Audio amplifier

related topics
{system, computer, user}
{rate, high, increase}
{album, band, music}
{@card@, make, design}
{math, energy, light}

An audio amplifier is an electronic amplifier that amplifies low-power audio signals (signals composed primarily of frequencies between 20 - 20 000 Hz, the human range of hearing) to a level suitable for driving loudspeakers and is the final stage in a typical audio playback chain.

The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification, equalization, tone control, mixing/effects, or audio sources like record players, CD players, and cassette players. Most audio amplifiers require these low-level inputs to adhere to line levels.

While the input signal to an audio amplifier may measure only a few hundred microwatts, its output may be tens, hundreds, or thousands of watts.

Contents

History

The audio amplifier was invented in 1909 by Lee De Forest when he invented the triode vacuum tube. The triode was a three terminal device with a control grid that can modulate the flow of electrons from the filament to the plate. The triode vacuum amplifier was used to make the first AM radio.[1]

Early audio amplifiers were based on vacuum tubes (also known as valves), and some of these achieved notably high quality (e.g., the Williamson amplifier of 1947-9). Most modern audio amplifiers are based on solid state devices (transistors such as BJTs, FETs and MOSFETs), but there are still some who prefer tube-based amplifiers, due to a perceived 'warmer' valve sound. Audio amplifiers based on transistors became practical with the wide availability of inexpensive transistors in the late 1960s.

Design parameters

Key design parameters for audio amplifiers are frequency response, gain, noise, and distortion. These are interdependent; increasing gain often leads to undesirable increases in noise and distortion. While negative feedback actually reduces the gain, it also reduces distortion. Most audio amplifiers are linear amplifiers operating in class AB.

Full article ▸

related documents
Wikipedia:Federal Standard 1037C terms/telephony terms
HyperTransport
Bally Astrocade
WAV
Address Resolution Protocol
DivX
Video on demand
Wormhole switching
GE-600 series
Distributed computing
BS2000
Extended Industry Standard Architecture
Packet switching
Video codec
Apple Desktop Bus
RDRAM
Intel 80386
Magnetic tape
Digital Visual Interface
High fidelity
Vorbis
Wikipedia:Federal Standard 1037C terms/telecommunication network terms
Internet Protocol Suite
Exidy Sorcerer
Tape drive
Digital signal processing
Blue Gene
Disk image
Signaling System 7
Linux distribution