Output Voltage Stability
The cross-load diagram is almost the same as that of the Seasonic M12-II 620 Bronze, which might be expected considering their identical circuit design.
The voltage on the +12V rail deflects the most from the default level either when there is a high load on the +12V rail and a very low load on the other rails or vice versa. In the range of real-life loads this voltage doesn't deflect more than 2%, though.
The +5V voltage goes further from the default level as the load on the +5V rail grows up. Still, it remains within 3% at loads below 60 watts, which is going to be enough for any modern PC configuration.
It’s worse with the +3.3V voltage which deflects the most when there’s a low load on the +3.3 rail combined with a low load on the +12V rail, as is typical of an idle computer. That’s not going to be a big problem, though.
Output Voltage Ripple
The overall level of high-frequency pulsation isn’t high, but there are occasional spikes of voltage above the permissible limits. The oscillogram for the +12V rail shows that such spikes coincide with the switching of transistors. Voltage spikes of this kind aren't good, but can hardly interfere with the operation of your computer.
The same goes for the low-frequency voltage ripple except that the voltage spikes are not so regular.
The PSU is cooled by an ADDA AD1212HB-A71GL fan (the same as in the SS-620GM). It’s rated for 2200 RPM, which is a very high speed for a PSU that comes bundled with a silence-oriented system case.
About 40% of the fan is covered with a transparent plate to optimize air flows.
It’s good that the fan starts out at a speed of below 500 RPM and keeps it until a load of almost 200 watts. But then it accelerates to 1000 RPM at 300 watts and becomes downright noisy at 400 watts. The fan reaches its top speed of over 2000 RPM at about 430 watts. It maintains the same speed afterwards and is surely not comfortable then.
Take note that the fan speed increases at a faster rate than the temperature inside the PSU: the difference in temperature between the incoming and outgoing air is constantly diminishing, which is indicative of a suboptimal fan regulation algorithm.
The aerodynamic noise of the fan’s impeller was accompanied with some mechanical sounds. This must be a defect of the particular sample of the fan because ADDA products are usually free from such problems.
All in all, the Antec Neo ECO 620C, just like its Seasonic progenitors, is almost silent at low loads but becomes average in noisiness at a load of 300 watts. At a load of 400 watts its noise is already uncomfortable.
Efficiency and Power Factor
The power factor notches 90% at a load of 70 watts, reaching 99.7% at the peak. That's an excellent result.
The PSU is over 82% efficient through most of the load range, which is somewhat lower than the efficiency of its Seasonic progenitor but sufficient for 80+Bronze certification (Antec didn’t take the trouble of getting it for some reason, limiting itself to the basic 80+ certification).
+5V Standby Source
The standby source is blameless. Its voltage deflects no more than 0.1 volts from the default level whereas the industry standard allows a 0.25-volt deflection.
The Antec Neo ECO 620C is in fact identical to the Seasonic S12-II Bronze with a rating of 620 watts. Compared to the latter, it has somewhat lower efficiency and stronger output voltage ripple but offers longer cables, particularly the mainboard's 4+4-pin one.
This model will not be quiet if you use your computer for anything harder than just web-browsing and movie-watching.