SD-EX200 (serv.man19) - Sharp Audio Service Manual (repair manual). Page 9

– 9 –

Adjust VRA100 and VRA101 so that the DC voltage between
speaker terminals + and - is set to 0 

±

 5 mV at AC 230 V.

Electronic

Voltage

SO421

AC 230 V

Set

Output:
Speaker Terminal

+

-

VR : 0
Input : AUX

L-CH Output
Offset Adjustment

R-CH Output
Offset Adjustment

VRA101

VRA100

1-BIT AMP. PWB

Since this CD system incorporates the following automatic
adjustment functions, readjustment is not needed when
replacing the pickup. Therefore, different PWBs and pickups
can be combined freely.
Each time a disc is changed, these adjustments are preformed
automatically. Therefore, playback of each disc can be
preformed under optimum conditions.

Input section
Signals from CNA101 are coupled by CA100 and CA101 and
then sent into the A/D converter IC (ICA100).

       modulation 1-bit converter
Signals from the A/D converter IC (ICA100) are converted to
1-bit signals and sent differentially. Refer to the technical
manual of SM-SX100 for the details of conversion to 1-bit
signals.

Low pass filter circuit
1-bit signals switched by the output IC (ICA101 and ICA102)
are converted to analog signals through the lowpass filter
consisting of LA101 ~ LA107. The low pass filter functions
when a frequency exceeds 20 kHz, and reduces it by approx.
3 dB when it reaches approx. 40 kHz.

Dynamic feedback circuit
The 1-bit signals switched by the output IC (ICA101 and
ICA102) oscillate between positive and negative voltage.
After resistance-division, the signals are fed back to the A/D
converter IC (ICA100) through NF resistance 75 kohms (RA155
~ RA158). The peak-to-peak voltage reaches approx. 5 V.