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WM8955

STEREO DAC FOR PORTABLE AUDIO APPLICATIONS

Wolfson Microelectronics plc 

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WM8955L

TONE CONTROL

The WM8955L provides separate controls for bass and treble with programmable gains and filter

characteristics. This function operates on digital audio data before it is passed to the audio DACs.

Bass control can take two different forms:

• Linear bass control: bass signals are amplified or attenuated by a user programmable

gain. This is independent of signal volume, and very high bass gains on loud signals

may lead to signal clipping.

• Adaptive bass boost: The bass volume is amplified by a variable gain. When the bass

volume is low, it is boosted more than when the bass volume is high. This method is

recommended because it prevents clipping, and usually sounds more pleasant to the

human ear.

Treble control applies a user programmable gain, without any adaptive boost function.

REGISTER BIT

ADDRESS

R12 (0Ch)

7

Bass Control

6

3:0

R13 (0Dh)

6

Treble Control

3:0

Table 3 Tone Control

LABEL

BB

BC

BASS

TC

TRBL

DEFAULT

DESCRIPTION

0

0

1111 (OFF)

0

1111

(Disabled)

Bass Mode

0 = Linear bass control

1 = Adaptive bass boost

Bass Filter Characteristic

0 = Low Cutoff (130 Hz at 48kHz sampling)

1 = High Cutoff (200 Hz at 48kHz sampling)

Bass Intensity

Code

BB=0

BB=1

0000

+9dB

15 (max)

0001

+9dB

14

0010

+7.5dB

13

…

(1.5dB steps) …

0111

0dB

8

…

(1.5dB steps) …

1011-1101 -6dB

4-2

1110

-6dB

1 (min)

1111

Bypass (OFF)

Treble Filter Characteristic

0 = High Cutoff (8kHz at 48kHz sampling)

1 = Low Cutoff (4kHz at 48kHz sampling)

Treble Intensity

0000 or 0001 = +9dB

0010 = +7.5dB

… (1.5dB steps)

1011 to 1110 = -6dB

1111 = Disable

Note:

1. All cut-off frequencies change proportionally with the DAC sample rate.

w

Product Preview Rev 0.4 May 2003

17

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