The History of Amplifier
By 1930, anyone familiar with electricity knew that the movement of metal through a magnetic field caused a disturbance that could be translated into an electric current by a nearby coil of wire. Electrical generators and phonograph (record player) pickups already used this principle. The problem in building a guitar pickup was creating a practical way of turning a string's vibration into a current.
After months of trial and error, Hawaiian steel-guitar player George Beauchamp — who, with Adolph Rickenbacker, formed the Electro String Company in the early 1930s — developed a pickup that consisted of two horseshoe magnets. The strings passed through these and over a coil, which had six pole pieces concentrating the magnetic field under each string.
When the pickup seemed to work, Beauchamp enlisted Harry Watson, a skilled guitar maker for National Guitars, to make an electric Hawaiian guitar. It was nicknamed the Frying Pan.
Electro String had to overcome several obstacles, however. To begin with, 1931 was the worst year of the Great Depression, and no one had money to spend on newfangled guitars. Furthermore, only the most farsighted of musicians saw the potential, and the U.S. Patent Office did not know if the Frying Pan was an electrical device or a musical instrument.
From the very beginning, Electro String developed and sold amplifiers. This is an obvious first step, really, because without an amplifier the new electric guitar would have been useless. The first production-model amp was designed and built by a Mr. Van Nest at his Los Angeles radio shop.
Soon after, Beauchamp and Rickenbacker hired design engineer Ralph Robertson to work on amplifiers. He developed the new circuitry for a line that by 1941 included at least four models. Early Rickenbacker amps influenced, among others, Leo Fender, who by the early 1940s was repairing them at his radio shop in nearby Fullerton, California.
By today's standards, the amps were pretty meek. Their output was about 10 watts, which is pretty low, and they used radio technology, vacuum tubes, and small loudspeakers. However, as the popularity of the electric guitar grew, there was a corresponding demand for louder amps.
The breach was filled by Leo Fender. In 1949, he worked with his engineer, Don Randall, to produce the first Super Amp model amplifier. With the Fender solid-bodied guitars (the Telecaster and Stratocaster) in general production, and the introduction of the Gibson Les Paul in 1952, the demand for amps went through the roof as the popularity of the solid body grew. Output rose to a reasonable 50 watts, with twelve-inch speakers, still the norm for guitar amps.
By the late 1950s, the British company Vox had produced the AC30, which is as much a classic amp today as the Fender Twin Reverb. The Vox was particularly popular with blues and rock musicians because it produced a warm tone, which musicians such as Jimi Hendrix, Jeff Beck, and other heavy-metal rockers discovered could be overdriven to create the fuzzy, distorted effect that has come to define the early 1960s rock guitar sound.
Splitting up a combo amp into individual components came about during the rock era of the 1960s. The amp became known as the head, and the speakers became known as the stack. You could get more powerful amps and much bigger speakers this way, and by combining various amps and speaker combinations, musicians could produce more volume.
As the 1960s wore on, and rock bands played bigger and bigger venues, power and volume once more became a problem. This was solved when the British engineer Jim Marshall produced a 100-watt amp connected to a stack of four twelve-inch speakers. Pretty soon the Marshall stack was the norm for rock concerts.
By the 1970s, the vacuum-tube technology of the 1930s was finally being replaced by cheaper and more predictable solid-state transistors, although musicians complained about the coldness of the sound as compared to the warmth of the tube amp. It was popular among those who liked a thinner, cleaner sound.
The transistors' brittle sound was offset by the wider frequency range and the ability to play cleanly (without distorting) at higher volumes. Different tubes could produce different sounds, but they needed to be replaced periodically because they came loose or burned out.
By the 1980s, amplifier makers went back to creating a valve sound, often creating hybrid models that featured tube preamps and solid-state power amplifiers, getting the best of both worlds. Today, a traditional guitar amp combines an amplifier and a loudspeaker in one unit, called a combo. They are compact and relatively easy to transport.