WM8962B datasheet(97/295 Pages) WOLFSON

97 / 295 page

WM8962

Rev 4.3

DAC SIGNAL PATH ENHANCEMENTS

The DAC signal path incorporates a number of sound enhancement features, as illustrated in Figure

31. These features are described more fully in the following sections.

DIGITAL AUDIO

INTERFACE

ADC

DAC

nd order HPF

st order LPF/HPF

3D Surround

DF1 Filter

ReTune

Dynamic Range Control*

Signal Enhancement Blocks

5-Band EQ

Dynamic Range Control*

nd order HPF

Virtual Surround Sound

HD Bass

ReTune

* Dynamic Range Control (DRC)

can be enabled on either the

ADC path or the DAC path, but

not on both at the same time

Figure 31 DAC Signal Enhancements

5-BAND EQ

VSS

HD Bass

DRC

DAC Signal Enhancement path

DAC

ReTune™

Second Order

HPF

5-band EQ

The 5-band EQ function is implemented in the DAC Signal Enhancement path.

The 5-band EQ can be used to support user preferences for different music types, such as allowing

selection of ‘rock’, ‘dance’, ‘classical’ or other user-defined EQ profiles. The 5-band EQ can also be

used to provide compensation for imperfect characteristics of other components in the audio chain,

such as the loudspeaker in portable applications in particular.

Note that the functionality of the 5-band EQ has similarities to some of the other DAC signal

enhancements; it is important to select the most appropriate processing block for each requirement.

The 5-band EQ provides a basic level of signal control, whilst the other enhancements can provide

superior performance in many cases.

Frequency compensation of loudspeakers and other components can be implemented using the DAC

ReTune function, which provides a more powerful capability to normalise the frequency response; this

is achieved through the use of calibrated measurement procedures. The 5-band EQ provides a

simpler and coarser type of signal control.

Reduction of bass frequencies (removing signal content that the speaker is unable to reproduce) can

be implemented using the 2nd order High Pass Filter (DAC HPF); this provides greater attenuation of

the bass frequencies, without affecting the desired pass-band.

Enhancement of bass frequencies (compensation for poor sensitivity in headphones or loudspeakers

at low frequencies) can be implemented using the HD Bass function; this is a more intelligent and

adaptive audio enhancement than the 5-band EQ.

Note that, when using the 5-band EQ to boost any frequency band, it is recommended to take care

not to introduce distortion, taking into account the gain that may be applied by other audio

enhancement functions.

The 5-band EQ allows the gain within five frequency bands to be controlled. The upper and lower

frequency bands are controlled by low-pass and high-pass filters respectively. The middle three

frequency bands are notch filters.

The 5-band EQ is enabled by setting the EQ_ENA register as described in Table 53.

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