41. The boy, a tinkerer, helped his dad repair projectors and build audio amplifiers for the movies, newly with sound. 42. An output transformer in an audio amplifier or radio receiver sends only the AC to the loudspeaker, for example. 43. The speakers are driven by a series of audio amplifiers that are usually powered by a portable diesel generator. 44. The electronic design was revised, and the audio amplifier was rather more complex, incorporating rotary bass and treble controls. 45. A low-pass filter in the audio amplifier filters the quench and RF frequencies from the output, leaving the AM modulation. 46. The data sheets of all these audio amplifiers should have sample schematics of simple circuits that you can start from. 47. It has two radio frequency amplifier stages, one grid-leak detector / amplifier and three class A audio amplifier stages. 48. :An audio amplifier , presumably. 49. One early application of PWM was in the Sinclair X10, a 10 W audio amplifier available in kit form in the 1960s. 50. The preceding stages in such a chain are low power audio amplifiers which perform tasks like adding electronic effects such as reverb.
