Shelby1420, the easiest way to look at the digital filter is that it removes the switching frequency from the analog waveform. These filters aren't perfect, which is the reason why some prefer upsampling of the source material. This creates a higher switching frequency which many argue has a positive effect since it aliases the noise outside the human hearing range. The waveforms I've attached are examples of the digital versus analog equivalency (pre versus post filtering). Without the filters in question the analog wavefore would look like its digital counterpart...which is ugly. Digital components that are known for sounding grainy are often because of poor filtering techniques or power supply jitter (which is another subject for the next installment!!!).