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 shows the improvement curve of the theoretical characteristics value by the SBM function when the quantize

noise is set to 0 dB when the SBM switch is turned OFF. You can find that it is improved move than 10 dB if below 3
kHz as shown in the figure.
The SBM function works only during analog recording. As the function can be used during playback regardless of
whether the SBM switch is ON/OFF, tapes recorded by SBM can be played back by other DATs.

Summary

Note on SBM

• SBM is the technique to improve S/N in auditory sense by changing the distribution of the frequency components of

quantize noises generated during A/D conversion and when the lower bits are discarded.
1 There are no effects to reduce the noise components in the inputs signal.
2 It is not a system to compress/extend the input signal itself.
3 It is carried out only during recording and therefore interchangeability with recorded tapes (playback on other DAT

decks, etc.) can be maintained without problems.

• With DTC-A8, PCM2600, PCM2800, SBM works during analog input recording (only fs 48k and 44.1 kHz)

24-bit data input

Quantizer

16-bit SBM output

Noise shaping filter

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: Coefficient

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The CXD2605Q is a 3rd generation LSI which carries out the recording and playback signal processing of the R-DAT
system with one chip. It is provided with the following functions.

• Recording signal modulation
• Playback signal demodulation (Adopts digital PLL)
• Error correction encoding (Parity generation, error detection and correction)
• Microprocessor interface (Sub code processing, system control)
• A/D, D/A interface (Including compensation, mute processing, etc.)
• Digital I/O interface
• RAM control
• Fs system clock generation
• Peak level meter

(This function is used for level detection for automatic writing of the start ID during recording.)

• Error count function
• Function for detection of between songs during digital recording from CDs

(This function is used for selecting the digital input of COAXIAL and OPTICAL for consumer use.)

The CXD2605Q is divided mainly into 9 blocks as shown in the block diagram in 

 The main functions of each

block are as follows.

1 DPLL (digital PLL) block

Extraction of playback clock from the playback RF signal and synchronization of playback data

2 PB (playback) block

SYNC detection, 10

n8 demodulation, demodulation of playback data and check

3 REC (recording) block

8

n10 modulation, generation of recording data, and generation of recording control signal

4 ECC (error correction) block

Generation C1, C2 parity during recording, C1 and C2 error detection and correction during playback

5 SUB I/O (microprocessor interface) block

Interface with microprocessor such as transmission and processing of control information and sub code data

6 AD/DA I/F (AD/DA interface) block

Generation of interleave and deinterleave addresses, and processing reference timings, interface with AD/DA system

7 D I/O (digital I/O interface) block

Modulation and demodulation of digital audio interface format signals (TX, RX) and Fs system clock generation

8 RAM I/F (RAM interface) block

Generation of RAM interface signal such as addresses

9 PLM (peak level meter) block

Detection of peak level in a certain period of time

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The CXA1364R is an IC which integrates the recording/playback amplifier, PCM equalizer, ATF analog signal
processing block of the R-DAT in one chip. The CXA1364R has following features.

• The recording/playback amplifier, PCM equalizer, ATF analog signal processing block are integrated in one chip,

reducing external parts and power consumption.

• Combination with a digital servo IC allows the configuration of a pilot AGC.
• The recording levels of the PCM signal and pilot signal can be adjusted independently.
• Compatible with 1/2 relative speed (half speed mode) mechanism (drum diameter : 15ø, drum rotation speed : 2000

rpm).

• Supports a drum diameter of 30ø and 4-head mechanism.

 shows the internal block and pin configuration diagram of the CXA1364R. The main operations of each block

are described below.

• REC AMP

The REC AMP has two channels-A and B. It serves as a current amplifier which amplifies and outputs direct and
alternating currents input (by 100 times) (the output is an open collector).

• REC GCA

The REC GCA is an amplifier which changes the recording signals from the digital signal processing IC (CXD2605Q)
from voltage to current and adjusts the current to the characteristics of heads A and B. The output current is connected
to the REC AMP inside the IC. The PCM recording current and pilot recording current can be adjusted independently
for Ach and Bch. The PCM recording period and pilot recording period are determined by logic.