Under the Hood
The Seasonic X-Series 1250W Gold power supply is based on the X-Series design, which becomes apparent as soon as the cover is removed. The most obvious feature is the +3.3V and +5V voltage regulators have been moved off of the main PCB (or daughter cards) and onto the modular DC connector board, which mounts to the front of the enclosure. This is a major innovation shared by all X-Series power supplies and offers several advantages.
• Reduced wiring results in less resistance to current flow and higher efficiency
• Reduced wiring also results in a cleaner layout with better airflow
• Reduced part count results in higher reliability and lower cost
(Courtesy of Seasonic)
The biggest advantage to moving the two VRMs onto the DC connector board is that it virtually eliminates the high current distribution wiring that previously had to route the +3.3V and +5V outputs to the connector panel. This distribution wiring had to carry high currents and therefore was subject to line resistance and voltage losses. With the new design, only +12V has to be delivered to the modular DC connector board, which can be distributed more efficiently with fewer and smaller wires (as voltage goes up, current goes down for the same power).
The Seasonic X-1250 main PCB is basically a +12V PSU that also includes a small -12V regulator and the +5VSB section. All of these output voltages are sent out via modular connectors soldered directly onto the front of the main PCB. Additional connectors supply all the other connectors directly from sockets soldered onto the modular DC connector board.
Seasonic X Series DC Connector Panel with 3.3V and 5V VRMs
Looking inside the Seasonic X-1250 PSU, you will see the three main Hitachi capacitors on the primary are rated at 390uF, 420V, and 105°C. The secondary features predominantly solid polymer capacitors with a few Nippon Chemi-Con electrolytic caps thrown in for good measure. Just like all previous X-Series power supplies we have seen, the layout and component selection appears to be excellent.