Seasonic S2FC discussion

[HammerSandwich]

Some of what I wish to cover has been mentioned in various places, but I'd like us to consolidate all relevant information about S2FC within the Super Silencer family in this topic. The same basic information should translate to the Super Tornado family as well, but I don't believe we should try to compare the SS and ST here. My first post will be pretty long, but I hope to begin things on the right foot.

Reading a bunch of reviews and threads has led me to some assumptions about the different Super Silencer models:
- All have the same circuit topology though individual component values may differ.
- All have the same efficiency.
- All have the same physical layout.
- All have the same airflow at the same fan voltage.
If anyone has clear information to the contrary, please post.

Because of these assumptions, I believe that all Super Silencer models produce the same heat load for a given power output. IOW, at 150w DC output, the 300AGX should waste the same 45w as the 400AGX (as seen in Table B here), and that 45w should require the same airflow to dissipate.

However, in his SS-300FS review, MikeC wrote, "Although Seasonic refers to power levels, the truth is that there is no direct power monitoring within the fan controller. The thermistor is the only monitoring device in the fan circuit." But in "Recommended Power Supplies," he wrote (about the SS-400FS APFC), "Noise performance is actually better than 300W-APFC model because fan speed is kept low to a higher temperature/load." This sounds ridiculous - and contrary - to me. And, as alluded to in MikeC's first quotation, Seasonic's website clearly shows the bigger AGXes keeping their fans slow to higher outputs.

This is a major problem for the consumer who wants the quietest PC at 120-150w of output.

So, I can finally get to my questions:
- Is S2FC different in the AGX models and the older -FS PSUs?
- Do the AGXes control fan speed by temp, load, or a combination?
- Is the 300AGX louder than the 400AGX at any load (up to 300w)?
- If yes, is this simply Seasonic's way to make us buy pricier PSUs?

Take it to town, guys.

[MikeC]

- Is S2FC different in the AGX models and the older -FS PSUs?
Hard to say. Seems similar, but it could have been tweaked for the new models. Let's just say that the general principle is the same, fine details of execution may differ. Keep in mind that Seasonic seems to to have come up with this fan control concept first -- and it was more or less adapted by both Nexus and Antec in some of their models.

- Do the AGXes control fan speed by temp, load, or a combination?
By temp. The contradictory comment you quoted... Seasonic has stated that the the fan speed controller is calibrated to keep the internal temp of the below some predetermined level. While they cannot say what precise power load this is, they can say it is ~XX watts given ~XX ambient case temp. ALL the thermal fan PSUs I know of do this in one fashion or another. Maybe very high price units meant for the industrial/server market have current-output-related fan speed control. But maybe not -- not much demand for low noise there.

- Is the 300AGX louder than the 400AGX at any load (up to 300w)?
No. They have exactly the same noise signature; they have the same fan, the same default start voltage. The only thing that would be different is the temp point (and associated power draw) at which the fan begins to speed up beyond the default start level.

- If yes, is this simply Seasonic's way to make us buy pricier PSUs?
Not yes, so... no. I think they would say it is they want to make sure each PSU model gets good enough cooling at high loads to be safe.

[HammerSandwich]

Thanks for the comprehensive reply, MikeC.

- Is the 300AGX louder than the 400AGX at any load (up to 300w)?
No. They have exactly the same noise signature; they have the same fan, the same default start voltage. The only thing that would be different is the temp point (and associated power draw) at which the fan begins to speed up beyond the default start level.

I'm still confused. If the efficiency and cooling are the same, shouldn't "the temp point (and associated power draw)" be the same too? It sounds like you're still saying that the 300w is louder somewhere in the 100-150w area. And that's a load that many of us can reach.

[MikeC]

I'm still confused. If the efficiency and cooling are the same, shouldn't "the temp point (and associated power draw)" be the same too? It sounds like you're still saying that the 300w is louder somewhere in the 100-150w area. And that's a load that many of us can reach.

What they (Seasonic) have told me is that the higher power models use higher rated core components -- which is how they get more power out of them in the first place. These components can withstand more heat, so Seasonic lets them run hotter. Hence, the S2FC is calibrated a bit differently from model to model.

And yes, it does mean the 300W gets louder than the 400W somewhere in that 100W-150W range. As you saw from my posts elsewhere that you already linked.

[wumpus]

There is something of a discrepancy with the results I obtained using the load tester, even with the electric-bulb-in-case simulation: The PSU fan in the real system seems to reach the same [fan speed] voltage level at 25~30% less power output. I am guessing that it has to do with the fact that the PSU load tester is a pure resistive load while the real PC (especially the power supply components in the motherboard) is a complex resistive/reactive load that is more difficult to drive. Something I will have to consider and solve(?)for my next PSU test review…

Is this going to be dealt with?

I think it's unacceptable that a premium $70 PSU marketed to the "quiet" crowd ramps up the fan so aggressively at a mere 152w draw from the wall, or 120w load.

Does anyone have any tips on how to mod the s2fc into a fixed speed 120mm fan? I hate to have to drop another $80+ on the 400w version just to get something that stays quiet at well under 1/2 its rated load.

[HammerSandwich]

These components can withstand more heat, so Seasonic lets them run hotter. Hence, the S2FC is calibrated a bit differently from model to model.

Thanks, that sounds like what I was missing. Doesn't make a lot of sense to me, based solely on the (very little) bit I know about electronic components; but I'll trust Seasonic here.

Any chance that when the next family of supplies comes out you can test a couple of different models?

[MikeC]

These components can withstand more heat, so Seasonic lets them run hotter. Hence, the S2FC is calibrated a bit differently from model to model.

Thanks, that sounds like what I was missing. Doesn't make a lot of sense to me, based solely on the (very little) bit I know about electronic components; but I'll trust Seasonic here.

Any chance that when the next family of supplies comes out you can test a couple of different models?

If you just go to any capacitor manufacturer's site, you'll find variants of caps of the same cap. value but rated for different wattages and temps. 85C on one, 105C on another, etc.

Different models -- yes, specifically at the fan rpm "elbow" point in the curve. It is VERY difficult to be precise with this tho.

And wumpus, I feel your frustration. If you're willing to forego your warranty, you could alywas just run a Zalman fanmate off the mobo & bypass the PSU fan controller... not that I am recommending this, but...