4.11.3 Digital Effects Filters
4.11.3.1 Shelf Filters
TLV320AIC3104EVM Software
The digital effect filters (the biquad filters) of the TLV320AIC3104 are selected using the check boxes
shown in Figure 20 . The De-emphasis filters are described in the TLV320AIC3104 data sheet, and their
coefficients may be changed (see Figure 18 ).
Figure 20. Enabling Filters
When designing filters for use with TLV320AIC3104, the software allows for several different filter types to
be used. These options are shown on a tab control in the lower left corner of the screen. When a filter
type is selected, and suitable input parameters defined, the response will be shown in the Effect Filter
Response graph. Regardless of the setting for enabling the Effect Filter, the filter coefficients are not
loaded into the TLV320AIC3104 until the Download Coefficients button is pressed. To avoid noise during
the update of coefficients, it is recommended that the user uncheck the Effect Filter enable check boxes
before downloading coefficients. Once the desired coefficients are in the TLV320AIC3104, enable the
Effect Filters by checking the boxes again.
A shelf filter is a simple filter that applies a gain (positive or negative) to frequencies above or below a
certain corner frequency. As shown in Figure 21 , in Bass mode a shelf filter applies a gain to frequencies
below the corner frequency; in Treble mode the gain is applied to frequencies above the corner frequency.
Figure 21. Shelf Filters
To use these filters, enter the gain desired and the corner frequency. Choose the mode to use ( Bass or
Treble); the response will be plotted on the Effect Filter Response graph.
TLV320AIC3104EVM and TLV320AIC3104EVM-PDK26 SLAU218 – August 2007
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