Theory Of Operation, Packlite Model A1 Amplifier - Bose PACKLITE A1 Manual

PackLite™ Model A1 Amplifier
1. General Overview
The Personalized Amplification System™ family of products currently consists of the PS1 power
stand, the L1 Cylindrical Radiator
can power up to two B1 bass modules. This is sufficient for most instruments with the exception
of some applications of bass guitar, drums (kick drum) and some types of recorded music
playback. For these types of instruments, an attractive solution is to provide an additional power
amplifier that can power two additional bass modules, and can be "daisy-chained" to power
additional modules. The A1 PackLite power amplifier is designed primarily for this application,
but also has the features required to be applicable as a general purpose power amplifier, spe-
cifically, input limiting and signal/clip LED indication.
The amplifier contains a line level input, a pass-through line-level output, and a switching power
amplifier optimized for a 4 ohm load. In its normal use, the amplifier drives one or two (8 ohm)
B1 bass modules. There are 120 and 230V versions for sale in the US and Europe/Australia.
2. Amplifier PCB Architecture
Note: Refer to the Amplifier Block Diagram, sheet 1 of 1 for the following. The information
inside the brackets [ ] is the schematic grid location on the sheet.
The amplifier comprises two PCB's, a Switch Mode Power Supply (SMPS)/Amplifier PCB and
an Input/Limiter PCB. The SMPS/Amplifier PCB filters the AC mains power, converts it to the
DC voltages required by the audio amplifier and the input/limiter PCB, and provides a switching
audio amplifier with 30 dB of gain.
The block diagram shows the amplifier board PCB architecture. The amplifier uses a three-wire,
grounded AC power configuration, with the cast aluminum chassis connected to earth ground.
Connectors
The amp pcb has connectors for AC power (con300) [C1], line-level audio in (J301) [C4],
speaker out (con301) [D4], control signals (J302) [B/C4], and DC voltage output (J303) [B4].
Switches
S301 [A3] is a DC bypass option for the ground connection, left open in production for best EMC
performance. S302 [A1] was a design option to allow a second grounding point on the board,
left closed in production for best EMC performance.
3. AC Power Input Filter Section
Note: Refer to the SMPS/Amplifier PCB Schematic Diagram, sheet 1 of 3 for the following.
L100, L101, C100, C109, C110, C111, and C112 [all located at B/C2] provide filtering to keep
radio frequencies off the power supply for compliance with FCC and EN55103 emissions re-
quirements. R102, R103, and R104 [B/C2] provide a DC discharge path for the capacitors on
the input to discharge when power is removed.
L100 and L101 are progresively wound common mode chokes with an impedance peak greater
than 450 kHz.
THEORY OF OPERATION
loudspeaker and the B1 bass module. The PS1 power stand
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