Preamplifier

A preamplifier ( preamp called - English: preamplifier, short preamp, also precursor) is an amplifier, for example, for test equipment and audio and video technology, which has the task of the input signals that originate from different sources, be adapted so that the actual amplifier operates in its optimum operating range. The adjustment may relate to the impedance, capacitance, the level of the frequency range, and frequency response, and the waveform. Depending on the requirements preamplifier can be executed as separate devices or integrated into the amplifier or the meter.

General

Examples are

• Measuring preamplifier different physical measurements of, for example, a digital display or an oscilloscope prepared.

• Audio Preamplifier - it adapts the signals from source devices such as radio, cassette recorder, CD and record player at the power amplifier / to the output stage to. Audio preamplifiers are part of any integrated amplifier ( "integrated" ); they are also available in separate housings and then hot preamp, high-level preamplifier ( without phono amplifier ) or phono preamplifier ( phono equalizes the signal and has a volume control).

• Preamplifier for instrumental gain ( electric guitar, electric bass, electric piano, synthesizers and other ). These are either part of an integrated unit (along with a power amp in an integrated amplifier ) or individual components. The preamplifier ( preamp ) contains the sound-affecting control elements ( standard elements: Gain, Bass, Mid, Treble, Presence) and is used to specify the desired sound characteristics, which, unlike in Hi-Fi, also clipping and deviations from linear transmission include consciously. Active electromagnetic pickups for electric guitar and bass guitar have a pickup in the housing integrated preamplifier, which is usually powered via 9V batteries with electrical tension. The so- reconditioned instrument sound will be adjusted via a power amplifier, which is also called final stage for output to a speaker system. Preamplifier are also in the field of audio recording without downstream stage for application.

Fundamentally, preamplifier, unless they work in the same, in the small signal operation. This means that only a small portion of the straight portion of the characteristic of the active device used is modulated. This allows preamps to produce exceptionally low harmonic content.

Quality characteristics of preamplifiers are usually (voltage) gain, linearity, wide frequency range, low noise, insensitivity to external magnetic fields and mechanical vibrations ( microphonics ) and high headroom. For audio applications relative bandwidths ( ratio of the upper to the lower cut-off frequency ) of three decades minimal criterion. In the high-frequency technology to be amplified relative bandwidths are usually very much smaller. Instead, are low noise and high headroom (ratio between nominal and maximum input voltage) at the forefront of optimization.

Almost always have preamplifier via actuators, the gain, output voltage, spectral components, etc. can change defined. These actuators are in the analog "world" usually potentiometers ( variable resistors) or variable capacitors ( for example in the FM input part of a radio receiver ). In the digital technology, for example, multipliers are used.