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The Amplifier
The Amplifier may be built into the projector or be provided as a separate unit, and in some cases it is housed in the loudspeaker assembly case. Its function is precisely the same as any other amplifier and it may be used to amplify sound from an electric gramophone or mike, as well as the impulses from the photocell.
The gramophone is no longer required to provide sound in synchronisation with the film, and it is easy to see why it is now known as the non-sync (non-synchronised).
The sound reproduced by the non-sync is often louder than film-sound, and this is because the photo-cell has a limit to the amount of light it can deal with. An over-loaded photo-cell is a rare occurrence in 16-mm. projectors, but it may be possible in some machines when the volume is turned on full. When this happens the cell can be seen to fluctuate with light, and a drumming noise may be heard from the loud-speaker. The photocell (but not the amplifier) is then working at its maximum efficiency. Any amplifier may become faulty in a hundred different ways, so always handle it with the utmost care.
It is the usual requirement to switch the amplifier on at least one minute before projecting, in order to give the valves time to warm up.
It is more than probable that you will find that the voltage supplied to the amplifier is different from that supplied to the lamp and motor, so look for some reference to this in your operators' instructions. You will also find, perhaps, that there is a small fuse somewhere in the amplifier, and on no account should this be changed for one of a higher rating. The amplifier fuse is usually one of 2-amps, and in the event of it blowing it must not be replaced by a 5-amp fuse. But 2-amp fuse-wire cannot be bought at every shop, so start looking for some now — do not wait until you need it in the middle of a show.
The output of an amplifier, in wattage, can be made to vary considerably by the current fed to it. Insufficient volume may therefore be caused by low voltage, a fault which can usually be speedily corrected by adjusting the transformer or resistance. But to increase the voltage above the correct rating for the amplifier would also cause a fault, and quite a serious fault it would be — a complete set of new valves being the remedy!
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