The Seasonic PRIME Titanium PSU (650W, 750W, 850W) Review: Mythical Performance

Founded over 35 years ago, Seasonic is one of the first PC power supply manufacturers and today their products are held in very high regard amongst PC enthusiasts. Despite their high popularity and recognition that the brand name has, the company is one of the very few that did not diversify towards other segments of the market. Seasonic is solely focused on the design, manufacturing and marketing of quality PC power supply units.

During the past several years, we reviewed several of Seasonic’s PSUs, including their latest 80Plus Gold and 80Plus Platinum series. Today we are having a look at their latest product series, the 80Plus Titanium certified PRIME. Seasonic designed the PRIME PSUs to offer the best possible performance and quality they could while keeping the price tag within reasonable limits. The series consists of five units, one fanless 600W model and four regular units with their maximum rated power output ranging from 650W to 1000W. In this review we are going to test three out of the five units of the series, the 650W, 750W and 850W versions. (It is worth noting that the 600W and 1000W versions not yet available to the North American markets, which is sometimes a limitation in our sampling.)

Model Price
Seasonic PRIME SSR-650TD $170 incl. shipping
Seasonic PRIME SSR-750TD $175 incl. shipping
Seasonic PRIME SSR-850TD $200 incl. shipping

Seasonic PRIME Titanium
Power specifications ( Rated @ 50 °C )
AC INPUT 100 – 240 VAC, 50 – 60 Hz
RAIL +3.3V +5V +12V +5Vsb -12V
650TD 750TD 850TD
MAX OUTPUT 20A 20A 54A 62A 70A 3A 0.3A
100W 648W 744W 840W 15W 3.6W
SSR-750TD: 750W
SSR-850TD: 850W


Packaging and Bundle

Seasonic kept their packaging very simple, elegant and functional. The artwork is limited to basic geometric shapes and metallic colors. Our early samples came with an error on the packaging as well – the PRIME units are covered by a 12-year warranty, not 10 years as indicated on our packaging. The packaging is very sturdy, with thick cardboard walls and polyethylene foam pieces protecting the product inside.

Inside the packaging, we found the necessary AC power cable, four typical 3M mounting screws, a good user’s manual, a few typical cable ties, five high-quality cable straps with the company logo, a metallic case badge, and a sticker. There were no thumbscrews or black screws included.

The PRIME PSUs are fully modular. Every cable, including the 24-pin ATX cable, is detachable from the chassis. With the exception of the 24-pin ATX cable that is enfolded in black nylon sleeving, the rest of the cables are “flat”, ribbon-like. All of the cables have black connectors and wires.

Connector Seasonic SSR-650TD Seasonic SSR-750TD Seasonic SSR-850TD
ATX 24 Pin 1 1 1
EPS 4+4 Pin 2 2 2
EPS 8 Pin
PCI-E 6+2 Pin 4 4 6
PCI-E 8 Pin
SATA 6 10 10
Molex 5 5 5
Floppy 1 1 1

External Appearance

The three Seasonic PRIME PSUs that we are reviewing today are almost identical physically, sharing the exact same design and proportions. One can only tell the difference between the models from either the sticker with the electrical specification of the PSU that is found at the top of the chassis, or from the number of connectors at the front side of the units. Do note that the chassis is 170 mm long, which is a bit longer than that of a typical ATX PSU and might be incompatible with some cases, especially ultra-compact designs.

Seasonic is trying to have the PRIME units aesthetically standing out of the crowd mainly by adding chrome parts on the sides and bottom of the chassis. Aesthetics are a subjective matter but we believe that the designer made the PRIME units a bit too shiny, when obviously the concept was to have them looking classy. The sides of the chassis are embossed, with a small vent opening that faces the rear of the unit. These vents are insignificantly small and their direction suggests that they are most likely just decorative elements rather than actual thermal improvements.

The rear side of the PSUs is perforated, with an elongated honeycomb pattern that has been optimized for reduced air drag (i.e. noise). There is a typical on/off switch next to the AC cable connection, and also a push button that turns the hybrid fan mode on or off. With the setting on, the fan will not start until the thermal control circuit defines that it is necessary for the cooling needs of the unit.

The front side of the PSUs are littered with the numerous connectors for their modular cables. Each unit has a different number of connectors that corresponds exactly to the number of cables they come with. The connectors are grouped into three categories; one just for the ATX cable, one for the Molex/SATA cables and one for the PCI-E and CPU cables. All of the PCI-E/CPU connectors are compatible with both of the CPU and PCI-E cables.

650W, 750W, 850W

Internal Design

All three of the units that we are reviewing today are using the same exact fan, the Hong Hua HA13525M12F-Z. It initially appears to be a common 135 mm fan but has a fluid dynamic bearing (FDB) engine, which combines the low noise operation of the sleeve bearing with the longevity of ball bearing engines. The fan has a maximum rotational speed of 1800 RPM.

Seasonic is the designer and a manufacturer that actually also supplies their products to other brands, so there is no hidden OEM behind the PRIME Titanium units, they are entirely of their own design and production. The three PRIME Titanium units that we are reviewing today are also sharing the same exact internal design. As a matter of fact: many of the components are identical, with the only actual difference being the rating of some of the primary components. The heatsinks are identical, as are most of the secondary side capacitors.

The secondary capacitors are either supplied by Nippon Chemi-Con and Nichicon (Solid state), or Nippon Chemi-Con and Rubycon (electrolytic). The filtering stage also is identical between the three units and consists of six Y capacitors, three X capacitors and two filtering inductors. A surge suppressing MOV is also present. All three units are even using the same two primary conversion bridges, which are comically oversized for the power requirements for any of the three units. The two bridges in each of the units could, in theory, handle up to 4.5kW with a mere 90V AC input. Differences occur with the two APFC capacitors at the primary side: the 650W model is using 2×400V/470μF capacitors, the 750W model one uses 400V/450μF plus one 400V/560μF, and the 850W model uses one 400V/470μF plus one 400V/680μF.


Seasonic PRIME Titanium 650W – Internal View

Technologically, the topology of the PRIME units is not alien by any of today’s standards. The primary inversion stage is a full bridge supported by an LLC resonant converter, and the secondary conversion stage is a synchronous rectifier that generates the 12V line, with DC-to-DC circuits for the secondary voltage lines. Seasonic managed to reach 80Plus Titanium efficiency standards simply by the proper selection of high quality active parts that have minimal thermal losses and cooperate well with each other. The flip side of this is the cost, which we will get to later. 


Seasonic PRIME Titanium 750W – Internal View


Seasonic PRIME Titanium 850W – Internal View

Cold Test Results

For the testing of PSUs, we are using high precision electronic loads with a maximum power draw of 2700 Watts, a Rigol DS5042M  40 MHz oscilloscope, an Extech 380803 power analyzer, two high precision UNI-T UT-325 digital thermometers, an Extech HD600 SPL meter, a self-designed hotbox and various other bits and parts. For a thorough explanation of our testing methodology and more details on our equipment, please refer to our How We Test PSUs – 2014 Pipeline post.

Seasonic PRIME Titanium Efficiency
(~25ºC Ambient Temperature Testing)
% Titanium
650TD 750TD 850TD
10 90% 93.1% 93.2% 92.9%
20 94% 94.2% 94.2% 94.1%
50 96% 96.3% 96.2% 96.1%
100 91% 94.8% 94.8% 94.8%

We usually expect to see an 80Plus Titanium certified unit to borderline pass or even fail the certification requirements during our testing. This is because we are supplying 230V AC to the unit and most models have been optimized for an 110V AC input, as the certification requirements are significantly lower and makes it slightly easier for the designer to meet them. Seasonic positively surprised us because all three of the new PRIME Titanium units are extremely efficient, easily meeting the stricter 80Plus Titanium performance requirements with an input voltage of 230V AC. The top efficiency of all three units is ~96.2% when operating at 50% capacity, with a nominal load range (20%-100%) efficiency average of 95.1% (650W model) to 95.3% (750W/850W models). The low load efficiency with the PRIME Titanium PSUs operating at 10% capacity is above 84.5%, which is much higher than the peak efficiency many low-cost PSUs can hope to achieve. Still, the efficiency of the units once they reach 20% capacity is so high that the thermal losses actually seem to drop instead of increasing.

Please note that we had the hybrid fan mode disabled during our testing in order to showcase the low load noise levels with the fan turned on. With the hybrid mode turned on, the fan starts when the load reaches about 20-25% of the unit’s rated capacity.

The internal operating temperatures of the Seasonic PRIME Titanium are very low, which is to be expected with such an efficient design. The cooling fan initially appears to have a “ladder” behavior, increasing its speed in steps in relation to the load, but the thermal control circuit is actually linear. When the units are operating in an ambient temperature environment, the speed increases are just very small in relation to the fan’s operating range, which appears as a step-like behavior on a chart. The fan of any of the three units did not even reach 50% of its rated speed at maximum load under these operating conditions, operating way below its optimal range and barely reaching audible sound pressure level figures.

The hybrid fan mode is the only thing that does not make much sense with these three units. If the setting is set to off, the fan will start as soon as the PSU is powered on regardless of the load, but will still retain its minimum possible rotational speed until the thermal control circuit decides that it needs to spin faster. The fans of the PRIME Titanium units are inaudible when running at such low speeds. If the setting is turned on, the fans will start before the point they become audible with the setting turned off, meaning that there is no practical difference at low loads whether the fan is spinning or not. Considering that the fans of the units are inaudible when spinning at their minimum speed, it might be wise to keep the hybrid mode turned off. Lower operating temperatures can only increase the longevity of a PSU, even one as good as this one.

Hot Test Results

The electrical performance of the new Seasonic PRIME Titanium units is unbelievable. We are unsure how Seasonic even managed such power quality and performance figures.

Seasonic SSR-650TD – Main Output
Load (Watts) 130.29 W 325.85 W 488.11 W 650.38 W
Load (Percent) 20.04% 50.13% 75.09% 100.06%
  Amperes Volts Amperes Volts Amperes Volts Amperes Volts
3.3 V 1.78 3.34 4.45 3.34 6.67 3.33 8.89 3.33
5 V 1.78 5.03 4.45 5.03 6.67 5.01 8.89 5.01
12 V 9.6 12.02 24.01 12.02 36.01 12.01 48.02 12
Line Regulation
(20% to 100% load)
Voltage Ripple (mV)
20% Load 50% Load 75% Load 100% Load CL1
3.3V + 5V
3.3V 0.2% 4 4 6 8 4 6
5V 0.25% 4 6 6 8 4 6
12V 0.15% 4 4 6 8 6 6

Seasonic SSR-750TD – Main Output
Load (Watts) 150.34 W 375.71 W 562.75 W 750.4 W
Load (Percent) 20.05% 50.09% 75.03% 100.05%
  Amperes Volts Amperes Volts Amperes Volts Amperes Volts
3.3 V 1.81 3.33 4.53 3.33 6.8 3.33 9.07 3.33
5 V 1.81 5.02 4.53 5.02 6.8 5.01 9.07 5.01
12 V 11.25 12.02 28.11 12.02 42.17 12 56.23 12
Line Regulation
(20% to 100% load)
Voltage Ripple (mV)
20% Load 50% Load 75% Load 100% Load CL1
3.3V + 5V
3.3V 0.2% 4 4 6 8 4 6
5V 0.25% 4 6 6 10 4 6
12V 0.18% 4 4 6 8 6 8

Seasonic SSR-850TD – Main Output
Load (Watts) 170.49 W 426.27 W 638.38 W 851.07 W
Load (Percent) 20.06% 50.15% 75.1% 100.13%
  Amperes Volts Amperes Volts Amperes Volts Amperes Volts
3.3 V 1.84 3.34 4.6 3.34 6.91 3.33 9.21 3.33
5 V 1.84 5.04 4.6 5.04 6.91 5.02 9.21 5.02
12 V 12.89 12.03 32.23 12.03 48.35 12.01 64.46 12.01
Line Regulation
(20% to 100% load)
Voltage Ripple (mV)
20% Load 50% Load 75% Load 100% Load CL1
3.3V + 5V
3.3V 0.2% 4 4 6 8 4 8
5V 0.25% 4 6 8 10 6 8
12V 0.15% 4 4 8 10 8 6

We had to check our readings down to the fourth decimal point, as the voltage regulation on the main 12V line is below 0.15%, meaning that a cheap 2-decimal point voltmeter might not even display a difference at all across the entire load range. The 3.3V/5V lines are a little less tightly regulated but still remain amongst the most stable that we have ever seen, with our worst result being 0.24% for the 5V line of the 850W model.

The power quality of all three PRIME Titanium units is insanely good, with our oscilloscope never reading a voltage ripple above 10mV under any operating conditions. We have never seen such effective filtering before on consumer level products.

Despite the exceptional efficiency of the PSUs, the fans are significantly more lively with the units operating into our hotbox, as the thermal control circuit is trying to maintain low internal operating temperatures. The PRIME Titanium units all begin with noise figures when lightly loaded but their fans will keep increasing their speed alongside with the load, reaching clearly audible figures with loads above 300 Watts and even becoming noisy with >46 dB(A) figures when they units are very heavily loaded. The maximum temperature that our instruments recorded was just below 80 °C, which is very low for an 850W PSU operating at maximum capacity, meaning that Seasonic could trade some of the thermal performance for better acoustics. These units do come with a 12-year warranty though, so the designer could perhaps not afford >90°C figures appearing into any of these units.  


In this review we had a look at Seasonic’s latest top series, the PRIME Titanium 650W, 750W and 850W PSUs. They are not the most powerful models on the market designed for quad-GPU beats, but they are the technologically best units that Seasonic is currently offering to consumers.

It is slightly ironic to label these units as Seasonic’s “technological pinnacle”, because they are not using any of the latest “leading” topologies or technologies. As a matter of fact, their core topology is relatively common and simple; just a typical input bridge converter and APFC circuit, a resonant LLC full bridge on the primary with synchronous rectification on the secondary. It is a configuration that we have seen many times in the past, yet no other designer before Seasonic has ever reached such performance figures with it.

Seasonic made it easy for us to summarize the entirety of these units’ performance in just one word: mythical. The very high efficiency that easily broke the 80Plus Titanium certification requirements with 230V AC input was a small surprise at first, but surprise turned to shock when we began testing the units inside our hotbox. Not only the high ambient temperatures hardly shook the efficiency of the units, the power quality and voltage regulation figures were just incredible.

The AnandTech Recommended Award
For the Seasonic PRIME Titanium Series

Before testing these three units, we would not believe that such performance would be possible with a consumer-grade PC PSU.

In terms of quality, Seasonic did not hold back at all. We found only top-tier quality components in the PRIME Titanium PSUs, even down to the least significant elements of the design. The fact that the three units that we have tested display almost indistinguishable performance under the same load conditions suggests that there are no discrepancies due to component characteristics. Seasonic covers the PRIME Titanium units with a 12-year warranty, which is more than reassuring. The only small issue here is that the designer had to sacrifice some acoustics performance to ensure that the internal temperatures of the units will remain very low, even under very adverse operating conditions.

So perhaps the only real enemy of the new Seasonic PRIME Titanium series is their own retail price tag. Seasonic aims to be the best vendor with their OEM designs, and it all comes at a cost. With the 650W, 750W and 850W units retailing for $160, $175 and $200 respectively, many regular users will be satisfied with the performance of an “average” 80Plus Gold certified unit that will cost half as much, or even less. With all that being said, the retail price of these three units is not forbiddingly high – super high end PSUs reaching 1200W and above can come in at similar W/$.

But for these price tags, you get one of the most stunning PSU designs available today, combined with high efficiencies and a long warranty to back it up. 

Buy Seasonic PRIME Titanium 650W on

Buy Seasonic PRIME Titanium 750W on

Buy Seasonic PRIME Titanium 850W on

Suggested Reading

  • The Andyson N500 Titanium PSU Review: High Efficiency For The Common PC
  • The Raidmax RX-700AT 700W 80Plus Titanium Power Supply Review
  • The SilverStone ST60F-TI Strider Titanium 600W PSU Review
  • Best PC Power Supplies: Holiday 2016


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