Seasonic M12D 850W: DC-to-DC Perfection?
by Christoph Katzer on November 26, 2008 12:00 AM EST- Posted in
- Cases/Cooling/PSUs
Introduction
We visited many power supply companies during the past year, and many of them have commented, "the power supply market is dead -- there's nothing new that can be done to attract more customers." That's not entirely wrong, as PSUs are one of the components most people only think about when their old unit fails, or when building a new system. However, it's still important for power supply companies to research new technologies and features, especially if they want to stand out from the crowd. The most recent feature to make its way onto the scene is DC-to-DC technology, with several companies now sporting high-end PSUs that use it. For example, we have the previously tested Enermax Revolution 85+, Silverstone's Zeus 1200W, and Antec's Signature Series.
DC-to-DC technology is nothing revolutionary, as power supplies have always had 3.3V and 5V rails; the difference is simply that instead of taking these directly from the transformer, these rails now split off from the 12V rail -- hence, DC-to-DC. Like other companies, Seasonic has worked on implementing this technology, but they didn't want to rush the new products to market. According to Seasonic representatives, they didn't want to have end-users beta testing the technology, instead waiting until their new PSUs were truly ready for public consumption.
Today we are looking at the long anticipated M12D series, which of course features DC-to-DC technology. We want to see if there's actually difference between Seasonic's offering and the other power supplies that use this tech. Enermax already showed us that they can reach 90% efficiency with a DC-to-DC PSU, so we want to see if Seasonic can match that achievement. There's also more to building a quality power supply than raw efficiency of course, as we discussed recently, but it is worth mentioning that Seasonic has achieved 80 Plus Silver certification.
The outward appearance of the new M12D series doesn't break new ground, with Seasonic once again using their standard black design. The casing is 160 mm long, which is slightly longer than usual, but Seasonic has built PSUs for other companies that use a longer casing (i.e. PC Power & Cooling Silencer 750 Quad). Besides the DC-to-DC technology, Seasonic includes a few other interesting features, including a custom Sanyo Denki fan. The PSUs are also supposed to have very tight voltage regulation and use only Japanese manufactured capacitors. The M12D series starts at 750W and 850W, which is definitely at the high end of what most users need. We know in the past Seasonic has tended to focus on more reasonable wattages, so hopefully we will see some of the wattage models in the future.
We are testing the 850W model today, which comes with two 12V rails each rated at 40A. Again, this isn't remarkably different from other Seasonic PSUs, but it does give users plenty of juice on each rail even with sudden large peak loads. The 3.3V rail is rated at 24A and 5V rail is 30A, both of which are fine for modern systems.
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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.