I have two of these filters in use. One is connected to the power supply of my ASUS NUC, which I use exclusively as a Roon Core. The other is connected to the power supply of my router, a Fritz!Box 6591 Cable. In both cases, the high-frequency noise of the switching power supplies is significantly reduced by using the Fosi filters. With an oscilloscope and an 8-ohm load (50 Watt), I measured 140mV AC ripple on the Delta (Brandname) switching power supply of my Roon Core for example. With the filter, this is reduced to only 16mV AC ripple, which consists almost entirely of 50 Hz residual noise from the mains voltage. The high-frequency noise has disappeared. However, with the Delta power supply of the ASUS NUC, it shuts down as soon as the filter is connected. You have to disconnect the Delta from the mains first, then connect the filter, and then you can connect the Delta power supply to the mains without any problems.







