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Final Analysis
Enermax chose to enter the SFX market with two models based on CWT's CSN platform. Their power density is quite high and the build quality is good. However, the performance of Enermax's ERV650SWT doesn't live up to our expectations. We'd like to see higher efficiency levels under normal loads, too.
Corsair's SF line-up, based on a Great Wall platform, sets a high bar for SFX power supplies. We know it's harder for these small PSUs to achieve similar performance as larger ATX models, but we want to see new products at least match the existing competition.
The strongest Enermax SFX PSU is fully modular. Unfortunately, though, it's equipped with an 80mm fan. To make matters worse, the fan profile is fairly aggressive, resulting in a lot of noise under moderate loads. A larger 92mm would have helped by moving a similar volume of air at lower RPM. It's only at light loads and under normal operating temperatures that the ERV650SWT's acoustic profile is acceptable. Most enthusiasts will find the noise annoying at higher load levels.
Due to limited space, CWT doesn't give this power supply a power switch. In our opinion, though, every PSU should have a power switch.
Load regulation is decent overall, and ripple suppression at +12V is quite good. The hold-up time we measured is really low, though (under 8ms). Of course, the ERV650SWT's PCB is small, leaving little room for a larger bulk cap or two in parallel. But we think CWT should adjust its design accordingly to accommodate larger bulk caps.
Although the +12V rail's transient response is good for an SFX unit, the 3.3V rail's performance is lousy in the same tests. Meanwhile, the 5VSB rail's efficiency is remarkable, showing that CWT paid extra attention to it at a time when other manufacturers are failing to update their 5VSB regulation circuits. The 80 PLUS program might not measure the 5VSB rail's efficiency, but it's still important. The same applies to vampire power.
With a small adjustment to the Revolution SFX 650W's price tag, Enermax would have an easier time competing against other PSUs in this category. A longer warranty would also help, especially since the competition more than doubles what Enermax offers. But a sleeve-bearing fan makes it difficult to go much beyond five years of coverage or so. We'd like to see Enermax use a larger fan with a more reliable bearing; this would solve a lot of the ERV650SWT's issues. It'd also be nice to see Enermax relocate the transient filter's PCB. Where it's installed now totally blocks airflow to the secondary side, making life difficult for a number of sensitive electrolytic capacitors.
Update, 7/21/17: Enermax informed us that the warranty of the product is actually five years long, although at the moment of the review Newegg lists it with a three-year warranty.
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