Circuit diagram

VCC
1
REF
2
AGND
3
DGND
4
OSC_O
5
VCO
6
CC1
7
CC0
8
OP1_OUT
9
OP1_IN
10
OP2_IN
11
OP2_OUT
12
LPF2_IN
13
LPF2_OUT
14
LPF1_OUT
15
LPF1_IN
16
IC1
HT8972
S
MIC1
MIC M300
GND
R1
10K
R6
100K
GND
R5
100K
+V
3
2
8 4
1
IC2A
LM358
+V
GND
R8
1K
C5
39pF
R9
560
C2 0
10µ
GND
RV1
22K
C7
1nF
R4
10K
R12
4K7
C1 1
6n8
C1 6
10µ
R11
4K7
R7
100K
GND
C3
100n
C2
100n
GNDGND
RV2
22KSHS
GND
+5V
C21
47µ
GND
GND
R2
10K
C9
6n8
C8
6n8
R1 4
4K7
R1 3
4K7
R3
10K
C6
560pF
GND
C10
6n8
C1 2
33nF
R16
3K3
GND
C1 9
10µ
RV3
47KSHS
GND
R1 7
2K7
C1 7
10µ
MIX OUT
R15
4K7
C1 8
10µ
RV4
10K
GND
SK6
OUTPUT SEL
GND
3
2
5
7
6 4 8 1
IC3
LM386N
GND
C2 2
10µ
+V
C23
100µ
C1 3
47nF
R1 8
10
GND
GND
MIX OUT
C1 4
1µ
+V
"FEEDBACK"
"DELAY"
SK1
9V DC
GND
C2 4
100µ
GND
SW1
POWER
+V
-
+
C4
100n
GND
SK5
INPUT SEL
GND
R1 0
330
ZD1
ZA5V1
GND
C1
100n
+5V
GND
D1
1N4007
GND
SK3
SPEAK ER
SK4
Line IN
SK2
Line OUT
C15
10µ
"INPUT L."
5
6
7
IC2B
LM358
GND
+V