Seventeam ST-650P-AF may be a good buy if you know what you are taking home. It presents a good efficiency (84%) if you pull between 40% and 60% from its labeled capacity (i.e., between 260 W and 390 W), dropping to around 83% if you pull 80% from its maximum capacity (i.e., 520 W). At light load (20% load, i.e., 130 W) it presents efficiency around 80%, dropping below the 80% mark at full load. So you should avoid this power supply if you are going to operate it at light load or at full load. It is important to keep in mind that we test power supplies at high temperatures and that is why efficiency results from our reviews are usually lower than announced by 80 Plus.
Voltage regulation was the highlight from ST-650P-AF. All voltages were closer to their nominal values than required, always staying below 3% of their official values (ATX specification allows voltages to be up 5% from their nominal values). This includes the -12 V output, which usually doesn’t like to stay in such tight tolerance. Noise and ripple levels were below the maximum allowed.
We’d like to remember that internally this power supply is identical to Seventeam ST-650Z-AF and SilverStone ST65EF, so all performance considerations are also valid for these other two products.
Coming with a very attractive USD 95 price tag, ST-650P-AF is a good option for the user that is building a PC that will pull between 260 W and 390 W. If, however, you are looking for “the best” 650 W on the market, then you should take a look at a different product.
The only feedback we need to give to Seventeam is for them to fix their website and product box and replace "Japanese capacitors" by "Japanese capacitor on primary" or similar wording, as "capacitors" lead the consumer to think that all capacitors inside the power supply are Japanese, which is not the case.