CLOUD MPA240 (01) PDF MANUAL

• 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 35°C.

• 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.

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.

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.

1. MIC LEVEL 1 to 4 – level controls for Mic Inputs 1 to 4

2. MUSIC SOURCE – selects active Line Input (1 to 6)

3. MUSIC LEVEL – adjusts level of selected Line Input

4. PEAK – illuminates if Mic or Line signals level are too high

5. MUSIC MUTE – illuminates when external Emergency Mute is active

6. MAINS – AC power switch with LED

7. Ventilation slots – forced-air cooling air intake

1. LINE 1 to LINE 6 – stereo line inputs for music sources

2. GAIN 1 to GAIN 6 – level trims for each line input

3. MUSIC EQ – LF and HF EQ adjustment for music channel

4. MIC 1 to MIC 4 – balanced mic inputs

5. GAIN 1 to GAIN 4 – level trims for each mic input

6. MIC EQ – LF and HF EQ adjustment for mic channel

7. ACCESS – external paging control input for Mic 1

8. LOW IMPEDANCE OUTPUT – speaker output for low-Z connection

9. LINE OUTPUT – for connection of 100V/70V/25V line distribution system

10. MUSIC MUTE – Emergency control input for muting music source

11. REMOTE MUSIC CONTROL – for connection of RL-1 or RSL-6 remote control panels

12. REMOTE/LOCAL – disables front panel controls when remote control is in use

13. IEC mains input

14. Mains fuse

15. Fan – forced-air cooling air exhaust

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 (2.0V).

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.

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). 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.

For a balanced connection:

PIN 1: SCREEN (GROUND)

PIN 2: COLD/ANTIPHASE (-)

PIN 3: HOT/PHASE (+)

For an unbalanced connection, connect pins 1 and 2 together.

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.

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.

Mic input 1 is equipped with an external access control input. This 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. 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.

• Chime: The internal chime generator will be activated if internal jumper J1 is set to ON.

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. The gain controls on the rear panel should be set at a level where microphone distortion does not occur even when the front panel level controls are fully clockwise.

Phantom Power

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. 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.

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. 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.

Microphone over music priority

A 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. 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.

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.

The MPA Series amplifiers are able to deliver their rated power into a 4 ohm load, as follows:

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/or parallel wiring should be employed to produce a total load impedance of not less than 4 ohms. 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 0V.

MPA Series amplifiers are fitted as standard with an output transformer that can be enabled by moving an internal connector. To convert the amplifier to high-voltage line operation, the low impedance output socket 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 toroidal transformer nearer the rear of the unit (same wire types).

Note that the low-impedance output will no longer be available once the transformer is plugged in. The secondary (output side) of the transformer is permanently wired to the line output connector (a 4-pin 5 mm-pitch screw terminal type), thus the high-voltage output will be active once the internal connector change has been made. 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: 100V, 70V and 25V; whilst these have a common 0V connection, the output is fully floating i.e. it is isolated from the rest of the amplifier. When the transformer is in use the maximum total combined load should not exceed the rated power for the amplifier model.

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. The filter reduces the output level of frequencies below 65 Hz, and ideally should be used if the line output transformer is in circuit. When this transformer is in circuit it is strongly recommended that the amplifier’s 65 Hz high pass filter is set ON.

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. 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.

MPA Series amplifiers are compatible with single channel Bose® Series II equalisation modules. EQ modules are available to suit loudspeakers such as Panaray MA12, Panaray 402-II, 502B, 502BEX, and Panaray LT Series models. 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.

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 is 47k ohms, allowing up to five amplifiers to be paralleled. The input impedance of the mic inputs is 2.4k ohms. A single 600 ohm microphone could therefore typically be connected to four paralleled mic inputs.

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.

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.

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.

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 °C, then increasing in speed above this temperature to a maximum speed at 70 °C.

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.