A power converter includes a transformer having a primary winding and a secondary winding, a primary side circuit coupled to the primary winding, and a secondary side circuit coupled to the secondary winding and configured to output a substantially direct current output. In order to improve audio performance, an audio system may customize audio settings based on characteristics of an attached speaker. The flow monitoring process generates flow statistical data for the plurality of flows. In this case, a construction is made up wherein the length of a group delay time produced in the digital type real time digital signal processing part can be set to a given value.