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 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 DC 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 plug top into a suitable 230 volt socket. Depress the double pole power switch on the
left-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 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 (anticlockwise) 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
