Casio AT-1 Service Manual page 13

Power Amplifier (LA4598)
The power amplifier is a two-channel amplifier with standby switch. The following figure shows the inter-
nal diagram of the amplifier.
Internal Diagram of LA4598
6
Ch1 IN
Ch1 N.F.
5
Pre GND 8
D.C. 7
10
Ch2 IN
Ch2 N.F. 11
Power Supply Circuit
The power supply circuit generates six voltages as shown in the following table. VDD voltage is always
generated. The others are controlled by APO signal output from the CPU.
Name Voltage
VDD +5 V
DVDD +5 V
AVDD +5 V
LVDD +4.5 V
VCC +9 V
VC +9 V
Input
Pre-drive
Amp.
Amp.
Bias circuit
Input
Pre-drive
Amp.
Amp.
CPU, Reset IC, Working strage RAM
DSP, Key controller, Sound source ROM, Effect RAM, DAC, KO siginal generator
DAC Filter
LED Driver
Pilot lamp
Power amplifier
Power
Amp.
TSD protector
Stand by
Power
Amp.
For operation of
— 11 —
2
Ch2 B.S.
3 Ch1 OUT
1 Power GND
VCC
4
9
Standby
12 Ch2 OUT
13 Ch2 B.S.