3
INTRODUCTION
The
E45
amplifier is designed for maximum reliability and minimum adjustment, as well as for top
quality sonic performance. Re-alignment will only normally be necessary after parts replacement in
the unlikely event of failure.
There are four PCBs contained within the basic unit (plus cross-over filters if fitted):
1. The main PCB (PCB710) containing the power amplification, which is located in the base of
the chassis.
2. The input PCB (PCB701) containing input, limiting and some control circuits.
3. The front panel display PCB (PCB703), which contains status LEDs and volume controls.
4. The power supply PCB (PCB712) switchmode power supply.
Refer to the relevant paragraphs for details of dis-assembly, repair, adjustments and re-assembly.
WARNING: REFER ALL SERVICING TO QUALIFIED PERSONNEL.
MAINTENANCE
All models incorporate filters in the air intake apertures. These should be cleaned or replaced
periodically, e.g. 6-12 months. The filter is fitted behind the blue front panel and can be replaced
without removing the front panel. The filter should be 'dry' cleaned, using a vacuum cleaner
preferably. Running the unit without a filter is not recommended unless it is within a 'clean room'.
Replacement filter material is available from MC
2
Audio.
No other regular maintenance is required.
NOTE: Any internal cleaning should only be carried out by a competent person.
CIRCUIT DESCRIPTION
1. GENERAL
The
E45
amplifier operates in modified class H with mixed bi-polar and FET output stages
powered from a switchmode power supply. This ensures optimum sonic quality and high
reliability. Full protection circuitry and preset limiting maintain the amplifiers within safe
operating parameters, even under adverse conditions. High quality, low noise operational
amplifiers are used through-out the pre-amp circuits, driving a hybrid IC/discrete output
amplifier.
PCB710, 701 - Circuit references are designated 1xx for Ch. A and 2xx for Ch. B. Single digit
and two-digit numbers are common to both Ch. A and Ch. B. In the following
description Ch. A references are given, with Ch. B references in brackets.
PCB703
- Circuit references are RR1-RR10 etc.
PCB712
- The power supply has 2 digit references and is dealt with in paragraph 7.
2. INPUT STAGE - PCB710, 701
* U101d (U201d) form a balanced input circuit with unity gain.
* CMR adjustment is by VR101 (VR201).
* J104 (J204) links the signal out to the crossover card when fitted. The signal then returns to
J103 (J203) on the gain control connections. The signal from the gain control then passes to
U101b (U201b).
