Pre-Production
WM8904
RETUNETM MOBILE PARAMETRIC EQUALIZER (EQ)
The ReTuneTM Mobile Parametric Equaliser is a circuit that can be enabled in the DAC path. The
function of the EQ is to adjust the frequency characteristic of the output to compensate for unwanted
frequency characteristics in the loudspeaker (or other output transducer). It can also be used to tailor
the response according to user preferences, for example to accentuate or attenuate specific
frequency bands to emulate different sound profiles or environments such as concert hall, rock etc.
The EQ is enabled using the EQ_ENA bit as shown in Table 23.
REGISTER
ADDRESS
BIT
LABEL
EQ_ENA
DEFAULT
DESCRIPTION
R134 (86h)
EQ1
EQ enable
0
0
0 = EQ disabled
1 = EQ enabled
Table 23 ReTuneTM Mobile Parametric EQ Enable
The EQ can be configured to operate in two modes - “Default” mode or “ReTuneTM Mobile” mode.
DEFAULT MODE (5-BAND PARAMETRIC EQ)
In default mode, the cut-off / centre frequencies are fixed as per Table 24. The filter bandwidths are
also fixed in default mode. The gain of the individual bands (-12dB to +12dB) can be controlled as
described in Table 25.
Note that the cut-off / centre frequencies noted in Table 24 are applicable to a DAC Sample Rate of
48kHz. When using other sample rates, these frequencies will be scaled in proportion to the selected
sample rate.
EQ BAND
CUT-OFF/CENTRE
FREQUENCY
1
2
3
4
5
100 Hz
300 Hz
875 Hz
2400 Hz
6900 Hz
Table 24 EQ Band Cut-off / Centre Frequencies
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
EQ Band 1 Gain
R135 (87h)
EQ2
EQ_B1_GAIN [4:0]
4:0
01100b
(0dB)
(see Table 26 for gain range)
EQ Band 2 Gain
R136 (88h)
EQ3
EQ_B2_GAIN [4:0]
EQ_B3_GAIN [4:0]
EQ_B4_GAIN [4:0]
EQ_B5_GAIN [4:0]
4:0
4:0
4:0
4:0
01100b
(0dB)
(see Table 26 for gain range)
EQ Band 3 Gain
R137 (89h)
EQ4
01100b
(0dB)
(see Table 26 for gain range)
EQ Band 4 Gain
R138 (8Ah)
EQ5
01100b
(0dB)
(see Table 26 for gain range)
EQ Band 5 Gain
R139 (8Bh)
EQ6
01100b
(0dB)
(see Table 26 for gain range)
Table 25 EQ Band Gain Control
PP, Rev 3.3, September 2012
59
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
