Why Amplifiers?

Abstract

You may remember seeing old ‘His Master’s Voice’ record labels with a dog listening to the sounds emerging from the horn of an early phonograph. In those days there were no valves or transistors, so manufacturers had to rely on mechanical ‘amplification’. The gramophone could produce sounds which, although limited in quality, could fill a medium-sized room. The large horn was a form of acoustic impedance-matching device, its shape being carefully designed (like many brass musical instruments) to throw the maximum amount of sound outwards. Such horns are still used today in horn-speakers for home use and for public-address systems; their output, watt for watt, is far greater than that of the conventional cone type.