L1® Compact
Portable Line Array System
Theory of Operation
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Service Manual |
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Reference Number 318882-TOP Rev. 00
Electronic Copy Only
L1 Compact - Theory of Operation
General
This document refers to schematic revision 01 for both the I/O Board and PS & Amp board.
The L1® Compact comprises a Power Stand base unit that houses input and output connectors and all electronics, a removable TwiddlerTM Array, and two extension sections used to raise the Twiddler Array to ear level when standing.
The electronics in the base are on two circuit boards: an I/O Board directly beneath the top cover, and the PS & Amp Board which is mounted vertically on the back wall of the enclosure.
I/O Connectors
•AC mains inputIEC connector
•XRL Microphone Input Jack
•1/8" Stereo Input Jack
•Two RCA Input Jacks
•¼” Balanced Input Jack
•¼” Line Out Jack
•Two RCA Line Out Jacks
Controls
•Power Switch - Switches the system on and off
•Mic Volume - Adjusts the Audio Output Level from the Microphone Input
•Mic Treble - Adjusts the Treble for the Microphone Audio Output
•Mic Bass - Adjusts the Bass for the Microphone Audio Output
•Channel 2 Volume - Adjusts the Audio Output Level from the Channel 2 Inputs:
-1/8" Jack, RCA Jacks, or ¼” Jack.
Indicators
•Power Indicator - Indicates power status: Blue = system on.
•Signal/Clip Indicator - Ch1 (Mic) and Ch2 - Indicates the level of the Audio Output:
-Green = Normal. Red = Over Maximum Audio Level.
Power Supply
The L1 Compact Power supply is a Flyback switching supply based on Power Integrations TOP258 which provides Under voltage, Over voltage, and Thermal Protection internally.
This produces four regulated DC Power Rails from the secondary: +28V and -28V for the amplifier (Philips / NXP TDA8920BTH) and +18V and -18V which are provided to the I/O board over the 10 pin ribbon cable. These +/-18V rails are post regulated on the I/O board to +/-15V by U315 & U316.
Diagrams – Pages 3 to 6
•L1 Compact Block Diagram
•L1 Compact PCB Layout
•L1 Compact I/O Board
•L1 Compact Channel 1 Input Section
•L1 Compact Channel 2 Input Section
2
L1 Compact - Theory of Operation
L1 Compact Power Stand Block Diagram
3
L1 Compact - Theory of Operation |
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L1 Compact PCB Layout |
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Brown = Line |
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Power Supply & Amplifier Board |
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Fuse |
NTC |
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Bridge & |
Power |
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Blue = Neut |
AC Line |
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ON |
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Main Caps |
Switcher |
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Filter |
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OFF |
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C1 & C3 |
TOP258 - U1 |
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IEC |
Yellow/Green |
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AC IN |
= GND |
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+28V |
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Amplifier |
-28V |
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Rectifiers |
Twiddler |
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Twiddler |
+18V |
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TDA8920BTH |
& Power Caps |
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Array |
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Bass |
-18V |
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I/O Board |
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Bass |
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Connector |
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Driver |
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Ribbon |
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I/O Board |
Cable |
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see next page |
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1 |
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2 |
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Volume |
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Volume |
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Treble
Bass
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Line |
Microphone |
Power |
Inputs |
Level |
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Line Out
4
L1 Compact - Theory of Operation
L1 Compact Input / Output Board
MIC Input & Pre-amp |
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1/8", RCA, & 1/4” Inputs & Pre-amp |
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see next page |
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see next page |
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CH1_TONE |
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CH2 Output |
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Schematic Sheet 2 |
U300A |
CH1 & CH2 SUMMER |
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Bass EQ
U308A-B
U309A-B
Bass Audio
High EQ
U301A-B, U302A-B U303A-B, U310B, U306B, U304B
High Audio
Schematic Sheet 3
Bass Limiter
U312A-B, U310A U500A-B, U312B
Bass Output
to Amp
U313B, U307B
High Limiter
U304A, U314B U391A-B, U306A
High Output
to Amp
U313A, U307A
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- |
+ |
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- |
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CN300A
Ribbon Cable to PS & Amp
Line Output
Driver
U317A-B
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+ |
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CN302A
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Line |
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CN302B |
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- |
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+ |
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Output |
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SG701, -02, -03, - |
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Spark Gaps |
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Card |
04, -05 |
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& EMI Filter |
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J301 |
- |
+ |
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J300 |
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¼” Jack (6MM) |
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RCA Jacks |
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+
5
L1 Compact - Theory of Operation
L1 Compact Channel 1 (Microphone) Input Section
Schematic Sheet 1
J100 |
Transistor Pre-Amp |
Mic Tone Match |
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Spark Gaps |
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SG100, SG101 |
Q101, Q102, Q103 |
U100A, U101A-B |
CH1 Output |
& EMI Filter |
Q104, Q105, Q106 |
U102A-B, U103B |
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& U100B |
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Microphone |
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VR100B |
VR100A |
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Volume
Schematic Sheet 2
CH1 Output |
Bass Adjust |
Treble Adjust |
CH1_TONE |
To CH1 & CH2 |
U103A, U104A |
U104B |
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SUMMER |
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VR101 |
VR101 |
Mic LED Driver |
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U106A-B, U107A-B |
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Bass |
Treble |
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L1 Compact Channel 2 Input Section
Schematic Sheet 1
3.5MM Jack Input Card
CN308B |
CN308A |
J200
RCA Jacks
U305A
Mic LED Driver
U300B, U205B,
U206A-B
Schematic Sheet 2
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Spark Gaps |
U305B |
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Ch 2 Volume |
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CH2 Output |
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SG202, -03, -04 |
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& EMI Filter |
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U205A, U204A |
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J202 |
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VR200B |
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1/4” Jack |
(6MM) |
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Pre Amp |
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VR200A |
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+ |
Spark Gaps |
+ |
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- |
SG200, SG201 |
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U501A-B |
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& EMI Filter |
U502B |
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U204B |
Select U207 |
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Tone Match |
Volume |
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U201A-B, U202A-B |
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6
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