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WM8777
BASS MANAGEMENT
Support is provided for Bass Management in the analogue domain. This might be used either in the
case where a partnering DSP has insufficient MIPs to support all required functions, or where an
analogue multi-channel input is required to be processed for use with ‘small’ bass-limited speakers.
Provision is made for single pole high pass filtering of each front, centre, surround or rear channel,
using a single external capacitor. The value of this capacitor may be chosen to set the required high-
pass corner frequency, typically the Dolby recommended 100Hz value being preferred. Use of extra
external FET switches would allow the system builder to adjust this corner frequency in the system.
To create the subwoofer channel signal, each of up to all 6 channels is summed into the LFE
channel using external discrete summing resistors, and the entire summed subwoofer signal then
low-pass band-limited using a further user selectable external capacitor value. This allows the gain
from each individual channel, and the overall bass corner response to be selected. Following this
summing stage, an integrated volume control allows the overall level of the subwoofer channel to be
set.
To front left tone network
LSUMOP
DAC
LFEVE
Bypass
AUX
PAD
PAD
+
+20dB to -100dB
To front right tone network
PAD
LFE
RSUMOP
DAC
Bypass
AUX
PAD
+
To centre tone network
CNTSOP
DAC
Bypass
AUX
LFESUM
PAD
PAD
+
100Hz Lowpass
LFESOP
PAD
DAC
Bypass
AUX
+
To front channels
LSUROP
DAC
Bypass
AUX
LRBMIN
+20dB to -100dB
+20dB to -100dB
+20dB to -100dB
+20dB to -100dB
PAD
PAD
+
100Hz Highpass
PAD
SURL
RSUROP
DAC
Bypass
AUX
RRBMIN
PAD
PAD
+
100Hz Highpass
PAD
SURR
LAUXOP
DAC
Bypass
LAUXBMIN
RAUXBMIN
PAD
PAD
PAD
+
100Hz Highpass
(or 10Hz if no bass management)
PAD
AUXL
RAUXSOP
DAC
Bypass
PAD
+
100Hz Highpass
(or 10Hz if no bass management)
PAD
AUXR
Figure 3 Bass Management Configuration
PP Rev 1.94 November 2004
19
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
