BFG MX-550 proved to be an excellent product if you stay inside its maximum labeled power.
If you pull up to 80% (440 W) from it, it will deliver at least 84.5% efficiency. Working with it at up to 60% (330 W) from its labeled maximum capacity you will see efficiency between 86% and 88%, which is terrific. Pulling its full labeled power efficiency dropped to 81.6% – not as great as the other results but still above the 80% mark.
Electrical noise level was very low, far below the maximum allowed, and the voltages were always within 3% from their nominal values.
We had two problems with this power supply. The first one was that it burned when we tried to overload it. It is good to remind, however, that the power supply protections entered in action and shut it down three times before we finally killed it. It is clear to us that this was an overheating issue and thus it would be better if BFG had used +12 V rectifiers with a bigger dissipation area (technical talk: used rectifiers with TO-247 packaging instead of TO-220).
The second issue was that the auxiliary fan didn’t kick in automatically: we had to manually rotate it with the tip of a pencil in order to turn in on. Maybe this was one of the reasons that lead the secondary heatsink to overheat and burn the +12 V rectifier.
These issues, however, won’t affect 99.99% of the users, so if you are a regular user you should not worry about them (we have to give BFG the benefit of the doubt on the fan issue and assume that we got a defective unit).
Another very important thing that affect all users: warranty. You have to register your power supply with BFG within 30 days of its purchase, otherwise you will only get a two-year warranty instead of the full five-year one. This is really tricky, as most users do not register their products with the manufacturer.
This power supply competes in price and features with Antec NeoPower 550 W, a power supply that achieved the same results as BFG MX-550 (high efficiency between 83.3% and 88%, low noise and ripple and perfect stability) in our tests and that we could overload up to 650 W with no problem (this model from Antec uses rectifiers with TO-247 packaging instead of TO-220 – in English: the rectifiers are physically biggers, allowing a better heat dissipation). Honestly, between the two our recommendation is the model from Antec , since we had no issues with it and it provides a little bit higher efficiency when delivering 550 W – plus no product registration is needed to get full 5-year warranty with Antec.
This does not mean that MX-550 isn’t a good product that will certainly please the average user.
