Self-Powered Concert Series
Service Manual
MP-2/4 Amplifier
Doc #: 05.033.040.01
Rev.: A
Date: 08/31/98
Page: 10 of 26
© 1998 Meyer Sound Laboratories, Inc. All rights reserved.
The 10-pin ribbon cable from the XLR board widens to 16 wires where it interfaces with the
Communications module which then continues to the TPL Control Board. The extra 6 lines
feed signals, such as output voltage and power, from the Amplifier/Heatsink module and the
TPL Control board to the Communications module. The 10 lines which connect to the Audio
Input board are also monitored by the Communications module for limiter activity and
polarity switch positions.
In the case of the MP-4, the ribbon cable expands to 21 lines (staggered on the 26 pin
connector). Of those 21 lines, 5 lines split off to connect to the second TPL Control Board
(allowing the additional signals to be monitored).
Additionally, the Communications module has a 9 pin power cable connecting to the Power
Supply board which provides supply voltages and fan current monitoring for the network.
4) TPL Control Board:
The TPL Control Board contains a chain of signal processing stages which produce a
complex amplitude and phase response for each channel. The TPL Control Board also provides
TruPower™ Limiting voice coil protection. This module is unique to each product in the Self-
Powered Concert Series. Amplifiers can be re-configured by simply changing this module with
another TPL Control Board (e.g. MSL-4 to a 650-P).
Audio signal from the Audio Input board is fed into a differential amplifier on the TPL
Control Board. Output from the differential amplifier is input into a Pre-Filter stage and is also
fed back to the Communications module (for monitoring input level). The Pre-Filter stage
filters "out-of-band" signals and on some versions includes pre-equalization prior to channel
separation. After filtering, the audio signal is fed to a Crossover stage to separate the signal into
its High and Low Channel components. Once separated, the signal goes thru a Phase Delay
Alignment stage (the MSL-4 and MSL-6 use an additional daughter board to provide a greater
amount of required phase delay). The signal is then passed to a Post Filter stage which sets the
complex response and overload parameters. After filtering and phase alignment, the signals
are fed to the TPL Limiter stage.
Note: On subwoofers, the low channel is fed into an Over Excursion Protection stage prior to the TPL
Limiter stage.
The TPL Limiter stage receives feedback from the TPL Detector (located on the TPL Control
Board), which monitors voltage and current on the Amplifier/Heatsink module (see sheet 2).
With this information, the TPL Limiter stage is able to provide very accurate limiting based on
the power absorbed by the voice coil. In addition, the TPL Limiter stage drives the limiter
LED's on the Audio Input board.
After the signal in each channel is fed thru the TPL Limiter stage, it passes thru an "unmute"
relay prior to being sent to Amplifier/Heatsink module. During normal power-up, these relays
pass the audio signal after receiving a signal from the "turn-on delay" circuit (see #2 - AC Mains
module).
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