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Seasonic Prime Titanium 650W PSU Review

Seasonic jumps onto the 80 PLUS Titanium wagon with three new units that belong to its Prime family. The 650 W model is under our scope today. Besides high efficiency, it also offers great performance, quiet operation, and nice looks.

Load Regulation, Hold-Up Time, And Inrush Current

To learn more about our PSU tests and methodology, please check out How We Test Power Supply Units. 

Primary Rails And 5VSB Load Regulation

Load Regulation testing is detailed here.

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Hold-Up Time

Our hold-up time tests are described in detail here.

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This hold-up time result is the longest that we have ever measured. Seasonic wasn't joking with its >30 ms hold-up time claim, that's for sure.

Inrush Current

For details on our inrush current testing, please click here.

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The inrush current is higher than normal due to the higher-capacity bulk caps.

Load Regulation And Efficiency Measurements

This first set of tests reveals the stability of the voltage rails, along with the PSU's efficiency. The applied load equals (approximately) 10 to 110 percent of the maximum load the supply can handle, in increments of 10 percentage points.

We conducted two additional tests. During the first, we stressed the two minor rails (5V and 3.3V) with a high load, while the load at +12V was only 0.1 A. This test reveals whether a PSU is Haswell-ready or not. In the second test, we determined the maximum load the +12V rail could handle with minimal load on the minor rails. 

Test #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan SpeedFan NoiseTemps (In/Out)PF/AC Volts
13.523A1.995A1.983A1.000A64.7290.94%490 RPM21.2 dB(A)39.33 °C0.957
12.247V5.009V3.324V4.991V71.1740.81 °C115.2V
28.075A2.991A2.976A1.199A129.7093.21%490 RPM21.2 dB(A)39.32 °C0.982
12.242V5.008V3.323V4.989V139.1540.91 °C115.2V
312.968A3.499A3.492A1.400A194.7993.57%490 RPM21.2 dB(A)39.75 °C0.989
12.238V5.007V3.319V4.985V208.1841.52 °C115.2V
417.954A3.996A3.640A1.604A259.7294.16%490 RPM21.2 dB(A)40.45 °C0.996
12.234V5.005V3.319V4.981V275.8342.51 °C115.2V
522.419A4.991A4.969A1.805A324.6293.42%490 RPM21.2 dB(A)41.50 °C0.993
12.229V5.004V3.319V4.980V347.4943.85 °C115.2V
626.986A5.996A5.966A2.004A389.6493.04%400 RPM18.2 dB(A)42.95 °C0.991
12.224V5.003V3.317V4.979V418.8045.87 °C115.1V
731.546A7.003A6.965A2.207A454.6092.59%480 RPM20.3 dB(A)43.17 °C0.992
12.220V5.002V3.316V4.977V491.0047.15 °C115.1V
836.115A8.003A7.965A2.410A519.5592.05%495 RPM20.8 dB(A)43.99 °C0.993
12.215V5.000V3.314V4.976V564.4148.45 °C115.1V
941.114A8.503A8.481A2.409A584.5691.56%555 RPM23.5 dB(A)44.53 °C0.994
12.209V4.999V3.313V4.978V638.4849.39 °C115.2V
1045.865A9.013A8.967A3.019A649.4790.99%670 RPM28.3 dB(A)45.47 °C0.995
12.204V4.998V3.312V4.965V713.7950.78 °C115.2V
1151.217A9.013A8.968A3.019A714.4190.48%700 RPM30.9 dB(A)46.68 °C0.996
12.197V4.996V3.312V4.964V789.5452.57 °C115.2V
CL10.098A12.012A12.005A0.000A101.1388.59%495 RPM20.8 dB(A)46.11 °C0.979
12.251V5.004V3.317V5.064V114.1549.92 °C115.2V
CL254.114A1.003A1.003A1.001A673.0391.38%670 RPM28.3 dB(A)47.05 °C0.995
12.191V5.002V3.308V4.983V736.5651.25 °C115.1V

Load regulation on all major rails is within 0.5 percent, as Seasonic promises. This is jaw-dropping performance that'll force the competition to push their engineering teams harder to catch up. Normally, very high efficiency levels suffer the side effect of loose load regulation since fewer components are used to minimize energy losses. Somehow Seasonic's engineers found a way to overcome this problem. At the same time, excellent load regulation results on the minor rails (including 5VSB) are obtained only with the use of an extra ATX cable that Seasonic provides. It has extra sense wires, though which we can directly measure the voltage levels on the 5V and 3.3V rails. It seems as though the SSR-650TD's normal bundled cable has loose pins; load regulation on the minor rails (again, including 5VSB) was above 1 percent with it. We notified Seasonic about this problem and its engineers are looking into it.

The efficiency this unit achieves is nothing less than amazing. Under 10 percent load, it easily surpasses the 90% mark. The same goes for our 20 percent and full load tests. Only under the middle load does the SSR-650TD fail to hit its required 94% efficiency level. Then again, the 80 PLUS organization certifies PSUs at a much lower ambient temperature than we do, allowing for higher efficiency levels. It is rare to see a PSU delivering 93.42 percent efficiency under mid-load at an ambient temperature above 40 °C.

Seasonic's fan curve is rather strange. With its start-up voltage of 2.5 V, the fan spins at 490 RPM. At slightly higher voltage (in the 3.2 to 3.6 V range), we get fewer RPM instead of the higher measurement we'd expect. The results were verified our results multiple times using both a scope and a digital tachometer. At least the fan's noise is super low. Even with the PSU delivering 110 percent of its max-rated capacity at 47 °C, our readings are close to 30 dB(A). The semi-passive mode doesn't last as long as Super Flower's Titanium-rated platforms, though we strongly believe that this is preferable since it doesn't allow the build-up of high temperatures inside of the PSU.

Aris Mpitziopoulos
Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.