Equalizer

A mixing console having a channel strip for modifying an input audio signal, said channel strip including 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 the 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.

In an equalizer including a state variable filter having a first integrator and a second integrator, thus providing said equalizer with a corner frequency variable over a plurality of discrete steps, which 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, and 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 levels in a plurality of discrete steps, a method of adjusting the corner frequency of said equalizer, which method comprises steps of:

• receiving an instruction to increment the corner frequency of the state variable filter by one step;
• identifying the current corner frequency of the state variable filter, by determining the 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), increasing 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), decreasing 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), increasing 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.