Baldwin Boxall A120 Operating Instructions Manual

A120

IA120

Issue 1 13/06/2001

Adept 120W Modular Amplifier

Operating Instructions

Baldwin Boxall Communications Ltd.

Wealden Industrial Estate, Farningham Road
Crowborough, East Sussex, TN6 2JR

Telephone: [phone] Fax: [phone]
Website: www.baldwinboxall.co.uk
Email: [e-mail]

C O M M U N I C A T I O N S

A120 MODULAR AMPLIFIER

The A120 is a modular amplifier mainframe that can accept up to 8 input modules and 1
output module to suit most Public Address requirements.

The A120 can be either mains (230V) or battery (24V) operated, and can be fitted with an
internal 1 amp battery charger AC1A (optional).

Preparation for Use

AC Supply

Connect to mains socket on rear of amplifier using the lead supplied.
IMPORTANT: This equipment must be earthed.

Loudspeaker Output DC Supply Input (battery)

The amplifier provides connections 23V – 30V DC. Note: Negative Earth
for either 100V or 50V line

Sub-Socket

The sub-socket found on the rear of the unit can be used for a variety of purposes: tape
recording, feeding other Adept amplifiers, feeding mixers, operating busy lamps, relays etc.

Pin 1 Provides 500mV signal output for
driving slave amplifiers or a tape recorder.
This output is direct from the power amplifier
input and after the master gain and tone
controls.

Pin 2 Output Signal Ground

Pin 3 As pin 1 but signal is derived prior to master gain and tone controls. Output impedance

10K ohms.

Pin 4 Open collector ‘busy’ indicator: 0V switched output used in conjunction with pin 5.

Pin 5 1A fused DC output at +24V, used in conjunction with pin 4 to provide an electrical

relay control supply for zoning purposes, priority circuit indicators or DC power for an
external tuner or signal processing and line pre-amplifiers.

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Fitting Input (IMP) and Mixer (MS) Modules

Input Pre-amplifiers, Mixer Stages and
lnfill (BP) Front Panels are inserted into
the front of the amplifier by slackening
the four self-tapping screws (two on
either side) which hold the top
aluminium extrusion in place. Raise
the front of the extrusion and insert the
module by locating bottom tab on
module into the bottom extrusion and
press the PCB into the edge connector.
When all Pre-amplifiers, Mixer Stage
and lnfill Panels are in position re­locate top extrusion and secure. See
diagram below.

Prior to inserting inputs ensure that the
dual in line switch has been adjusted in
accordance with the notes on later
pages - see relevant IMP data.
All input modules have detachable
knobs and spindles, thus any input
module can be converted to a pre-set mode.

NOTE: Ensure that AC and DC power are disconnected before removing or inserting modules.

Rear Panel Connections

See relevant IMP or MS instruction manual for connection details.

MS and PA Dual Bus Lines

The input mother board on all mixer amplifiers has 2 Bus Lines, which are selectable via the DIL
switch on most IMP modules.
Audio routed on the MS Bus passes through tone and gain controls on the MS stage.
Audio routed on the PA Bus pass directly to the power amplifier stage via a level raising amplifier on
the mother board itself.
This bus is normally used to route critical audio signals such as 20 KHz for line surveillance,
emergency announcements and alarm signals.
The following IMP modules feed this bus automatically IMP20, 21, and 33.
An MS1 need not be fitted if the MS Bus is not required.
If any of the IMP modules are configured to use the MS bus, then an MS stage must be fitted.

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A120 Technical Specification

Rated Output Power (RMS)

1

120 Watt 83 Ohms
Output Voltages Obtainable 50V & 100V
Output Regulation <1.3dB
Distortion (1KHz @ rated output)

1

<0.5%
Frequency Response –3dB @ 30Hz – 20KHz
Input Sensitivity Depends on IMP module used
Output noise (ref rated output) -80dB
Supply Voltages

AC Supply 50 – 60Hz 220 – 240V
DC Supply 23 – 30V

Power Consumption

Quiescent AC 18VA
Quiescent DC 0.25A
Rated Output @ 1KHz, AC 300VA
Rated Output @ 1KHz, DC 9A

Fuse Protection

AC 5 x 20mm 3.15A (T)
DC 6.3 x 31.75mm 10A (F)
Battery 6.3 x 31.75mm 10A (F)
24V DC Aux output 5 x 20mm 1A (F)

Terminations

AC Supply Input 3 pin DIN - IEC 6A
DC Supply Input (battery) 3 pin screw terminated connector
Signal Input 240 deg 5 pin DIN locking
Aux Input / Output 240 deg 5 pin DIN locking

2

2

Loudspeaker 3 pin screw terminated connector

Dimensions

Depth (front to rear) 380mm (15”)
Width (rack mounting) 482.6mm (19”)
Width (free standing) 455mm (18”)
Height 88mm (3½”) 2U

Weight 7.6Kg (16¾ lb)

1

230V AC Supply

2

For connection details see relevant IMP instruction manual

Installation Notes

The front of the amplifier is completed by the insertion of a combination of Input Modules and Infill Panels (BPl,

1.

BP3).

2. When a pre-amplifier is fitted, a Mixer Stage is normally used.
Always ensure amplifier is turned off when inserting modules.

3.

4. Always earth equipment.

5. Ensure correct fuses are inserted.

Provide adequate air-flow around amplifier.

6.

7. When fitting DIN plugs, ensure screen connection does not touch the casing of the plug, thus avoiding earth loops.

AVOIDING GROUND LOOPS: As supplied all Adept main frames have the common
negative battery supply input bonded to the chassis, mains earth. For some applications it
may be necessary to remove this bond to avoid for example ground loops by disconnecting
the green yellow wire between pin 4 of input socket 8 and the chassis.
Ground loops on a system will cause a line frequency hum to be produced from the
loudspeakers and is best avoided using isolated input modules (for example IMPX selected
to line input, etc) especially if inputs are required to be wired in parallel.

Low Voltage Directive
73/23/EEC as amended
by 93/68/EEC

EMC Direct ive
89/336/EEC as amended
by 92/31/EEC and 93/68/EEC

Applies only when the items
are correctly fitted and operated
in or with products of our
manufacture and are installed
in a recommended enclosure

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