| 摘要 |
A circuit for providing an output signal to an audio transducer includes a digital path that receives a digital input signal. The digital path includes a selectable digital gain 12 and a DAC 14. The circuit also includes an analogue signal path that receives a converted signal from the DAC 14 and has a selectable analogue gain 16. Responsive to the signal level, a controller 20 predicts the occurrence of an event for changing the digital gain 12 and the analogue gain 16. Having predicted the need to change the gain settings, the controller 20 adjusts the gain near a zero crossing of the signal. The adjustment of gain in both the digital and analogue portions of the signal path allows noise and dynamic range to be improved. The invention aims to minimise audio artefacts such as clicks and pops, by switching the gains at zero crossings of the signal. The controller 16 may also predict the peak trend of a signal envelope (fig.4) and adjust the gain settings accordingly to prevent clipping. |
