1. Before the electronic age, inventors had to find ways to concentrate sound waves to make audio (sound) louder, things like the "ear trumpet" and the "megaphone". These mechanical means of sound amplification were only partially adequate. Record players did exist before electronic amplification, but the sound was scratchy and not very loud.

2. Lee de Forest, an American inventor, built the first vacuum tube, the Audion, in 1906. De Forest’s breakthrough was creating the first device that could take a weak electrical signal and use it to control a much larger electrical current, effectively "magnifying" the sound. "Vacuum tube" is an American word. In Britian they call them "valves". The French call them "lampe", and in German it's "röhren". The "transistor", invented at Bell Labs in 1947 by John Bardeen, Walter Brattain, and William Shockley, does the same thing as vacuum tubes, but in a much smaller space and with minimal wasted energy.

3. In 1954, Morris Tanenbaum at Bell Labs and Gordon Teal at Texas Instruments independently developed the first silicon transistors. Silicon, as in "Silicon Valley", was a cheaper and much more stable material to use in manufacturing of transistors, which led to the explosion of the semiconductor industry.

4. Electronic amplification of sound made modern television, High Fidelity (Hi-Fi) record players, and ( in 1931), electric guitars possible.