DC offset is an imbalance that sometimes occurs in A/D converters (see WFTD archive “A/D Converter“). When working with audio it is desirable to have only the audio program material passed through the signal path. Almost by definition audio, being a periodic waveform, is an AC (Alternating Current) signal. DC (direct current) is of the non alternating or periodic variety and thus has no constructive purpose as part of an audio signal. It is merely a constant voltage that is present which can eat up headroom (see WFTD archive “Headroom“) and cause clicks and pops during editing.