Structure
Amplifiers consist of one or more circuit stages which have unique responsibilities in the modification of the input signal. The power amplifier or output stage produces a high current signal to drive a speaker to produce sound. This means that the signal does not really increase in amplitude, but it has a higher energy content. One or more preamplifier stages precede the power amplifier stage. The preamplifier is a voltage amplifier that amplifies the guitar signal to a level that can drive the power stage: the signal is made larger, but without significantly increasing its energy content. There may be one or more tone stages which affect the character of the guitar signal: before the preamp stage (as in the case of guitar pedals), in between the preamp and power stages (as in the cases of effects loop or many dedicated amplifier tone circuits), in between multiple stacked preamp stages, or in feedback loops from a post-preamp signal to an earlier pre-preamp signal (as in the case of presence modifier circuits). The tone stages may also have electronic effects such as equalization, compression, distortion, chorus, or reverb. Amplifiers may use vacuum tubes (in Britain they are called valves), or solid-state (transistor) devices, or both.
There are two configurations of guitar amplifiers: combination ("combo") amplifiers, which include an amplifier and anywhere from one to four speakers in a wooden cabinet; and the standalone amplifier (often called a "head" or "amp head"), which does not include a speaker, but rather passes the signal to a speaker cabinet or "cab". Guitar amplifiers range in price and quality from small, low-powered practice amplifiers, designed for students, which sell for less than US$50, to expensive amplifiers which are custom-made for professional musicians and can cost thousands of dollars.
Read more about this topic: Guitar Amplifier
Famous quotes containing the word structure:
“The question is still asked of women: “How do you propose to answer the need for child care?” That is an obvious attempt to structure conflict in the old terms. The questions are rather: “If we as a human community want children, how does the total society propose to provide for them?””
—Jean Baker Miller (20th century)
“Vashtar: So it’s finished. A structure to house one man and the greatest treasure of all time.
Senta: And a structure that will last for all time.
Vashtar: Only history will tell that.
Senta: Sire, will he not be remembered?
Vashtar: Yes, he’ll be remembered. The pyramid’ll keep his memory alive. In that he built better than he knew.”
—William Faulkner (1897–1962)
“There is no such thing as a language, not if a language is anything like what many philosophers and linguists have supposed. There is therefore no such thing to be learned, mastered, or born with. We must give up the idea of a clearly defined shared structure which language-users acquire and then apply to cases.”
—Donald Davidson (b. 1917)