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**** You can display and check results of the adjustment from the test mode (display in hexadecimal, 2's complement)
"7F~0,FF~80"
↓
Hexadecimal
"127~0,-1~-128"
1) OFST adjustment
Reference
00 (h)
Example
02 = VC
Result of the VC offset adjustment is +26mV, thus the circuit offset must be -26mV.
* Offset adjustment of FE and ABCD is implemented based on result of the adjustment done on the VC.
2) IV adjustment
Reference
pre_disc: 16 (h)
Example
06 = 1V (with rec_disc)
Gain is varied by +2dB against the reference value.
Gain is adjusted approximately by 1dB according to difference of steps from the reference. The smaller the value
represents higher gain.
3) EF.B adjustment
Reference 0F (h)
Variable gain volume can be computed based on difference from the reference.
Example
0A = EFB
Gain of E signal is varied by -0.75dB against F signal.
(4) AGC adjustment
Reference
30(h)
Variable gain volume can be computed based on difference from the reference.
Example
27 = FACC
Variable gain volume is -1.8dB. * The same applies to the tracking, too.
(5) Focus bias adjustment
Reference: 00(h)
Variable bias volume can be computed based on difference from the reference.
Example
FA = BIAS
Volume of bias applied = -6*13mV = -78mV.
1.2.2 Signal Processor Block
Data read from disc is conducted to RFIC, then entered to this IC as EFM signal.
The signal is subjected to EFM demodulation and ACIRC (error correction), then stored in DRAM once. As needed, the
signal is transferred from DRAM to this IC, and ATRAC expanded and then converted to audio data.
This data is output from the built-in DAC as analog audio data.
Incorporates a 20-bit DAC with an 8-times over-sampling filter and a secondary analog LPF (fc = 97 kHz).
Pickup
amplifier
Conversion from hex to decimal
Decimal
⇒
2*13mV = +26mV
rec_disc: 08 (h)
⇒
1 (dB)*(08 - 06) = +2dB
⇒
0.15 (dB) * (0A - 0F) = 0.75dB.
⇒
20log (27 (h)/30 (h)) = -1.8dB.
⇒
FA(h) - 100(h) = -6.
IC201
IC101
I
RF
comp
RF
amplifier
J
DRAM
IC202
EFM
ACIRC
Memory
Demodulation
Demodulation
Demodulation
ATRAC
DAC
LPF
CX-683
audio output
9
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