| 摘要 |
The application relates to digital to analogue conversion circuits having dynamic gain control. A digital variable gain element (102) may apply gain to an input digital signal (DIN) upstream of a DAC (101) to make better use of the input range of the DAC and an analogue variable gain element (103) applies a compensating analogue gain. Again controller (201) has a gain allocation module (204) for controlling the allocation of gain between said digital and analogue variable gain elements in response to changes in a signal level of the input digital audio signal. In the present invention the gain allocation module is operable in first and second modes of operation where the response to reductions in signal level is slower in the first mode than in the second mode of operation. A low-level detector (202) monitors the input digital audio signal so as to detect a low-level part of the signal and the gain controller changes from the first mode to the second mode following detection o fa low-level part of the input digital audio signal. The response of the gain allocation module in the second mode is preferably fast enough such that the digital gain can be changed to a target setting suitable for the low-level part of the signal before it is received at the digital gain element. |
