This document provides a schematic for an audio effects circuit board. The circuit board can be configured for either echo or surround sound mode using jumpers and preset controls. In echo mode, preset controls adjust the echo effect sound delay and depth. In surround mode, preset controls adjust the sound delay. The circuit includes connections for a microphone input, auxiliary audio input, output, and power supply, as well as components to process the audio signal.

1. ECHO
AUDIOMIC
SUR
+V
VCC
VCC
+V
+V
AUDIO LEVEL
AM
SOUND
DELAY ADJ
5 VDC
GND
GND
GND
INPUT
CN2
OUT
CN2
OUT
+
C13
4.7uF/63V
+
C13
4.7uF/63V
+
C2
10uF/50V
+
C2
10uF/50V
VCC1
REF2
AGND3
DGND4
OSC_O5
VCO6
CC17
CC08 OP1_OUT 9
OP1_IN 10
OP2_IN 11
OP2_OUT 12
LPF2_IN 13
LPF2_OUT 14
LPF1_OUT 15
LPF1_IN 16
U2 HT8970U2 HT8970
C21
47nF
C21
47nF
J1
JUMPER
J1
JUMPER
C24
0.1uF
C24
0.1uF
R14 12KR14 12K
C16
33nF
C16
33nF
+
C8
4.7uF/63V
+
C8
4.7uF/63V
+
C5
4.7uF/63V
+
C5
4.7uF/63V
C23
0.1uF
C23
0.1uF
C22
0.1uF
C22
0.1uF
R6
15K
R6
15K
R5
100K
R5
100K
C19
560pF
C19
560pF
C1
0.1uF
C1
0.1uF
PR1 22K PRESETPR1 22K PRESET
R8 10KR8 10K
+
C9
100uF/25V
+
C9
100uF/25V
C7
5600pF
C7
5600pF
+
C4
4.7uF/63V
+
C4
4.7uF/63V
CN3
SUPPLY INPUT
CN3
SUPPLY INPUT
C25
0.1uF
C25
0.1uF
R16 10KR16 10K
+
C12
4.7uF/63V
+
C12
4.7uF/63V
R18 15KR18 15K
IN OUT
GND
U3
78L05
U3
78L05
+
C14
10uF/50V
+
C14
10uF/50V
PR3
50K PRESET
PR3
50K PRESET R17 2.2KR17 2.2K
+
C15
10uF/50V
+
C15
10uF/50V R13
15K
R13
15K
R19
470E
R19
470E
C3
0.1uF
C3
0.1uF
CN1
AUX AUDIO
CN1
AUX AUDIO
R9 12KR9 12K
C10
0.1uF
C10
0.1uF
R12 1KR12 1K
R7
100K
R7
100K
PR2
22KPRESET
PR2
22KPRESET
MK1
CONDENSOR MIC
MK1
CONDENSOR MIC
C18 560pFC18 560pF
R2
100K
R2
100K
3
2
1
84
-
+
U1A
LM358-
+
U1A
LM358
R3 100KR3 100K
R15 15KR15 15K
C11 560pFC11 560pF
R10 4.7KR10 4.7K
C20
47nF
C20
47nF
R1
10K
R1
10K
R4
1K
R4
1K
+
C6
1uF/63V
+
C6
1uF/63V
D1
RED LED
D1
RED LED
CN3 Connector : Supply Input 5 VDC
CN1 Connector : Aux Audio Input
CN2 Connector : Output
PR1 Preset : Input Signal Audio Level Adjust
J1 : M - Mic input, A - Aux Audio Input
For Echo Mode :
Omit : C17
PR3 Preset : Echo Effect Sound Delay Adjust
PR2 Preset : Echo Depth Adjust
For Surround Mode :
Omit : R10, R14 & C13
PR3 Preset : Sound Delay Adjust