Casio CTK-750 Manuale Utente

— 12 —

The power amplifier is a two-channel balanced amplifier with standby switch. The following figure shows
the internal diagram of the amplifier.

Internal Diagram of LA4620

Input
Amp.

Pre-drive
Amp.

Power
Amp.

RL Short
Protector

Input
Amp.

Pre-drive
Amp.

Power
Amp.

Terminal
Protection
Circuit

Ripple
Filter

Pop Noise
Prevention
Circuit

Input
Amp.

Pre-drive
Amp.

Power
Amp.

RL Short
Protector

Input
Amp.

Pre-drive
Amp.

Power
Amp.

16

10

11

13

2

12

14

15

17

18

1

23

22

21

20

19

3

5

4

9

7

8

6

IN11+

IN11-

IN12-

PriGND

IN21+

IN21-

IN22-

NC

DC

MUTE

VCC2

ADJ

Boot22

OUT22

PoGND2

OUT21

Boot21

VCC1

Boot21

OUT12

PoGND1

OUT11

Boot11

+

-

-

+

+

-

-

+

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 from the CPU.

VDD

+5.1V

CPU,  Reset IC, Gate array, Working strage RAM

DVDD

+5.3V

DSP, Key touch LSI, Sound source ROM, Effect RAM, DAC

AVDD

+5.2V

DAC, Filter

LVDD

+5.2V

LED driver

VCC

+12V

Pilot lamp

VD

+12V

Power amplifier