In 1927 the United States people DE forrester invented the vacuum triode, created the human electroacotechnology first. In 1927, bell LABS invented the negative feedback technology, make sound technology development haentered a new era, is the typical such as Williamson amplifier, the successful use of the negative feedback ampltechnology, and the distortion degree of greatly reduced. In the 1950 s, tube amplifier development reached a climax periokinds.
 
of tube amplifier emerge in endlessly. Due to the tube amplifier tone sweet, fruity, still for enthusiasts preference.the 1960 s the emergence of the transistor, make broad sound lovers into a wider sound heaven and earth. Tramplifier has exquisite moving tone, low distortion, a wide frequency response and dynamic range etc. In the early 1960 s,the United States launched in audio technology of new members - integrated circuit, by the 70 s, the integrated circwith.
 
its high quality and reasonable price, small volume, function paper has sound world known. Developed so far, tthick film sound integrated circuit, operational amplifier IC is widely used in audio circuit.Japan produced the first littlfield effect power tube. Due to the field effect power tube with tube pure thick, sweet tone and dynamic range of 90 dTHD < 0.01% (100 KHZ) characteristics, soon in the acoustic boundary pop. Today's many amplifier is used the mosfets

as final output. Family combined sound species usually speak combination sound have desktop music center and console audio system two kinds big. Because of the requirements of music center have relatively high sounquality, so it's two speakers general volume is larger. Edit this section two, the structure of the host audio classification oof the two and layered. In one of the combined sound, it's all part of the circuit (including the record player) in a casthis

structure are used for low-end combination of sound. In the layered combination sound, according to the grade of the machine different points of the layer is different also. Layered more music center are: record player a layer, CD player a layer, tuner a layer, double cassette tape deck a layer, tone controller a layer, the main power amplifierlayer. In the hierarchical less music center, the record player, CD player each layer, and the other is a layer.Miniaturization, digital, specialization, the film and television change is a family sound will be an inevitable trend of development.