Sony DTC-A8 / PCM-2600 / PCM-2800 Service Manual ▷ View online
— 28 —
MASTER (A-B HAED)
RF(REC/PB) AMP
IC1
RF
SIGNAL
REC DATA
A
B
A'
B'
MASTER
DAT DSP
CXD2605Q
IC503
RFDT(PB)
REDT(REC)
"REPRO"
INPUT
MONITOR
"INPUT"
ADDT
(DADT)
PEAK LEVEL
DETECTOR
IC702
S-RAM
IC804
SLAVE
DAT DSP
CXD2605Q
IC803
DADT
RF (PB) AMP
IC51
SLAVE (A'-B' HEAD)
RF
SIGNAL
RFDT
SBM
DIGITAL FILTER
IC308
DIGITAL FILTER
D/A CONVERTER
IC314
TX
S-RAM
IC504
RX
ADDT
DADO
DRUM
MOTOR
M904
D0 - D7
A0 - A14
Fig. 3-2. Signal Processing System Structure (PCM-2800)
Fig. 3-2.
shows the structure of the PCM-2800 signal processing system.
The head drum section is as shown in the figure composed of a 4-head system. In addition to the normal A-B head, it is
provided with a playback monitor A’-B’ head, enabling simultaneous monitoring and playback (RAW (Read After Write)
function) during recording. During normal recording, the master DAT DSP (IC503) sets into the recording mode, and
after recording signal processing of the analog input or digital input signal is performed, it records on the tape from the
A-B head via the master RF (REC/PB) amplifier (IC1). During this time, when the INPUT monitor switch is set to
“INPUT”, the input signal is output directly to the D/A converter (IC314) and audio meter circuit. When set to the
“REPRO” side, the playback signal from the A’-B’ head is input to the slave DAT DSP (IC803) through the slave RF
(PB) amplifier (IC51), and is output via “REPRO” of the INPUT monitor switch after playback signal processing in the
DSP.
During playback, the master DAT DSP is set into the playback mode, and the playback signal from the A-B head is
input to the master DAT DSP via the master RF amplifier regardless of the INPUT monitor switch position. Playback
signal processing is carried out inside the DSP and the playback signal is output in the same way. In this way, the A-B
head and master DAT DSP are used during the normal recording and playback, and the A’-B’ head and slave DAT DSP
are used during simultaneous monitoring and playback (RAW) during recording.
provided with a playback monitor A’-B’ head, enabling simultaneous monitoring and playback (RAW (Read After Write)
function) during recording. During normal recording, the master DAT DSP (IC503) sets into the recording mode, and
after recording signal processing of the analog input or digital input signal is performed, it records on the tape from the
A-B head via the master RF (REC/PB) amplifier (IC1). During this time, when the INPUT monitor switch is set to
“INPUT”, the input signal is output directly to the D/A converter (IC314) and audio meter circuit. When set to the
“REPRO” side, the playback signal from the A’-B’ head is input to the slave DAT DSP (IC803) through the slave RF
(PB) amplifier (IC51), and is output via “REPRO” of the INPUT monitor switch after playback signal processing in the
DSP.
During playback, the master DAT DSP is set into the playback mode, and the playback signal from the A-B head is
input to the master DAT DSP via the master RF amplifier regardless of the INPUT monitor switch position. Playback
signal processing is carried out inside the DSP and the playback signal is output in the same way. In this way, the A-B
head and master DAT DSP are used during the normal recording and playback, and the A’-B’ head and slave DAT DSP
are used during simultaneous monitoring and playback (RAW) during recording.
— 29 —
3-1. Micro Processor Interface
Fig. 3-3. Micro Processor Interface Signal Connection Diagram
Fig. 3-3.
shows the signal connection diagram of microprocessor interfaces among the main microprocessor (IC501),
DAT DSP CXD2605Q (IC503), mechanism microprocessor (servo process, IC502), and display microprocessor (IC701).
The main microprocessor which controls the whole system transmits and receives the following information with the
DAT DSP CXD2605Q by the serial data (SDSI, SDSO) synchronized with the data transmission sync signal (SBSY) and
the data transmission clock (EXCK).
The main microprocessor which controls the whole system transmits and receives the following information with the
DAT DSP CXD2605Q by the serial data (SDSI, SDSO) synchronized with the data transmission sync signal (SBSY) and
the data transmission clock (EXCK).
• Recording/playback, analog IN/digital IN mode information
• Main-ID, Sub-ID, flag
• Sub data (PACK data)
• Control information such as sampling frequency setting
• Main-ID, Sub-ID, flag
• Sub data (PACK data)
• Control information such as sampling frequency setting
The main microprocessor transmits the function mode and mechanical mode information and also transmits linear
counter data, etc. obtained using FG data by the serial data (DTO, DTI) synchronized with the serial clock (SCK) based
on the communication request signal (REQ) to the mechanical microprocessor (servo process).
Information such as display data and key input is transmitted with the display microprocessor using the serial data (SI,
SO) in the same way as the mechanical microprocessor. Filter coefficient and mode are set for the SBM digital filter
(IC308) and D/A converter (IC314) using the serial data with the same timing as the latch clock signal (LATCH) and
shift clock signal (SHIFT).
counter data, etc. obtained using FG data by the serial data (DTO, DTI) synchronized with the serial clock (SCK) based
on the communication request signal (REQ) to the mechanical microprocessor (servo process).
Information such as display data and key input is transmitted with the display microprocessor using the serial data (SI,
SO) in the same way as the mechanical microprocessor. Filter coefficient and mode are set for the SBM digital filter
(IC308) and D/A converter (IC314) using the serial data with the same timing as the latch clock signal (LATCH) and
shift clock signal (SHIFT).
11
7
8
12
46
59
49
50
51
44
48
XMECHA-REQ
REQ
XMECHA-BSY
BSY
DM DI
DM DO
DM CK
XDISP-REQ
XDISP-ACK
DTO
SCK
52
44
54
53
55
DTI
MECHA MICON
(SERVO PROCESS)
IC502
7
8
10
9
79
DISPLAY
MICON
IC701
SO
SI
SC
REQ
ACK
23
24
25
26
EXCK
SDSI
SDSO
SBSY
55
54
53
52
SR-CK
SR-DTO
SR-DTI
XSBSY
DAT DSP
CXD2605Q
IC503
MAIN MICON
IC501
SBM
DIGITAL FILTER
IC308
40
41
42
MODE
SHIFT
LATCH
ATT
SHIFT
LATCH
34
35
36
XADLD
AUSO
AUSC
XDALD
DIGITAL FILTER
D/A CONVERTER
IC314
23
24
25
38
EXCK
SDSI
SDSO
XCS
SLAVE
DAT DSP
CXD2605Q
IC803
34
XSLV-SEL
38
XCS
97
XMST-SEL
PCM-2800
— 32 —
SECTION 5
SIGNAL CIRCUIT
5-1. Outline of SBM (Super bit Mapping)
The SBM is a function which markedly expands the dynamic auditory and visual range by reducing noises which are
especially conspicuous in the audible range to human beings.
especially conspicuous in the audible range to human beings.
Highly accurate pulse A/D converter
The analog input audio signal of this unit converts into the 24-bit quantized digital data through the pulse A/D converter
and decimation filter. As the number of quantize bits in the standard DAT format is the same as CDs (16 bits), the
difference is 8 bits. This means that because quantization is carried out at a higher accuracy than when quantization is
carried out at 16 bits, the quantized noise is lesser and detailed music information is contained.
For SBM, when this 24 bit data is converted to 16 bits which can be recorded on DAT, the upper 4 bit information in the
lower data which was originally discarded is incorporated into the 16 bits to improve sound quality.
When the lower bit information is incorporated into the 16 bits, calculation is carried out based on the “audibility” of
human beings. Generally the audible range of human beings is 20 Hz to 20 kHz. But the sound in this range is not heard
at a consistent sensitivity, human beings are most sensitive to 3 kHz to 4 kHz sound as shown in
and decimation filter. As the number of quantize bits in the standard DAT format is the same as CDs (16 bits), the
difference is 8 bits. This means that because quantization is carried out at a higher accuracy than when quantization is
carried out at 16 bits, the quantized noise is lesser and detailed music information is contained.
For SBM, when this 24 bit data is converted to 16 bits which can be recorded on DAT, the upper 4 bit information in the
lower data which was originally discarded is incorporated into the 16 bits to improve sound quality.
When the lower bit information is incorporated into the 16 bits, calculation is carried out based on the “audibility” of
human beings. Generally the audible range of human beings is 20 Hz to 20 kHz. But the sound in this range is not heard
at a consistent sensitivity, human beings are most sensitive to 3 kHz to 4 kHz sound as shown in
Fig. 5-1
and
insensitive to higher and lower sounds
Fig. 5-1. Audible Characteristics of Human Beings
Noise shaping filter
This is the same with quantize noises. Therefore, the audible dynamic range can be expanded not by lowering the
quantized noises of the audible range consistently but by lowering sounds that have high sensitivity. For SBM to make
use of this principle, frequency characteristics taking into consideration audible characteristics is given to the noise
reduction filter and quantization characteristics with high sensitivity is reduced as shown in
quantized noises of the audible range consistently but by lowering sounds that have high sensitivity. For SBM to make
use of this principle, frequency characteristics taking into consideration audible characteristics is given to the noise
reduction filter and quantization characteristics with high sensitivity is reduced as shown in
Fig. 5-2
, and by feeding
back the error discarded during quantization to the input, the lower bit information is again input to the upper bit.
Sound voltage level
(dB)
(dB)
Frequency
(Hz)
(Hz)
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