Audio international AI-LDC1 User manual

7300 Industry Drive, North Little Rock, AR 72117
Phone: [phone] Fax: [phone]
www.audiointl.com
Installation Manual
AI-LDC, AI-LDC1, and AI-LDC2
Channel Stereo Pre-Amplifier
Document # 540044
a DeCrane Aircraft Company

Audio International, Inc. AI-LDC, AI-LDC1, AI-LDC2 Installation
Document # 540044, Rev. A, 11/2000 Page 1 of 12
Document Revision History
Rev. Level Date Description
IR 10/1997 Initial Release
A 11/2000 Layout Update
Reference Documents
Document # Description
521883 Rev IR AI-LDC Outline Drawing
521884 Rev IR AI-LDC1 Outline Drawing
521881 Rev IR AI-LDC2 Outline Drawing
Service Bulletin List
Service
Bulletin # Subject Manual Revision Revision Date
Table of Illustrations
Illustration # Description Page #
2.2 Block Diagram – Typical Application 5
6.0 Reference Drawings 11
PROPRIETARY INFORMATION NOTICE: Despite any other copyright notice, this document and
information disclosed herein contains confidential, proprietary designs owned by Audio
International, Inc. Neither this document nor the data contained herein shall be reproduced, used,
or disclosed to anyone without the written authorization of Audio International, Inc.

Audio International, Inc. AI-LDC, AI-LDC1, AI-LDC2 Installation
Document # 540044, Rev. A, 11/2000 Page 2 of 12
Table of Contents
Section Description Page
1.0 General Information …………………………………………….. 3
1.1 Introduction ………………………………………………………… 3
1.2 Purpose of the Equipment ……………………………………….. 3
1.3 Operational Features……………………………………………… 3
1.4 Optional Equipment ………………………………………………. 4
2.0 Application ………………………………………………………... 4
2.1 Introduction ………………………………………………………… 4
2.2 Block Diagram –Typical Application ……………………………. 5
3.0 Installation ………………………………………………………… 5
3.1 Prior to Installation ………………………………………………… 5
3.2 Unpacking and Inspection ……………………………………….. 5
3.3
Cautions &Warnings ……………………………………………... 6
3.4 Wiring Requirements ……………………………………………... 6
3.5 Physical Characteristics ………………………………………….. 7
3.6 Electrical Characteristics …………………………………………. 7
3.7 Mating Connector Information …………………………………… 8
3.8 Pinout Assignments and Descriptions ………………………….. 9
3.9 Post-Installation Test ……………………………………………... 10
4.0 Troubleshooting …………………………………………………. 10
4.1 General Troubleshooting Procedures …………………………... 10
4.2 Troubleshooting Chart ……………………………………………. 10
5.0 Specifications …………………………………………………… 10
6.0 Reference Drawings …………………………………………….. 11

Audio International, Inc. AI-LDC, AI-LDC1, AI-LDC2 Installation
Document # 540044, Rev. A, 11/2000 Page 3 of 12
AI-LDC, AI-LDC1, AI-LDC2
Channel Stereo Pre-Amplifier
1.0 General Information
1.1 Introduction
This manual contains information for the proper installation of the Audio
International, Inc. (AI) Channel Stereo Pre-Amplifier, Model No’s: AI-LDC,
AI-LDC1, and AI-LDC2. Also included are physical and electrical
characteristics of the unit.
1.2 Purpose of the Equipment
1.2.1 The AI-LDC is a stereo pre-amplifier especially designed for input
level matching and amplification. It is especially useful in
eliminating ground loop noise, common mode noise, and increasing
signal-to-noise ratios. The unit features differential inputs and
left/right gain control for balancing.
1.2.2 The AI-LDC1 is the AI-LDC with the added feature of remote
volume control with LED output. This feature is useful is useful for
providing volume control to fixed level audio sources such as
VCR’s, CD’s, and cassettes. Discrete, momentary ground inputs
may be used to increase or decrease the output level.
1.2.3 The AI-LDC2 combines two (2) AI-LDC units into one (1) housing.
This feature provides dual stereo preamplifier capability.
1.3 Operational Features
Listed below are key features of the AI-LDC:
q Source level matching
q Gain adjustment matches left and right audio output signals together
q Differential input
q Small case for ease in mounting

Audio International, Inc. AI-LDC, AI-LDC1, AI-LDC2 Installation
Document # 540044, Rev. A, 11/2000 Page 4 of 12
1.4 Optional Equipment
Audio International, Inc. offers a comprehensive family of Cabin Control
Modules. These modules provide convenient solutions for a variety of
frequently encountered interfacing needs or special requirements and are
an important part of AI’s “building block”system for configuring total cabin
management.
Contact your AI representative for details.
2.0 Application
2.1 Introduction
The AI-LDC is a stereo pre-amplifier designed for input level matching and
amplification. This audio component is built to rugged aircraft standards
and is easily incorporated into new or existing cabin audio systems. The
unit is useful for eliminating ground loop noise, common mode noise, and
increasing signal-to-noise ratios. The AI-LDC contains source level
matching, balance and amplification, differential input, and a small case
for ease in mounting.
The AI-LDC1 is identical to the AI-LDC with the added feature of remote
volume control with LED output. This feature is useful for providing
volume control to fixed level audio sources. A bar graph driver is provided
for volume level presentations. The correlation between the volume
setting and the bar graph driver is factory set but may be adjusted by the
customer. Two (2) methods of volume control are available. However,
only one (1) method may be used at one (1) time.
• Discrete, momentary ground inputs may be used to increase or
decrease the output level. Simply apply a ground to the volume up
or down input for the desired action.
• For potentiometer control, a voltage from 0 to +28 VDC will vary the
output proportionally. A 0 VDC input will correspond to minimum
output and a +28 VDC input will correspond to the maximum
output. A 10 k-ohm (0.5 watt) linear potentiometer is
recommended.
• Power up is at minimum volume.
The AI-LDC2 is two (2) AI-LDC units incorporated into one (1) compact
housing. This feature adds dual stereo preamplifier capability for use with
two (2) stereo sources. .

Audio International, Inc. AI-LDC, AI-LDC1, AI-LDC2 Installation
Document # 540044, Rev. A, 11/2000 Page 5 of 12
2.2 Block Diagram –Typical Application
3.0 Installation
3.1 Prior to Installation
3.1.1 Careful consideration of the location of this module is necessary
during the design and layout of the aircraft cabin. Some of the
items to be considered include:
• Space
• Available power supply
• Environmental conditions (temperature, humidity, etc.)
• Length of cable runs
3.1.2 The AI-LDC unit shall be installed to conform to the standards
designated by the customer, installing agency, and existing
conditions as to the unit location and type of installation.
3.1.3 Mounting screws are required to secure the unit. Refer to
Section 6.0, Reference Drawings, for mounting hole diameters and
configuration.
3.1.4 The unit shall be located to allow easy gain adjustments. Gain
controls shall be accessible for system adjustments and periodic
maintenance.
3.2 Unpacking and Inspection
3.2.1 Carefully open the packaging and remove the AI-LDC. Verify that
all components have been included in the package per the packing
list. Inspect the unit for shipping damage.

Audio International, Inc. AI-LDC, AI-LDC1, AI-LDC2 Installation
Document # 540044, Rev. A, 11/2000 Page 6 of 12
3.2.2 If damage has occurred during shipping, a claim should be filed
with Audio International WITHIN 24 hours and a Return Request
Authorization Number shall be obtained from AI. Refer to the
front cover of this manual for address and telephone number of
Audio International, Inc. Repackage the unit in its original
packaging materials and return it to AI following instructions given
by the AI representative. If no return is necessary, retain the
packing list and the packing materials for storage.
3.3 Cautions and Warnings
3.3.1 It is important to do a pin-to-pin power and ground check on all
connectors. Ensure that power and ground are applied only where
specified. Damage to the unit may result if power or ground is
applied to the wrong points.
3.3.2 DO NOT connect or disconnect the module while power is applied.
3.3.3 DO NOT remove any factory-installed screws. Damage to the units
may result and void any warranties.
3.3.4 ESD (Electro Static Discharge) guidelines shall be followed.
3.4 Wiring Requirements
3.4.1 Introduction
The installing agency shall supply and fabricate all external cables
and mating connectors. The length and routing of external cables
should be carefully studied and planned before attempting
installation of the equipment. Allow adequate space for installation
of cable and connectors. Avoid sharp bends and placing cables
near aircraft control cables. Maintain a MINIMUM clearance of
three (3) inches from any control cable. If wiring is run parallel to
combustible fluid or oxygen lines, maintain a separation of six (6)
inches between the lines.

Audio International, Inc. AI-LDC, AI-LDC1, AI-LDC2 Installation
Document # 540044, Rev. A, 11/2000 Page 7 of 12
3.4.2 Power Wires
All power and ground wires shall be 24 AWG, MINIMUM. Power
ground wires shall be grounded within twelve inches of the unit. All
wires shall be in accordance with the standard military specification
of MIL-W-22759 or equivalent. Protect power wires with circuit
breakers or fuses located close to the electrical power source bus.
3.4.3 Audio Lines
All audio lines require twisted, shielded cable with the cable shields
grounded at the source. Twisted shielded cable shall be in
accordance with the standard military specification of
MIL-DTL-27500 or equivalent.
3.5 Physical Characteristics
3.5.1 Refer to Section 5.0 for unit dimensions.
3.5.2 Refer to Section 6.0 for attachment points.
3.5.3 When mounting the unit, allow sufficient space for mating
connectors.
3.5.4 Gain controls are provided by single-turn potentiometers located on
the rear of the unit, opposite the connector. To increase the signal,
turn the potentiometers clockwise. To reduce the signal, turn the
potentiometers counter-clockwise. Use caution when adjusting as
excessive pressure and torque can damage the potentiometers.
3.6 Electrical Characteristics
3.6.1 One 25-pin provides +28 VDC power, left/right audio output, and
left/right audio input. The pin provisions are different for each
model. Refer to 3.8 for pinout assignments and descriptions.

Audio International, Inc. AI-LDC, AI-LDC1, AI-LDC2 Installation
Document # 540044, Rev. A, 11/2000 Page 8 of 12
3.6.2 Electrical Specifications
Electrical Power
(LDC & LDC2) +28 VDC at 300 mA, MAXIMUM
Power
(LDC1) +28 VDC at 500 mA, MAXIMUM
Input Signal Low-Level 200 mV to 2V,
differential
Output Signal
(LDC & LDC2) Low-Level 3V, MAXIMUM
Output Signal
(LDC) 2 to 10V, adjustable
Input Impedance 5 k
Frequency
Response 20 Hz to 20 kHz
Signal-to-Noise >90dB
Total Harmonic
Distortion
(LDC & LDC2) <0.01%
Total Harmonic
Distortion
(LDC1) <0.05%
3.7 Mating Connector Information
All wiring harnesses to the unit shall be supplied and fabricated by the
installing agency. All models utilize the same mating connector.
Part Number Description
DBMA-25S Mating Connector
DB24659 Backshell
D20419-18 Male Screwllock

Audio International, Inc. AI-LDC, AI-LDC1, AI-LDC2 Installation
Document # 540044, Rev. A, 11/2000 Page 9 of 12
3.8 Pinout Assignment and Descriptions
AI-LDC AI-LDC1
Pin # Description Pin # Description
1 +28 VDC Power In 1 +28 VDC Power In
2 Ground 2 Ground
3 R+ Audio Input 1 3 R+ Audio Input 1
4 R- Audio Input 1 4 R- Audio Input 1
5 L+ Audio Input 1 5 L+ Audio Input 1
6 L- Audio Input 1 6 L- Audio Input 1
7 N/C 7 R+ Audio Output
8 N/C 8 R- Audio Output
9 N/C 9 L+ Audio Output
10 N/C 10 L_ Audio Output
11 R+ Audio Output 11 Volume Up Switch
12 R- Audio Output 12 Volume Down Switch
13 L+ Audio Output 13 Potentiometer Control
14 L- Audio Output 14 #1 LED Output
15 N/C 15 #2 LED Output
16 N/C 16 #3 LED Output
17 N/C 17 #4 LED Output
18 N/C 18 #5 LED Output
19 N/C 19 #6 LED Output
20 N/C 20 #7 LED Output
21 N/C 21 #8 LED Output
22 N/C 22 #9 LED Output
23 N/C 23 #10 LED Output
24 N/C 24 LED Common +15 VDC
25 N/C 25 LED Common +15 VDC
AI-LDC2
Pin # Description
1 +28 VDC Power In
2 Ground
3 R+ Audio Input 1
4 R- Audio Input 1
5 L+ Audio Input 1
6 L- Audio Input 1
7 R+ Audio Input 2
8 R- Audio Input 2
9 L+ Audio Input 2
10 L- Audio Input 2
11 R+ Audio Output 1
12 R- Audio Output 1
13 L+ Audio Output 1
14 L- Audio Output 1
15 R+ Audio Output 2
16 R- Audio Output 2
17 L+ Audio Output 2
18 L- Audio Output 2
19 N/C
20 N/C
21 N/C
22 N/C
23 N/C
24 N/C
25 N/C

Audio International, Inc. AI-LDC, AI-LDC1, AI-LDC2 Installation
Document # 540044, Rev. A, 11/2000 Page 10 of 12
3.9 Post-Installation Test
2.9.1 Load the audio source with selected material. With the aircraft and
audio power “ON”, apply power to the unit.
2.9.2 Verify that the selected material may be heard through the
headphone and/or speaker system. Rotate the potentiometer
controls on the rear of the unit to increase/reduce the audio signal
as necessary.
4.0 Troubleshooting
4.1 General Troubleshooting Procedures
Many problems can be isolated with the following general techniques:
• To verify power to the unit, recheck +28 VDC power is applied to the
proper pins on the unit. Use a voltmeter to verify correct level.
• Reset by removing power from the unit for at least one (1) minute and
reapply power. Verify to see if the problem still exists.
• Recheck all connections to the unit for security. Check all harness
runs for possible pinching. Recheck all pinouts for application
accuracy.
4.2 Troubleshooting Chart
Problem Possible Cause Solution
No sound ½ Unit improperly
installed
½ No audio material in
source unit
• Verify +28 VDC power and audio
input is present
• Insert audio material in source
unit
Poor audio
quality ½ Audio controls are not adjusted properly • Adjust audio potentiometer
controls
5.0 Specifications
Physical Specifications
Housing Aluminum
Weight AI-LDC: 0.30 lb / 0.14 kg
AI-LDC1: 0.33 lb / 0.15 kg
AI-LDC2: 0.32 lb / 0.145 kg
Dimensions
(l x w x h) 3.1" x 5.0" x 1.05" 7.9 cm x 12.7 cm x 2.7 cm

Audio International, Inc. AI-LDC, AI-LDC1, AI-LDC2 Installation
Document # 540044, Rev. A, 11/2000 Page 11 of 12
6.0 Reference Drawings
6.1 The following diagrams show the unit dimensions and connector locations
for the AI-LDC, AI-LDC1, and AI-LDC2.

Audio International, Inc. AI-LDC, AI-LDC1, AI-LDC2 Installation
Document # 540044, Rev. A, 11/2000 Page 12 of 12
6.2 The following shows the REAR view of the specific models showing the
left and right gain control adjustment locations and bar-graph/balance
adjustment locations, if applicable.
AI-LDC
AI-LDC1
AI-LDC2