Abbingdon Music Research Dual Mono Pre-Main Amplifier AM-77 User manual

AM-77 Reference Class
Dual-Mono Pre-Main Amplifier
Owner’s Manual

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FCC Declaration of Conformity - United States only
This device complies with Part 15 of the FCC rules. Operation is subject to the following two conditions: (1) This device may not cause
harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.
FCCWARNING:
Changes or modifications to this unit not expressly approved by the party responsible for compliance could void the user's authority to
operate the equipment.
NOTE:
This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to Part 15 of the FCC Rules.
These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment
generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause
harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation.
If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off
and on, the user is encouraged to try to correct the interference by one or more of the following measures:
- Reorient or relocate the receiving antenna.
- Increase the separation between the equipment and receiver.
- Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.
- Consult the dealer or an experienced radio/TV technician for help.
Canadian Notice (Avis Canadien)
Class B Equipment
This Class B digital apparatus meets all requirements of the Canadian Interference-Causing Equipment Regulations.
Cet appareil numérique de la classe B respecte toutes les exigences du Règlement sur le matériel brouilleur du Canada.

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This products complies with the EMC Directive (89/336/EEC) and the Low Voltage Directive (73/23/EEC) issued by the Commission
of the European Community.
Compliance with these directives implies conformity to the following European Norms (in parentheses are the equivalent international
standards and regulations):
o EN55022 (CISPR 22) - Electromagnetic Interference
o EN55024 (IEC61000-4-2, 3, 4, 5, 6, 8, 11) - Electromagnetic Immunity
o EN61000-3-2 (IEC61000-3-2) - Power Line Harmonics
o EN61000-3-3 (IEC61000-3-3) - Power Line Flicker
o EN60950 (IEC60950) - Product Safety

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The exclamation point within an equilateral triangle is intended to alert the user to the presence of important
operating and maintenance (servicing) instructions in the literature accompanying this component.
This component weighs over 40 kilograms. Do not place this component on an unstable cart, stand, tripod,
bracket or table as the component may fall causing serious injury to a child or adult and serious damage to the
unit. An appliance and cart combination should be moved with care. Quick stops, excessive force and uneven
surfaces may cause the component and cart combination to overturn.
Any mounting of the device on a wall or ceiling should follow the manufacturer’s instructions and should use a
mounting accessory recommended by the manufacturer.
Read and follow all the safety and operating instructions before connecting or using this component.
All warnings on the component and in its operating instructions should be adhered to.
Retain this Owner’s Manual for future reference.
Do not use this unit near water; for example, near a bath tub, washbowl, kitchen sink, laundry tub, in a wet
basement or near a swimming pool.
Unplug the component from the wall outlet before cleaning. Never use benzine, thinner or other solvents for
cleaning; use only a soft damp cloth.
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WARNINGS

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Care should be taken so that objects do not fall, and liquids are not spilled into the enclosure through any
openings.
This component should be serviced only by qualifiedAMR service personnel when:
A. The power cable or the power input socket has been damaged;
B. Objects have fallen, or liquid has been spilled into the component;
C. The component has been exposed to rain or liquids of any kind;
D. The component does not appear to operate normally or exhibits a marked change in performance;
E. The component has been dropped or the enclosure has been damaged.
DO NOT ATTEMPT SERVICING OF THIS UNIT-YOURSELF. REFER SERVICING
TO QUALIFIED AMR SERVICE PERSONNEL
Upon completion of any servicing or repairs, request the service point’s assurance that only AMR Authorised
Replacement Parts with the same characteristics as the original parts have been used, and that the routine
safety checks have been performed to guarantee that the component is in a safe operating condition.
REPLACEMENT WITH UNAUTHORIZED PARTS MAY RESULT IN FIRE,
ELECTRIC SHOCK OR OTHER HAZARDS

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On placement
With a total of 2 thermionic electron valves, the AM-77 may become warm during operation. This is normal.
Given this, it is imperative that theAM-77 when installed, its location or position DOES NOT interfere with its
properventilation.
For example, it should not be situated on a bed, sofa, rug or similar surface that may block the top or bottom
ventilation openings; or placed in a built-in installation, such as a bookcase or cabinet, that may impede the flow
of air through its top and bottom ventilation openings.
Do not place the component in a location near heat sources, or in a place subject to direct sunlight, excessive
dust, or mechanical shock. Do not place the component in an inclined position. It is designed to be operated in a
Precautions
This equipment has been tested and found to comply with the limits set out in the EMC Directive using a
connection cable shorter than 3 metres.
On power sources
The mains power cable should be routed so that it is not likely to be walked on or pinched, especially near the
plug or back panel receptacle. The component should not be disconnected from theAC power source as long as
it is connected to the wall outlet, even if the component itself has been turned off.
If this component is not going to be used for a long time, be sure to disconnect the component from the wall
outlet. To disconnect the AC power cable, grasp the plug itself; never pull the cable.
CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN
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horizontal position only. Do not place heavy objects on the component.
Keepthe component awayfrom equipment withstrong magnets, suchas microwave ovens orlarge loudspeakers.
To prevent fire or shock hazard, do not place vessels filled with liquids, such as vases, on the component.
Touch-Sensitive Buttons
On the front fascia of this AMR component are touch-sensitive buttons. Due to the wide variance of climes
around the world, instances may arise where to activate a button:
- the touching finger may be required to be in contact with both the button and the front fascia to register;
- the touching finger may have to touch the chassis to discharge any static electricity prior to button selection.
Running-In
AMR estimates that theAM-77 may take between 300-500 operating hours for all of the internal components to
be fully-broken in. Please anticipate the sonic performance of theAM-77 to settle only after it has been used for
this approximate length of time.
Stand-By
Please note that the solid state section needs to find its equilibrium and due to the (unavoidable) use of electro-
lytic capacitors (and an effect called soakage) around 24-48 hours of ‘standby’ (or operation) are required to
stabilise performance. Therefore, ‘standby’ does not shut down the solid-state sections, only the valves.

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Contents
WARNINGS 5
Section 1 - Unpacking and Setup 11
1a. Unpacking 12
1b. Setup
Section 2 - Component Overview 15
2a. Start-Up
Section 3 - Advanced Features 25
3a. Labeling of Inputs and Setting Level Offset 25
3b. Setting Fixed Input Level 28
3c. OptiMains® Protection for Excessive Under/Over-Voltages 30
3d. OptiProtect® Speaker Overload Protection 31

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Section 4 - System Configurations 33
4a. OptiOperation® Different System Configurations 33
4b. Switching and Connection Diagrams for Different Modes 41
Section 5 - Additional Connectivity 53
5a. Input for iPod/other portable music players 53
5b. ‘HiFi/Pro’ Switches for Balanced XLR inputs 54
5c. RS232 ‘Options’ Connector 55
Section 6 - Technical Features 57
Appendix - Troubleshooting & Maintanence 58
Troubleshooting 58
Maintenance 58
Specifications 59