SilverStone Decathlon 700 W Power Supply Review

[nextpage title=”Introduction”]

Decathlon 700 W (a.k.a. DA700) from SilverStone features a full modular cabling system, where even the main motherboard cable is connected through it, a very uncommon configuration (usually on power supplies with modular cabling system the main motherboard cable comes from inside the unit). This unit also features active PFC and a 120 mm fan, with the manufacturer saying it can deliver its labeled power at 50° C. Let’s see if this is true and if this unit is a good option.

Figure 1: SilverStone Decathlon 700 W.

This power supply is a bigger than other products on the same power range, being 7 3/32” (180 mm) deep instead of 6 19/64” (160 mm) or even 5 ½” (140 mm), and also having a slight ¼” (6.35 mm) projection for the modular cabling system, making it to have a total depth of 7 11/32” (18.6 cm).

As mentioned, this product has a 120 mm on its bottom side, which is our preferred configuration. We think, however, that SilverStone could have installed a bigger 140 mm fan (the modular cabling system could have prevented this implementation though).

As explained, on this power supply all cables use the modular cabling system, including the main motherboard cable (which uses a 20/24-pin connector), the EPS12V cable and the ATX12V cable, which use separated cables.

Figure 2: SilverStone Decathlon 700 W.

Figure 3: SilverStone Decathlon 700 W.

This power supply comes with three auxiliary power cables for video cards: one with an 8-pin connector and two featuring two 6-pin connectors each.  This is a very versatile configuration, even though we prefer to see power supplies using individual cables for each video card power connector. It would be also better to see all connectors using 6/8-pin plugs.

On the peripheral side this unit comes with two SATA power cables containing four SATA power plugs each and two peripheral power cables containing three standard peripheral power plugs and one floppy disk drive power plug each.

All wires are 18 AWG, which is adequate for a power supply on this power range.

This power supply is manufactured by Impervio, the same manufacturer behind OCZ EliteXStream 1,000 W. It is interesting to note that SilverStone uses different vendors for their other power supply series. For example, Strider ST50F is manufactured by FSP.

Now let’s take an in-depth look inside this power supply.[nextpage title=”A Look Inside The Decathlon 700 W”]

We decided to disassemble this power supply to see what it looks like inside, how it is designed, and what components are used. Please read our Anatomy of Switching Power Supplies tutorial to understand how a power supply works and to compare this power supply to others.

Some things caught immediately our attention. The first one was the fact that this power supply uses two transformers. Of course during our review we will see how they are connected.

The second thing was how the modular cabling system was implemented. Usually modular cabling systems use a small printed circuit board to hold the connectors and make the current distribution between them, and this printed circuit board is connected to the main printed circuit board using some wires. On this power supply, however, each plug is connected individually to the main printed circuit board, which is a better way to make this connection, even though it increases the number of necessary wires.

And the third thing that caught our attention was that on this power supply the main AC connector is soldered directly to the printed circuit board. This is the first time we’ve seen such configuration. We will discuss more about this in the next page.

Figure 4: Overall look.

Figure 5: Individual connectors on the modular cabling system.

Figure 6: Overall look.

Figure 7: Overall look.

[nextpage title=”Transient Filtering Stage”]

As we have mentioned in other articles and reviews, the first place we look when opening a power supply for a hint about its quality, is its filtering stage. The recommended components for this stage are two ferrite coils, two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor, yellow component on the pictures below) and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components, usually removing the MOV and the first coil.

This power supply is flawless on this stage. Its AC connector isn’t a regular plug but in fact a full line filter (we’ve seen similar component being used on another power supply manufactured by Impervio, OCZ EliteXStream 1000 W). It also has two more ferrite coils and one more X capacitor than necessary, plus one X capacitor and two Y capacitors after the rectifying bridge. The MOV is located after the rectifying bridge.

Figure 8: Transient filtering stage.

In the next page we will have a more detailed discussion about the components used in the Decathlon 700 W.

[nextpage title=”Primary Analysis”]

On this page we will take an in-depth look at the primary stage of Decathlon 700 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBJ1506 rectifying bridge in its primary, capable of delivering up to
15 A at 100° C. This component is amazingly overspec’ed: at 115 V this unit would be able to pull up to 1,725 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 1,380 W without burning this component. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.

Figure 9: Rectifying bridge.

The active PFC circuit uses two 20N60C3 power MOSFET transistors, which are probably the most popular transistors for this function. Each one is capable of handling up to 300 A @ 25° C in pulse mode (which is the case) or up to 45 A @ 25° C or 20 A @ 110° C (note the difference temperature makes).

The active PFC circuit uses three capacitors from Toshin Kogyo (TK) labeled at 85° C connected in parallel. Even though TK is a Japanese vendor, they sell rebranded Taiwanese OST capacitors. When capacitors are connected in parallel their capacitances are added. This is a very common trick to achieve a higher capacitance without using a capacitor that is physically bigger and would not fit the form factor proposed by the manufacturer. Since each cap has a capacitance of 150 µF together they are equivalent to a bigger 450 µF cap.

This power supply uses two SPW16N50C3 power MOSFET transistors on the traditional two-transistor forward configuration on its switching section. Each transistor is capable of handling up to 48 A in pulse mode or up to 10 A @ 100° C in continuous mode.

Figure 10: Active PFC diode, active PFC transistors and switching transistors.

The two transformers are driven by the two switching transistors, so the two transformers share the entire primary side from the reviewed power supply.

This power supply uses a discrete active PFC/PWM controller instead of using an integrated circuit that has this circuit already ready to use. On this power supply this circuit was built using one LM339 comparator, one UC3845B current mode controller and one UCC3818A PFC controller.

Figure 11: PFC/PWM controller.

[nextpage title=”Secondary Analysis”]

As you know by now, SilverStone Decathlon 700 W has two transformers. The first one (T1) and part of the second one (T2) are used to produce the +12 V output, through the use of two Schottky Rectifiers. The +5 V output is produced by the second transformer through the use of one rectifier, while the +3.3 V output is produced by one output from T1 and one output from T2 connected in parallel and using one rectifier. So basically two transformers are used just to replace one big transformer, not bringing any other benefit besides that on the project that is used by this unit.

The +12 V output is produced by two 63CPQ100 Schottky Rectifiers, each one capable of handling up to 60 A at 153° C (30 A per internal diode). The maximum theoretical current the +12 V line can deliver is given by the formula I / (1 – D), where D is the duty cycle used and I is the maximum current supported by the rectifying diode (which in this case is made by two 30 A diodes in parallel). Just as an exercise, we can assume a typical duty cycle of 30%. This would give us a maximum theoretical current of 86 A or 1,029 W for the +12 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used.

Figure 12: +12 V rectifiers.

The +5 V output is produced by one S60SC4M Schottky Rectifier, which is able to handle up to 60 A at 126° C (30 A per internal diode). The maximum theoretical current the +5 V line can deliver is given by the formula I / (1 – D), where D is the duty cycle used and I is the maximum current supported by the rectifying diode (which in this case is made by one 30 A diode). Just as an exercise, we can assume a typical duty cycle of 30%. This would give us a maximum theoretical current of 43 A or 214 W for the +5 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used.

The +3.3 V output is produced by another S60SC4M Schottky Rectifier. The maximum theoretical current the +3.3 V line can deliver is given by the formula I / (1 – D), where D is the duty cycle used and I is the maximum current supported by the rectifying diode (which in this case is made by two 30 A diodes in parallel). Just as an exercise, we can assume a typical duty cycle of 30%. This would give us a maximum theoretical current of 43 A or 141 W for the +3.3 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used.

As you can see the rectifiers are clearly overspec’ed, which is always nice to see.

The -12 V output is produced by one LM7912 voltage regulator integrated circuit, which has a current limit of 1.5 A.

On the same heatsink you can also see the rectifier used for the +5VSB output, an SBL1060CT, which is capable of delivering up to 10 A at 95° C (5 A per internal diode), so the maximum theoretical current limit for this output is of 5 A or 25 W.

It is always good to remember that the real current/power limit for each output will depend on other factors, like the coils and the width of the printed circuit board traces.

Figure 13: +5VSB rectifier, +3.3 V rectifier, +5 V rectifier and -12 V voltage regulator.

The outputs are monitored by a PS232 integrated circuit, which supports the following protections: over current (OCP), under voltage (UVP) and over voltage (OVP). Any other protection that this unit may have is implemented outside this integrated c
ircuit.

Figure 14: Monitoring integrated circuit.

As you can see in Figure 13, this unit has two thermal sensors, which is usually implemented when the power supply has over temperature protection (OTP). SilverStone does not list this protection and as mentioned we couldn’t have access to PS232 datasheet.

All the electrolytic capacitors from the secondary are Taiwanese from Teapo and labeled at 105° C as usual.

[nextpage title=”Power Distribution”]

In Figure 15, you can see the power supply label containing all the power specs.

Figure 15: Power supply label.

Since this power supply features a single rail design, there is not much to talk about here. It was interesting to notice that inside the power supply the +12 V wires were grouped into four rails, which allows the manufacturer to create a product with four rails by installing individual over current protections (OCP) on them. The difference between a single rail design and a multiple rail one is the number of over current protections. On the single rail design only one circuit is used monitoring all +12 V wires. On multiple rail design the power supply has individual over current protection circuits for each group of +12 V wires (the so-called “rails”).

Now let’s see if this power supply can really deliver 700 W.[nextpage title=”Load Tests”]

We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology.

First we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under each load. In the table below we list the load patterns we used and the results for each load.

If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (e.g., the +5 V output working at +5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. On the “Total” row we are using the real amount of power being delivered, as measured by our load tester.

+12V1 and +12V2 are the two independent +12V inputs from our load tester and since this power supply has a single rail design the two inputs were connected to the only +12 V rail available on the power supply.

Input	Test 1	Test 2	Test 3	Test 4	Test 5
+12V1	5 A (60 W)	10.5 A (126 W)	15.5 A (186 W)	20.5 A (246 W)	25 A (300 W)
+12V2	5 A (60 W)	10.5 A (126 W)	15.5 A (186 W)	20.5 A (246 W)	25 A (300 W)
+5V	1 A (5 W)	2 A (10 W)	4 A (20 W)	6 A (30 W)	10 A (50 W)
+3.3 V	1 A (3.3 W)	2 A (6.6 W)	4 A (13.2 W)	6 A (19.8 W)	10 A (33 W)
+5VSB	1 A (5 W)	1.5 A (7.5 W)	2 A (10 W)	2.5 W (12.5 W)	3 A (15 W)
-12 V	0.5 A (6 W)	0.5 A (6 W)	0.5 A (6 W)	0.5 A (6 W)	0.5 A (6 W)
Total	140.5 W	283.3 W	420.9 W	556.9 W	696.0 W
% Max Load	20.1%	40.5%	60.1%	79.6%	99.4%
Room Temp.	47.2° C	47.3° C	49.1° C	49.4° C	53.3° C
PSU Temp.	52.8° C	52.3° C	52.8° C	53.2° C	56.9° C
Voltage Stability	Pass	Pass	Pass	Pass	Pass
Ripple and Noise	Pass	Pass	Pass	Pass	Pass
AC Power	167 W	328 W	489 W	659 W	852 W
Efficiency	84.1%	86.4%	86.1%	84.5%	81.7%
Final Result	Pass	Pass	Pass	Pass	Pass

This power supply is a very good product. It can really deliver its labeled power at more than 50° C, has outstanding voltage stability, an outstanding low noise level and a decent efficiency.

Efficiency was always above 84% when we pulled up to 80% (560 W) of the power supply nominal power, peaking 86% if you pull between 40% and 60% of the nominal maximum power (between 280 W and 420 W). When we pulled 700 W from this unit efficiency dropped to 82%, but still above the 80% mark.

Voltages were always inside 3% from their nominal values, which is terrific (the only exception was the +5VSB output during test number five, which dropped to 4.81 V, but still inside the 5% tolerance set by the ATX standard).

Noise level was always low, including the -12 V output, which usually has a high ripple. At 100% load noise level at -12 V output was only 14 mV (the maximum allowed is 120 mV).

Below you can see noise level when we were pulling 696 W (test number five) from this power supply. Just to remember, the maximum allowed for the +12 V outputs is 120 mV peak-to-peak and the maximum allowed for the +5 V and +3.3 V outputs is 50 mV peak-to-peak.

Figure 16: Noise level at +12V1 input from our load tester with the reviewed unit delivering 696 W (50.6 mV).

Figure 17: Noise level at +12V2 input from our load tester with the reviewed unit delivering 696 W (66.2 mV).

Figure 18: Noise level at +5 V input from our load tester with the reviewed unit delivering 696 W (14.2 mV).

Figure 19: Noise level at +3.3 V input from our load tester with the reviewed unit delivering 696 W (17.8 mV).

Now let’s see if we could pull even more power from Decathlon 700 W.

[nextpage title=”Overload Tests”]

Before overloading power supplies we always test first if the over current protection (OCP) circuit is active and at what level it is configured.

OCP kicked
in when we tried to pull more than 63 A from +12 V. The label says that the +12 V output has limit of 58 A, so OCP was configured the way we like: close to the limit printed on the label.

Below you can see the maximum values we could pull from this power supply with its outputs until inside ATX specs, even though noise level at +12V2 input from our load tester was at 130 mV, a little bit above the maximum allowed. If we tried to pull a lot more current the power supply would shut down, which is terrific, meaning you won’t burn your power supply if you try to pull more than it can handle. We are not sure which protection kicked in, because since ripple was very high maybe the protection that entered in action was over voltage (OVP) or under voltage (UVP) and not over power (OPP).

Input	Maximum
+12V1	33 A (396 W)
+12V2	27 A (324 W)
+5V	10 A (50 W)
+3.3 V	10 A (33 W)
+5VSB	3 A (15 W)
-12 V	0.5 A (6 W)
Total	811 W
% Max Load	115.9%
Room Temp.	50.9° C
PSU Temp.	51.8° C
AC Power	1,020 W
Efficiency	79.5%

Even though this power supply could deliver 811 W, overloading this unit isn’t recommended, as noise level increased a lot as mentioned and also efficiency dropped below the 80% mark.

[nextpage title=”Main Specifications”]

SilverStone Decathlon 700 W power supply specs include:

• Nominal labeled power: 700 W at 50° C.
• Measured maximum power: 811 W at 50.9° C.
• Labeled efficiency: 80% minimum.
• Measured efficiency: Between 82% and 86%.
• Active PFC: Yes.
• Modular Cabling System: Yes (for all cables, including the main motherboard one).
• Motherboard Power Connectors: One 20/24-pin connector, one EPS12V connector and one ATX12V connector.
• Video Card Power Connectors: One 8-pin connector and four 6-pin connectors.
• Peripheral Power Connectors: Six in two cables.
• Floppy Disk Drive Power Connectors: Two.
• SATA Power Connectors: Eight in two cables.
• Protections: over voltage (OVP, not tested), over current (OCP, tested and working), over power (OPP, tested and working) and short-circuit (SCP, tested and working).
• Warranty: 3 years.
• Real manufacturer: Impervio
• More Information: https://www.silverstonetek.com.tw
• Average price in the US: USD 155.00.

* Researched at Newegg.com on the day we published this review.

[nextpage title=”Conclusions”]

SilverStone Decathlon 700 W is a very good power supply, really being able to deliver its labeled power at 50° C, featuring a full modular cabling system where even the main motherboard cable is connected to, outstanding voltage stability, very low noise level and very good efficiency, between 84% and 86% for most scenarios (at 100% load efficiency was 82%, which isn’t bad at all). The presence of four 6-pin connectors and one 8-pin connector for video cards is also a very welcome feature, even though we think SilverStone should have used only 6/8-pin connectors.

The only thing we can see is against buying this power supply its price. If you decide to buy it, make sure to purchase it at a place like Newegg.com that will offer you a mail-in rebate that will make the final price to drop to a decent level: USD 130. Otherwise you may want to look for other options. For example, Zalman ZM-600HP (which is a 700 W power supply labeled as 600 W product) and OCZ StealthXStream 700 W are both sold on the USD 100 price range at Newegg.com. These two other power supplies, on the other hand, have only two power connectors for video cards.