Page 1
2 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 Twiddler TM 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 input- IEC 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 ampli-
fier (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
L1 Compact - Theory of Operation
