Since the Lumiere brothers put the first film on the screen in 1894, the film sound technology has been accompanied by its simultaneous development. In the early days of the film, because there was no power amplifying device, the method of dubbing by the on-site personnel was used. High-end screening places sometimes used dubbing workers who were almost as many as the number of actors. Most movies are silent because they are not available.
In 1928, the world's first sound film was finally interviewed. However, due to its use of electronic tubes, its benefits were only between 1% and 2%. Moreover, as the use time increases, the electrode gradually ages and the tube eventually stops working.
The birth of the transistor in 1947 caused a revolutionary qualitative change in the sound-reducing amplification technology. People can finally hear sounds with sufficient sound pressure and better audio quality in the cinema. In the 1960s, tubes have been widely used in various industries.
However, human beings are pursuing 100% perfect animals. We plan to require an amplifier with an energy consumption ratio of 100% and a sound output distortion of 0%. The ultimate benefit of transistor Class A amplifiers is 25%, and Class B amplification can increase the theoretical benefit to 78.5%. However, crossover distortion and overload distortion for Class B amplification are not acceptable to the user. Therefore, the R&D personnel integrated the two technologies of AB to form an amplifying circuit called AB, but the benefit is drastically low, and the theoretical value is only about 40%. However, the stagnation of this technology is almost 50 years. In the past 50 years, there have been few new technological breakthroughs.
In 2010, the US FOCUX company used the digital amplification principle for the first time in film reverberation technology. This revolutionary technology application has improved the power efficiency to more than 90%, and there are almost no problems such as crossover distortion and phase distortion.
In 2013, Chen Xing Technology launched the digital audio processor M28, which is the latest cinema processing product specially designed for the new digital cinema environment. It can receive audio signals from a variety of digital audio sources and process them. Control anywhere in the network. The M28's high reliability ensures that viewers can get a first-class video viewing experience at any time, anywhere. The Zhichen M28 can help you take advantage of the exciting new entertainment opportunities that digital cinema brings. Not only powerful but also very economical, it is the best choice for digital cinema sound system. No matter whether it is before or after the film screening, the audience can always enjoy the perfect surround sound effect without the source of the program. influences.
The so-called digital amplification technology, also known as the class D amplification technology, is in a completely different way of working with the previous class AB amplification. The power amplifier tube of the digital power amplifier works in the switching state. In theory, the internal resistance of the transistor is zero when the transistor is turned on, and there is no voltage at both ends. Of course, there is no power consumption. At the time of cutoff, since the internal resistance is infinite, the current is zero. Does not consume any power. Therefore, the transistor itself as an amplifying element does not consume power itself, and the utilization rate of the power source is very high. Because of its working state in the switch state, there is naturally no so-called intermodulation distortion, crossover distortion, overload distortion, etc., and because of its use of pulse modulation amplification, ordinary electromagnetic interference has no effect on it. These characteristics are incomparable to the traditional amplifiers in terms of sound quality, which makes the user feel the transparency, resolution, and tranquility of the background. Moreover, due to its high efficiency and low loss, its heat dissipation structure can be made very small and simple, and the whole machine is only 1/4 to 1/2 of the volume of the conventional power amplifier.
The concept of digital power amplifiers was proposed as early as the 1960s and 1970s, but the technical conditions were limited and the progress was slower. In 1983, MBSandler et al. proposed the basic structure of a class D amplified PCM digital power amplifier: how to turn the PCM signal into a PWM (pulse widening signal). The sound information is buried in the duty cycle or pulse density of the pulse. The signal density is represented by the pulse density, where the pulse density is large, indicating that the voltage is high; in a rare place, the voltage is low. This laid the foundation for modern digital amplification theory.
There are two ways to obtain the audio PWM code. One is to directly generate PWM digital audio by analog-to-digital conversion of the analog audio signal. The second is to convert other encoded digital audio, such as PCM encoding of CD, into a PWM code by digital signal processing technology. After obtaining this, the signal is used to control the large current switching MOSFET power tube, and the power tube outputs a large energy PWM code. The magnitude of the output voltage is determined by the supply voltage, which is determined by the impedance of the load speaker and the form of the circuit. The power tube works in the switching state. As long as the switching characteristics are good, the linearity requirement is almost no, and the manufacturing cost is lower than that of the audio tube. This type of MOSFET is very common in industrial control, and it is convenient to take materials. In order to make better use of the new and popular productions on the market, the Chenxing M28 can add two digital audio inputs in addition to the digital audio of the digital cinema server. The Chen Xing M28 can receive almost 8 channels of AES audio from any digital cinema server. At the same time, fiber optic and S/PDIF coaxial digital inputs can also receive digital audio output signals from civilian products. The microphone and analog asynchronous input make the M28 even more powerful.
In the early days, due to the technical development limitations of MOSFETs, such amplifiers were only used in low-power applications. As the stability and power of MOSFETs increased, they were gradually applied to high-power circuits.
The superiority of digital power amplifiers is obvious. As the products mature and stabilize, large-scale digital amplification completely replaces analog amplification is only a matter of time.
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