The output voltage ripple is within the allowable limits at a load of 350W. There’s no additional low-frequency pulsation at the output: this must be due to the increased capacitance of the high-voltage capacitors in comparison with the A300M-C model.
The “green zone” for the +12V voltage has moved rightward in the cross-load diagram and this voltage doesn’t sag even at high loads. That’s another advantage over the A300M-C model. The +5V voltage is somewhat higher than necessary in the load range typical of a modern PC, but it never violates the allowable limits.
The PSU uses a 120x120x25mm fan (Yate Loon D12SH-12).
The fan is rotating at a constant speed until a load of 250W. Then its speed begins to grow up. If the initial speed were some 300rpm lower, the AX400-PN might be regarded as a quiet PSU but it is only average in this respect in reality.
The efficiency reached 80% at one point but kept a little below that value on average. The power factor is higher than with the A300M-C, but didn’t make it to 0.65.
Thus, the Tsunami Hercules AX400-PN is an improved version of the Hercules A300M-C: an output power higher by 50W, no signs of overheat when working at full load, and improved electric characteristics (particularly a more stable +12V voltage). This PSU will be a good choice for a microATX system including a rather advanced CPU and graphics card. Unfortunately, the short length of the cables may be an obstacle to using the AX400-PN in full-size system cases.