Installation - Adastra A Series Manual

INTRODuCTION
The ADASTRA amplifiers are designed for industrial use in factories, offices and public buildings.
Three microphone inputs are provided. In addition a LINE input is also available which can be used for
music sources and similar higher signal sources. There is also an output suitable for feeding the ADASTRA
952.976 slave amplifier in the same series thus making amplifier stacking a possibility. Provision is made
for connecting to either 100 volts to line or low impedance loudspeakers. The amplifier can be used from
either a 220-volt AC or a 24-volt DC power source. Within the packaging will be found a 3 core 230-volt
mains lead terminated with a IEC connector at one end and a 13 amp plug top fused at 5 amps at the
other.
NOTE: If you are connecting the amplifier to two-wire power source i.e. have no earth pin available then
essential that a suitable wire is run from the chassis binding post adjacent to the mains lead on the rear to
a proven earth.
WARNING: DO NOT CONNECT THE MAINS SUPPLY TO THE AMPLIFIER UNTIL ALL THE NECESSARY
INPUT AND OUTPUT CONNECTIONS HAVE BEEN MADE.
FRONT PANEL viewed from left to right. See the front page for a diagram.
Three controlled channels are provided.
MIC 1 and MIC 2 are on the extreme left with the LINE, BASS and TREBLE cut controls towards the right
hand side. The MASTER control is next with the signal monitoring and the mains on/off switch at the
extreme right.
REAR PANEL viewed from left to right. See the front page for a diagram.
On the left is found the IEC input incorporating a mains fuse. Next is the chassis binding post with the DC
input terminals adjacent to the loudspeaker termination. Towards the right there is the SLAVE OUT phono
socket which can be used for recording purposes. Next are the LINE OUT and LINE IN sockets followed by
the mono jack socket for MIC 2 with the VOX (ducking) on/off switch adjacent. At the extreme right is the
XLR3 socket for MIC 1.
See the specification panel for full technical details.
PROTECTION The amplifier is automatically protected for short, open circuit and overheating. A short or
open circuit on the loudspeaker line is indicated by the POWER indicator pulsing slowly on and off.
Overheating in excess of 105°C is protected by a thermal cut out and if this occurs then the amplifier will
cut out completely. The cause is usually by the placing of papers on top of the amplifier or by enclosing it
in a poorly ventilated place. If this happens remove any restrictions on ventilation and leave the amplifier
switched off for five minutes. This will restore the protection circuits to their monitoring mode. If the fault
had existed for some time then the fuse located adjacent to the IEC connector on the rear panel may also
need replacement. In this case the POWER indication on the front panel will fail to illuminate.

INSTALLATION

MIC1 is for a balanced microphone on an XLR3 socket: twin screened wire should be used for connection.
Termination follows the convention i.e. pin 1 – Screening; pin 2 - Signal go; pin 3 – Signal return.
MIC 1 has the added facility of being able to duck all other inputs on the presence of a signal. No
additional wiring is required and the switch to activate this facility (VOX) will be found at the rear.
MIC 2, and MIC 3 when fitted, are for unbalanced low impedance microphones and are terminated with
rear mounted jack sockets. Single screened wire should be used for connection the inner core being
connected to the tip with the outer screening to the body of the mono jack plug.
If it is necessary to connect balanced microphone to one of the unbalanced inputs then of the two inner
screened wires one should be connected to the jack plug tip whilst the other is connected to the jack plug
body together with the outer screening.
Compact disc and tape players will use the LINE IN phono (RCA) socket and need to be terminated with a
phono (RCA) plug, the live (inner) wire going to the central pin with the outer screening being soldered to
the body.
If a recording facility is required then suitable feed can be found by using the SLAVE OUT socket at the rear.
Connect as for players (see above)
This socket can also be used for distributing a signal to up to ten ADASTRA 952.976 slave amplifiers.
Caution Care must be taken when fitting any connectors to avoid damaging the cable or the connector
through excessive heat from the soldering tool.
LOuDSPEAkERS
All connections to the loudspeaker terminals should be made suing suitable spade lugs crimped or
soldered to the loudspeaker cables. Any other method can give rise to short circuit. There is provision for
both 100 volts line and low impedance loudspeakers but it is not advisable to use both together.
Low Impedance loudspeakers should he connected in a series parallel arrangement such that the total load
is never less than 8 ohm. i.e. two 4 ohm loudspeakers could be connected in series and connected between
the common and the 8 ohm tap. Care should be taken with this arrangement that the volume level is
carefully controlled, as it is possible to damage loudspeakers by using too high a volume setting.
The 100 volt line loudspeakers should be connected to the common and the 100 volt line terminals taking
care that the sum of the wattage of all the loudspeakers on he line does not exceed the total power
available from the amplifier.
Please Note that all the loudspeaker terminals are fully floating with respect to chassis. In the event of
cross talk to other services or instability then it may be beneficial if the 'com' terminal is strapped to the
earth binding post.
Please remember that a low impedance loudspeaker system requires heavy cable feeding the loudspeakers
to minimize losses. For a widespread installation (i.e. a factory system) it is far better and more cost
effective to use the 100 volt line system.
MOuNTING BRACkETS.
These will be found in the packaging with the mains lead.
The mounting holes can be used in one of two ways:
1. As ears for use when mounting the amplifier into an equipment rack.
2. To mount the amplifier on top of a shelf.
BATTERY OPERATION
A 24V (for 120W, 952.973 & 952.976) or a 12V (for 30W, 952.967 & 60W, 952.970) battery can be
connected using suitable spade lugs crimped and soldered to the battery cables. Care must be taken to
ensure that the terminals lie in the spaces provided and do not swing to one side and thus short out on the
mounting screws. Polarity should be observed when connecting to the amplifier although there is reverse
polarity protection.
The power output will be reduced on battery working, the output also depending on the state of the
battery.
Please note that the power switch does not control the 12V/24V supply to the amplifier. If battery On/Off
control is required then a separate switch will need to be installed remote to the amplifier.
SETTING uP
When all connections have been made, check that all controls are at zero then plug the mains lead
provided into the amplifier and the 13 amp plug top into a suitable 230 volt socket. Depress the double
pole power switch on the right-hand side of the front panel. Observe that the POWER LED illuminates.
Advance the MASTER control to 6 on its scale then using a local microphone in MIC 1 socket slowly advance
its volume control whilst speaking into the microphone. Observe the SIGNAL indicator on the right hand
side whilst doing so. As the control is advanced the indicator will start flashing in time with the peaks of
speech. This indicates that a signal is being passed to the loudspeakers. The control should be set such that
the peaks of sound keep the SIGNAL indicator almost continuously lit but that the PEAK indicator only
shows on rare occasions or not at all.Continuous illumination of the PEAK led indicates that the amplifier is
being overloaded. If the MIC 1 control is at maximum without achieving the desired output then it will be
necessary to increase the MASTER setting a little and recommence the setting up procedure until a
satisfactory level of output is achieved.
It may be that, before this setting can be achieved, a howl-round point is reached where the system
appears to become unstable, if this is so then the nearest loudspeaker and the microphone you are using
are in each others' sound fields and need to be repositioned the one with the other. If the 100 volt line
system is being employed you can reset the nearer loudspeaker to a lower wattage tap to minimize the
howl-round.
The object of this setting-up exercise is to balance the MASTER and MIC 1 controls such that neither is at a
very low or a very high setting in relation to each other. When this initial setting-tip procedure has been
completed try the other input channels in a similar manner. Make a note of the control settings for future
reference.
Most tape and CD players have additional level controls of their which can be usefully employed to fine
balance their volume levels with the LINE or the AUX control.
The bass and treble cut controls should initially be set to their minimum (anti-clockwise) positions for
setting up. Once this has been carried out then these can be set for personal taste. However when speech
is being transmitted into a noisy or reverberant environment then intelligence can he significantly
improved by rotating the bass cut control fully clockwise. When horn type loudspeakers are in use then the
control must be set fully clockwise to minimize the risk of low frequency damage to the loudspeakers.
INTERFERENCE
Whilst this equipment complies in all respects with EMC legislation its use in an industrial environment
where there are many potential sources of interference means that steps may need to be taken to
minimize any difficulties.
Always check that the amplifier has a good earth. In the event of interference secure the services of a
qualified electrician to carry out tests on the socket in use to ensure that a low resistance earth path exists.
Do not position the amplifier very close to large transformers. television monitors and computers
CIRCUIT DIAGRAMS ARE AVAILABLE ON REQUEST
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AMPLIFIER MANuAL