Seasonic M12D 850W: DC-to-DC Perfection?
by Christoph Katzer on November 26, 2008 12:00 AM EST- Posted in
- Cases/Cooling/PSUs
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.
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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.
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mindless1 - Saturday, November 29, 2008 - link
First of all, in a design like this no they don't produce their airflow at a significantly lower RPM. You've fallen victim to dubious free air ratings, and ignored that lower quality fans tend to increase in noise level sooner due to wear.Second, choosing 140mm fan means you can't pick among many of the good fan makes which the Sanyo Denkis are. Let's just leave a good fan alone instead of replacing it with something junky.
Mr Perfect - Wednesday, December 3, 2008 - link
I'm going by fan testing from SPCR, not the manufacturer's fluff specs. From what they've seen, to hit x cfm rate, a 80mm is going to have to spin faster then a similarly built 92mm, while that 92mm is going to rev higher then a 120mm, and presumably any good 120mm is going to be rotating faster then any quality 140mm at the same real CFM.And cheap fans are definitely not what I was suggesting.
emboss - Wednesday, November 26, 2008 - link
Yes, it's me harping on about ripple and noise again :)There appears to be no ripple in the traces you have shown. The "ripple" figures you quoted are actually noise figures. However, I suspect that the ripple is still there, just overwhelmed by the noise. A low-pass filter to cut off anything more than 1 MHz or so would possibly clean it up and allow ripple numbers to be be determined.
Also, the comparison of 12V1 and 12V2 is just a waste of space. They both come from the same place (they just have independent current limiting, that's all).
jabber - Wednesday, November 26, 2008 - link
This is where I see a future for PSU tech. As more people want to create HTPC/Music Servers I think it would be really good to be able to buy PSUs that deliver high quality, stable, filtered, clean power with the minimum of RFI hash etc.Units would only need to be around the 300-400w mark (could probably get away with 250w).
Would be nice to be able to get stripped down motherboards with traces designed to be as short as possible and ultra quality power circuits to go with them with.
mindless1 - Saturday, November 29, 2008 - link
You are entirely misunderstanding the issues. The power supplied to the system is not directly driving anything where the ripple matters. Voltages are stepped down on the mainboard itself which is a separate more local source of noise, IF that noise would've mattered. A decent audio card will have a linear regulation stage and the digital circuits don't care about a minor bit of ripple.IOW, there is no reason to believe it would make a difference.
Also, stripped down motherboards with short traces also has no point. These are digital circuits while you are thinking in terms of crude analog audio where the traces need be short because the designer didn't properly shield or ground-plane the circuits. Within the analog audio circuits on boards, the traces ARE short, as much so as reasonably possible. Even then, it's drifting the wrong direction since we've had digital output for audio.
Bottom line- all you need is a good audio card with digital output. There will be zero difference which board or PSU you choose so long as they otherwise worked fine.
Mr Perfect - Wednesday, November 26, 2008 - link
ROFL. I'm sure that Monster would be all over that market segment. One thousand dollar 400watt power supplies with gold plated connectors, EMI shielding, and "audiophile grade" filtered power.Granted, clean power is what sets the good power supplies apart from the chaff, but as soon as you step into the music realm, the marketing machine rules supreme.
jabber - Thursday, November 27, 2008 - link
Indeed there could be an element of that. However, unlike hifi gear which only gets tested by listening. These components, as they are still PC based would be subject to decent technical testing as per websites such as these.Extravagant claims would soon be put to the test. Unfortunately thats not something that is done quite nearly enough in the audio world.
djc208 - Wednesday, November 26, 2008 - link
Since you've been posting all these great articles on not only PSUs but also energy requirements and effeciency it's really made me look realistically at my system.I picked up a kill-a-watt a few weeks ago and put it on the plugs for my desktop and my server and the numbers I saw completely re-alligned my expectations. Neither of those systems pull over 200W with anything I throw at them. The server isn't high end stuff but has lots of drives spinning and runs 24/7.
The desktop isn't a gaming monster but even plugged into the wall outlet for the UPS I maxed out at about 250W, and that's with the 19" CRT on the same outlet.
So thanks for the education, it's saved me money already. I needed to replace the server PSU and saved money by shopping in the right portion of the spectrum as well as shooting for max efficiency at the wattage I saw vice some bloated "recomendation".
computerfarmer - Wednesday, November 26, 2008 - link
If the 5v and 3.3v draw from the 12V rail(DC to DC) then what does the 40A rating per rail mean? Is this the rating after the draw from the other rails? What is the max amp draw from both 12V rails?The reason for this question came from looking at the specs from "Antec Signature850". See here http://www.antec.com/usa/productDetails.php?lan=us...">http://www.antec.com/usa/productDetails.php?lan=us... This has rail 1&2 at 22A each and Rails 3&4 at 25A each, yet the total is 65A max.
How is anyone supposed to understand these specs?
valdir - Wednesday, November 26, 2008 - link
The ripple measurements need a more severe judgment, since they are higher than, for example, Corsair's TX750 and worst of all, they have a very bad waveform, with very high frequency components.