One of the 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 three Ultra X units compare to some other popular power supplies on the market.
(click to enlarge)
As you can see from the graph, all three of the Ultra Products power supplies are heavy weights in their class.
DC Output Voltage Load Regulation
To simulate real world and maximum loading conditions, the Ultra power supplies were connected to the load tester, supplied with 115 VAC, and allowed to burn-in for 24 hours before voltage readings were taken. In this test we are interested in seeing how well a PSU can maintain the various output voltages while operating under different loads. The DC output voltages were measured with a FLUKE digital multimeter.
The ATX12V V2.2 tolerance for voltages states how much each output (rail) is allowed to fluctuate and has tighter tolerances for the +12V outputs.
The following tables list the DC voltage results at different loads for the three Ultra PSUs while operating on 115 VAC, 60 Hz.
The Ultra X-Pro EE 600W did an outstanding job of regulating all of the DC outputs across the full load range. These are some of the best results I have ever seen — ultra-good!
Note: Even though the X-Pro EE 600W power supply has one common +12V output I still used four separate loads during testing, which because of slight differences in cables and connectors resulted in slight differences between the measured +12V voltages (labeled +12Va thru d).
To confirm that the Ultra X-Pro EE 600W power supply does in fact have a single, high-capacity +12V rail, I bridged two of the CSI3711A Programmable DC loads together and then loaded a single PCI-E connector to 400W (33.3A) no problem.
While the voltage regulation isn’t quite as good as the previous 600W unit, both the Ultra X-Pro and X-Finity 800W power supplies stayed within the required specifications, all the way up to their maximum rated capacity of 800 watts output.
AC Ripple (electrical noise) on DC Outputs
The amount of AC ripple present on the 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 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 noise 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 each power supply complied with the ATX standard. The following table lists the ripple/noise results during all of the load tests for the seven main output voltages of interest.
During the AC ripple tests, the two Ultra 800W PSUs delivered outstanding results. While the X-Pro EE 600W power supply did a very good job of minimizing the AC noise on the DC outputs, the two workstation/server class 800W power supplies did an even better job of keeping the AC components to a minimum. This is very good, especially while outputting an 800W combined load.