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Service
MODEL: L-12/16/20
www.altoproaudio.com
Version 2.0
CONTENTS
1. Introduction......................................................................2
2. Specification.....................................................................3
3. Black Diagram..................................................................5
4. Schematic Diagram............................................................6
5. PCB Layout.....................................................................25
6. Wiring Diagram................................................................41
7. Test Procedure.................................................................42
8. Exploded Views & Mechanical Part List...............................46
9. BOM................................................................................49
1. Introduction
ALTO L12,L16,L20 FEATURES
CHANNEL STRIPS.
AUX send 1/2 switch-able to PRE/POST fader
60 mm high precision faders
Each input channel with Mute, SOLO function, low cut filters-75Hz, 18 dB/OCT and Overload
& signal present LEDs.
Group "SUB" 1-2", "SUB3-4", or "main L-R" mix send switch-able
4 AUX sends with master control and SOLO function per channel: 2 ¡Ñ PRE/POST fader
switch-able for monitoring/digital EFX application, 2 ¡Ñ post fader(for internal digital EFX or
as external send)
4-band fixed EQ on stereo line channels
3-band EQ with Swept mid on microphone channels
Channel inserts and direct output on each mono channel plus main mix inserts for flexible
connection of outboard equipment.
MASTER SECTION
24-bit DSP effect built in
True stereo 9-band graphic EQ
Adjustable mono main output by control level
BNC socket for connecting gooseneck lamps.
Separate outputs for 4 submaster control to enable more flexible routing
Separate subwoofer crossover and output
Special XLR Subwoofer out with 75Hz low pass
Control room/phone matrix
2 headphone outputs
2.8. TECHNICAL SPECIFICATION
Specification (L-12/16/20)
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
Sensitivity range +15dBu to 45dBu
Stereo input channels
Line input Balanced/unbalanced
Frequency response 10Hz to 55kHz, + 3dB
Distortion (THD & N) 0.005% at +4dBu, 1kHz
Impedances
Microphone input 1.4kOhm
Channel Insert return 2.5kOhm
All other inputs 10kOhm or greater
Tape out 1kOhm
All other output 120Ohm
Equalization
Hi shelving + 15dB @12kHz
Mid bell (mono) + 15dB @100Hz to 8kHz
Hi Mid (stereo) + 15dB @ 3kHz
Mid low (stereo) + 15dB @500Hz
Low shelving + 15dB @80Hz
Low Cut filter 75Hz, 18dB/oct.
DSP Section
A/D and D/A converters 24 bit
DSP resolution 24 bit
Type of effects Hall, Room, Vocal & Plate REVERBS
Mono & Stereo DELAY (max DELAY TIME 650ms)
Chorus, Flanger & Reverb MODULATIONS
REVERB+DELAY, REVERB+CHORUS,
REVERB+FLANGER combinations
Presets 256
Controls 16-position PRESET Selector
16-position VARIATION selector
PEAK LED
MUTE SWITCH with LED indicator
Main Mix Section
Noise (Bus noise) Fader 0 dB, channels muted: 100dBr (ref.:+4dBu)
Fader 0dB, all input channels assigned and set to
UNITY gain: 90dBr (ref.:+4dBu)
Max output +22dBu balanced XLR,
+22dBu unbalanced, 1/4" jacks
AUX Returns gain range - to +15dB
AUX Sends max out +22dBu
329
Power supply
Main voltage USA/Canada 100 120V~, 60Hz
Europe 210 240V~, 50Hz
U.K./Australia 240V~, 50Hz
Power Consumption 70 watts
Fuse 100 120V~ : T800mAL
210 240V~ : T500mAL
Main connection Standard IEC receptacle
30 4
3. Block Diagram
1 2 3 4 5 6 7 8 9 10 11 12
ALTO L-20
RIGHT-BUS
SOLO(PFL)
EFX SEND
LEFT-BUS
MID AUX SEND
CTRL/R
CTRL/L
LOGIC
AFL-R
AFL-L
BLOCK DIAGRAM
SUB1
SUB2
SUB3
SUB4
AUX1
AUX2
AUX3
AUX4
LO (FREQ) HI AUX SEND1
GAIN LEVEL R 3c
PHANTOM RN 4d
(TRIM) TN 2b
POWER
PAN
ASSIGN
AUX1 T 1a AUX SEND 1/2/3 (PRELIMINARY)
+48V FADER
LEFT-BUS S 5e
CH1 2 + MUTE
3 80 100Hz-8kHz 12K
AFL-L (AUX SEND 2/3 IDENTICAL)
MIC IN 1 3-BAND EQ
-
+/-15db RIGHT-BUS AUX/DFX SEND
AFL-R
SOLO R 3c
SOLO(PFL) AUX SEND 4 RN 4d
SUB1 ( ON) LEVEL TN 2b
CH1 T 1a AUX SEND 4
LINE IN
AUX4 S 5e
D SUB2 D
MIC GAIN:0~60dB MONO OUTPUT
LINE IN TRIM:+15dB~-45dB SUB3 AFL-L MONO LEVEL
R 3c
AFL-R RN 4d
3c R TN 2b
4d RN SUB4 SOLO(PFL) SOLO
T 1a
2b TN ( ON)
1a T SOLO LED AFL-L S 5e
INSERT DFX SEND
75Hz
5e S AFL-R
HI PASS MAIN MIX
SOLO SOLO(PFL) LEVEL MAIN OUT
( ON)
AUX1 R
T
POST LEFT-BUS
CH2-CH12 IDENTICAL TO CH1
S
SG/OL AUX1
PRE +4dB/MIC
AUX2
2
-20dB=SG(FLICKER) 3
+15dB=OL(GLOW) AUX2 1
3c R AUX3
4d RN DIRECT OUT
2b TN (CH1-CH12 ONLY) MAIN MIX LEFT
LINE OUT 1a T AUX3
AUX4 R
5e S T
RIGHT-BUS S
AUX4
+4dB/MIC
2
GAIN 3
PHANTOM (TRIM) 1
-20dB=SG(FLICKER) AFL-L
POWER
+48V +15dB=OL(GLOW)
MAIN MIX RIGHT
2 + SG/OL AFL-R
3
MIC IN 1
- EQ ON MAIN INSERT
SOLO(PFL) R 3c
SOLO LED RN 4d
CH13/14 & GEQ TN 2b
T
CH15/16 ONLY
1a
75Hz
SOLO S 5e
HI PASS
LO L-M M-H HI ( ON)
ASSIGN
MAIN INSERT
FADER BALANCE LEFT-BUS
R 3c
C 3c R MUTE RN 4d C
4d RN GEQ TN 2b
- 80 500 3K 12K
2b TN RIGHT-BUS T 1a
1a T 4-BAND EQ
LEFT(MONO) + +/-15db S 5e
5e S
SUB1
3c R
4d RN - 80 500 3K 12K
2b TN SUB2
RIGHT 1a T 4-BAND EQ
+ +/-15db
5e S
SUB3 2TK TAPE IN 2TK TAPE OUT
STEREO TRIM
STEREO INPUT CHANNELS (CH13-20) CH'S 17/18 & 19/20 ONLY LEFT-BUS LEFT LEFT
SUB4
AUX1
2TK TO MAIN
POST
AUX1 RIGHT RIGHT
PRE AUX2 RIGHT-BUS
2TK TO MAIN
AUX2
STEREO AUX RTN1 AUX3
3c R
4d RN
-
SUB OUT
2b TN AUX3 R
LEFT(MONO) 1a T
+ AUX4 SUB1 T SUB1
S
5e S
LEVEL AUX4
SUB1
3c R LEVEL 3c
4d RN RN 4d
2b TN - LEFT-BUS LEFT-BUS TN 2b
RIGHT 1a T SUBMIX 2 3 4 IDENTICAL TO SUB1 T 1a SUB1 INSERT
+ RIGHT-BUS
5e S SUB INSERT 2 3 4 IDENTICAL TO SUB1 INSERT S 5e
RIGHT-BUS
SUB1 TO MIX
AUX1
DFX TO
MONITOR
AUX2
DFX TO LEFT-BUS
STEREO AUX RTN2 MONITOR
3c R RIGHT-BUS
4d RN
2b TN -
LEFT(MONO) 1a T
AUX RETURN 2TK SUB1/2
B + SOLO B
5e S AFL-L SOLO ACTIVE
LEVEL
3c R
4d RN
- AFL-R FROM SUB2
2b TN
RIGHT 1a T MAIN MIX SUB3/4
+
5e S SOLO(PFL)
SOLO LED FROM SUB3
LEFT METER
STEREO AUX RTN3 ASSIGN TO SOLO FROM SUB4
3c R C-R/PHONES ( ON)
4d RN - LEFT-BUS CONTROL ROOM SOURCE
2b TN
LEFT(MONO) 1a T + CTRL-R-L
5e S CTRL-R-L RIGHT METER
LEVEL
CTRL-R-R
3c R
4d RN
- RIGHT-BUS
2b TN SOLO CTRL
RIGHT 1a T
+ CTRL-R-R
5e S
PHONES OUTPUT
LEFT-BUS R
AFL-L AFL L
STEREO AUX RTN4 T
S
PHONE A
3c R
4d RN - RIGHT-BUS
2b TN
LEFT(MONO) 1a T +
5e S SUB1 R
LEVEL AFL-R AFL R T PHONE B
S
3c R
4d RN
- SUB2 PHONES
2b TN LEVEL
RIGHT 1a T
+ SOLO MODE
5e S DFX RETURN TO SUB3
AUX1
PFL LED ( AFL) CTRL ROOM OUTPUT
SOLO(PFL) SOLO(PFL) (LEVEL SET) ( PFL ) R
T LEFT
SUB4 S
AUX RTN4
ASSIGN TO
A A
AUX2 R
R T RIGHT
DFX OUT T S
S FX OUT L
FX OUT R CTRL ROOM
DSP BOARD LEVEL
PRESETS
DFX SEND
VARIATIONS
MUTE
RIGHT-BUS
SOLO(PFL)
DFX SEND
LEFT-BUS
Titel
CTRL/R
CTRL/L
ALTO MIXING CONSOLE
LOGIC
AFL-R
DSP FOOTSWITCH
AFL-L
SUB1