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Seasonic Super Tornado 300 ATX12V v1.3 PSU

September 2, 2003 -- by Mike Chin

Product Seasonic Super Tornado 300 PSU (ATX12V v1.3 compliant)

Model SS-300FB Active PFC rev 1.1
Manufacturer Sea Sonic Electronics
Supplier Sea Sonic Electronics
Price US$65

The Super Tornado 300 is the second of three new "Super" family of power supplies from Seasonic. Regular SPCR readers will recall the Super Silencer 400 reviewed a little over a month ago. The Super Silencer 400 was notable for its low noise and excellent efficiency, which measured 78%, meeting Seasonic's claim.

The Super Tornado is based on the same circuit topology. What is different is the use of a 120mm fan to increase airflow and cooling potential. This does necessitate a host of mechanical changes, including reduced height heatsinks and components to accommodate the 1" depth of the fan, a completely different case and so on. This is not the first 120mm fan PSU to be reviewed at SPCR; the Fortron-Source 120mm fan 350W Aurora review published just a few days ago is the first.

The name Tornado will probably raise the eyebrows of most silent PC enthusiasts. It does not inspire confidence about the noise level of this power supply. In fact, this model is rated for a noise level of just 22 dBA (at one meter, one assumes...), which is 3 dBA quieter than the Super Silencer. The idea Seasonic appear to have been trying to get across is that the 120mm fan has as much or more cooling power than the noisy multiple-80mm fan PSUs which have become so common. There are at least 2 other models slated for release in the fall -- a 350W and a 400W model.

As with the Super Silencer, the Super Tornado features a new box design that grabs your attention and sells you on its features. Most of the images in this section come from the box.

The main cover photo shows a stamped fan grill for the big120mm fan. This stamped grill is remarkable in that it really does not appear to pose any more airflow resistance than the wire grill preferred on better quality PSUs. There are the phrases "Ultra Cool 120mm Fan" (in case you didn't notice the big fan?) and "Energy Saving" (Again, one wants to ask why throw ultra into the mix when super is already in the name?!)... and 8 feature icons:

1) 120mm fan -- let's not beat this one into the ground... but one additional advantage claimed for this 120mm fan PSU is that in a tower case, the stress on the bearing is more even, meaning that it should last longer than axial fans mounted perpendicular to gravity (as with conventional 80mm fan PSUs)..

2) S2FC - 22 dBA. Seasonic's excellent fan control circuit; and they're claiming a noise level of 22 dBA, although no distance or power level is cited anywhere. The S2FC circuit was described in detail in the review of the SS-300-APFC. In essence, it keeps a relatively powerful fan running at extremely low speed until and unless a fairly high load and temperature is reached. After that point, the rate of fan speed change follows an exponential curve so that the maximum RPM / airflow is saved for the highest load. In this way, the PSU runs very quietly under normal and even fairly demanding loads, yet has the full cooling power of the fan when it is needed.

3) Ultra Ventilation. Refers to the open mesh used for the air exhaust grill, which is said to allow a high 80% free flow.

4) Active PFC - 99%. The high AC/DC conversion efficiency is combined with Active Power Factor Correction for a PF of 0.99. This results in extremely low energy waste, as explained in detail on the back of the box.

5) 80% Efficiency. In PSUs, this specification refers to how much power is lost when converting AC voltage to DC voltage. A voltage and power output level is usually specified. The 80% efficiency rating is for 240V, at full power. The rating for 120V is 78%; it is almost always lower for the 120VAC input. Regardless, these are the highest efficiency numbers I have seen claimed for any PC PSU, except for the previously reviewed Super Silencer 400. The most common number seen is 65%, with 70% being the "standard" number claimed for more high-end PSUs.

6) Forward Converter. This is a reference to more advanced circuitry that replaces the usual bridge rectifier circuit. I understand that it is what makes the high 78% / 80% efficiency possible.

7) Free Input: 100-240VAC. This refers to automatic AC input circuitry which allows the unit to run without manual switching at any AC voltage from 100V to 240V.

8) Doctor Cable. First seen in the Super Silencer 400, it's a cable management kit consisting of a spiral cable cover made of translucent soft plastic, a handful of zap-straps (locking cable ties) and a large cable mount. The image below from one of the box side panels tells the story. The parts themselves are commonplace in electronics parts stores, but its inclusion in the PSU package is unique. It's practical, generous and well thought out.

9) Warranty coverage is provided for a period of 3 years, which is very generous. Seasonic has an on-line RMA system to expedite service if and when it becomes necessary. The warranty card refers to Full details of the warranty can be seen there.


The sample came with the usual power cord, 4 mounting screws, a multi-page manual, a warranty card, and the "Dr. Cable" cable management kit. The basic appearance of the Seasonic Super Tornado 300 is not much different from other 120mm fan PSUs such as the recently reviewed Fortron-Source Aurora.

Note the absence of a 110-220VAC switch in the photo above. The photo below shows the PSU from behind, upside down. All the intake air vents are visible. There are very few vents other than the back exhaust panel. This ensures that most of the air from the fan is blown out the exhaust on the other side. One can only conjecture that the few slots visible on the back and sides might provide some level of airflow around hot components on the other side of the slots.

Cables & Connectors - There are 7 wire sets. The longest cables are long enough to reach just about anywhere even in a full tower case, and 8 Molex 4-pin connectors are probably enough for fully loaded PCs. Serial ATA power connectors or adapter are not provided.

  • 2 cables, 33" long, each with three 4-pin IDE drive connectors and 1 floppy drive connector
  • 1 cable, 19" long, with two 4-pin IDE drive connectors
  • 1 cable, 19" long, with main 20-pin ATX connector
  • 1 cable, 23" long, for 12V (P4) connector
  • 1 cable, 23" long, for 3.3V connector
  • 1 cable, 23" long, for PSU fan RPM monitoring (3-pin motherboard header)

Opening the cover exposes modest size heatsinks with a geometry that seems well optimized to maximize surface area, and a clean, uncluttered layout. As with the Super Silencer 400, the top and bottom halves of the PSU fit very snugly. There is, BTW, a little paper label over one of the screws that hold the cover on which states WARRANTY VOID IF REMOVED.

The fan is a "SuperRed" 120mm ball bearing model CHB12012AS-A rated for 12VDC and 0.19A current made in China by Cheng Home Electronics Co Ltd. This is the same brand used in the Super Silencer 400. The company is based in Taiwan, according to their web site. Seasonic says this fan has an airflow rating in free air of a massive 61 CFM and a noise level of

This view above shows the 3-pin plug to the 120mm fan, which has RPM monitoring. One 220uF 400VDC capacitor is used for the full range Active PFC circuit. BTW, the exhaust grill panel did get bent a bit while being handled; it was easy to straighten it out before putting the cover back on.

Like in the Super Silencer 400, an unusual aspect of the fan circuitry is that its ground is isolated from the rest of the PSU, apparently to ensure that the fan voltage does not sag even with high loads on the main output lines. Normally, only the positive voltage lead to the fan needs to be tapped; the negative voltage can be read from any black lead on any output connector, a 4-pin Molex being the most convenient. Not so here. Both positive and negative leads to the fan had to be tapped to measure the fan voltage.


The Seasonic Super Tornado 300 is the second PSU we've seen that is compliant with Intel's ATX12V Version 1.3 Power Supply Design Guide released a few months ago. (See details in SPCR's Recommended PSUs article.) The first was the Seasonic Super Silencer 400. One of the changes from version 1.2 to 1.3 is the removal of the –5V rail. It is no longer required, and Seasonic's Super family does not provide it. Apparently its absence does not cause any conflict with recent motherboards produced prior to the v1.3 guide.

The specifications here come from a technical Seasonic document (EA-V30FB01-4: Jul 10, 2003) that provides a lot of detail. Some of the information here contradicts slightly the info in their product brochures and retail box.

Efficiency, for example, is cited in this document as >74% at full power output with 120VAC and >77% at full power output with 240VAC. This is substantially lower than the 78% and 80% cited in the marketing materials.

Note the high current 18A capacity of the 12V line. This is one of the most significant changes in the ATX12V guidelines from V1.2 to V1.3.

Output Capacity:

AC Input
AC Input 100-240V ~7A 50/60 Hz
VDC Lines
Voltage Regulation
Max Current (peak*)
18A (20A)
2A (2.5A)
Max Output
Total Output
300W (340W peak*)

*Peak minimum duration 1 second

4-in-1 Protection: Over voltage / over power / over temperature / short circuit protection. One presumes all of these conditions will cause the PSU to shut itself down.

Operating Temperature: 0 to 50° C. Relative humidity: 20% to 80%. The rated power will reduce from 100% to 80% from 40° C to 50° C linearly.

MTBF (mean time between failure): Typically over 100,000 hours at 25° C under full load, excluding the DC fan.

There are 13 logos for safety and EMC approvals:


Parameters Tools
DC load on PSU DBS-2100 PSU load tester
Ambient temperature
Any number of thermometers
DC voltage regulation
Heath / Zenith SM-2320 multimeter
AC power
Kill-A-Watt Power Meter
The core PSU test tool on SilentPCReview's test bench is the DBS-2100 load tester, made specifically for testing computer power supplies. The machine consists of a large bank of high power precision resistors along with an extensive selection of switches on the front panel calibrated in Amps (current) and grouped into the 5 voltage lines: +5, +12, -12V, +3.3, +5SR. Leads from the PSU connect into the front panel.

The DC output connector closest to the PSU on each set of leads is used for hookup to ensure that the current is distributed through as many short leads as possible. The wires get very hot when pushing a PSU to high output.

The Seasonic Super Silencer was tested at 5 DC output power levels:

65W: A very typical DC power draw by many system at low / modest load.
90W: Established previously as a typical max power draw of a midrange desktop PC.
150W: For higher power machines.
300W: Rated output.

Care was taken to ensure that the load on each of the voltage lines does not exceed the ratings for the PSU. The PSU was left running 10 minutes at each power level before measurements are recorded.

The DBS-2100 is equipped with 4 exhaust fans on the back panel. A bypass switch toggles the fans on / off so that noise measurements can be made. The resistors get very hot under high loads.

Kill-A-Watt AC Power Meter is plugged into an AC outlet on the side of the DBS-2100 in the above picture. The AC power draw of the PSU is measured at each of the 4 power loads. The Kill-A-Watt is used to measure:

Efficiency (in AC-to-DC conversion) at each power level. This is the efficiency figure provided by PSU makers, obtained by dividing the DC power output (as set on DBS-2100 load) by the AC power consumption. Efficiency varies with load, and also temperature. The main advantage of high efficiency is that less power is wasted as heat. This means a cooler PSU that requires less airflow to maintain safe operating temps (read: quieter).

Power Factor (PF). Read directly off the Kill-A-Watt. In simple terms, it tell us how much AC power is lost to harmonics (unnecessary electromagnetic energy) while driving the PSU. In practical technical terms, it is the difference between the V(voltage) x A(amperes) and AC power in Watts measured by Kill-A-Watt.

PF varies somewhat with load. The ideal PF is 1.0, which means no AC power is lost. A PF of 0.5 means that to deliver 100W in AC to a PSU, your electric company actually uses 200W and this is often shown in your electric bill as savings (depends on your electric utility company and your account with them). 100W is lost or wasted. Active PF Correction (PFC) power supplies usually have a PF of >0.95. Passive PFC units usually run 0.6 - 0.8. Non-PFC units usually measure 0.5-0.7. PF is not significant in terms of noise, heat or performance for a PC, but it is relevant to electricity consumption and energy conservation.

The Heath / Zenith SM-2320 digital display multimeter, a fairly standard unit, is used to measure the fan voltages and the line voltages of the PSU output. The latter is done via the terminal pin on the front panel, above the connections for the DC outputs from the PSU.

The Test Lab is a spare kitchen measuring 12 by 10 feet, with an 8 foot ceiling and vinyl tile floors. The acoustics are very lively and allows even very soft noises to be heard easily. The PSU under test is placed on a piece of soft foam to prevent transfer of vibrations to the table top. Temperature in the lab was 24C. This is something of a problem as PSUs usually operate in environments that easily reach 45C. Sited next to or above the CPU, the PSU is always subject to external heat. This brings us to the next topic...

In-case Thermal Simulation

The solution is a AC bulb in an empty case with the PSU mounted normally. The distance between the bottom of the PSU and the top of the bulb is about 7 inches. A 60W bulb was used for the 65W and 90W load test, then swapped for a 100W bulb for the higher load tests. The bottom front vent of the case and its bezel have been modified for unrestricted airflow; the approximate size of the intake hole is the equivalent area of a 92mm fan.

The PSU must cope with the heat generated by the light bulb plus whatever heat it generates within itself. In a real system, there would be other air exhausts paths and mostly likely at least one case fan. So a Panaflo 80mm L fan was mounted on the back panel of the test case and connected to a voltage controller. The PSU was run through its load range with the fan turned on to 7V, about the level at which most PC silencers would run their case fan.

Noise Measurements

A highly accurate calibrated B&K model 1613 sound level meter on temporary loan from the University of BC's acoustics lab was used for noise measurements.

This professional caliber SLM dates back to 1978, weighs over 10 pounds, and is completely analog in design. It has a dynamic range that spans over 140 dB. The microphone used has a 1" diaphragm that's very responsive to low sound levels and low frequencies. The unit's absolute sensitivity reaches below 0 dBA -- at one point in the midband (1kHz) it was reading -4 dBA for background noise in the UBC anechoic chamber.


Measurements were made at 4 output power levels: 65W, 90W, 150W and 300W . The PSU was allowed to run for ~10 minutes at each power level before measurements were recorded. The room temperature was 24C. Two samples were tested in exactly the same way. The difference between them was less than 1% for any measurement. Shown here are the measurements from one of the two -- neither had any significant superiority.

Table A. Load on the PSU*


*The absence of the -5V line is not an error; the ATX12V v1.3 PSU Design Guide eliminates the need for this line. The load on each line was carefully readjusted to ensure the correct total power delivered.

Table B. On test bench, 24C ambient temperature

DC Power
AC Power
Internal Heat*
Power Factor
Fan Voltage
dBA @ 1 m
Exhaust Temp

*The difference between AC input and DC output is lost as internal heat in the PSU.

Table C. In-case thermal simulation , over light bulb, with case fan turned off

DC Power
Light bulb
Case Temp
Exhaust Temp
Fan Voltage
dBA @ 1 m


1. EFFICIENCY was excellent. Even at the low 65W load level where most PSUs fail to reach even 65%, the Super Tornado started with an amazing 75.6%. The highest efficiency reached was 77% at a very low 90W and also at 150W. The efficiency of the Super Tornado betters all other PSUs tested at SPCR by a big margin -- except for the Super Silencer 400, which reached 78%.

Whether this sample can be considered to have met its published specs depends on which specs one goes by. By the more technical specification document, which states minimum efficiency as being higher than 74% at 120VAC input, it clearly has; by the marketing materials, which claim 78%, it hasn't quite made it.

As with the Super Silencer 400, the most significant result of this high efficiency is that the PSU always runs cooler than other models. This will have a real effect on noise in actual use, as the thermal fan speed controller will keep the fan spinning slower over a wider variety of loads than with a lower efficiency PSU.

2. VOLTAGE REGULATION was excellent, within -/+2% on all lines in any combination of loads tried (somewhat at random). It was often within -/+1%. The low and high voltage seen on each of the main lines is shown:

  • +12V: 12.02 to 12.28
  • +5V: 4.92 to 5.14
  • +3.3V: 3.3 to 3.42

It should be noted that I have no way of testing line regulation, so AC conditions are steady-state, not dynamic as it would be (potentially) in a real PC; I have no way to vary input AC voltage at this time. The AC line voltage in the lab as measured by the Kill-a-Watt power meter is usually within a couple of volts of 120V.

3. POWER FACTOR was 0.98~0.99 at all power levels, as good as can be. This and the high efficiency may help you save money on your electric bill and make you feel environmentally (morally?) superior.

4. NOISE was extremely low on startup and very low throughout the testing. In essence, it is the new champ among quiet fan-cooled PSUs.

The 120mm SuperRed fan, at the ~4.7V start fan voltage, made so little noise that I had to get within about a foot to hear anything at all with the unit sitting on the test bench. My wife, who has more sensitive hearing, picked it up at about 3' distance but found that it was very faint. With my ear right up against the unit, there was a faint trace of electronic sizzle -- this would turn into coil buzz if it got loud enough, but in both Tornado samples, the noise remained at the same super-low level at all times. It is inaudible for all practical purposes. The fan noise consisted of a faint "chugga-chugga" sound and a periodic "shhh-shhh-shhh" as if something was rubbing softly. All this was, I emphasize again, with my ear within about 6 inches of the fan.

Noise measurements were made in the live test room in the evening. With all equipment turned off in the 23C temp room, the ambient noise was measured at ~17 dBA. Measured noise did not change when the Seasonic was turned on with a 65W load 1 meter away from the sound level meter. In other words, turning the Super Tornado on did not add any noise that could be heard above the ~17 dBA background ambient noise level. There was also no change in audible noise with the PSU at 90W load. In case there is any doubt, this is extremely quiet performance under these loads, better than any other PSU tested at SPCR thus far.

At the 150W load, the fan speed seemed to turn a corner and started to rise. Left running at 150W load for about 15 minutes, the fan speed climbed for several minutes till 7.25V was reached. Then, the fan voltage dropped steadily and stabilized at about 5.5V. That is where the 22 dBA was measured. Almost all the noise consisted of the whooshing of air turbulence.

The ~17 dBA measured at low-med load is 5 dBA quieter than the Seasonic Super Silencer 400. It is quieter than the Nexus NX3000, which measures about 3 dBA higher under the same conditions. The Tornado's base noise performance approaches the start noise level of the 14dB SilenX 400 PSU. It easily beats the SilenX 400 in any real application because the Tornado remains at virtually the same noise level up to quite a high output level while the SilenX 400 noise tends to rise almost immediately after turn-on.

At full load, with the fan voltage at the full 12V, the PSU is quieter in the case than out by itself on the test bench. This is because inside the case, the fan gets placed farther away from the measuring microphone -- and the human ear. One of the side benefits of this fan / PSU configuration. Even though 37 dBA @ 1 meter is plainly audible, the noise is not at all annoying, due to the broadband pink noise the whooshing most closely resembles.

5. COOLING: The high efficiency of the Super Tornado 300 allowed it to remain cool even in the in-case thermal simulation with a 100W bulb. Table C details the results, which are self-explanatory: Along with the Super Silencer 400, it is the coolest running PSU yet encountered. In a real system, running a without any case fan is a very viable option with the Super Tornado.

Usually, using the thermal speed controlled fan in the PSU as the only heat exhaust causes the fan to speed up as the PSU heats up, thereby adding back the noise removed with the case fans. The in-case thermal simulation results suggests this is not likely to happen with the Super Silencer, at least not with loads up to ~150W. Given that most systems draw less than 150W even at 100% loads, this promises very quiet operation.


You may be aware that

Intel's ATX12V v1.3 PSU Design Guide has guidelines for low noise PSUs

. Section 5.7 on page 54 of the Guide calls for a maximum sound power level in a PSU designated as low noise to emit no greater than 4.0 Bels sound power at 50% load and ambient intake air temperature of 43C.

While 4.0 Bels is not exactly super quiet, the conditions of 50% power load and 43C air temp makes this a very tough standard to meet, especially for high power PSUs. Few models even on our Recommended quiet PSU list would pass this test. Most quiet PSUs are quiet at power loads under 150W.

The Super Silencer 400 review checked to see whether it would pass; it probably would not. At the time, I conjectured that a 300W version of the Seasonic "Super" family might well pass because of the lower load level it would have to pass: 150W instead of 200W. The Super Tornado 300 might be an even better candidate because of its fan's higher airflow at lower RPMs.

It is difficult to make a precise conversion of Bels (sound power) to decibels (sound pressure level), but 4.0 Bels usually falls 32~33 dBA @ 1 meter in most environmental conditions. The 100W light bulb in the case was raised and brought closer to the intake vents to get closer to the 43C intake temp required.

Final Result: YES! In the closest match to specified conditions, at an intake temperature of 39~41C with the PSU running at 150W load, the noise measured 28 dBA @ 1 meter. Given this result, the Super Tornado would most likely pass a formal, more stringent test for the section 5.7 low noise guideline in Intel's ATX12V v1.3 PSU Design Guide.


The Seasonic Super Tornado 300 is a superbly executed power supply.

  • It is fully compliant with the ATX12V v1.3 PSU Design Guide.
  • It has very high efficiency - above 75% at all power levels and up to 77% max.
  • It will be quieter in real applications than any other fan-cooled PSU examined by SPCR thus far. Even while delivering ~150W power in a tower case, the noise is not likely to exceed ~25 dBA @ 1 meter.
  • It is one of a tiny number of PSUs that could meet Intel's tough definition of a low noise PSU as per their ATX12V v1.3 PSU Design Guide. At this point, the only other candidate is Seasonic's own Super Silencer 300. No other PSUs we know of have the combination of high efficiency and intelligent fan design required to meet that "low noise PSU" designation challenge.

The Super Tornado 300 runs cool enough that in many systems, it is quite feasible to dispense with a case fan, thus eliminating another noise source. Yet, because of the high airflow potential of the 120mm fan, system cooling may not be compromised.

Inside a case powering a real system, the Seasonic Super Tornado 300 will probably run quieter than any other PSU examined by SPCR. The asking price of US$65 is not low but when you consider the low noise with high performance, high efficiency, high current capability, handy "Doctor Cable" kit and 3-year warranty, the price certainly does not look high.

And even for the diehard silencers who lurk in the SPCR forums, there's little reason to consider modifying the Seasonic Super Tornado 300. It's about as quiet as a fan-cooled PSU can be. Unless efficiency can be leaped up to say 90%, it's difficult to imagine how an effectively fan-cooled PSU could be made quieter. The Seasonic Super Tornado 300 deserves an unconditional recommendation from SPCR.

Our thanks to Seasonic for the review samples and for their kind support. Please check the new Seasonic USA web site for information about where to buy.

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