Cooler Master Silent Pro Gold 800 W Power Supply Review

[nextpage title=”Introduction”]

Silent Pro Gold is the 80 Plus Gold-certified power supply family that Cooler Master is releasing this month with models ranging from 800 W to 1,200 W, coming with some unique design choices. Let’s see if the 800 W model will live up to the expectations.

This unit is manufactured by Enhance Electronics.

Figure 1: Cooler Master Silent Pro Gold 800 W power supply.

Figure 2: Cooler Master Silent Pro Gold 800 W power supply.

Cooler Master Silent Pro Gold 800 W is relatively a short unit, being 6 ¼” (160 mm) deep, using a 120 mm fan on its bottom and active PFC circuit, of course.

This unit offers a modular cabling system with seven connectors (all using the same color: gold), two for video card power connectors and five for peripheral and SATA power connectors, with three cables permanently attached to the power supply. The cables included are:

• Main motherboard cable with a 20/24-pin connector, 19 ½” (49 cm) long (permanently attached to the power supply).
• One cable with two ATX12V connectors that together form one EPS12V connector, 23 5/8” (60 cm) long (permanently attached to the power supply).
• One cable with one six-pin connector and one six/eight-pin connector for video cards, 23 5/8” (60 cm) to the first connector and 4” (10 cm) between connectors (permanently attached to the power supply).
• Two cables with one six-pin connector and one six/eight-pin connector for video cards each, 23 5/8” (60 cm) to the first connector, 3 ¾” (9.5 cm) between connectors (modular cabling system).
• Three cables with three SATA power connectors each, 19 ¾” (50 cm) to the first connector, 3.5” (9 cm) between connectors (modular cabling system).
• One cable with two standard peripheral power connectors, 17 ¾” (45 cm) to the first connector, 4” (10 cm) between connectors.
• One cable with two standard peripheral power connectors and one floppy disk drive power connector, 17 ¾” (45 cm) to the first connector, 4” (10 cm) between connectors.

Here we saw more flaws than we’d like to see for a supposedly high-end “Gold” power supply. Although this unit supports the installation of up to three video cards that require two auxiliary power connectors each, these six connectors are installed in three cables instead of using individual cables. The distance between video card, SATA and peripheral power connectors is simply too short – instead of using the standard 5 7/8” (15 cm) distance between connectors, for some reason Cooler Master decided to go cheap and use 4” (10 cm) or less. On the other hand, the cables that are permanently attached to the power supply got thicker (16 AWG) wires, which is nice to see (with one exception: the connection between the six-pin and the six/eight-pin connectors is done using 18 AWG wires). The cables used on the modular cabling system use 18 AWG wires, which is the correct gauge to be used.

Figure 3: Cables.

Now let’s take an in-depth look inside this power supply.

[nextpage title=”A Look Inside The Cooler Master Silent Pro Gold 800 W”]

We decided to disassemble this power supply to see how it looks inside, what the design is 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.

This page will be an overview, and then in the following pages we will discuss in detail the quality and ratings of the components used.

Figure 4: Overall look.

Figure 5: Overall look.

Figure 6: Overall look.

Figure 7: Printed circuit board.

[nextpage title=”Transient Filtering Stage”]

As we mentioned in previous 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), 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 in this stage, with two Y capacitors and three X capacitors, more than the minimum required, plus one X capacitor after the rectifying bridge.

Figure 8: Transient filtering stage (part 1).

Figure 9: Transient filtering stage (part 2).

Now let’s have a more detailed discussion about the components in the Cooler Master Silent Pro Gold 800 W.

[nextpage title=”Primary Analysis”]

On this page we will take an in-depth look at the primary stage of the Cooler Master Silent Pro Gold 800 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBU1006 rectifying bridge in its primary, supporting up to 10 A at 100° C. This bridge is attached to the same heatsink used by the primary transistors. At 115 V this unit would be able to pull up to 1,150 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 920 W without burning itself out. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.

Figure 10: Rectifying bridge.

In the active PFC circuit two STW25NM50N power MOSFET transistors are used, each one capable of delivering up to 22 A at 25° C or 14 A at 100° C in continuous mode (note the difference temperature makes), or up to 88 A in pulse mode at 25° C. These transistors present a resistance of 140 mΩ when turned on, a characteristic called RDS(on). This number indicates the amount of power that is wasted, so the lower this number the better, as less power will be wasted, thus increasing efficiency.

This power supply uses two electrolytic capacitors to filter the output from the active PFC circuit. The use of more than one capacitor here has absolutely nothing to do with the “quality” of the power supply, as laypersons may assume (including people without the proper background in electronics doing power supply reviews around the web). Instead of using one big capacitor, manufacturers may choose to use two or more smaller components that will give the same total capacitance, in order to better accommodate space on the printed circuit board, as two or more capacitors with small capacitance are physically smaller than one capacitor with the same total capacitance. Cooler Master Silent Pro Gold 800 W uses two 270 µF x 420 V capacitors in parallel; this is equivalent of one 540 µF x 420 V capacitor. These capacitors are Japanese, from Matsushita (i.e., Panasonic) and labeled at 85° C. It would be nice if Cooler Master had added capacitors rated at 105° C here.

In the switching section, another two STW25NM50N power MOSFETs are used in a slightly modified two-transistor forward configuration. In the standard two-transistor design, two transistors and two diodes are used; in this power supply one of the diodes was replaced by a MOSFET transistor, and this was probably done to increase efficiency.

Figure 11: Switching transistor, transistor used to replace one of the diodes, switching transistor, active PFC diode and active PFC transistors.

The switching transistors are controlled by a CM6802 PFC/PWM combo controller.

Figure 12: Daughter board containing the PFC/PWM controller on the primary side and the monitoring circuit on the secondary side.

Figure 13: PFC/PWM combo controller.

Now let’s take a look at the secondary of this power supply.

[nextpage title=”Secondary Analysis”]

The Silent Pro Gold series uses a very different design in its secondary. First, the transformer has an embedded heatsink. This design is being called “Hybrid Transformer” by Cooler Master and according to them it allowed the transformer to be reduced 25%. Then the transistors used as rectifiers are placed as close as possible to the transformer terminal in order to reduce loss caused by longer routes on the power supply printed circuit board. In fact these transistors are soldered on a small printed circuit board together with the transformer, and the transformer and the transistors are added to the main printed circuit board as if they were a single piece. This design is being called “Hyper Path” by Cooler Master.

Figure 14: “Hybrid Transformer” and “Hyper Path” designs.

As could be implied by the explanation above, this power supply uses a synchronous design, which means the Schottky rectifiers were replaced with MOSFET transistors. This change allows the power supply to achieve higher performance.

On top of that this unit uses a DC-DC design, meaning that it is basically a +12 V power supply with the +5 V and +3.3 V outputs being generated using two separated switching power supplies connected to the +12 V rail. This design is proving to be the best choice in order to achieve high efficiency.

Two IPP023N04N MOSFETs are used to produce the +12 V rail and, as explained, are installed on the transformer module. Each transistor is capable of delivering up to 90 A at 100° C with an RDS(on) of only 2.3 m§Ù, which provides very little loss (i.e., increases efficiency).

The maximum theoretical current each 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. Just as an exercise, we can assume a typical duty cycle of 30%.

The +12 V rail is also used by the +5 V and +3.3 V rails as well; if all power was pulled from the +12 V rail alone, we are talking about a maximum theoretical current of 129 A or 1,543 W at 100° C.

Of course this is a theoretical number and we are just doing an exercise here. The real amount of current/power each output can deliver is limited by other components.

In Figures 15 and 16 you can see one of the DC-DC modules (the unit has one for the +5 V output and one for +3.3 V output). Each DC-DC module has two STD85N3LH5 (55 A at 100° C, 5.4 m§Ù resistance) and two IPD060N03L (50 A at 100° C, 6 m§Ù resistance) transistors and one APW7073 PWM controller.

Figure 15: DC-DC conversion module.

Figure 16: DC-DC conversion module.

The outputs are monitored by a PS232S integrated circuit that is soldered on the printed circuit board shown in Figure 12. This circuit supports over voltage (OVP), under voltage (UVP) and over current (OCP) protections. The interesting thing is that this circuit offers six over current protection channels (one for +3.3 V, one for +5 V and four for +12 V), but the manufacturer decided to configure this unit as a single-rail product, using only one of the +12 V OCP channels available.

Figure 17: Monitoring circuit.

All capacitors present on the main printed circuit board are also Japanese, from Chemi-Con, but some Taiwanese capacitors from Teapo are used on the modular cabling system. So although the manufacturer advertises this unit as having Japanese capacitors, it is important to bear in mind that this doesn’t mean that ALL capacitors are made in Japan.

[nextpage title=”Power Distribution”]

In Figure 18, you can see the power supply label containing all the power specs.

Figure 18: Power supply label.

As you can see, according to the label this unit has a single +12 V rail, so there is not much to talk about here.

Now let’s see if this power supply can really deliver 800 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. In the “Total” row we are using the real amount of power being delivered, as measured by our load tester.

The +12VA and +12VB inputs listed below are the two +12 V independent inputs from our load tester. During this test both inputs were connected to the power supply single rail (+12VB input was connected to the power supply EPS12V connector and all other cables were connected to the load tester +12VA input).

Input	Test 1	Test 2	Test 3	Test 4	Test 5
+12VA	5.5 A (66 W)	12 A (144 W)	18.5 A (222 W)	23 A (276 W)	29 A (348 W)
+12VB	5.5 A (66 W)	11 A (132 W)	16 A (192 W)	23 A (276 W)	29 A (348 W)
+5V	2 A (10 W)	4 A (20 W)	6 A (30 W)	8 A (40 W)	10 A (50 W)
+3.3 V	2 A (6.6 W)	4 A (13.2 W)	6 A (30 W)	8 A (26.4 W)	10 A (33 W)
+5VSB	1 A (5 W)	1.5 A (7.5 W)	2 A (10 W)	2.5 A (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	163.2 W	329.4 W	488.8 W	646.4 W	802.4 W
% Max Load	20.4%	41.2%	61.1%	80.8%	100.3%
Room Temp.	45.9° C	45.8° C	44.2° C	46.3° C	44.5° C
PSU Temp.	40.3° C	41.0° C	41.0° C	41.9° C	45.6° C
Voltage Regulation	Pass	Pass	Pass	Pass	Pass
Ripple and Noise	Pass	Fail on -12 V	Fail on -12 V	Pass	Fail on -12 V
AC Power	186.6 W	366.8 W	554.8 W	729.0 W	931.4 W
Efficiency	87.5%	89.8%	88.1%	88.7%	86.1%
AC Voltage	113.4 V	111.5 V	110.4 V	108.5 V	104.7 V
Power Factor	0.961	0.983	0.988	0.988	0.992
Final Result	Pass	Pass	Pass	Pass	Pass

Cooler Master Silent Pro Gold 800 W can really deliver its labeled wattage at high temperatures.

Being an 80 Plus Gold power supply, the manufacturer promises a 90% efficiency under typical load (i.e., 50% load or 400 W) and 87% efficiency at light (20% load, i.e., 160 W) and full (800 W) loads. In our tests efficiency at full load was at 86.1% – as we have been exhaustively explaining in our reviews, Ecos Consulting, the company behind 80 Plus, tests power supplies at 23° C, while we test them between 45° C and 50° C, and efficiency drops with temperature. Therefore our tests are more rigorous (and more realistic) than those conducted in order to get the 80 Plus certification (click here to learn more).

Voltage regulation was very good, with all voltages within 3% of their nominal values (i.e., voltages closer to their “face value” than required by the ATX12V specification that allows a 5% tolerance for all positive voltages and 10% for -12 V). The exception was for the -12 V output, which was outside this tight regulation but was still inside the proper range.

Noise and ripple was always higher than we’d like to see  in a supposedly high-end product. As you can see below, with the unit delivering 800 W, noise level at +12 V was around 95 mV. While still below the maximum allowed (120 mV), we always prefer to see power supplies presenting a noise level below half of the limit. The -12 V output failed to stay within proper range. During test one it was presenting a noise level of 108.2 mV, increasing to 120.6 mV on test two, 137.2 mV on test three, 119.2 mV on test four and 164.4 mV on test five. While this output is not as important as the others and is mainly used by some audio cards, we have to point out this flaw.

Below you can see the results for the power supply outputs during test number five. The maximums allowed are 120 mV for +12 V and -12 V and 50 mV for +5 V and +3.3 V. All values are peak-to-peak figures.

< img class="aligncenter size-full wp-image-614" src="http://hardwaresecrets.com/wp-content/uploads/CM_SilentPro800w_12v11.gif" alt="Cooler Master Silent Pro Gold 800 W power supply" width="545" height="473" />Figure 19: +12VA input from load tester during test five at 802.4 W (95.2 mV).

Figure 20: +12VB input from load tester during test five at 802.4 W (96.6 mV).

Figure 21: +5V rail during test five at 802.4 W (17.8 mV).

Figure 22: +3.3 V rail during test five at 802.4 W (16.5 mV).

Let’s see if we can pull even more from Cooler Master Silent Pro Gold 800 W.

[nextpage title=”Overload Tests”]

The maximum we could pull from this power supply can be seen below. If we increased one amp at any output the unit would shut down, which is great. At this configuration noise level at +12 V was high, around 105 mV, but still below the maximum allowed (120 mV). Noise level at -12 V was once again outside specs, at 150.2 mV.

Input	Overload Test
+12VA	32 A (384 W)
+12VB	32 A (384 W)
+5V	20 A (100 W)
+3.3 V	20 A (66 W)
+5VSB	3 A (15 W)
-12 V	0.5 A (6 W)
Total	958.2 W
% Max Load	119.8%
Room Temp.	44.4° C
PSU Temp.	46.8° C
AC Power	1,142 W
Efficiency	83.9%
AC Voltage	102.4 V
Power Factor	0.993

[nextpage title=”Main Specifications”]

Cooler Master Silent Pro Gold 800 W power supply specs include:

• ATX12V 2.3
• EPS12V 2.92
• Nominal labeled power: 800 W continuous, 960 W peak.
• Measured maximum power: 958.2 W at 44.4° C.
• Labeled efficiency: 90% under typical load (i.e., 400 W load), 80 Plus Gold certified
• Measured efficiency: Between 86.1% and 89.8% at 115 V (nominal, see complete results for actual voltage).
• Active PFC: Yes.
• Modular Cabling System: Yes, partial.
• Motherboard Power Connectors: One 20/24-pin connector and two ATX12V connectors that together form an EPS12V connector.
• Video Card Power Connectors: Three six-pin connectors and three six/eight-pin connectors, one cable with two connectors permanently attached to the power supply and two cables with four connectors on the modular cabling system.
• SATA Power Connectors: Nine in three cables (modular cabling system).
• Peripheral Power Connectors: Four in two cables (modular cabling system).
• Floppy Disk Drive Power Connectors: One.
• Protections: Over voltage (OVP), under voltage (UVP), over current (OCP), over power (OPP), over temperature (OTP) and short-circuit (SCP).
• Warranty: Five years
• More Information: https://www.coolermaster-usa.com
• MSRP in the US: USD 180.00

[nextpage title=”Conclusions”]

Cooler Master Silent Pro Gold 800 W will come with a USD 180 suggested price tag, which is not bad for an 80 Plus Gold unit, especially because on-line stores usually sell units for less than the suggested price.

The problem is that we think Corsair HX850W is better than Cooler Master Silent Pro Gold 800 W and it costs less (USD 160). You see, Ecos Consulting, the company behind 80 Plus, gave Corsair HX850W their Gold certification, but Corsair decided to downgrade this unit to Silver because it couldn’t deliver 87% efficiency at full load at real-world temperatures. So according to Ecos Consulting  both units are “80 Plus Gold,” and thus we have a valid comparison.

Some small flaws we found in Cooler Master Silent Gold 800 W include:

• Although supporting three video cards that require two auxiliary power connector each, video card connectors share the same cable instead of using individual cables, a problem not found in Corsair HX850W.
• Corsair HX850W has 12 SATA power connectors and 12 peripheral power connectors. Cooler Master Silent Gold 800 W has nine and four, respectively.
• Presence of some Taiwanese capacitors on the modular cabling printed circuit board instead of having absolutely all capacitors made in Japan, a problem not found in Corsair HX850W, where absolutely all caps are Japanese.
• Noise level above specs at -12 V output. With Corsair HX850W this problem didn’t happen, however in our tests we found a high noise level at +5VSB output instead, but Corsair sent us their oscilloscope screenshots showing low noise level, and we had to assume that our equipment was misreading the results for some reason.
• Although inside specs, noise level at +12 V was higher than we’d like to see in a high-end product.
• You get 50 W more labeled power by buying this unit from Corsair.

This new 800 W power supply from Cooler Master can be an option – the price is right, in our opinion, and in fact this unit presents a better cost/benefit ratio than OCZ Z-Series 850 W (which is also 80 Plus Gold), for example. But the savvy user who understands that the 80 Plus certification is many times only a marketing badge and does not represent the real-world performance of a power supply will probably save money and make a better choice by picking the Corsair HX850W.