Alto L-6 User manual

www.altoproaudio.com
Version1.0
MODEL: L-6

CONTENTS
1. Introduction…………………………………………………………….2
2. Specification…………………………………………………………....3
3. Black Diagram………………………………………………………….4
4. Schematic Diagram……………………………………………………5
5. Wiring Diagram………………………………………………………..10
6. PCB Layout…………………………………………………………….11
7. Test Procedure………………………………………………………..16
8. BOM……………………………………………………………………..22

1. Introduction
The L-6 is 2 mono MIC/LINE channels with MIC PREAMPS plus 2 stereo channels perfect for keyboards, MIDI
equipment or other stereo sound sources and a 2-track input/output for recording and playback in a mixer small enough
to carry in your board luggage: you can find great 3-band equalizers in each chhannel,one AUX sends,one stereo returns,
phantom power and accurate peak LED and level meters. Plus of course our ultra low noise circuitry and exceptional
build quality.
- 2 MIC Input Channels with gold plated XLRs and balanced Line Inputs.
- 2 Stereo Input Channels with balanced TRS Jacks.
- Ultra-low noise discrete MIC Preamps with +48 V Phantom Power.
- Extremely high headroom –offering more dynamic range.
- Balanced Inputs for highest signal integrity.
- Warm , natural 3-band EQ on each channels.
- Peak LEDs on each mono Channels and each stereo Channels.
- Adjusts the input sensitivity on each stereo channels.
- 1 AUX Sends per channel for external effects and monitoring.
- Balanced TRS and XLR outputs, Control Room and Headphone Outputs.
- 2-Track Inputs assignable to Main Mix, Control Room / Headphone Outputs.
- Highly accurate 6 segment Bar graph Meters.
- Performance and excellent noise figures
- Rugged construction ensures long life even under the most demanding conditions
- Manufactured under ISO9001 certified management system

Mono input channels
Microphone input Electronically balanced, discrete input configuration
Frequency response 10Hz to 55kHz, +3dB
Distortion(THD & N) 0.005% at +4dBu, 1kHz
Gain range 0dB to 60dB (MIC)
SNR (Signal to Noise Ratio) 115dB
Line input Electronically balanced
Frequency response 10Hz to 55kHz, +3dB
Distortion (THD & N) 0.005% at +4dBu,1kHz
Stereo input channels
Line input Unbalanced
Frequency response 10Hz to 55kHz,+3dB
Distortion (THD & N) 0.005% at +4dBu,1kHz
Impedance
Microphone input 1.4kOhm
All other inputs 10kOhm or greater
Tape out 1kOhm
All other output 120Ohm
Equalization
Hi shelving +15dB @ 12kHz
Mid bell +12dB @ 2.5kHz
Low shelving +15dB @ 80Hz
Main Mix Section
Noise (Bus noise) Fader 0dB, channels muted:100dBr (ref.:+4dBu)
Fader 0dB, all input channels assigned and set to
UNITY gain: (ref.: +4dBu)
Max output +22dBu balanced XLR
+22dBu unbalanced , 1/4” jacks
AUX return gain range OFF to 15dB
AUX send max out +22dBu
DSP section
A/D and D/A converters 24 bit
DSP resolution 24bit
Type of Vibraflange, Funky, Rockabilly, bigstage, vibrato 1-
4, Flanger1-4, Chorus 1-4
Presets 16
Presets 16-positon preset bank selector
Controls FX level, reverb level Clip LED
Power supply (AC/AC adapter)
Main Voltage USA/Canada 100 12V~, 60Hz
Europe 210 230V~,50Hz
U.K./Australia 240V~, 50Hz
Power consumption 15Watts
Physical
Net weight 1.4kg (xxxlb)
Shipping weight Xxx kg (xxxlb)
Dimension (W*D*H) 185m
m
×230mm×35/55m
m

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ALTO MIXING CONSOLE
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L-6 BLOCK DIAGRAM VER030701
A2(C)
MONO INPUT CHANNELS ( 1-2 )
2 1 3
MIC IN
+48V
3-BAND EQ
12K2.5K80
SG/OL
LEFT-BUS
RIGHT-BUS
AUX-1
RIGHT BUS LEFT BUS
AUX 1
STEREO INPUT CHANNELS (3-6)
EQ 12K2.5K80
LEFT BUS
RIGHT BUS
AUX 1
STEREO AUX RETURN 1
RIGHT BUS LEFT BUS
AUX 1 AUX SEND
MAIN OUT
LEFT BUS
RIGHT BUS
2
1 3
2TK TO MIX
2
1 3RIGHT BUS
LEFT BUS
TAPE IN
RIGHT
2-TRACK
21
3
2TK TO CTRL ROOM
21
3
PHONES OUTPUT
LEFT METER
RIGHT METER
+/ 15db
3-BAND EQ
12K2.5K80
+/ 15db
3c 5e 1a 4d 2b
LEFT 3c
5e 1a 4d 2b
RIGHT
MAIN MIX
AUX SEND1
T R S
MAIN MIX LEFT
T R S
MAIN MIX RIGHT
T R S
CONTROL ROOM OUTPUT
LEFT
T R S
RIGHT
T R S
PHONES
T R S
& PHONES
CONTROL ROOM
LEFT
TAPE OUT
LEVEL
AUX RETURN1
T
R
S
RN TN
T
R
S
RN TN
PAN
PHANTOM
LINE IN
GAIN
-
+
POWER
-
+
-
+
LO MID HI
1 2 1 2
AUX1
LEVEL
POST
PRE
BALANCE
AUX1
LEVEL
LO MID HI
SG/OL
3c 5e 1a 4d 2b
LEFT(MONO)3c
5e 1a 4d 2b
RIGHT
T
R
S
RN TN
T
R
S
RN TN
-
+
-
+
MIC GAIN:0~60dB LINE IN TRIM:+15dB~-45dB
EFX SEND
DSP BOARD
PRESETS
FX LEVEL
REVERB LEVEL
EFX SEND
LEFT-BUS
RIGHT-BUS
AUX-1
EFX SEND
AUX 1
AUX1
1 2 1 2
POST
PRE

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INPUT STAGE
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ALTO L-6 VER030709A2(C)
R1
4R7
R3
4R7
C16
1n
C15
1n
C19
1000u/10V
R4
4R7
VR12
O10K
R15
1K50
R35
2K49 3
21
U2A
4580M
R58
5K11
C25
22P
C52
47u/25V
R20
20K
2
1
3
4
X1
JY-5042-030G
3c
5e
1a
4d
2b
X3
JY-6351G-02-250
T
R
S
RN
TN
C5
330P
C11
10n
R48
470R
R34
2K49
C8
47u/63V
C7
47u/63V
R12
4K02
R11
4K02
C1
22u/35V
C2
22u/35V
R9
6K81
R7
6K81
LINE IN1
MIC 1
PH PWR
TR5
HR
TR1
A1316
R16
1K50
-VCC
VCC
R38
2K49
R37
2K49
C13
10n
R49
470R
TR7
HR
TR2
A1316
-VCC
VCC
3
21
U1A
4580M
5
67
U1B
4580M
C21
22P
C22
22P
R55
5K11
R54
5K11
R43
2K49
-VCC
R42
2K49
TR8
HR
VCC
R40
2K49
D6
BAS316
VCC
R19
20K
-VCC
R62
10K0
R63
10K0
R56
5K11
C23
22P
MIC GAIN=0~-60dB
LINE IN GAIN=+15~-45dB
3c
5e
1a
4d
2b
X5
JY-6351G-02-250
T
R
S
RN
TN
LINE IN 3/4
3c
5e
1a
4d
2b
X6
JY-6351G-02-250
T
R
S
RN
TN
LEFT(MONO)
RIGHT
3
21
U7A
4580M
R116
10K0
C27
22P
C61
47u/25V
R115
10K0
C26
22P
R113
10K0
C169
100P
R114
10K0
C170
100P
5
67
U7B
4580M
R125
10K0
C33
22P
C72
47u/25V
R124
10K0
C31
22P
R122
10K0
C171
100P
R123
10K0
C172
100P
R23
20K
R26
20K
PRE-CH5
PRE-CH6
3c
5e
1a
4d
2b
X7
JY-6351G-02-250
T
S
RN
TN
LINE IN 5/6
3c
5e
1a
4d
2b
X8
JY-6351G-02-250
T
R
S
RN
TN
LEFT(MONO)
RIGHT
3
21
U10A
4580M
R136
10K0
C32
22P
C81
47u/25V
R133
10K0
C34
22P
R121
10K0
C173
100P
R130
10K0
C174
100P
5
67
U10B
4580M
R135
10K0
C36
22P
C82
47u/25V
R134
10K0
C35
22P
R131
10K0
C175
100P
R132
10K0
C176
100P
R27
20K
R28
20K
L6G(1/4)
PCB# L6MAIN.PCB
PRE-CH7
PRE-CH8
EQ HI
12KHZ
C121
18n(M) VR15
B50K
R78
6K8
VR14
B50K
R77
6K8
LO
R112
10K0
C56
47u/25V
5
67
U3B
4580M
R186
1M
C149
22P
R106
1K1
VR17
B50K
R69
1K3
MID
R94
910R
C127
12n(M)
R95
910R
C109
33n(M) C110
33n(M)
C139
12n(M)
C134
18n(M)
C57
47u/25V
VR25
W50K
AUX-1
R170
68K
R172
4K7
C145
2.2u/50V R79
6K8
TR12
BR
TR11
BR
R195
1K50 VCC
LD1
RED
R193
30K
3
21
U3A
4580M
VR24
W50K
PEAK
C58
47u/25V R199
3K9
R209
36K
C151
22P
C60
47u/25V
R220
5K1
LEVEL
AUX-POST
R223
5K1
R221
5K1
LEFT-BUS
RIGHT-BUS
PAN
80HZ
2.5K
J1
POST
(PRE)
VR18
B50K
R173
4K7
R174
4K7
EQ HI
12KHZ
C123
18n(M) VR5A
B50K
R86
6K8
VR7A
B50K
R84
6K8
LO
R126
10K0
C62
47u/25V
3
21
U8A
4580M
R187
1M
C153
22P
R107
1K1
VR6A
B50K
R70
1K3
MID
R96
910R
C128
12n(M)
R97
910R
C114
33n(M) C115
33n(M)
C140
12n(M)
C135
18n(M)
C64
47u/25V
VR28
W50K
AUX-1
R249
47K
R179
4K7
C147
2.2u/50V R88
6K8
TR16
BR
TR15
BR
R197
1K50 VCC
LD3
RED
R242
22K 3
21
U9A
4580M
VR1A
W50K
PEAK
C65
47u/25V R201
3K9 R211
36K
C154
22P
C68
47u/25V
R227
5K1
LEVEL
AUX-POST
R224
5K1
R228
5K1
LEFT-BUS
RIGHT-BUS
BAL
PGND
80HZ
2.5K
EQ HI
12KHZ
C124
18n(M) VR5B
B50K
R87
6K8
VR7B
B50K
R85
6K8
LO
R127
10K0
C73
47u/25V
5
67
U8B
4580M
R189
1M
C156
22P
R109
1K1
VR6B
B50K
R73
1K3
MID
R100
910R
C130
12n(M)
R101
910R
C113
33n(M) C116
33n(M)
C142
12n(M)
C136
18n(M)
C74
47u/25V
80HZ
2.5K
R117
10K0
R128
10K0
R248
47K
R243
22K 5
67
U9B
4580M
VR1B
W50K
C66
47u/25V R202
3K9
R210
36K
PGND
C155
22P
C77
47u/25V
LEVEL
R119
10K0
R118
10K0
J3
POST
(PRE)
PRE-CH7
PRE-CH8
VR21
B50K
R176
4K7
R180
4K7
EQ HI
C125
18n(M) VR8A
B50K
R91
6K8
VR10A
B50K
R89
6K8
LO
R138
10K0
C75
47u/25V
3
21
U11A
4580M
R190
1M
C157
22P
R110
1K1
VR9A
B50K
R74
1K3
MID
R102
910R
C131
12n(M)
R103
910R
C117
33n(M) C120
33n(M)
C143
12n(M)
C137
18n(M)
C76
47u/25V
VR29
W50K
AUX-1
R251
47K
R182
4K7
C148
2.2u/50V R93
6K8
TR18
BR
TR17
BR
R198
1K50 VCC
LD4
RED
R244
22K 3
21
U12A
4580M
VR2A
W50K
PEAK
C78
47u/25V R204
3K9 R213
36K
C158
22P
C80
47u/25V
R230
5K1
LEVEL
AUX-POST
R229
5K1
R231
5K1
LEFT-BUS
RIGHT-BUS
BAL
PGND
80HZ
2.5K
EQ HI
C126
18n(M) VR8B
B50K
R92
6K8
VR10B
B50K
R90
6K8
LO
R137
10K0
C83
47u/25V
5
67
U11B
4580M
R191
1M
C160
22P
R111
1K1
VR9B
B50K
R75
1K3
MID
R104
910R
C132
12n(M)
R105
910R
C118
33n(M) C119
33n(M)
C144
12n(M)
C138
18n(M)
C84
47u/25V
80HZ
2.5K
R139
10K0
R140
10K0
R250
47K
R245
22K 5
67
U12B
4580M
VR2B
W50K
C79
47u/25V R203
3K9
R214
36K
C159
22P
C85
47u/25V
LEVEL
R129
10K0
R141
10K0
J4
POST
(PRE)
PRE-CH5
PRE-CH6
VR23
B50K
R181
4K7
R183
4K7
5
67
U2B
4580M
R61
5K11
C30
22P
C53
47u/25V
R24
20K
2
1
3
4
X2
JY-5042-030G
3c
5e
1a
4d
2b
X4
JY-6351G-02-250
T
R
S
RN
TN
LINE IN2
MIC 2
R2
4R7
R5
4R7
C18
1n
C17
1n
C20
1000u/10V
R6
4R7
VR13
O10K
R17
1K50
R36
2K49
C6
330P
C12
10n
R50
470R
R45
2K49
C9
47u/63V
C10
47u/63V
R14
4K02
R13
4K02
C3
22u/35V
C4
22u/35V
R10
6K81
R8
6K81
PH PWR
TR6
HR
TR3
A1316
R18
1K50
-VCC
VCC
R39
2K49
R46
2K49
C14
10n
R51
470R
TR10
HR
TR4
A1316
-VCC
VR20
B50K
VCC
R108
1K1
R72
1K3
MID
R98
910R
C129
12n(M)
C150
22P
R188
1M
R99
910R
5
67
U6B
4580M
C111
33n(M)
C69
47u/25V
C112
33n(M)
R120
10K0
LO
3
21
U4A
4580M
R81
6K8
C141
12n(M)
5
67
U4B
4580M
C28
22P
VR19
B50K
C133
18n(M)
C29
22P
R82
6K8
R60
5K11
VR16
B50K
R59
5K11
C122
18n(M)
R47
2K49
12KHZ
-VCC
EQ HI
C70
47u/25V
R44
2K49
VR27
W50K
TR9
HR
VCC
AUX-1
PGND
R171
68K
R41
2K49
R177
4K7
D7
BAS316
PAN
C146
2.2u/50V
RIGHT-BUS
VCC
R83
6K8
LEFT-BUS
TR14
BR
R226
5K1
TR13
BR
R222
5K1
R178
4K7
R196
1K50
C24
22P R175
4K7
R57
5K11
VCC
R64
10K0
AUX-POST
VR22
B50K
R65
10K0
LD2
RED
R22
20K
LEVEL
R194
30K
-VCC
80HZ
3
21
U6A
4580M
R225
5K1
2.5K
C71
47u/25V
VR26
W50K
J2
POST
PEAK
C152
22P
(SOLTON 1K2)用
(PRE)
C59
47u/25V
R212
36K
R200
3K9
L6G.S01 L6G.S02 L6G.S03
84
U2C
4580M
C185
100n
C184
100n
C186
100n
C183
100n
VCC
-VCC
C187
100n
C188
100n
84
U4C
4580M
84
U6C
4580M
84
U8C
4580M
C190
100n
C191
100n
C196
100n
C197
100n
C199
100n
C200
100n
C201
100n
C202
100n
84
U1C
4580M
84
U3C
4580M
84
U7C
4580M
C179
100n
C189
100n
C180
100n
C192
100n
C181
100n
C195
100n
C182
100n
C198
100n
84
U11C
4580M
84
U12C
4580M
84
U10C
4580M
84
U9C
4580M
VCC
-VCC

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Date: Drawn By: Sheet
RevisionModel No:
8-Sep-2003 KEVIN LIN.
SEND & MAIN OUT & 2TK & CTRL R & PHONES
42of
ALTO L-6 VER030709 A2(C)
C230
100P
C86
47u/25V R254
150K
R246
22K
C231
100P
C87
47u/25V R253
150K
R247
22K
VR3B
W50K
VR3A
W50K
3
21
U13A
4580M
5
67
U13B
4580M
84
U14C
4580M
R255
270K
C37
22P
C88
47u/25V
R232
5K11
R256
270K
C38
22P
C93
47u/25V
R233
5K11
84
U19C
4580M
84
U13C
4580M
84
U15C
4580M
C204
100n
C203
100n
+VCC
-VCC
C206
100n
C205
100n
C97
47u/25V
R31
20K 3
21
U14A
4580M
R32
10K0
C166
22P
C100
47u/25V
R147
10K0
R237
5K1
C98
47u/25V
R30
20K 5
67
U14B
4580M
R33
10K0
C163
22P
C99
47u/25V
R148
10K0
R236
5K1 LEFT-BUS
RIGHT-BUS
2TK TO MIX
R257
27K
2TK TO
R258
27K
3
21
U15A
4580M
5
67
U15B
4580M
VR4B
W50K
VR4A
W50K
C90
47u/25V
C89
47u/25V
R206
3K9
R205
3K9
R215
36K
R217
36K
C40
22P
C39
22P
C91
47u/25V
C95
47u/25V
R142
10K0
R145
10K0
84
U18C
4580M
AUX RETURN 1
R-METER
R29
20K
C92
47u/25V
3
21
U21A
4580M
R216
36K
C41
22P
L-METER
AUX-1
C177
100P
C178
100P
ROOM
LEFT-BUS
RIGHT-BUS
CONTROL
PHONES/
CTRL ROOM
1
2
3
4
5
6
7
8
CN1
2.5-8P
PGND
+VCC-VCC
PH PWR
C207
100n
C208
100n
C209
100n
C210
100n
C211
100n
C212
100n
LEFT-BUS
RIGHT-BUS
AUX-1 AUX-SEND1
AUX-RTN1-L
AUX-RTN1-R
2TK- N-L
2TK- N-R
2TK TO CR-R
2TK TO CR-L
SW4A
PS-22E85L
SW4B
PS-22E85L
SW3B
PS-22E85L
2TK TO CR-R
2TK TO CR-L
SW3A
PS-22E85L
2TK-IN-L
2TK-IN-R
+5VD
L6G (2/4)
DGND
84
U21C
4580M
C215
100n
C216
100n
3c
5e
1a
4d
2b
X10
JY-6351G-02-250
AUX SEND1
R265
120R
R264
120R
T
R
S
RN
TN
3
21
U17A
BA15218N
5
67
U17B
BA15218N
C162
22P
R144
10K0
R261
120R
3c
5e
1a
4d
2b
X9
JY-6351G-02-250
R266
120R
PHONES
R260
120R
R259
120R
3
21
U16A
BA15218N
5
67
U16B
BA15218N
R143
10K0
C161
22P
3c
5e
1a
4d
2b
X11
JY-6351G-02-250
T
R
S
RN
TN
CTRL ROOM R
3c
5e
1a
4d
2b
X12
JY-6351G-02-250
T
R
S
RN
TN
CTRL ROOM L
R263
120R
R262
120R
R267
120R
R268
120R
5
67
U18B
4580M
3
21
U18A
4580M
R238
10K0
C164
22P
LEFT-BUS
RIGHT-BUS
C167
22P
R239
10K0
C102
47u/25V
C101
47u/25V
3
21
U19A
4580M
R218
36K
C165
22P
R207
3K9
C94
47u/25V
VR11B
W50K
MAIN MIX
VR11A
W50K
R219
36K
C168
22P
R208
3K9
C103
47u/25V
C96
47u/25V
C104
47u/25V
R146
10K0
R149
10K0
MAIN MIX
LEFT
RIGHT
R274
39K
R275
39K
5
67
U19B
4580M
3c
5e
1a
4d
2b
X13
JY-6351G-02-250
T
R
S
RN
TN
MAIN R (UNBAL)
3c
5e
1a
4d
2b
X14
JY-6351G-02-250
T
R
S
RN
TN
MAIN L (UNBAL)
R270
120R
R269
120R
R271
120R
R272
120R
R277
1K
R278
1K
L(WHITE)
R(RED)
TAPE INTAPE OUT
14
25
3 6
X17
SCP6873NS3232
2TK-IN-L
2TK-IN-R
2TK-IN-L
2TK-IN-R
AUX-SEND1
84
U16C
BA15218N
84
U17C
BA152 8N
R281
47R
R280
47R
C105
47u/25V
C106
47u/25V
C217
100n
C218
100n
+VCC
-VCC
SW1B
PS-22E85L
SW1A
PS-22E85L

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Titel Size File: Date: Drawn By:
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RevisionModel No:
8-Sep-2003 KEVIN LIN.
DISPLAY STAGE
43of
ALTO L-6 VER030709
A4
8
914
U24C
LM339
1
6
7
U24B
LM339
1
6
7
U23B
LM339
8
914
U23C
LM339
1
6
7
U25B
LM339
8
914
U25C
LM339
LD9
GR LD10
GR LD11
GR LD12
GR LD13
YEL LD14
RED
R284 120R
R285 560R R288
820R R291
820R R289
3K9 R292
5K6 R290
22K
+VCC
R287
47R
-VCC
PGND
10
11 13
U24D
LM339
5
42
U24A
LM339
5
42
U23A
LM339
10
11 13
U23D
LM339
5
42
U25A
LM339
10
11 13
U25D
LM339
LD20 GR LD21
GR LD22
GR LD23
GR LD24
YEL
-VCC
LEFT METER
(-30) (-10) (-4) (0) (+10) (+18)
3 21
U22A
4580M
R299
100K
R301
100K C236
47u/25V
PGND
TR21
HR
+VCC
D1A
DA204K
D1B
DA204K
TR22
HR
R273
120R
R52 470R
R53
470R
R151
10K0
PGND
5 67
U22B
4580M
R300 100K
R302
100K C237
47u/25V
PGND
L-METER R-METER
312
U24E
LM339
312
U25E
LM339
312
U23E
LM339
84
U22C
4580M
C219
100n
C220
100n
R282
47R
R283
47R
C107
47u/25V
C108
47u/25V
+VCC
-VCC
PGND
LD6
RED
LD19
GR
R184
4K7
R286
2K
PGND PGND
PH PWR
PWR ON
PHANTOM
+VCC
R304
10K0
R303
10K0
PGNDPGND
L6G (3/4)
C238 47P C239
47P
D2 RLS4148
D3 RLS4148
D4 RLS4148
D5 RLS4148
RIGHT METER
LD25 RED

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Titel
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File:
Date: Drawn By: Sheet
RevisionModel No:
8-Sep-2003 KEVIN LIN.
UDASP IN/OUT SECTION
44of
ALTO L-6 VER030709
A2(C)
C42
22P C243
1.5nF
C240
4.7uF 5
6
7
U29B
4580M
R154
10K0
R305
68R
R307
10K0
R152
10K0
R153
10K0
3
2
1
U29A
4580M
R155
10K0
C245
1.5nF
C242
4.7uF 5
6
7
U30B
4580M
R161
10K0
R306
68R
R157
10K0
R160
10K0 R163
10K0
C241
4.7uF
5
67
U31B
4580M
3
21
U31A
4580M
C244
1.5nF R159 10K0
R158
10K0
C45
22P
R162
10K0
C43
22P
R309
2K2
R156
10K0
AUX-SEND1
12 34 56 78 910 1112 1314 1516
CN2
HEADER 8X2 1
2
3
4
COM
EN1
SDB161PVB15FS
1 2 3 4 5 6 7 8
AR1
680R*4
DGND
+5VD
GND
R312
220R
R311
7K5
LD8
RED
84
U29C
4580M
84
U31C
4580M
84
U30C
4580M
C224
100n
C225
100n
C226
100n
C227
100n
+VCC
-VCC
C229
100n +5VD
DGND
C249
10uF
UDASP IN/OUT SECTION
JP1
PGND
1
2
4
8
3
2
1
U32A
LM393
5
6
7
U32B
LM393
R185
4K7
+VCC
R279
1K
C222
100n
R192
1M R310
2M2
R315
820K
D8A
RB400D
PEAK(FLICKER)
MUTE(GLOW)
VARIATION
84
U32C
LM393
C247
33P
C246
33P
L6G (4/4)
AUX-SEND1
RETURN1
STEREO AUX
3c
5e
1a
4d
2b
X15
JY-6351G-02-250
3c
5e
1a
4d
2b
X16
JY-6351G-02-250
RIGHT 1
LEFT 1 EFXRTN-L
EFXRTN-R
AUX-RTN1-L
AUX-RTN1-R
VR30
W50K
VR31
W50K
C250
4.7uF
C251
4.7uF
REVERB LEVEL
FX LEVEL

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1
2
3
4
5
6
7
8
CN1
2 5-8P
1
2
3
4
5
6
7
8
CN3
2.5-8P
1 2 3
CN1
2P-2.5
L6PWR
L6G
+48V
GND
GND
-15V
GND
+15V
+5V
GND
+48V
GND
GND
-15V
GND
+15V
+5V
GND
ADAPTOR
TG00077
AC 110V/220V
AC INPUT HA00027
power switch
L6PIN.Sch
Titel Size File: Date: Drawn By:
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RevisionModel No:
8-Sep-2003 J.S.TASY
L-6 Wiring Diagram
11o
f
ALTO L-6 VER030710
A4
L-6

PCB : L6G

Bottom Overlay

To
p
Overla
y

PCB : L6G Top Layer

Finished product test procedure
1. Instruments
APtester
Double trace oscillometer
Voltmeter
2. Functions test
a. Input the proper AC power supply, turn on the main power, POWER LED will be
illuminated (green). Then switch on PHANTOM power, PHANTOM LED will be
illuminated (red), use a voltmeter to test the first pin and second pin of each MIC
(MIC 1, MIC 2), the volt of phantom power should be 46V(±2V). then power off
the switch.(Note: please turn off the switch when you are doing the steps of test
procedure as follows)
b. Set all TRIM, LEVEL, EQ, AUX knobs to the position of 0, set PAN to the
position of LEFT. All buttons to the position of OFF.
c. Input the signal from balanced sockets (MIC 1 & MIC 2), input the signal from t
unbalanced sockets (LINE IN 3/4&LINE5/6),
d. Input the signal to the unbalanced AUX RENTURN sockets separately, test the
balanced output (LEFT & RIGHT) of MAIN MIX OUTPUT, which should be
5dBu (±1dB) THD + N<0.003%.
e. Insert the RCA plug to L& R of TAPE IN separately:
First, press 2TK TO MIX button, test the unbalanced outputs (LEFT&RIGHT) of
MAIN MIX OUTPUT, CONTROL ROOM and PHONE (need stereo plug for
testing) separately, which should be 0dBu(±1dB) THD + N<0.006%.the output of
TAPE OUT is 0dBu(±1dB)
Then release 2TK TO MIX button (OFF), no input from CONTROL ROOM,
when press 2TK TO CONTROL ROOM, test the output, which is 0dBu (±2dB)
THD + N<0.002%.
f. Input +15dBu 1kHz sine wave (load out 600Ω, BNC-Unbalanced) through
LINE 1, when turn MAIN MIX LEVEL counter-clockwise to the minimize, all

LEVEL LEDs will turned off, when turn MAIN MIX LEVEL pot clockwise to the
maximize, the LEVEL LEDs will be illuminated in sequence. test that whether the
relating LED is illuminated when the level of output signal reaches the exactly
value as LED shows . If so, test the maximize output level (before clipping) is
20dBu(±1dB) THD + N<0.1%.)
Adjust TRIM knob of CH 1 clockwise, PEAK LED will be illuminated (red). And
test all PEAK LEDs from CH 1 to CH6
3. frequency response test
When Test the inputs of LINE 1, LINE 2, LINE 3, LINE 4, LINE 5, LINE 6
separately as follows, the frequency response curve of MAIN MIX OUTPUT
(LEFT & RIGHT) (the preset of all knobs are the same as function test step 2.b)
a. Open S8RESP1.atl test procedure, press and release the LOW CUT switch, test
the frequency response curve of LINE 1, LINE 2 LINE 3, LINE 4 , please refer
to the following figure.
(Remark: don’t need to test L6 with this step)
A
udio Precision 07/22/03 15:41:30
-50
+20
-40
-30
-20
-10
+0
+10
d
B
m
20 20k50 100 200 500 1
k
2k 5
k
10k
Hz

b. Turn EQ HI &LOW knob to the MAX and the MIN (EQ MID at the middle), test
the frequency response, the frequency response curve is shown as follows, please
refer to the following figure.
c. Turn EQ MID to the MAX and the MIN (EQ HI &LOW at the middle), test the
frequency response, the frequency response curve is shown as follows, please
refer to the following figure.
Audio Precision 07/21/03 15:54:30
-30
+20
-25
-20
-15
-10
-5
+0
+5
+10
+15
d
B
m
20 20k50 100 200 500 1k 2k 5k 10
k
Hz
Audio Precision 07/21/03 15:52:05
-30
+20
-25
-20
-15
-10
-5
+0
+5
+10
+15
d
B
m
20 20k50 100 200 500 1
k
2k 5
k
10k
Hz

Remarks: the frequency response test of normal instruments:
a. Turn EQ LOW knob of the relating channel clockwise to the max (+15), the
output is +15dBu(± 2dB), then turn EQ LOW knob of the relating channel
counter-clockwise to the min. (-15), the output is –15dBu(± 2dB);
b. Input the signal at 2.5kHz, Turn EQ MID knob of the relating channel
clockwise to the max (+12), the output is +12dBu(± 2dB), then turn EQ MID
knob of the relating channel counter-clockwise to the min. (-12), the output is –
12dBu(± 2dB);
c. Input the signal at 15kHz, Turn EQ HIGN knob of the relating channel clockwise to
the max (+15), the output is +15dBu(± 3dB), then turn EQ HIGH knob of the relating
channel counter-clockwise to the min. (-15), the output is –15dBu(± 3dB);
4. test DSP
a. Input the signal from MIC1, output the signal from MAIN MIX OUTPUT, turn
AUX RTN2(DFX)clockwise to the MAX, turn PRESETS and VARATIONS knobs,
the signal will be processed by DSP, if the level of the signal is over-high, PEAK
LED will be illuminated to red, press DFX MUTE button, Bypass the signal, press
the footswitch, which is connected to DFX FOOSWITCH, the signal will get out of
BYPASS.
b. Input the signal from MIC 1 to MIC 4, output the signal from AUX SEND S1, turn
AUX 2 /DFX TO AUX 1 counter-clockwise to the MAX., turn PRESET and
VARATIONS knobs, the signal will be processed by DSP. (do not need to test L6
with this step)
5. Sampling test
Connecting L 6 to a power amplifier and speakers, listening to the sound, no noise is OK.
Company preset: turn all volume knobs to the MIN. other control knobs to the middle,
all switches to the position of OFF.
DONE