Realize the AV realm of two speakers-virtual surround sound technology QS7779

Dolby directional logic surround sound of Fengmo Global is captivated by its magnificent sound field and realistic space sense, accurate sound image positioning, and Dolby Digital AC-3 is even more fascinating for enthusiasts. However, the penetration rate of home theaters built with this technology in the home is not very ideal: because the entire system needs to configure 5-6 speakers, multi-channel power amplifier, which is expensive, and also has certain requirements for the listening environment and speaker placement For Chinese people, the economy is not very affluent, and the living environment is not very spacious (the listening environment is mostly more than ten square meters). There is a certain financial burden. It is also difficult to place 5-6 speakers reasonably.

In response to these problems, the audio industry has launched a new generation of surround sound technology-virtual surround sound technology. The entire system has a simple composition, low cost, high cost performance, and low requirements for the positioning of the speaker, which is not limited by the listening environment area. , Only two speakers can produce the effect that is very close to the Dolby multi-sound effect. Virtual surround sound technology is to decode the Dolby surround signal and perform virtualization processing, then mix with the main channel and use a pair of speakers Amplifier can produce Dolby multi-channel effect, can feel the sound of front, back, left, right and up and down, sound image positioning is accurate, very wonderful, immersive feeling, truly realize the home theater of two speakers!

Virtual surround sound technology is a signal processing technology that uses the human head sound transfer function HRTF (Head Related Transfer FuncTIon). By performing complex calculations on the decoded multi-channel signal with HRTF, the sound in the three-dimensional space is processed according to HRTF. The sound entering the human ear conforms to the human binaural effect and the pinna effect, so using two speakers can produce a surround effect that is very close to Dolby multi-channel, and you can feel the sound emitted at any point in the space. Like accurate positioning, you can feel the position of the front, back, left, up and down of the sound, which is very wonderful. I ca n’t believe such a sound technology if I do n’t experience it myself!

The "virtualization" of Dolby surround sound is the special processing of the surround channel according to the principles of human physiology and psychoacoustics, creating a phantom image of the surround sound source from the back or side of the listener. The principles that affect human ear hearing are: â‘  binaural effect; â‘¡ pinna effect; â‘¢ frequency filtering effect of human ear; â‘£ head sound transfer function HRTF. However, the physiological status of people of different ages, genders, and races differs greatly, and the head sound transfer function HRTF has great differences. Therefore, to achieve accurate sound localization for virtual surround sound, a strong sense of presence is required. For efficient and accurate calculation of HRTF, based on the introduction of American Stereo Review 98.8, there are currently six kinds of virtual surround sound schemes for listening comparison: Q-Surrornd of Canada Q-Sound Company is the best. Q-Surround was developed by a large number of audio engineers and experts in the Q-Sound laboratory who spent several years testing the sound source localization characteristics of the human auditory system through a large number of listening tests. Q-Surround can maintain the original Some fidelity, with a strong sense of space and surrounding, sound positioning is quite accurate.

According to the psychoacoustics and physiological acoustics of the human ear, human hearing is based on the binaural effect. According to research, both ears are located on both sides of the skull, and the sound from the same sound source is due to the blocking effect of the head and the sound source and the two ears. The distance, the sound reaching the two ears has a certain time difference, phase difference and intensity difference, and has the spatial spectrum characteristics of HRTF. The human brain will judge the direction of the sound according to these differences, and the spatial direction of the sound will be generated in the human brain. image. Virtual surround sound technology is built based on these basic principles, so only two speakers can be used to produce sound with accurate, realistic, and live effects, so that the listener feels immersive and can feel behind him The sound produced.

Virtual surround sound technology is an economical and simple home theater solution, widely used in power amplifiers, car stereos, large-screen TVs, active speakers, multimedia computers, DVDs, VCDs, etc. For fans who already have power amplifiers, just Make a finished board of virtual surround sound processor, add it between the sound source and the power amplifier to upgrade. In order to facilitate the majority of enthusiasts, here is a virtual surround sound processor circuit (see Figure 1). Its peripheral components are simple, easy to manufacture, and the effect is good!

The QS7779 in the picture is designed by the famous Seponix audio company in the United States, and produced and packaged by Yamaha Corporation in Japan. The chip adopts Q-SurroundTM, the top technology of Canada Q-Sound Lab, and is certified by Q-Sound Lab. It can decode the mixed signal of Dolby Pro Logic and Dolby Digital AC-3 and perform 3D Virtualization, Dolby multi-channel effect can be produced through two speakers. Pins 4, 5, 17, and 18 are the input and output terminals of the left and right channel signals, pin 6 is the central signal output, and pin 7 is the central signal input terminal (generally pins 6 and 7 are connected through a 3.9k resistor. The chip board's evaluation board circuit is designed to be centrally adjustable), pin 23 is a positive power supply, pin 11 is a power ground, pin 16 is a mute control terminal (open at high level, the output is silent), and pin 12 is a three-dimensional virtual Processing level switch (strong at high level and weak at low level), pin 13 is through and 3D virtual surround sound processing control terminal (high level is through, low level is 3D virtual surround sound on).

The basic characteristics and parameters of QS7779: ① can decode Dolby directional logic and Dolby Digital AC-3 surround sound mixed signal and realize three-dimensional virtual surround sound processing; ② 24-pin SSOP (SMD) package; ③ working voltage: DC5－ 13V (typical application 9V); ④ Signal-to-noise ratio dynamic range: 110dB; ⑤ It can also produce a strong surround and spatial 3D stereo enhancement effect for ordinary two-channel sound sources, which is very lively.

It is recommended to assemble a high-performance AV combination solution here: audio source → virtual surround sound processor (QS7779) → volume tone (such as LM4610N, etc.) → power amplifier (such as 3886, 7294, 1514, 1875, etc.) → speaker protector → speaker In addition, the effect of BBE is better (added between the tone and the virtual surround sound processor). The power supply parts such as the power supply of the ring cow, the power amplifier level and the front level, etc., need a little grounding method during assembly. Will forget!

Finally, I will talk about some of the author's experiences. Before I touched and listened to the QS7779, the author has always been skeptical of the virtual surround sound technology. How can the two speakers create a Dolby multi-channel effect? Obviously two speakers are placed in front, what could possibly be heard behind the shell explosion? Will the plane fly overhead from behind? ... a series of question marks drove me to act quickly, and produced a finished board of Figure 1 (the components are imported high-quality fever products) and listened to it. The audio source was a Supervision VCD, and its output was connected to QS7779, and then QS7779 was output. Connected to the front input of the front and rear power amplifiers of the sound and sound SA38 / SP338, the speakers are dual 6-inch half with super bass, the TV is a large musical screen, and a Dolby disc "Broken Arrow Action" is put into the DVD player , Looking forward to the appearance of the wonderful virtual surround sound, and indeed turned the author's series of question marks into exclamation marks! There is indeed an accurate sound image localization, and the sound is very shocking. For example, the sound effect of an aircraft flying from the front direction: when passing through, the sound of the aircraft moves from the right speaker to the left speaker, and when the virtual surround sound processing is turned on, you hear the right front direction flying to your left and rear, and feel the aircraft flying overhead The sound is very realistic. Make people feel as if they are immersed in the world ..., without too much description here, let the readers experience it and feel it!

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Virtual surround sound processor chip QS7779

The author of virtual surround sound technology came into contact in 1999 ...

Published on 2006-04-17 23:51 • 3094 views

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