Although Seasonic's SSR-600TL is fanless, up to 600W of capacity, two EPS connectors, and four PCIe connectors allow it to support a highly capable gaming system.
The increased efficiency that this Prime platform offers enables its high capacity, despite a lack of active cooling, since energy losses are kept to a minimum. When it comes to passive PSUs, the only way to ramp up capacity while maintaining normal dimensions is to improve efficiency. That's exactly what Seasonic did with its SSR-600TL. This is the most efficient PSU we've tested in the 600-700W category. Its overall efficiency score is just a hair away from Corsair's AX1600i, which dominates thanks to its digital platform and totem-pole bridgeless PFC converter. With smaller bulk caps (since the ones it uses are totally overkill), Seasonic's SSR-600TL could probably steal that lead from Corsair. Not to take anything away from the AX1600i. The capacity difference between those two units is huge, and higher capacities make it tougher to keep overall efficiency at award-winning levels.
The SSR-600TL is hands-down the best (and most powerful) fanless PSU that money can buy. It offers amazingly high efficiency levels, super-tight load regulation on all rails, and excellent ripple suppression. Its hold-up time is beyond anything we were expecting, and its transient response is satisfactory for this capacity range. Such a highly capable PSU has no trouble serving as the foundation for an enthusiast-oriented gaming PC. That it's also completely silent is icing on the cake.
We didn't notice any coil whine from our sample. Passive PSUs that suffer from this can get particularly annoying, since the lack of a fan makes electrical noises easier to perceive. Depending on age and hearing ability, we all detect coil whine differently. So, we asked several folks ranging from 25 to 41 years old to sit in a room with the SSR-600TL operating under different load conditions. None of them heard anything from 50cm away.
The Prime Fanless 600W's only serious drawback, then, is its high price tag, and every passive power supply is going to have the same issue. If you want to spend less and a semi-passive PSU is good enough, there are more affordable options in Seasonic's portfolio that we'd still call quiet. But if you're looking for something to put into a special-purpose PC (for a recording studio or hemi-anechoic noise testing chamber), then your best bet is a passive unit that costs more. Good PSUs are an investment, after all. No good comes from going cheap on them.
Disclaimer: Aris Mpitziopoulos is Tom's Hardware's PSU reviewer. He is also the Chief Testing Engineer of Cybenetics, and developed the Cybenetics certification methodologies apart from his role on Tom's Hardware. Neither Tom's Hardware nor its parent company, Purch Media, are financially involved with Cybenetics. Aris does not perform the actual certifications for Cybenetics.