inside a small custom-made anechoic chamber with internals that are completely covered by specialized soundproofing material (Be Quiet! Noise Absorber Kit). The background noise inside the anechoic chamber was below 30 dBA during testing and the results were obtained with the PSU operating at 40-46°C ambient.



The following graph illustrates the fan's output noise throughout the PSU's entire operating range. The same conditions of the above graph apply to our measurements, but the ambient in this case was between 28°C and 30°C.



Thanks to its semi-passive operation and the quiet fan, the PSU features a fairly silent operation under normal conditions.