Alto ACL2-Pro Service Manual

Service Manual

Model: ACL2 PRO

Compressor/Limiter

www.altoproaudio.com

Version: 1.1

CONTENTS

1. Specification

2. Block Diagram

3. Schematic Diagram

4. Printed Circuit Board

5. Wiring Diagram

6. Test Procedure

7. Electrical Parts List

8. Exploded Views & Mechanical Parts List

9. Troubleshooting

10. Notes

SPECIFICATIONS FOR ACL2 PRO

INPUT

Connectors XLR and 1/4” TRS (Pin 2 and Tip hot)

Type Electronically balanced/unbalanced, RF filtered

Impedance Balanced >50Kohm, Unbalanced>25Kohm

Nominal operating level +4dBu/-10dBV switchable

Max input level >+24dBu balanced and unbalanced

CMRR Typically>50dB at 1KHz

OUTPUT

Connectors XLR and 1/4” TRS (Pin 2 and Tip hot)

Type Electronically balanced/unbalanced, RF filtered

Impedance Balanced 120ohm, Unbalanced>60ohm

Max output level >+21dBu,+20dBm balanced and unbalanced

SIDECHAIN INPUT

Connectors 1/4” TRS (Tip hot)

Type RF-rejecting, DC de-coupled, unbalanced input

Impedance >10Kohm

Max input level >+24dBu

SIDECHAIN OUTPUT

Connectors 1/4” TRS (Tip hot)

Type RF-rejecting, DC de-coupled, unbalanced output

Impedance 2Kohm

Max input level >+21dBu

SYSTEM SPECIFICATIONS

Bandwidth 20HZ to 20kHz, +0/-0.5dB

Frequency Response 0.35Hz to 200kHz,+0/-3dB

Noise >-95dBu, unweighted, 22Hz to 22kHz

THD

IMD <0.1% Typical SMPTE
Crosstalk

Stereo Coupling True RMS detection

<0.008% Typical at +4dBu, 1kHz, unity gain
<0.04% Typical at +20dBu, 1kHz, unity gain

<-100dB, 22Hz to 22Khz

EXPANDER/GATE SECTION

Type Interactive Expander (Interactive Ratio Control)

Threshold variable (OFF to +15dB)

Ratio variable (1:1 to 1:8)

Attack <1ms/50dB, program dependent

Release variable (SLOW:100ms/1dB,FAST:100ms/100Db)

COMPRESSOR SECTION

Type Interactive Compressor (Interactive Knee Adaptation)

Threshold variable (-40dB to +20dB)

Ratio

Threshold Characteristic variable (Interactive or Hard Knee)

Manual Attack Time variable (0.5ms to 100ms / 20dB

Manual Release Time variable from 0.05 ms to 5s / 20dB

Auto Attack Time Typical 15ms at 10dB, 5ms at 20dB, 3ms at 30dB

Auto Release Time Program dependent, typical 125dB/s

Output level variable (-20dB to +20dB)

variable (1:1 to

∞:1)

PEAK LIMITER SECTION

Type Interactive Gain Control Peak Limiter

Threshold variable (+4dB to OFF (+22dBu))

Ratio

Stage 1 Limiter Type Clipper

Attack Time “zero”

Release Time “zero”

Stage 2 Limiter Type Program Limiter

Attack program dependent, typ. <5ms

Release program dependent, typ. 20dB/s

∞:1

FUNCTION SWITCHES

SC EXTERN

SC MON

INTERACTIVE

CONTOUR Allows for frequency dependent detection.

AUTO

I/O METER

IN/OUT Relay controlled hard-bypass

OPERATING LEVEL

COUPLE

Switches the detector section to the external SC
input.
Monitoring the external SC input, disengaging the
normal audio.
Enables the “Interactive Knee Adaptation”
characteristics.

Enable the automatic and program dependent setting
of the Attack-/Release times, disengaging the manual
Attack-/Release controls.
Switches between input and output for the Level
Meter.

Changes the internal reference level from +4 dBu
to –10dBu.
Linking both channels for stereo operation. Channel 1
becomes master.

INDICATORS

GAIN REDUCTION

INPUT/OUTPUT LEVEL

Expander/Gate Threshold 2 LED for under “+” and above “-“

Compressor Threshold 3 LEDs for under “+”,Interactive “0” and above “-“

Peak Limiter Threshold 1 LED for indication of limiter function.

Function switch LED indicator for each

12 element LED display:
1/2/4/6/9/12/15/18/21/24/27/30 dB.

8 element LED display:

-30/-24/-18/-12/-6/0/+3/+6/+9/+12/+18 dB

POWER SUPPLY

USA/Canada ~120VAC, 60Hz
U.K./Australia ~240VAC, 50Hz

Mains Voltages

Fuse

Power consumption 14 Watts

Mains Connection Standard IEC receptacle

Europe ~230VAC, 50Hz

General Export Model

100-120VAC : 400mA (SLOW-BLOW)
200-240VAC : 200mA (SLOW-BLOW)

~100-120VAC,
~200-240VAC, 50-60Hz

PHYSICAL

Dimension W(483.0)*D(198.0)*H(44.2) mm

Net Weight 3.3Kg

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31 of

EASON YANG

RevisionModel No:

Drawn By:

Sheet

ACL2 PRO VER040820

16-Sep-2004

FP-CH1MN.Sch

COMPRESSOR : FRONT PANEL ( CH1 )

Titel

Size

A3

File:

Date:

-15V

T4-1

T3T4IC29-7

T3

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X20-3

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SW14-1

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CH1-LEVEL

CH2-REDUCTION

CH2-LEVEL

CH1-REDUCTION

CH1-LEVEL

CH2-REDUCTION

1

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CH2-REDUCTION

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CH2-LEVEL

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CH2

FP- CH2 SCH

THRESHOLD

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BR : 2SC2412(NPN)

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COMPRESSOR/LIMITER

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COMPRESSOR/LIMITER

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COMPRESSOR/LIMITER

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INETRACTIVE

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COMPRESSOR/LIMITER

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4148

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PS-22E85L

BYPASS

4

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12
11
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9
8
7
6
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3 3uF

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VR15

OUTPUT GAIN

SC MON

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7

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4

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R228

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1

3

3

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R201

R199

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LM339

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LD31

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HR

T16

RELEASE

HR

COMPRESSOR/LIMITER

2

IC23A

LM339

4

IC21A

TL064

2

R182

220K

TL064

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3

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7

8

SC EX T

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5

6

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PS-22E85L

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PS-22E85L

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6

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12

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RD

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7

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PS-42E85L

D30

I/O METER

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2

P

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PS-22E85L

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SW12A

PS-22E85L

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INETRACTIVE

D31

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13

P

5

6

2

3

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RD

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P

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R225

47K

R224

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PS-22E85L

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4

3

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R226

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D29

EXPANDER/GATE

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2

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12

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P

SW14B

PS-22E85L

I/O ME T E R

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4

R177

C24

2

R163

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-15V

3

YE

3

VR9

B50K

THRESHOLD

1

CH2-LEVEL

1uF

C48

IC 24D

TL064

17K4 1%

R153

R152

24K9 1%

P

5

6

LD66

GN

4K7

R176

10K

10N

R174

20K

10K

R175

T3-1

R171

3N3

C22

1:N RATIO

VR10

B10K

EXPANDER/GATE

D20

4148

D19

4148

20K

R167

3K

R166

R165

10K 1%

R162

523K 1%

10M

R158

R159

10K

C20

47P

10K

R157

47K

R155

14

IC19D

TL064

12

13

47K

R154

13

IC 18A

CA3086

2
9

1

1110

IC 19A

TL064

3

2

SW15A

PS-22E85L

1

BYPASS

9

IC20D

1

3

IC 18D

2

LD67

GN

8

IC 22C

TL064

10

14

TL064

12

13

8

D21

4148

C23

100K

9

10

R170

10K

2

1K5

R169

2K2

R168

7

IC 20B

TL064

5

6

7

IC 19B

TL064

5

6

R164

10M

-15V

R161

4K99 1%

8

IC19C

TL064

T4-1

9

10

R160

-15v

10M

R156

1413

12

4

6

CA3086

IC 18C

1

4148

PEAK LIMITER

2

8

2

THRESHOLD

HR : 2SA1036(PNP)

+15V

+15V

3

9

+15V

P

SW11D

PS-42E85L

10

INTERACTIVE

LD65

P

4

YE

SW11B

PS-42E85L

BR : 2SC2412(NPN)

D41

4148

D40

4148

R143

6 8K 1/4W

T13

HR

100K

R139

+15V

LD60

RD

COUPLE

LIM

LD52

RD

THRESHOLD

+15V

C31

0 22uF

2K2

R216

R215

2K2

R214

T17

BR

R188

523K 1%

6

R205

10K

2

3

VR16

P

SW13A

PS-42E85L

3

SW16A-2

14

13

1M

R173

680K

R172

2 2uF

IC 20C

C21

4M7

12

5 3

8 7

CA3086

1

AUTO

7

SW13C

PS-42E85L

IC 21D

TL064

-15V

RELEASE

EXPANDER/GATE

-15V 12

TL064

IC20A

TL064

3

1uF

D42

-15V

IC18E

CA3086

IC 18B

CA3086

D37

D36

T11

SW8B

C30

1M

4148

IC24A

7

A20K

11

5

PS-42E85L

R217

4 7uF/100V

4148

TL064

3

IC 24C

5

R206

EXPANDER/GATE

LD27

LD28

PM BFJ112

T3

4

1

TL064

10

IC24B

560K

12

6

RD

3

2

3K

-15V

2

8

1

P

P

THRESHOLD

GN

(-)

(+)

D39

G

D

T3-1

5

D38

R213

9

TL064

R207

-15V

LD63

4148

S

470R

GN

C32

4148

4K7

R212

R208

32 of

VER040820

EASON YANG

RevisionModel No:

Drawn By:

Sheet

ACL2 PRO

16-Sep-2004

FP-CH2.SCH

COMPRESSOR : FRONT PANEL ( CH2 )

A3

Titel

Size

File:

Date:

BR

T14

D49

-15V

6

P

4 7uF/100V

T3-1

4M7

47K

R210

47K

10

R144

6 8K 1/4W

-15v

47K

R142

47K

R141

-15V

1M

R140

1

PMBFJ112

T12

T4

T4-1

R138

4 7K 1/4W

BR

T18

4148

D35

47K

R211

D34

4148

D33

4148

R209

47K

IC29-7

11

12

P

SW8D

PS-42E85L

COUPLE

1 2 3 4 5 6 78

D

C

B

A

D

8

C

B

A

VER040820

33 of

EASON YANG

RevisionModel No:

Drawn By:

Sheet

ACL2 PRO

7654321

IC17E

IC16E

C38

+15V

C37

C36

C35

C34

411

TL064

312

LM339

47uF/50V

104P

104P

104P

104P

-15V

IC24E

IC23E

+15V

TL064

LM339

C44

47uF/50V

C43

104P

C42

104P

C41

104P

C40

104P

411

312

-15V

+15V +15V

16-Sep-2004

FP-LED.SCH

COMPRESSOR : FRONT PANEL ( DISPLAY )

A3

Titel

Size

File:

Date:

R48

30K

R49

47K

LD46

GN

LD47

LD44

GN

LD45

GN

10

4

LD43

14

IC9C

LM339

9

R51

100R

RD

1

IC8B

LM339

7

13

IC9D

R47

T4

HR

1 8K 1/4W

CH2

LEVEL(dB)

INPUT/OUTPUT

R32

15K

T3

HR

R31

1 8K 1/4W

LM339

11

R50

110R

R33

39K

2

IC8A

LM339

5

8

6

LD42

1

IC9B

LM339

6

7

200R

R52

RD

LD41

RD

14

IC8C

LM339

8

9

GN

2

LM339

IC9A

5

4

R53

402R 1%

RD

LD40

13

IC8D

LM339

10

11

IC10D

IC7A

GN

LD48

13

LM339

10

11

R54

806R 1%

RD

LD39

2

LM339

5

4

IC10C

IC7B

YE

LD49

14

LM339

8

9

R55

1K58 1%

LD38

1

LM339

6

7

LD50

1

IC10B

LM339

6

7

R56

3K24 1%

LD37

RD

14

IC7C

LM339

8

9

LD51

IC10A

IC7D

RD

R59

22R 1/4W

2

LM339

5

4

R57

LM339

11

6K34 1%

13

R58

8K06 1%

LD36

RD

2

IC6A

LM339

5

10

-15V

CH2-LEVELCH1- LEVEL

+15V

RD

LD35

4

RD

LD34

1

IC6B

LM339

6

7

RD

LD33

14

IC6C

LM339

IC6D

8

9

RD

LD32

13

LM339

10

11

-15V

CH2-REDUC TION

YE

RD

CH2

411

IC15E

TL064

411

IC14E

TL064

411

IC13E

TL064

411

IC12E

TL064

312

IC5E

LM339

312

LM339

IC4E

312

IC3E

LM339

312

IC2E

LM339

312

LM339

IC1E

R34

411

IC22E

TL064

411

IC21E

TL064

411

IC20E

TL064

411

IC19E

TL064

R30

C33

104P

22R 1/4W

312

IC10E

LM339

312

LM339

IC9E

312

IC8E

LM339

C39

R60

104P

22R 1/4W

R17

GAI N RE D U CT I O N (dB)

1 8K 1/4W

30K

R18

T2

CH1

312

IC7E

LM339

INPUT/OUTPUT LEVEL(dB)

312

LM339

IC6E

1K

R35

1K

R19

47K

GN

LD18

13

IC4D

HR

LM339

10

11

R20

110R

2K

R36

LD19

GN

14

IC4C

IC4B

LM339

8

9

100R

R22

R21

2K

R37

R38

3K

HR : 2SA1036(PNP)

BR : 2SC2412(NPN)

LD20

GN

LD21

1

LM339

7

200R

2

IC4A

LM339

6

5

4

R23

402R 1%

LD22

GN

13

IC5D

LM339

10

11

R24

806R 1%

R40

R39

3K

GN

IC5C

R25

3K

R41

3K

LD23

YE

LD24

YE

14

LM339

9

1K58 1%

1

IC5B

LM339

IC5A

6

7

8

3K24 1%

R27

R26

2

LM339

5

6K34 1%

4

R42

LD25

3K

R43

RD

R29

22R 1/4W

R28

8K06 1%

R44

3K

3K

+15V -15V

3K

R45

33K

R46

R2

15K

R3

CH1

CH2

+15V +15V

R1

1 8K 1/4W

39K

RD

RD

LD17

2

IC3A

T1

HR

LM339

5

4

LD16

RD

1

IC3B

LM339

6

7

LD15

RD

14

IC3C

LM339

8

9

RD

LD14

13

IC3D

LM339

10

11

RD

LD13

2

IC2A

LM339

5

4

LD12

1

IC2B

LM339

6

7

LD11

RD

RD

14

IC2C

LM339

8

9

RD

LD10

13

IC2D

LM339

10

11

LD9

2

IC1A

LM339

5

4

LD8

RD

1

IC1B

LM339

6

7

LD7

RD

14

IC1C

LM339

8

9

RD

LD6

13

IC1D

LM339

10

11

-15V

1 2 3 4 5 6 78

CH1-REDUC TION

CH1

3K

R15

R8

3K

R7

R5

R4

1K

1K

R6

2K

2K

R9

R10

3K

3K

3K

R11

3K

R12

R13

R14

3K

3K

R16

33K

GAI N RE D U CT I O N (dB)

D

C

B

A