Seasonic M12D 850W: DC-to-DC Perfection?

Conclusion

It has been a while since we first heard about the M12D at CeBIT, so Seasonic has certainly taken time in preparing this product for release. Our Seasonic contact told us they found several problems with DC-to-DC modules during development and they didn't want to release their product until they were sure they had solved the problem. According to Seasonic, they build the best DC-to-DC topology available, and our results seem to support this claim with high efficiency, low ripple, and tight voltage regulation on the 12V rail. Of course, their competitors offer similar results with only minor differences, so determining who is actually best is a matter of splitting hairs.

The M12D offers everything a high-end power supply should, with a simple, sleek appearance -- you won't find any flashy LED fans here. Build quality is extremely good as usual, and they use capacitors from one of the best vendors around, Nippon Chemi-Con. We weren't entirely convinced about the heatsink design initially, but the results speak for themselves and we have to give them credit. The heatsinks do an exceptional job of cooling the components and respond quickly to increased airflow. Of course, higher fan speeds help, but Seasonic has always been conservative in that area and we don't expect them to change.

Running at up to 50% of its rated output, the M12D 850W will satisfy pretty much any user. It is extremely quiet, staying under 17dB(A), and it's also efficient and well regulated. Seasonic informed us that they don't think most users go above 50% load anyway, and they simply like to have some headroom "just in case". We would agree with that assessment, with many users running 800W and larger power supplies even if they only use a single graphics card. Whether you use one graphics card or three, you still want high efficiency and good quality, and that's what Seasonic provides with the M12D.

Depending on your input voltage, you can stay above 85% efficiency (230VAC) or 83% efficiency (120VAC) across a large range of loads. Having high efficiency at lower loads is particularly useful, since many systems sit idle most of the time. Maximum efficiency tops out at 89%/88% (230VAC/120VAC), and European users will appreciate the fact that efficiency stays at close to 89% from loads of ~250W to 550W. Voltage regulation on the 12V rails is also outstanding, staying within 1% of 12.00V throughout testing.

Looking at the competition, the Enermax Revolution 85+ needs to be mentioned -- that's the most direct competitor right now, since we're still waiting for both of these power supplies to become available. Enermax has slightly higher efficiency, but Seasonic has better voltage regulation so it's pretty much a tie. Noise levels are also similar, so it really comes down to price. The 950W Revolution 85+ has an MSRP of $319 or €249, and the M12D 850W MSRP is $299 or €199. Enermax has a slightly higher maximum output, so prices should be very comparable (with an edge to Seasonic in Europe).

The Antec Signature Series 850W is already available with a street price of $230 -- far below the MSRP of these other units. The Antec Signature has lower efficiency, higher acoustic noise, and larger voltage regulation, but it's not dramatically worse in any of these areas. Other power supplies such as the Enhance-built Zalman ZM850-HP also post similar results but only really excel in areas such as acoustic noise. One definite advantage of the Seasonic M12D over the others is that it's only 160mm long, which is crucial if you want to use this sort of power supply in a smaller mid-tower case.

Overall, it has been well worth the wait for this Seasonic unit. They put a lot of effort into making a great power supply with very good performance and high efficiency. We can't really fault the Seasonic (or any other manufacturer) too much for high acoustic noise at maximum load, since they want to minimize RMAs and few users will actually reach maximum load anyway. Focusing more on the performance and acoustics for loads of 50% or less makes sense, and for such users Seasonic delivers a great result. Anyone looking for a power supply that can deliver anywhere from 80W to 600W of output without hurting your ears will find a lot to like with the Seasonic M12D 850W.