Introduction

Silencer Mk II is the latest power supply series from PC Power & Cooling, featuring a synchronous design with DC-DC conversion, single +12 V rail, 80 Plus Silver certification and an amazing 7-year warranty. Let’s see if the 750 W model is a good option.

As far as we can tell this unit is manufactured by Highpower.

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Figure 1: PC Power & Cooling Silencer Mk II 750 W power supply.

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Figure 2: PC Power & Cooling Silencer Mk II 750 W power supply.

The PC Power & Cooling Silencer Mk II 750 W is 6 19/64” (160 mm) deep, using a 135 mm fan on its bottom. This fan is a Globe Fan RL4Z-B1352512H, which is a ball-bearing fan with a maximum rotation of 1,500 rpm and a maximum airflow of 106.86 cfm.

This unit features active PFC, of course, and following PC Power & Cooling tradition, it doesn’t come with a modular cabling system. In fact, OCZ, the owner of PC Power & Cooling, decided to keep units with a single +12 V rail and no modular cabling system under PC Power & Cooling brand, while selling power supplies with modular cabling systems and multiple +12 V rails under their own brand.

The cables included are the following:

• Main motherboard cable with a 20/24-pin connector, 19 ¾” (50 cm) long
• One cable with one ATX12V connector, 23 5/8” (60 cm) long
• One cable with one EPS12V connector, 23 5/8” (60 cm) long
• Two cables with one six-pin auxiliary power connector for video cards each, 19 ¼” (49 cm) long
• Two cables with one six/eight-pin auxiliary power connector for video cards each, 19 ¼” (49 cm) long
• Two cables with four SATA power connectors each, 20 7/8” (53 cm) to the first connector, 5 1/8” (13 cm) between connectors
• One cable with four standard peripheral power connectors, 17 ¾” (45 cm) to the first connector, 5 1/8” (13 cm) between connectors
• One cable with three standard peripheral power connectors and one floppy disk drive power connector, 17 ¾” (45 cm) to the first connector, 5 1/8” (13 cm) between connectors

All wires are 18 AWG, except the +3.3 V (orange) wire on the main motherboard cable, which is thicker (16 AWG).

The cable configuration is perfect for a 750 W product, supporting two very high-end video cards that require two power connectors each, and we liked that the cables are long and each video card power connector is installed on an individual cable.

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Figure 3: Cables.

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

A Look Inside The PC Power & Cooling Silencer Mk II 750 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.

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

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Figure 4: Overall look.

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Figure 5: Overall look.

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Figure 6: Overall look.

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Figure 7: Printed circuit board.

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), and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components, usually removing the MOV and the first coil. 

In this power supply, this stage is flawless. It has one X capacitor and two Y capacitors more than the minimum required, plus one X capacitor after each rectifying bridge.

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Figure 8: Transient filtering stage (part 1).

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Figure 9: Transient filtering stage (part 2).

In the next page we will have a more detailed discussion of the components used in the PC Power & Cooling Silencer Mk II 750 W.

Primary Analysis

On this page we will take an in-depth look at the primary stage of PC Power & Cooling Silencer Mk II 750 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses two GBJ1506 rectifying bridges on its primary, but they are not attached to a heatsink. Each bridge supports up to 15 A at 100º C, so in theory, you would be able to pull up to 3,450 W from the power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 2,760 W without burning themselves. Of course, we are only talking about these components, and the real limit will depend on all the other components in this power supply.

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Figure 10: Rectifying bridges.

The active PFC circuit uses two SPW24N60C3 MOSFETs, each one capable of delivering up to 24.3 A at 25º C or 15.4 A at 100º C in continuous mode (note the difference temperature makes) or 72.9 A in pulse mode at 25º C. These transistors present a 160 mΩ resistance when turned on, a characteristic called RDS(on). The lower this number the better, meaning that the transistors will waste less power and the power supply will achieve a higher efficiency.

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Figure 11: Active PFC transistors.

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 absolute 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. PC Power & Cooling Silencer Mk II 750 W uses two 390 µF x 400 V capacitors connected in parallel; this is the equivalent of one 780 µF x 400 V capacitor.

These capacitors are Japanese, from Chemi-Con, and are labeled at 105º C. This is good for two reasons: first, Japanese capacitors do not leak; and second, usually manufacturers use 85º C capacitors here, so it is good to see a manufacturer using a capacitor with a higher temperature rating.

In the switching section, another two SPW24N60C3 power MOSFET transistors are used. The specs for these transistors were already published above.

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Figure 12: Active PFC diodes and one of the switching transistors.

This power supply uses the famous CM6800 active PFC/PWM combo controller in its primary.

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Figure 13: Active PFC/PWM combo controller.

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

Secondary Analysis

This power supply uses a synchronous design in its secondary, meaning that the Schottky rectifiers were replaced by MOSFET transistors in order to increase efficiency. On top of that this unit uses a DC-DC project, meaning that this unit is basically a +12 V power supply, with the +5 V and +3.3 V outputs being generated by two small power supplies attached to the +12 V output.

The +12 V output is generated by three AOT480 MOSFETs, each one capable of handling up to 180 A at 25º C or up to 134 A at 100º C in continuous mode, or up to 500 A at 25º C in pulse mode, with an RDS(on) of only 4.5 mΩ.

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Figure 14: +12 V transistors.

The +5 V and the +3.3 V outputs are generated by two small power supplies available on small daughter boards attached to the +12 V rail. Each of these power supplies is comprised of four IPD060N03L MOSFETs (50 A at 100º C, 6 mΩ resistance) and one APW7073 PWM controller.

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Figure 15: One of the DC-DC converters.

This power supply uses a PS224 monitoring integrated circuit, which supports over voltage (OVP), under voltage (UVP) and over current (OCP) protections. The over current protection circuit available in this integrated circuit has four channels, one for +3.3 V, one for +5 V, and two for +12 V. However, in this power supply only one +12 V OCP channel is used, as it has a single-rail design.

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Figure 16: Monitoring circuit.

Electrolytic capacitors from the secondary are also Japanese, from Chemi-Con, and labeled at 105º C.

One curious thing we noticed was the adaptation the manufacturer did to add an extra electrolytic capacitor to the +12 V rail (see in Figure 17).

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Figure 17: Additional electrolytic capacitor for the +12 V rail.

Power Distribution

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

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Figure 18: Power supply label.

This power supply has a single-rail design, so there is not much to talk about here.

Now let’s see if this power supply can really deliver 750 W.

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.

The +12VA and +12VB inputs listed below are the two +12 V independent inputs from our load tester. Since the reviewed unit has a single +12 V rail, both inputs were connected to the power supply single +12 V rail (+12VB 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 A (60 W)	11 A (132 W)	16 A (192 W)	22 A (264 W)	27 A (324 W)
+12VB	5 A (60 W)	10 A (120 W)	16 A (192 W)	21 A (252 W)	27 A (324 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 (19.8 W)	8 A (26.4 W)	10 A (33 W)
+5VSB	1 A (5 W)	1 A (5 W)	1.5 A (7.5 W)	2 A (10 W)	2.5 A (12.5 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	150.1 W	302.4 W	453.9 W	602.5 W	750.4 W
% Max Load	20.0%	40.3%	60.5%	80.3%	100.1%
Room Temp.	47.1º C	47.6º C	48.4º C	46.8º C	47.5º C
PSU Temp.	46.3º C	46.8º C	47.6º C	46.7º C	47.3º C
Voltage Stability	Pass	Pass	Pass	Pass	Pass
Ripple and Noise	Pass	Pass	Pass	Pass	Fail on -12 V
AC Power	174.0 W	342.7 W	517.7 W	699.0 W	891.0 W
Efficiency	86.3%	88.2%	87.7%	86.2%	84.2%
AC Voltage	111.1 V	109.4 V	105.7 V	103.6 V	101.6 V
Power Factor	0.949	0.981	0.989	0.993	0.995
Final Result	Pass	Pass	Pass	Pass	Pass

The PC Power & Cooling Silencer Mk II 750 W can really deliver its labeled wattage at high temperatures.

Efficiency was very high at all times, peaking at 88.2%. At full load, however, we saw efficiency at 84.2%, which is a tiny bit below what is promised by 80 Plus Silver certification (85% minimum at 20% and 100% loads; 88% minimum at 50% load). This normally happens in our tests, since, for obtaining the 80 Plus certification, power supplies are tested at a room temperature of only 23º C, which is too low. We test power supplies between 45º C and 50º C and efficiency drops with temperature. Therefore we consider our tests more realistic than the ones conducted by 80 Plus.

Voltage stability was another highlight from the PC Power & Cooling Silencer Mk II 750 W, with all voltages inside 3% of their nominal values (i.e., voltages were closer to their nominal value than needed, as ATX spec allows voltages to be up to 5% from their nominal values, 10% for -12 V). This includes the -12 V output, which usually doesn’t like to stay within a tolerance this tight. The only exception was +3.3 V during test five, which was still inside the proper range.

And finally we have noise and ripple, which were always at very good levels (i.e., low). Below you can see the results for test number five. As we always point out, the limits are 120 mV for +12 V and -12 V outputs, and 50 mV for +5 V and +3.3 V outputs and all numbers are peak-to-peak figures.

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Figure 19: +12VA input from load tester at 750.4 W (69.6 mV).

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Figure 20: +12VB input from load tester at 750.4 W (68.2 mV).

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Figure 21: +5V rail with power supply delivering 750.4 W (27.6 mV).

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Figure 22: +3.3 V rail with power supply delivering 750.4 W (18.4 mV).

Now let’s see if we could pull more than 750 W from this unit.

Overload Tests

Below you can see the maximum we could pull from this power supply. If we increase by one amp on any given output, the power supply shuts down, which is great. During this test noise levels at +12VA (287.4 mV), +12VB (312.0 mV) and -12 V (355.4 mV) were way above the maximum allowed.

Input	Overload Test
+12VA	32 A (384 W)
+12VB	32 A (384 W)
+5V	15 A (75 W)
+3.3 V	15 A (49.5 W)
+5VSB	3 A (15 W)
-12 V	0.5 A (6 W)
Total	895.8 W
% Max Load	119.4%
Room Temp.	47.6º C
PSU Temp.	51.0º C
AC Power	1,099 W
Efficiency	81.5%
AC Voltage	109.5 V
Power Factor	0.949

Main Specifications

PC Power & Cooling Silencer Mk II 750 W power supply specs include:

• Nominal labeled power: 750 W at 50º C, 880 W peak
• Measured maximum power: 895.8 W at 47.6º C
• Labeled efficiency: 88% at typical load (i.e., 50% load, 375 W), 80 Plus Silver certified (85% minimum at 20% and 100% loads; 88% minimum at 50% load)
• Measured efficiency: Between 84.2% and 88.2% at 115 V (nominal, see complete results for actual voltage)
• Active PFC: Yes
• Modular Cabling System: No
• Motherboard Power Connectors: One 20/24-pin connector, one ATX12V connector and one EPS12V connector
• Video Card Power Connectors: Two six-pin and two six/eight-pin connectors on separated cables
• SATA Power Connectors: Eight in two cables
• Peripheral Power Connectors: Seven in two cables.
• Floppy Disk Drive Power Connectors: One.
• Protections: Over voltage (OVP) and over current (OCP). Although not listed by the manufacturer, this unit also has under voltage (UVP) and short-circuit (SCP) protections
• Warranty: Seven years
• Real Manufacturer: Highpower
• More Information: http://www.pcpower.com
• Average price in the US*: USD 160.00

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

Conclusions

The PC Power & Cooling Silencer Mk II 750 W is a very good 750 W power supply: high efficiency, voltages very close to their nominal values (3% voltage regulation instead of 5%), very low noise and ripple on its outputs and an amazing seven-year warranty. In summary, it is a very good power supply that won't let you down.

This unit faces a very fierce competition from models that have similar performance and may cost a little bit less, like XFX 750 W Black Edition (USD 140, single-rail, modular cabling system), Seasonic S12D 750 W (dual-rail, no modular cabling system), Seasonic M12D 750 W (dual-rail, modular cabling system) and Corsair HX750W (USD 150, single-rail, modular cabling system). As you can see, both XFX 750 W Black Edition and Corsair HX750W cost less and have modular cabling systems, making them better options, in our opinion. This model from PC Power & Cooling has and Corsair HX750W come with an impressive seven-year warranty.

Of course there are more affordable 750 W units on the market, but not with the high efficiency presented by the models listed above. If you are looking for a more affordable 750 W unit, our recommendation is the OCZ Fatal1ty 750 W, which provides good performance for its price range.