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4.9.3 Digital Effects Filters
4.9.3.1 Shelf Filters
TLV320AIC34EVM Software
The digital effect filters (the biquad filters) of the TLV320AIC34 are selected using the checkboxes shown
in Figure 17 . The De-emphasis filters are described in the TLV320AIC34 data sheet, and their coefficients
may be changed (see Figure 15 ).
Figure 17. Enabling Filters
When designing filters for use with TLV320AIC34, 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
TLV320AIC34 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 checkboxes before
downloading coefficients. Once the desired coefficients are in the TLV320AIC34, 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 18 , 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 18. 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.
SLAU232 – December 2007 TLV320AIC34EVM-K 25
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