主权项 |
1. An equalizer for applying equalization to an input audio signal, said equalizer including:
a state variable filter having a first integrator and a second integrator, and having a variable corner frequency that is controlled by a first multiplying digital-to-analog converter (MDAC) coupled to said first integrator and a second multiplying digital-to-analog converter (MDAC) coupled to said second integrator, wherein said first multiplying digital-to-analog converter (MDAC) and said second multiplying digital-to-analog converter (MDAC) are each configured to provide variable attenuation in a plurality of discrete steps; a digital attenuation controller coupled to and configured to adjust the attenuation of said first multiplying digital-to-analog converter (MDAC) and said second multiplying digital-to-analog converter (MDAC) independently, and wherein, to effect a one-step increase in the corner frequency of the state variable filter, said digital attenuation controller is configured to determine attenuation levels of said first multiplying digital-to-analog converter (MDAC) and said second multiplying digital-to-analog converter (MDAC), and: in response to determining that the attenuation of said first multiplying digital-to-analog converter (MDAC) is equal to the attenuation of said second multiplying digital-to-analog converter (MDAC), increase the attenuation of said first multiplying digital-to-analog converter (MDAC) by one step and leaving the attenuation of said second multiplying digital-to-analog converter (MDAC) unchanged, in response to determining that the attenuation of said first multiplying digital-to-analog converter (MDAC) is one step higher than the attenuation of said second multiplying digital-to-analog converter (MDAC), decrease the attenuation of said first multiplying digital-to-analog converter (MDAC) by one step and increasing the attenuation of said second multiplying digital-to-analog converter (MDAC) by one step, in response to determining that the attenuation of said second multiplying digital-to-analog converter (MDAC) is one step higher than the attenuation of said first multiplying digital-to-analog converter (MDAC), increase the attenuation of said first multiplying digital-to-analog converter (MDAC) by one step and leaving the attenuation of said second multiplying digital-to-analog converter (MDAC) unchanged. |