DC Load Regulation and AC Ripple
Testing Methodology
Establishing an accurate load is critical to testing and evaluating a PC power supply. PCPerspective’s power supply test bench can place a precise DC load on the PSU under test. Each power supply is tested under controlled, demanding conditions up to its maximum rated load (at 40ºC). Our current suite of tests includes:
• DC Load Regulation
• AC Ripple and Noise
• Efficiency
• Differential Temperature
• Noise
The SilverStone SX800-LTI 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.
• (2) CSI3710A Programmable DC load (+3.3V and +5V outputs)
• (4) CSI3711A Programmable DC load (+12V1, +12V2, +12V3, and +12V4)
• (2) 200W Precision resistor load bank (+12V5 and +12V6)
• Switchable precision resistor load bank (-12V and +5VSB)
• Agilent 34401A digital multimeter (Accuracy ±0.0035% vDC)
• Extech 380803 Power Analyzer (Accuracy ±0.5% of full scale)
• DS1M12 "StingRay" digital oscilloscope (20M S/s with 12 Bit ADC)
• Extech Model 407738 digital sound level meter (Accuracy ±1.5 dB)
The following cables/connectors were used to connect the power supply to the PCPerspective power supply test equipment.
• (1) 20+4 pin ATX
• (1) 8-pin EPS/ATX12V
• (4) 6-pin PCI-E
• (6) SATA
• (3) Molex
DC Output Load Regulation
To simulate demanding and maximum loading conditions, the SX800-LTI power supply was connected to the load testers and supplied with a constant 120 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 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. We have included a second table of expanded tolerances (±1% to ±6%) for reference.
The following tables list the DC voltage results for the SilverStone SX800-LTI PSU while operating on 120 VAC, 60 Hz.
The SX800-LTI power supply produced very good voltage regulation on the three main DC outputs staying within ±2% of the recommended ATX guidelines; even better than SilverStone’s claim of ±3%. We’re off to a good start!
AC Ripple and Noise on the DC Outputs
The amount of AC ripple and noise present on the DC outputs was checked using a digital 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. We adjust the O-scope time base to look for AC ripple at both low and high frequencies. The 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 main output voltages of interest.
Overall the SX800-LTI power supply exhibited very good AC ripple and noise suppression on all of the DC outputs except for the +3.3V rail. While still within the ATX recommended guidelines, the +3.3V output showed a lot more AC ripple than we like to see, especially under load, and was well above 50% of the recommended limit. The other three rails look good but the +3.3V rail needs work.
I do not quite get it. Who
I do not quite get it. Who needs 800W in SFF PC? 800W is required for top/overclocked SLI or Crossfire configuration only.
Perhaps if Corsair comes out
Perhaps if Corsair comes out with something like the TWO…..which I would do an SLI config on to play on the name or something….
Works well with an ATX
Works well with an ATX adapter and would be perfect in an mATX case (which supports SLI) meaning you have more breathing room. Also, more options is never a bad thing.
So, overclocking your CPU and GPU can tax a PSU, and therefore that extra headroom is good to have.
Finally, it’s Titanium rated. Perhaps they didn’t want to put their best components in a 400W PSU, so they are doing more of a “one size fits many” configuration here.
You just don’t see a lot of good quality PSUs in the lower end of the scale, and that’s in part due to a consumer education issue, but also, it costs more for each SKU you pump out. In other words, it’s an efficiency thing on the manufacturing side as well.
I will buy it, not because I
I will buy it, not because I need that extra wattage, but I need to push the silentness to the limit. With only use 200watt on my ITX, means with 800watt psu, It will be in 40% of its fan envelope, which sometime even the fan still not kicked on. Problem with psu without fan, is the hizzing sound
Quite obvious, the sweet spot
Quite obvious, the sweet spot is 50% usage on a PSU. When you get closer to 100% load, there is a chance that capacitors will pop. Also caps lose capacitance over time. I suppose it won’t matter if you upgrade every year though.
I always enjoy your power
I always enjoy your power supply reviews. Very insightful and thoughtful. It almost seems like Silverstone was trying to cut corners a bit on cost here. Using sleeve bearing fan, and cheap Rubycon capacitors is very unfortunate. I agree they should have used a much higher quality fan, and a much better Japanese capacitor. And that warranty is not good either. Very surprised Silverstone did this. They have always had such a good reputation for quality. An otherwise nice SFX power supply though.
This PSU proves there’s no
This PSU proves there’s no need for ATX PSUs anymore, which saves wasted space. You can run two 1080Ti cards and a high-end CPU from this PSU, which already is quite over the top. With more sensible hardware there’s even a lot of room for overclocking.
Some brands have already started releasing mATX and ATX cases that support SFX PSUs only, like Silverstone, Lian-Li and Thermaltake, with more to come.