— 7 —
FILTER BLOCK
Since the sound signals from the DAC are stepped waveforms, the filter block is added to smooth the
waveforms.
Filter Block
IC104
From DAC
To main volume
EQUALIZER BLOCK
The equalizer block boots low frequencies to compensate for the reduced response of the built-in speakers.
From main volume
To power amplifier
Equalizer Block
IC103
DAC (IC105: UPD6379GR)
The DAC receives 16-bit serial data output from the CPU. The data contains digital sound data of the melody,
chord, bass, and percussion for the right and left channels. The DAC converts the data into analog waveforms
and output them to each channel separately.
POWER AMPLIFIER (IC102: LA4598)
The power amplifier is a two-channel amplifier with standby switch.
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
+
-
-
+
+
-
-
+
