Sony KD-34XBR2 Training Manual page 64

S Board
Chart 12-1 shows the functions of all four ICs on the S board.
IC / Name
IC4401 / TruSurround
IC4403 / Audio Process
IC4404 / Low Pass Filter Speakers ON
IC4402 / Variable/Fixed
Audio Buffer
IC4401 TruSurround
Both Sel_L and Sel_R audio signals enter the S board and are applied to IC4401. IC4401 either passes the audio
out of the IC or creates a 3D sound field when the TruSurround mode is activated from the menu. When acti-
vated, Main Micro IC001 outputs a HIGH at the " S Mode" line that can be checked at the S board (CN4401/pin 6).
Chart 12-2 shows IC4401' s control voltage.
IC4403 Audio Process
Audio Process IC4403 controls all other audio effects from volume, tone, balance, to echo effects used in the
menu' s Simulated Audio Mode and BBE Mode (RA-5A chassis only). IC4403 output takes two paths. The main
path leaves the S board as the High output. The second path goes into a Low Pass Filter IC4404 to remove the
high frequencies before leaving the board as the woofer output.
A Board
Two power amplifier ICs are fed by a zener protected 24Vdc source. One power amp processes both channels
of the high frequency signal and the other processes the low frequency signal from the low pass filter. The power
amplifiers can be muted when speakers are turned OFF from the menu. When the speakers are turned OFF, the
variable or fixed line output is enabled.
Chart 12-1 - S Board ICs
Mode used
When TruSurround
is selected from the
" Effects" menu.
All modes
When speakers are
switched OFF
Chart 12-2 - TruSurround IC4401 Control Voltage
Audio Effect
Off CN4401/pin 6
Simulated CN4401/pin 6
TruSurround CN4401/pin 6
Produces the surround sound illusion when stereo sound is
input. S Mode from Main Micro IC001/pin 88 (CN4401/pin 6)
goes HIGH to turn on Surround Sound.
Controlled by serial data from Main Micro IC001 (B board –
not shown)
Sets Volume, Tone, Balance, & Simulated Mode (echo effect
for mono signals).
Passes only the low frequencies to the internal midrange spk.
Rear panel audio output jacks can be used to feed an
external Dolby 5.1 channel or DTS amp or headphones.
Location
0Vdc (OFF)
0Vdc (OFF)
5Vdc (ON)
61
12. Audio Block
Purpose
Voltage