Audio technology-development history can be divided into tubes, transistors and integrated circuits, FET four stages. 　　

In 1906 the Americans DeForest invented the vacuum triode, human electro-acoustic techniques. 1927 Bell Laboratories invented the negative feedback technology that enables audio technology has entered a new era, typical as Williamson amplifier, the more successful use of the feedback, make amplifier distortion significantly reduced. The 1950s on, the development of vacuum tube amplifier reached a peak period, various electron tube amplifier. Due to a vacuum tube amplifier tone sweet, round, still favor for enthusiasts. 　　

The 1960s transistors, and allows a large audio enthusiasts into a broader sound world. Transistor amplifier is smooth and mellow timbre, low distortion and wide frequency response and dynamic range, etc. 　　At the beginning of the 1960s, the United States first launched audio technology in new members — integrated circuits, to the early 1970s, integrated circuit to its quality and cheap, small size, functionality and other features, it has become sound Territories know. Now, thick film sound integrated circuits, magnifying integrated circuits are widely used in audio circuit. 　　

In the mid-70s, Japan produced the first field effect transistor. Because the field effect transistor with tubes pure thick, sweet timbre and dynamic range over 90dB, THD (0.01% (100kHz), and soon in the audio sector. Today's many amplifiers are field effect transistor output as the last stage. 　

The kind of family phonograph usually speak phonograph with desktop machines and floor type machines. Because of the requirement of phonograph high sound quality, so its two speakers generally have larger volume. 　　

The structure of the host (layer) Division, sound has one of the two categories and layered. In one of the machines, it's all part of the circuit (including record player in a shell, which is generally used to grade machines. In hierarchical phonograph, depending on the grade of different machine as the number of tiers. Tiered more machines are: a record player, CD player, tuner with a layer of a layer, dual card recording and playing sounds, and tones of the controller layer and a layer of the main power amplifier. In hierarchical fewer machines, record player, CD player at one level, the other as a layer. 　

Miniaturization, digitization, specialization, film and television is the family sound inevitable-micro audio. Mini desktop machines have a long history of more than 10 years ago has advanced micro machines. But due to listen and speakers, stereo record player, tape deck, there is no good solution, so it stays at the lower grades. In order to create compact audio world, not only from the amplifier, control part, or speakers, but also from the tuner, CD player and recording deck parties for consideration. 　　

Digital audio. Digital technology is a new technology, digital audio in solving the noise simulation distortion problems. Audio using digital technology, records of digital signals from the sampling frequency to quantitative characteristics, there is a clear resolution, no color dithering, get is a very clear image. And can be interchanged and super computer, this device with analog recording and playback as second to none. Digital recording time, names, addresses, together with the writer zone, with mini-keyboard to complete cataloging, replace the track number, and remote control features that enable you to automatically search need to track, easy to use. Mini Stereo and television sound equipment integration. Digital audio with electro-acoustic techniques, video technology, computer technology, they are in the family can constitute a heaven-one multimedia, film and audio system. Such a system, can hear various additions in input will need to enter and function of the signal is converted, through computer treatment can make the audience see the various image and hear different voices. 　

Look at the implications of dB. 　　

In DB is an electronics use very broad, it is measured and compared to a system of power, voltage and current size relative units. Later, because advances in technology, recognizing the human voice response is logarithmic regularity, so have a unit is Bell (Bel) is the name of the inventor of the telephone. Its expression is: Bel = lg (Po) P/P is the power measured Po is the reference power: Bel represents the base-10 logarithm of a find-Bel is too big, it was as a new unit, is decibels (DB) Bel divided by 10 is dB expression is: dB = 10lg (P/Po), dB = E/20lg (Eo), dB = 20lg (I/Io).