Sony HDW-750 Maintenance Manual page 85

Audio control is accomplished by the FP CPU (IC801 :
with built-in flash RAM) on the FP-121 board when it
receives the audio mode information from the SS CPU
(IC1) on the SS-92 board.
The IFA-11 board has the front microphone block (20 dB
or 30 dB) selector circuit that is fixed to the 20 dB position
during the stereo mode.
The APR-59 board consists of the audio control IC
(IC103), memory IC (IC104), and monitor amplifier block
(IC106, IC109, ICQ101, IC102, etc.)
The AL-43 board constitutes the final amplifier stage
(Q101, IC102, IC201 and IC202) that is connected to the
CNB-15 board. Output signals of CH1 and CH2 are output
from the 5-pin connector (CN301) on the AXM-24 board.
The AXM-24 board consists of the LINE-IN/MIC-IN/+4.8
V MIC-IN selector switch (S101 and S102), 3-pin input
XLR connector automatic detection circuit (Q403 to Q407)
and the microphone amplifier (30 dB) circuit.
When the main power is turned on, the FP CPU (IC801) on
the FP-121 board receives the initialization of the respec-
tive ports, the locking information of the TG (IC200) PLL
circuit of the DVP-18 board from the SS CPU (C1) of the
SS-92 board, and releases the reset of the audio control IC
(IC103) on the APR-59 board and sets the register data. It
finally releases the audio mute (so the analog EE sound
can be monitored).
The front microphone signal passes through the MA-103
board, IFA-11 board and MB-898 board, and then enters
the input signal selector block of the FP-121 board (IC5 to
IC8).
The rear input signal passes through the AXM-24 board,
CNB-15 board and MB-898 board, and then is sent to the
input signal selector block of the FP-121 board (IC5 to
IC8).
The FP CPU (IC801) on the FP-121 board obtains the
switch position information of the FRONT/REAR/WIRE-
LESS selector switch by reading the 2-bit signal of each
switch (S1 to S4) as it selects the LINE SELECT (IC16)
switch. In accordance with the obtained switch position
information of FRONT/REAR/WIRELESS, the FP CPU
(IC801) selects the desired audio signal by driving the
input signal selector block (IC5 to IC8).
HDW-750/750CE V1
The CH1 and CH2 audio signals that are selected by the
input selector block (IC5) of the FP-121 board are sent to
the VCA block (IC12 and IC14) via a differential amplifier
(IC1 : balanced/unbalanced conversion).
The output signal from the VCA block (IC12 and IC14)
passes through the 10 dB ATT (IC108) and is sent to the
manual controlled amplifier (20 dB) and the AGC amplifi-
er (32 dB).
The amplifier outputs are selected by the AUTO/MANU-
AL selector switch (S101), pass through the balanced-to-
unbalanced conversion amplifier (IC105) for A/D conver-
sion and are sent to the A/D CONVERTER (IC106 : 20-bit
digital output). The output signal of the A/D converter
passes through the digital selector switch (IC102) of the
APR-59 board, and is sent to the audio control IC (IC103 :
AD1).
The CH3 and CH4 audio signals that are selected by the
input selector block (IC7) of the FP-121 board, are attenu-
ated by about _12 dB in the differential amplifier (IC2 :
balanced-to-unbalanced conversion), pass through the 10
dB ATT (IC405) and are sent to the AGC controlled
amplifier (32 dB).
The output signal from the AGC controlled amplifier (32
dB) passes through the balanced-to-unbalanced conversion
amplifier (IC304) for A/D conversion and is sent to the A/
D CONVERTER (IC305 : 20-bit digital output). The
output signal of the A/D converter passes through the
digital selector switch (IC102) of the APR-59 board, and is
sent to the audio control IC (IC103 : AD2).
The 20-bit digital audio signal that is delayed by the audio
control IC (IC103) of the APR-59 board, is output from the
audio control IC (IC103 : ENC), passed through the MB-
898 board and is sent to the DVP-18 board.
The output signal from the A/D CONVERTER (IC106 and
IC305) on the FP-121 board is a 20-bit signal while the CA
adapter output signal is a 16-bit signal. Due to this differ-
ence, these two signals are selected within the audio
control IC (IC103) of the APR-59 board. The audio
playback signal is supplied with the 20-bit signal that is
converted to the 16-bit signal internally and is then output.
The output frequency and level of the test tone that is
generated by the audio control IC (IC103), are fixed at
1kHz and _20dBu (fixed).
The IN/OUT signal diagram of the audio control IC
(IC103) of the APR-59 board is shown in Fig. 2.
1-26. Circuit Description
1-26-4. Audio System
1-69