| Reviews about the Silencer 750 Quad (Black) |  |
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Introduction and FeaturesPC Power & Cooling has been in the business of building high-performance PC switching power supplies since 1986 and they have earned one of the best reputations in the industry for performance and reliability. Today PC Power & Cooling offers several lines of high-quality power supplies ranging in capacity from 300W all the way up to 1kW. Their Turbo-Cool units are targeted towards high-end applications where clean power and reliability are the top priorities. PC Power & Cooling's Silencer power supplies also feature performance and reliability but with an emphasis on quiet operation at an affordable price. In this review we will be taking a detailed look at PC Power & Cooling's flagship Silencer power supply, the Silencer 750 Quad. This unit is available with either a traditional black paint job or with a brilliant copper finish.
The PC Power & Cooling Silencer 750 Quad power supply features a single, high-capacity +12V rail capable of delivering up to 60A (720W). The Silencer 750W comes with four PCI-E connectors and not surprisingly is NVIDIA SLI and ATI CrossFire certified. PC Power & Cooling Silencer 750 PSU Key Features:
The Silencer 750W Quad power supply comes securely packed in a traditional PC Power & Cooling box.
The bundled accessories include a heavy duty power cord, mounting screws, and printed Installation Instructions.
Establishing an accurate load is critical to testing and evaluating a PC power supply. PCPerspective's power supply test bench can place a precise 2,000 watt DC load on the PSU under test. Each power supply is tested under controlled, real-world conditions up to its maximum rated load (at 40ºC), using both 115 VAC and 240 VAC line voltage. Our current suite of tests includes:
The Silencer 750W power supply was evaluated on both features and performance. A full range of equipment was used to test the power supply under controlled load conditions.
OK, it's not quite the same as the $100,000 Chroma 8000 that PC Power & Cooling uses, but for us mere mortals it's the next best thing!
(PC Power & Cooling's Chroma 8000 PSU Test Rig) A Closer LookThe Silencer 750W Quad power supply we received for review features a bright powder-coat copper finish. (The Silencer 750W is also available with a standard matte black finish.) The copper-color finish is striking and goes nicely with the black sleeved cables and trim.
The back panel contains an 80mm cooling fan, power receptacle, and On-Off switch. The Silencer 750W power supply incorporates universal AC input (automatically adjusts to the AC line voltage) so there is no little red voltage selector switch.
The single 80mm cooling fan is made by Adda (AD0812UB-A71GL). This is a popular medium-speed fan that features dual ball bearings and is rated for up to 3,900 rpm, 50.0 CFM, and 41.0 dBA at 12V. To help minimize noise, the fan speed is automatically controlled by the internal component temperature (speeds up as the combined load and temperature increases). As we will see in the next section, PC Power & Cooling also leaves plenty of clearance around the intake area of the fan to minimize turbulent airflow created by nearby components. This also helps reduce noise.
The slotted grill on the front and side allows air to flow into the power supply for cooling the internal components.
The Silencer 750 Quad power supply is rated for a combined, maximum output power of 750 watts (825W peak) at up to 40°C ambient air temperature (internal case air temperature). It is interesting to note that all of the PC Power & Cooling Turbo-Cool series power supplies are rated for up to 50°C. This is one of the key differences between a Silencer and Turbo-Cool unit. Reducing the airflow to make the PSU quieter also limits the maximum safe operating temperature. Specifications for the Silencer 750W Quad (courtesy PC Power & Cooling)
Single +12V output The PC Power & Cooling Silencer 750W PSU incorporates a single, powerful +12V output. This is a trend we are seeing in newer power supplies. Some manufacturers are no longer creating multiple +12V outputs by implementing current limiting circuits into their design to conform to the 240 VA maximum guidelines – no single output should exceed 240 VA (12V x 20A = 240 VA). Having multiple current limited +12V outputs can lead to power distribution problems, particularly with some power-hungry video cards. Delivering a single, powerful +12V output is a much better approach IMHO. The PC Power & Cooling Silencer 750W power supply has a full assortment of cables and connectors. All of the cables are hard-wired into the PSU chassis, which eliminates potential problems caused by the added resistance of modular cable connectors. At high power, even a little resistance can lower the delivered voltage and possibly cause overheating as contacts oxidize over time. The wiring harnesses measure approximately 19" to 24" long to the first connector and all of the cables are covered with black plastic mesh sleeving.
The following drawing illustrates the various connectors and cables lengths.
(Courtesy of PC Power & Cooling) Note: The current shipping version of the Silencer 750 Quad features four 6-pin PCI-E connectors. Starting in May, the Silencer 750W power supply will be fitted with two 6-pin PCI-E connectors and two 8-pin PCI-E connectors (6-pin/2-pin split). These new 8-pin PCI-E connectors are designed to be used with the next generation of power hungry video cards, which may require both a 6-pin and an 8-pin PCI-E connector to operate. I was expecting the PCI-E 2.0 8-pin connectors to feature four +12V wires and four common leads, similar to an 8-pin EPS motherboard connector. However, this is not the case. The new PCI-E 2.0 specification has not been fully confirmed and from what I have been told, the extra two wires in the new 8-pin PCI-E connector will enable the video card to handshake with the PSU to insure adequate power is available for the GPU to run full throttle. Here are a few pictures showing the layout and components inside the Silencer 750W Quad power supply. PC Power & Cooling has been using Seasonic to manufacture the Silencer power supply line for about 5 years. Seasonic is known for building high-quality units and has an excellent reputation in the power supply industry. It is important to note however that PC Power & Cooling does not re-label products as many do (Seasonic has no product of their own similar to the Silencer 750). PC Power & Cooling actually designs their PSUs and owns the tooling, printed circuit boards (their name is on them), safety certifications, etc., along with all other product rights. Seasonic (and others) are simply contracted to build the PSUs to PC Power & Cooling's demanding specifications. So don't get the idea you're going to find the same PSU with PC Power & Cooling's legendary performance and reliability with someone elses name on it! Their reputation has been earned, not bought.
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(click to enlarge) One feature that PC Power & Cooling uses to help minimize noise in the Silencer 750W PSU is a 1" gap in front of the Adda cooling fan. They claim that the primary cause of system-related fan noise is air turbulence at the inlet side of the fan... caused by obstructions in the air stream such as capacitors, heatsinks, etc. Personally, I would argue that fan speed is the primary cause of fan noise but you get the idea.
(click to enlarge) Leaving extra clearance around the intake area of the fan helps reduce noise by minimizing turbulent airflow created by nearby components as air enters the fan and impacts the fan blades.
(click to enlarge) Load Regulation, Line Regulation and Cross-LoadingDC Output Load Regulation Of course one of the first things we want to see is how well this PSU can regulate the DC outputs and maintain rock-solid voltages. To simulate real world and maximum loading conditions, the Silencer 750W PSU was connected to the load testers and supplied with a constant 115 VAC. In this test we are interested in seeing how well a PSU can maintain the various output voltages while operating under different loads. The new ATX12V V2.2 tolerance for voltages states how much each output (rail) is allowed to fluctuate and has tighter tolerances now for the +12V outputs.
The following table lists the DC voltage results at the different loads for the PC Power & Cooling Silencer 750W PSU while operating on 115 VAC, 60 Hz.
The PSU produced excellent load regulation on all of the outputs across a broad range of loads; even when delivering 750 watts of DC power. All the major outputs were rock-solid, very good! DC Output Line Regulation In this test we are interested in seeing how well a PSU can maintain the various output voltages while the AC input line voltage changes. In the previous Load Regulation test, the AC line voltage was held constant at 115 VAC. Now we will look at how much the DC outputs change as the AC line voltage is changed from 120 VAC down to 90 VAC.
The Line Regulation test was performed with the combined DC loads set to 600W. The AC input voltage to the power supply (via the Extech power analyzer) was adjusted using a Powerstat variable autotransformer. No measurable change in the DC outputs... like a rock. Cross-Loading Test PC switching mode power supplies provide multiple DC output voltages. Ideally, the total load should be distributed across all the main outputs (+3.3V, +5V, +12V). This means that the combined +3.3V and +5V load should be proportional to the combined +12V load – as one increases, so should the other. Unfortunately, this is not always the case, especially in newer PCs that predominately use +12V and may put only minimal loads on the +3.3V and/or +5V rails. Cross-loading refers to imbalanced loads. If a PC pulls 500W on the +12V outputs and only 50W (or less) on the combined 3.3V and +5V outputs, the resulting voltage regulation may suffer. A few years ago the reverse was true. It was common for some motherboards (especially AMD) to pull a heavy load on the +5V rail and a minimal load on the +12V rail. At the time, one common practice was to place a dummy load on the +12V output to help balance the overall load, which often resulted in better voltage regulation. (Increasing the +12V load caused the +5V output voltage to increase!)
In the first test we put a very heavy load (60A/720W – the maximum rated capacity) on the +12V output and a very light load on the remaining outputs. Sure enough, the Silencer 750W had no problems delivering the advertised 60A on the +12V rail. Even with this large imbalance, the voltages all look very good. In the second test we reversed the cross-load and placed a very heavy load (170W) on the +3.3V and +5V outputs with a very light load (2A/24W) on the +12V rail. Once again, the Silencer 750W passed this test without problems. In both tests the measured AC ripple remained consistent with the values observed during the other tests and stayed well under control. It's interesting to note that the overall power supply efficiency for the first cross-load test (heavy +12V load) was much higher (85.1%) than for the second cross-load test (74.8%). This illustrates a common trait of most PC switching power supplies – the +12V section is more efficient than the +3.3V/5V section. AC Ripple, Power Factor and EfficiencyAC Ripple and Noise on the DC Outputs The amount of AC ripple and noise present on the DC outputs was checked using an oscilloscope. This AC component may be present in the KHz range where most switching power supplies operate or it may be more prevalent at the 60 Hz line frequency. I adjusted the O-scope time base to look for AC ripple at both low and high frequencies. The new ATX12V V2.2 specification for DC output noise/ripple is defined in the ATX12V Power Supply Design Guide.
Ideally we would like to see no AC ripple (repetitive) or noise (random) on the DC outputs – the cleaner the better! But in reality there will always be some present. I measured the amplitude of the AC signal (in millivolts, peak-to-peak) to see how well the power supply complied with the ATX standard. The following table lists the ripple/noise results during all of the load tests for the four main output voltages of interest.
The Silencer 750W power supply exhibited excellent AC ripple suppression across the entire load range. Of course as the load increased, so did the magnitude of the AC ripple, but that's normal and to be expected. All values stayed well below the recommended limits, even at the maximum rated output – very good! Power Factor (PF) Power factor (PF) is one of those mysterious properties of AC that even most electrical engineers have a hard time explaining. I'm only presenting a brief overview of the subject – for a more detailed discussion about PF, please see my expanded comments in this review.
AC Volts x AC Amps = VA (Volt Amp) Purely Resistive AC Load: VA =
Inductive/Reactive AC Load: VA x PF =
AC Volts x AC Amps x PF =
Power factor is defined as the ratio of true power (measured in watts) to apparent power (measured in Volt Amps). It measures how effectively AC power is being used by a device. The difference between true power and apparent power is expressed as the power factor and results from the way true power and apparent power are measured. Ideally we would like to have true power and apparent power equal to one another, which would result in a PF of 1.00 or 100% effective power utilization. I measured the AC Power Factor with an Extech power analyzer at both 115 VAC and 240 VAC input voltages. The Silencer 750W power supply uses Active PFC circuits so as expected; the majority of readings were close to 1.0.
Note: A power supply with active PFC is more environmentally friendly (doesn't pollute the AC transmission grid with harmonics) and will draw less current, but it will not save you money on your monthly electric bill unless you are a commercial user whose bill is based on PF and usage. Efficiency The overall efficiency of a power supply is very important, especially when operating at higher power levels. The less waste heat generated the better! Efficiency is defined by the power output divided by the power input and is usually expressed as a percentage. If a PSU were a 100% efficient (which none are) 600 watts of AC power going in would result in 600 watts of DC power coming out (with no waste heat to dissipate). In the real world there are always inefficiencies and power is lost in the form of heat during the conversion process.
The latest revisions to the ATX12V Power Supply Design Guide V 2.2 have continued to increase the efficiency recommendations for PC switching mode power supplies and now lists both required and recommended minimum efficiencies.
I measured the AC power input to the Silencer 750W PSU with the Extech power analyzer while the total DC load was found by adding all the individual +3.3V, +5V, +12V, -12V and +5VSB loads together.
The overall efficiency of the Silencer 750W power supply is very good and appears to peak out around 300W~400W, which is where many users are likely to be operating. Note that efficiency will almost always be higher at the 240 VAC line voltage versus 115 VAC (as the voltage goes up the current goes down, and since line/component loses are proportional to current, less current means lower loses).
There is a growing awareness among users, PC manufacturers and electric utilities regarding the money and natural resources that could be saved by adopting higher efficiency power supplies. One group that is spearheading this new movement is Ecos Consulting. You can learn more about their efforts to promote power supplies with better than 80% efficiency by visiting the 80 Plus Program website. Spending a little more money up front to purchase a high efficiency power supply may very well pay for itself over the lifetime of the PC, especially when you are using this much power... :) Differential Temperature, Noise and WeightDifferential Temperature and Noise Levels To simulate real world operation the Silencer 750W power supply was mounted in a modified mid tower case (Lian Li PC60) for testing. Some of the warm exhaust air from the PSU under test is recirculated back into the case, which allows the internal case air temperature to increase with load, just like it would in a real PC. The internal case air temperature is allowed to increase up to 40ºC and then held constant from then on at 40ºC. The differential temperature across the Silencer 750W power supply was calculated by subtracting the internal case air temperature (T in) from the temperature of the warm exhaust air flowing out the back of the power supply (T out). Thermocouples were placed at the air inlet and exhaust outlet. The ambient room air temperature was 21ºC (70ºF) +/- 0.5ºC during testing. T out = temperature of air exhausting from power supply T in = temperature of air entering power supply ∆T = T out - T in Sound pressure level readings were taken 3' away from the rear of the case in an otherwise quiet room. The ambient noise level was ~30 dBA.
Below 500W output, the Silencer PSU is relatively quiet (but not silent). Temperatures gradually build as the load increases and above 600W, the cooling fan speeds up to where it is noticeable. Note the differential temperature actually dropped slightly at maximum load because the cooling fan had kicked into high gear at this point. Unfortunately, I was not able to measure the SPL when the power supply was running at the higher loads because all the cooling fans on the programmable DC loads were also running at this point. Physical Size and Weight The PC Power & Cooling Silencer 750W Quad power supply measures: 150 x 86 x 180mm (5.9" x 3.4" x 7.1" W x H x D). Note the Silencer 750W enclosure is 180mm deep (a standard ATX PSU is 140mm long) so make sure it will fit in your case before purchasing one. And last but not least, a basic measures of any ATX power supply is the unit's overall physical weight. This may seem rather simplistic but it generally holds that more industrial grade components and larger heatsinks equal a better PSU. The following graph illustrates how the Silencer 750W Quad PSU compares to some other popular power supplies on the market.
(click to enlarge) ConclusionsLike a rock... The PC Power & Cooling Silencer 750 Quad is an excellent power supply that delivers on all the advertised claims. It produces very stable, clean DC outputs efficiently, with minimal noise at an affordable price. Highly recommended! The Silencer 750 Quad power supply is available directly from PC Power & Cooling for $199.00 USD and Newegg.com has it in stock for $199.99 USD as well.
Strengths:
Weaknesses:
For excellent performance, quality and value, the PC Power & Cooling Silencer 750 Quad power supply earns the PCPerspective Editors Choice Award.
Silencer 750 Quad Power Supply I would like to thank our friends at PC Power & Cooling for sending us the Silencer 750W PSU to review – thanks! |
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