Cloud MPA SERIES Installation And User Manual - User Manual

Download PDF User Manual

Full Text Searchable PDF User Manual

MPA SERIES

MIXER-AMPLIFIER

Installation and User Guide

MPA Series User Manual v1.2

Safety Information ........................................ 4

Safety Notes regarding Installation ........................4

Conformities .................................................. 4

Safety Considerations and Information ................4

Caution - High Voltages ............................................4

Caution - Mains Fuse ................................................4
Caution - Servicing ....................................................4

General Description ...................................... 5

Schematic Diagram ...................................... 5

Front Panel Description ............................... 6

Rear Panel Description ................................. 6

Music Inputs ................................................... 7

Sensitivity & Gain Control .......................................7

Music Source Select ..................................................7
Music Level Control ..................................................7
Remote Control of Music Source .........................7

Select and Level ..........................................................7

Music Equalisation ......................................... 8

Music Priority ................................................ 8

Microphone Inputs ........................................ 8

Gain Control ...............................................................8
Microphone Access Input .........................................8

Front Panel Microphone Level Controls ..... 8

Microphone Equalisation .............................. 8

Microphone Priority ...................................... 9

Microphone over music priority ............................9
Mic 1 over Mics 2-4 priority ...................................9

Chime ............................................................. 9

Power Amplifier Stage and Outputs............ 9

Line Output .................................................................9
Low impedance operation .......................................9

High pass filter

..........................................................10

Music Mute(Fire Alarm Interface) ............. 10

Bose® Equalisation Modules ..................... 10

Installation Instructions ..........................................10

General Notes ............................................. 11

Multi-zone Applications ..........................................11

EMC Considerations ...............................................11
Earthing ......................................................................11

Ventilation ..................................................................11

Technical Specifications .............................. 12

Location of internal jumpers, etc. .............. 13

Factory Default Jumper Settings ...........................13

Contents

MPA Series User Manual v1.2

Safety Information

Safety Notes regarding Installation

•

Do not expose the unit to water or moisture.

•

Do not expose the unit to naked flames.

•

Do not block or restrict any air vent.

•

Do not operate the unit in ambient temperatures above

•

Do not touch any part or terminal carrying the

hazardous live symbol ( ) while power is supplied to

the unit.

•

Do not perform any internal adjustments unless you

are qualified to do so and fully understand the hazards

associated with mains-operated equipment.

•

The unit has no user-serviceable parts. Refer servicing

to qualified service personnel.

•

If the moulded plug is cut off the mains lead for any

reason, the discarded plug is a potential hazard and

should be disposed of in a responsible manner.

For more detailed information refer to the rear of the manual.

Safety Notes

Conformities

This product conforms to the following European EMC

Standards:

BS EN 55103-1:1997
BS EN 55103-2:1997

This product has been tested for use in commercial and
light industrial environments. If the unit is used in controlled
EMC environments, the urban outdoors, heavy industrial
environments or close to railways, transmitters, overhead
power lines, etc., the performance of the unit may be
degraded.
The product conforms to the following European electrical
safety standard:

BS EN 60065:2002

The MPA Series was developed and manufactured with high
quality materials and components, which can be recycled
and/or reused.
The WEEE symbol indicates that

electrical and electronic equipment

must be disposed of separately from

normal waste at the end of its

operational lifetime.
Please dispose of this product by taking it to your local
collection point or recycling centre.

Safety Considerations and Information

The unit must be earthed. Ensure that the mains power

supply provides an effective earth connection using a three-

wire termination.
When the mains switch is in the off ‘O’ position the live

and neutral conductors of the mains transformer are

disconnected.

Caution - High Voltages

Do not touch any part or terminal carrying the hazardous

live symbol ( ) while power is supplied to the unit.
Terminals to which the hazardous live symbol refers require

installation by a qualified person.

Caution - Mains Fuse

Replace the mains fuse only with the same type and rating as
marked on the rear panel.
The fuse body size is 20mm x 5mm.

Caution - Servicing

The unit contains no user serviceable parts. Refer servicing

to qualified service personnel. Do not perform servicing

unless you are qualified to do so.

Disconnect the power cable from the unit before removing

the top panel and do not make any internal adjustments with

the unit switched on.
Only reassemble the unit using bolts/screws identical to the

original parts.

MPA Series User Manual v1.2

fig.1: MPA Series Schematic Diagram

General Description

The Cloud MPA Series is a range of mixer-amplifiers with applications in Licensed, Retail, Leisure and similar venues.

Three models are available to suit different output power requirements (60, 120 or 240 watts); otherwise all models have

identical facilities.

The mixer-amplifiers have inputs for six stereo line signals and four microphone signals. Front panel controls are provided

for music source selection, music level and microphone levels. All pre-set controls are located on the rear panel with further

configuration jumpers mounted on the main PCB.

A remote level control or combined level control/music source selector can be wired to the unit for installations that require
remote control.

Schematic Diagram

MPA Series User Manual v1.2

Front Panel Description

MIC LEVEL 1 to 4

- level controls for Mic Inputs 1

to 4

MUSIC SOURCE

– selects active Line Input

(1 to 6)

MUSIC LEVEL

– adjusts level of selected Line Input

PEAK –

illuminates if Mic or Line signals level are too

high

MUSIC MUTE –

illuminates when external

Emergency Mute is active

MAINS –

AC power switch with LED

Ventilation slots –

forced-air cooling air intake

Rear Panel Description

LINE 1 to LINE 6 –

stereo line inputs for music

sources

GAIN 1 to GAIN 6 –

level trims for each line input

MUSIC EQ –

LF and HF EQ adjustment for music

channel

MIC 1 to MIC 4 –

balanced mic inputs

GAIN 1 to GAIN 4 –

level trims for each mic input

MIC EQ –

LF and HF EQ adjustment for mic channel

ACCESS –

external paging control input for

Mic 1

LOW IMPEDANCE OUTPUT –

speaker output

for low-Z connection

LINE OUTPUT –

for connection of 100 V/

70 V/25 V line distribution system

MUSIC MUTE –

Emergency control input for muting

music source

REMOTE MUSIC CONTROL – f

or connection of

RL-1 or RSL-6 remote control panels

REMOTE/LOCAL –

disables front panel controls

when remote control is in use

IEC mains input

Mains fuse

Fan –

forced-air cooling air exhaust

PEAK

MUSIC

MUTE

POWER

LEVEL

MAINS

OFF

fig.2: MPA Front Panel

fig.3: MPA Rear Panel

MPA Series User Manual v1.2

Music Inputs

The unit has six stereo line inputs; these inputs are suitable

for most music sources such as compact disc players, tape

players, satellite receivers and the like. Each stereo input is

summed internally to mono.
All inputs are unbalanced and use RCA phono sockets. The

input impedance is 47k ohm.

Line 6 input can be configured to have priority over any

other music source, see Music Priority, page 8.

Sensitivity & Gain Control

All six stereo line inputs have a preset gain control on the

rear panel adjacent to the respective input sockets. The gain

control has a range of 20 dB allowing the input sensitivity to
be varied from -12 dBu (200 mV) to +8 dBu (2.0 V).

The preset gain control should be adjusted so that all the

input signals are operating at the same level and that the

front panel level control has an optimum range of control.

Music Source Select

This front panel six position switch is used to select the

desired music signal. Remote control of source selection is

possible with a remote control plate (RSL-6), See

fig.4

Music Level Control

A front panel mounted music level control is provided.
Remote control of music level is possible by connecting a

remote control plate (either RSL-6 or RL-1), See

fig.4

Remote Control of Music Source

Select and Level

The MPA Series mixer-amplifiers are compatible with

standard Cloud remote control plates Types RSL-6 (music

source select and level) and RL-1 (level only).
Either type of plate may be connected at the rear 3-pin
5 mm-pitch screw terminal connector (Remote Music

Control), using the wiring shown in

fig.4

Use two-core (RSL-6 or RL-1) or single-core (RL-1 only)
screened cable to connect the remote level plate (max

length 100 metres).
Pressing the button adjacent to the rear panel connector

activates the remote control plate and disables both the

front panel level and source select controls. If an RL-1 is

being used, the internal jumper J4 should be moved from

its default ‘SW’ setting to ‘FR’, to override the disabling of

the front panel source select switch. See

fig.7

for location of

jumpers.

1 2 3

REMOTE MUSIC

CONTROL

CONNECTOR

1 2 3

REMOTE LEVEL CONTROL WIRING

RL-1

SINGLE-CORE SCREENED CABLE MAY BE USED

1 2 3

REMOTE MUSIC

CONTROL

CONNECTOR

1 2 3

REMOTE SOURCE & LEVEL CONTROL WIRING

RSL-6

USE TWO-CORE SCREENED CABLE

fig.4: RL-1 and RSL-6 Wiring

SCN

BALANCED CONNECTION

UNBALANCED CONNECTION

MIC INPUTS

PIN 1: SCREEN (GROUND)

PIN 3: HOT/PHASE (+)

PIN 2: COLD/ANTIPHASE (-)

fig.5: Microphone Input Wiring

MPA Series User Manual v1.2

Music Equalisation

One set of independent bass and treble controls is provided

for the music signals. These preset controls are located

on the rear panel below the line input sockets. The treble

control has a range of ±10 dB at 10 kHz and the bass
control has a range of ±10 dB at 50 Hz.

Music Priority

A Juke Box, Digital Sound Store or other audio source can

be given automatic priority over all other music inputs by

connecting it to Line 6 input and moving internal jumpers

5A and 5B from the OFF position (factory default) to the

ON. When this mode of operation is selected, the unit

will operate normally until a signal is detected on Line 6,

when the selected source (usually background music) is

muted, allowing the source connected to Line 6 to replace
it. Once the signal on line 6 stops, the selected source will

smoothly restore to its former level. The time taken for the

restoration is set in the factory at 3 seconds, but it may be

set at 6 or 12 seconds with internal jumper J7. (3s is suitable
for announcements, but the longer times may be more

appropriate when a jukebox or similar is the Line 6 source.)

See

fig.7

for location of jumpers.

Microphone Inputs

Four microphone inputs are provided; the microphone pre-

amplifiers are an electronically balanced, transformer-less
design configured for optimum low noise performance. The
input impedance is greater than 2 kΩ and is suitable for
microphones in the 200 Ω to 600 Ω range.

Inputs are via 3-pin 3.5 mm-pitch screw terminal connectors
on the rear panel.
Connect microphones as shown in

fig.5

. Note that if using an

unbalanced microphone, pins 1 and 2 should be connected
together.
Phantom power is available on any or all of the mic inputs,
and is activated by setting internal jumpers J9 to J12 (for
mic inputs 1 to 4 respectively) to the ON position. See

fig.7

for location of jumpers.
Care should be taken to ensure that phantom power is
activated only when the microphone connected to the
input requires external phantom power; damage to the
microphone may result otherwise.

Gain Control

A mic gain control (of the preset type) is provided adjacent
to each input connector.

The gain can be adjusted from 10 dB to 50 dB. A high

overload margin is maintained at all gain settings.

Microphone Access Input

Mic input 1 is equipped with an external access control

input; this is a 2-pin 5 mm-pitch screw terminal connector

adjacent to the Mic input 1 connector. The access input

is primarily intended to provide compatibility with paging

microphones and their associated switching arrangements.

By default, the access function is bypassed.

To use the function, it must be enabled by moving internal

jumper J13 from its default ON setting to OFF. See

fig.7

for

location of jumpers. Once enabled, the microphone input

is muted while the pins of the access connector are open-

circuit. When the pins are connected together, Mic input 1

becomes active for use.

The access input can also trigger the following functions:

•

Mic 1 Priority over Mics 2-4

Activation of Mic 1 via the access input will give Mic 1

priority over Mics 2, 3 and 4 if internal jumper J8 is set

to ON. See

fig.7

for location of jumpers. See also Mic 1

over Mics 2-4 priority, page 9.

•

Chime

The internal chime generator will be activated if internal
jumper J1 is set to ON. See

fig.7

for location of jumpers.

See also Chime, page 9.

Front Panel Microphone Level
Controls

A separate level control is provided for each mic input and
these provide the user with a convenient means of adjusting
the audio level of the microphones.
The microphone signals are routed directly to the power
stage and are unaffected by the operation of the music level
control.
The gain controls on the rear panel (see Gain Control)
should be set at a level where microphone distortion does
not occur even when the front panel level controls are fully
clockwise.

Microphone Equalisation

The four microphone inputs are summed together and are

routed to the power stage via a fixed high pass filter and
an adjustable EQ section. The fixed filter attenuates the

signal below 100 Hz, which helps to reduce the effects of
microphone handling noise.
The two preset EQ controls are on the rear panel adjacent

to the mic inputs; the LF and HF controls provide ±10 dB

of adjustment below 100 Hz and above 5 kHz respectively.
After installation, some test announcements should be made,

MPA Series User Manual v1.2

ideally by the people who will normally make them. The Mic

EQ should be adjusted if necessary to maximise voice clarity.

Microphone Priority

MPA Series mixer-amplifiers provide two separate

microphone priority functions. One of these enables the

microphones to have priority over music, the other allows

Mic 1 to have priority over the other microphones.

Microphone over music priority

Fully automatic voice operated priority (VOX function) is

available for the microphone signals. This function is enabled

by internal jumper J6 (default setting is ON). When enabled,

the music signal is automatically attenuated by 30 dB when

a microphone signal is detected, allowing the message to be
clearly heard. Normal music operation is restored smoothly

after the announcement ends.
Note that the presence of a signal on any of the four mic

inputs will operate this function.

Mic 1 over Mics 2-4 priority

If internal jumper J8 is set to ON (the default setting is

OFF), Mic inputs 2, 3 and 4 will be muted whenever the
Microphone Access Input is enabled. This ensures that Mic 1

will always have priority over any other microphones in use

when Mic 1 is used for paging.
Note that if jumper J13 is left at its default setting of ON,

Mics 2, 3 and 4 will be permanently disabled by this function,
leaving Mic 1 as the only active microphone input.

Chime

The MPA Series amplifiers have an internal pre-

announcement chime generator. The chime is triggered by
the Microphone Access Input, if enabled by jumper J1 being
set to ON. J1’s default setting is OFF.
An internal preset rotary control is provided to adjust the
chime volume; the front panel level controls have no effect
on the chime level. See

fig.7

for locations of internal controls.

Power Amplifier Stage

and Outputs

Line Output

The MPA Series amplifier’s output stage incorporates

an output transformer suitable for driving 100 V, 70 V or

25 V line speaker distribution system. The secondary (output

side) of the transformer is permanently wired to the line

output connector (a 4-pin 5 mm-pitch screw terminal type).

A safety cover is fitted over the connector, which may be

removed to connect the speaker cable. Replace the cover

after the connection has been made.
The transformer secondary has 3 line outputs: 100 V, 70 V
and 25 V; while these have a common 0 V connection, the

output is fully floating i.e., it is isolated from the rest of the

amplifier. The maximum total combined load should not

exceed the rated power for the amplifier model (see table

below).
When driving 100/70/25 V line circuits, it is strongly

recommended that the amplifier’s 65 Hz high pass filter is

set ON (see High pass filter - page 10).

Low impedance operation

To convert the amplifier to low impedance operation, the

primary winding of the toroidal transformer nearer the

rear of the unit should be unplugged from CON8 on the

main pcb (a short pair of heavy red and black wires), and
replaced by the spare plug connected to the rear panel low
impedance output socket (same wire types). Refer to

fig. 7

(page 13) for the location of this connector. Note that the
100/70/25 V line outputs will no longer be available once
the transformer is unplugged even though the transformer
secondary is still connected to the line output connector.
The low impedance output is available on a 2-pin 5 mm-pitch
screw terminal connector on the rear panel. Note that one
of the output pins is connected internally to 0 V.

The MPA Series amplifiers are able to deliver their rated

power into a 4 ohm load, as follows:

Model

Rated Power

MPA60

60 watts

MPA120

120 watts

MPA240

240 watts

The maximum output power will be reduced with higher
load impedances. When using multiple low-impedance

loudspeakers (normally 8 ohms) with a single amplifier, series

and parallel wiring should be employed to produce a total
load impedance of not less than 4 ohms.

MPA Series User Manual v1.2

High pass filter

A high pass filter is provided to protect speakers,

transformers etc. from the effects of low frequency signals.

The filter is enabled by the internal jumper J2 (see fig.7

). The

filter reduces the output level of frequencies below 65 Hz,

and ideally should be used if the line output transformer is
in circuit.

Music Mute

(Fire Alarm Interface)

In some installations (such as licensed premises or retail

outlets within a shopping mall), there may be a local

authority or fire service requirement to mute the music

signals from a fire alarm control panel when an alarm

condition arises. The MPA Series amplifiers include a

facility to mute the music signals only (i.e., mic inputs are

still active), via the Music Mute input. This is a 2-pin 5 mm-
pitch screw terminal connector on the rear panel, and the

contacts are fully isolated.
Activation of the Music Mute is often via a relay mounted

close to the MPA Series amplifier, powered by the fire alarm

control panel. Other arrangements may exist depending

on the design of the fire control system and the fire alarm

installation company should be consulted when making the

connection. The MPA Series amplifiers will mute on either a

contact closure at the Music Mute input (NO) or an open-

circuit (NC). Selection of NO or NC operation is made with
internal jumper J14. NO is the factory default. See

fig.6

Bose® Equalisation Modules

MPA Series amplifiers are compatible with single channel

Bose® Series II equalisation modules. EQ modules are

available to suit the following Bose® loudspeakers:
•

Panaray MA12

• Panaray 402-II, 502B and 502BEX
•

Panaray LT Series:

Models 3302, 4402, 9402 and 9702.

Modules to suit other models are available – please enquire.

Installation Instructions

Refer to the pcb layout diagram (see

fig.7

) for the location

of the Bose EQ module connector and its associated bypass

jumper J3.

To install an EQ module, proceed as follows:
1. Switch off the power and isolate the unit from the

mains.

2. Remove the top panel.
3. Remove jumper J3 from the main pcb.
4.

Plug the Bose® equalisation module onto its connector;

note that the connector has two notches on one
side which engage with lugs on the module’s mating

connector to ensure correct orientation.

5. Replace the top panel.

REMOTE MUSIC MUTE TERMINATIONS

MUSIC MUTE

INPUT

RELAY

NORMALLY OPEN (NO)

CONNECTION

MUSIC MUTE

INPUT

RELAY

NORMALLY CLOSED (NC)

CONNECTION

fig.6: Remote Music Mute

MPA Series User Manual v1.2

General Notes

Multi-zone Applications

Where the sound system specification calls for separate

control in several zones, MPA Series amplifiers can be used

in multiples.
Signal sources can be connected to several inputs as

required, but care must be taken to ensure the output stage

of the signal source is capable of driving the resulting lower

input impedance.
The impedance of the line inputs (music inputs) is 47k ohms

and it is reasonable to assume that most op-amp based

signal sources are able to drive a 10k ohm load, allowing up

to five amplifiers to be paralleled.

The input impedance of the mic inputs is 2.4k ohms, making

them suitable for microphones with a nominal impedance

of 600 ohms or less. A single 600 ohm microphone
could therefore typically be connected to four paralleled

mic inputs. If this guideline figure cannot be adhered to,

the use of suitable mic or line distribution amplifiers is

recommended.
To avoid any problems associated with differences in

mains supply earthing, we recommend that all MPA Series

amplifiers used in a multi-zone application should be co-

located and connected to a common mains supply.

Note that when using multiple MPA Series amplifiers in a

19” rack, suitable ventilation arrangements must be made to

ensure that lower amplifiers do not cause those above to

overheat (see Ventilation for further information).

EMC Considerations

MPA Series amplifiers fully conform to the relevant

electromagnetic compatibility (EMC) standards and are
technically well behaved. You should experience no problems
interfacing units to other items of equipment and under
normal circumstances, no special precautions need to be
taken.
If the unit is to be used in close proximity to potential
sources of HF disturbance such as high power
communication transmitters, radar stations and the like, it is
suggested that input signal leads be kept as short as possible.
Always use balanced interconnections wherever possible. If

the MPA Series amplifier is mounted in a 19” rack, do not
locate the unit in close proximity to a powerful amplifier of
any kind, which may radiate a strong magnetic field from the

power transformer.

Earthing

When several mains powered units are connected together

via their signal cables, there is a risk of one or more earth

loops which may cause an audible hum on the system even

with the gain controls set to minimum.

The 0 V rail of an MPA Series amplifier is directly coupled to

the chassis ground. No interconnection problems should be

encountered, but if there is any hum or other extraneous

noise when source equipment is connected, the situation can
generally be remedied by observing the following guidelines:

•

Always connect sources using balanced connections

wherever possible, with the cable screen only connected

at the receiving end (amplifier input).

•

Use audio isolating transformers (readily available from

trade suppliers) at the inputs if necessary. These will

ensure that the amplifier is electrically isolated from the

source equipment.

•

The signal source units should be located as close as

possible to the amplifiers and the metal housing of

the various units should not be electrically connected

together through the equipment rack. If this is a
problem, rack isolating kits are available from specialist

hardware suppliers. If the problem persists, try to

connect all interconnected units, including power

amplifiers to a common power source to ensure a

common ground is provided.

Ventilation

MPA Series amplifiers are force cooled by a thermostatically-

controlled fan. The fan is operative at all times, remaining
at low speed at internal temperatures below 50 ºC, then
increasing in speed above this temperature to a maximum
speed at 70 ºC.

Always allow adequate space around the amplifier(s) to
allow a free flow of air through the unit(s). In 19” rack

applications we recommend leaving 1U of rack space above
and below each unit. Plain 1U blank panels, not slotted
ventilation panels should be used, as the latter reduce the
effect of forced-air cooling.

The direction of airflow in MPA Series amplifiers is from
front-to-rear; it is recommended not to mix the amplifiers

with other equipment employing forced-air cooling which
acts in the opposite direction within the same rack.

In free standing applications we recommend fitting the
feet supplied and placing the unit on a flat surface and

leaving the ventilation slots on top of the unit free from any
obstructions.

MPA Series User Manual v1.2

Technical Specifications

Line Inputs

Frequency response

Low-Z output

+0 dB/-1 dB from 20 Hz – 20 kHz (65 Hz filter switched out)

High voltage outputs

+0 dB/-2 dB from 20 Hz – 20 kHz (65 Hz filter switched out)

Distortion

Low-Z output

<0.03% @ 1 kHz, 1 dB below full power (80 kHz bandwidth)

High voltage outputs

<0.04% @ 1 kHz, 1 dB below full power (80 kHz bandwidth)

Sensitivity

195 mV (-12 dBu) to 2.0 V (+8 dBu)

Input Gain control

20 dB range

Input impedance

47k ohms

Headroom

>20 dB

Noise

-90 dB 22 Hz –22 kHz, at speaker output, relative to full power

Equalisation

HF: ±10 dB/10 kHz LF: ±10 dB/50 Hz

Microphone Inputs

Frequency response

Low-Z output

-3 dB @ 100 Hz (3

. order filter); -1 dB @20 kHz

High voltage output

-3 dB @ 100 Hz (3

. order filter); -2 dB @20 kHz

Distortion

<0.03% @ 1 kHz, 1 dB below full power (80 kHz bandwidth)

Gain range

40 dB range

Input Impedance

>2k ohms (balanced)

Phantom Power

15 v, switchable per-input by jumpers

Headroom

>20 dB

Noise

-127 dB EIN 22 Hz-22 kHz (150 ohms)

Equalisation

HF:

10 dB/5 kHz LF:

10 dB/100 Hz

Outputs

Output Power* (any out-

put, 1kHz continuous sine

wave @ <0.07% THD+N)

MPA60

60 watts

MPA120

120 watts

MPA240

240 watts

Protection

Fixed level signal limiter max gain reduction of 20 dB, DC protection, IV limiting & short

circuit protection, switch-on delay

Cooling

Forced-air, front-to-rear airflow, thermostatically controlled