The creation and advancement of the electric amplifier began in 1906 with the invention of the triode, a form of electric amplification containing three active electrodes of which vacuum tubes are a variety, by De Forest (Leach, 1995). This invention became the primary focus of the amplification industry, resulting in the discovery of stable operating vacuum tubes by Langmuir of General Electric in 1913. Consequently, the Japanese established a vacuum tube laboratory in 1914 and created a prototype high-quality vacuum tube in 1916. With the beginning of radio broadcasts in Japan, in 1925, vacuum tube technology quickly spread to England and North America (Okamura, 1994). The electric pickup, a device that translates the disturbance in a magnet field into and electric signal, became practical enough for production in 1931, thus creating a need for electrical amplification. These first amplifiers, made by the company Electro String, had an output of approximately ten watts and utilized the same technologies as early radios, specifically vacuum tubes. The growing popularity of electrical amplification quickly caused demand for louder amplification. Leo Fender filled this need in 1949 with the first 50-watt amplifiers, which is still the standard wattage today. The late 1960s saw the next leap in amplifier technology in the invention of 100-watt amplifiers, which were loud enough for large arena-sized shows, by Jim Marshall (Hamm, 1972). In the 1970s, solid-state technology amplifiers replaced tube amplifier technology. These amplifiers were cheap and physically durable (Horowitz & Hill, 1989).
An Introduction to Electrical Amplification
At the most basic level, an electric amplifier is a device that increases the output of a signal or current beyond that of the original output. The addition of a power supply, a wall outlet for example, increases the output, matching the power supply’s additional output to that of the original, but with greater amplitude (Leach, 1995). The qualities of an electrical amplifier are broken into categories: gain, bandwidth, efficiency, and linearity. Gain is the ratio of output to input power in decibels. Bandwidth is the range of frequencies for which the amplifier functions correctly, standardized around a difference of less than one decibel from the intended. Efficiency is the percentage of the power source successfully added to the output (McCorquodale, n.d.). Although there are other varieties of electrical amplification, the only form functional for the amplification of electrical signals to pure audio is nonlinear amplification via vacuum tubes and solid-state technologies. Nonlinear amplifiers are those whose components follow nonlinear power laws and as a result generate distortion (Liptak, 2005).
Methods of Electrical Amplification
Vacuum tubes, or thermionic valves, are triodes, possessing three active electrodes, and contain a cathode, grid, and...