Virtual surround sound processor chip QS7779

The virtual surround sound technology was only touched by me in 1999. This technology only needs two speakers to produce Dolby multi-channel effects. It can feel the sounds of the front, rear, left and right, the sound positioning is accurate, and the experience is immersive. It's amazing, it's hard to believe that there is such a sound technology if you don't experience it for yourself. To be honest, I did n’t believe it before I tried the QS7779 virtual surround sound processor, and I always held a skeptical attitude. After listening to the QS7779, I was convinced that it is true that there is this advanced audio technology!

Virtual surround sound technology is a signal processing technology that uses the human head sound transfer function HRTF. By decoding the mixed signal of Dolby directional logic or Dolby Digital AC-3, the multi-channel signal is calculated by HRTF. The sound in the three-dimensional space is processed according to HRTF, so that the sound entering the human ear conforms to the binaural effect and the pinna effect of the human, and accordingly generates a sound image in the spatial direction of the human brain, so the virtual surround sound technology can be generated with two speakers The sound positioning is accurate and realistic, and the sound with a live effect makes the listener feel like being there. What is even more wonderful is the sound that can be felt behind him!

Here we will introduce the application of virtual surround sound processing chip QS7779 to readers. QS7779 has two types: QS7779CM and QS7779PM. The latter is CM in I2C bus control mode, and PM is 3-wire serial control mode. Both can be applied. For parallel control, high and low levels can be used to control, the performance is the same.

QS7779 is designed by the famous American Seponix audio company and produced and packaged by Japan Seiko Corporation (NPC). The chip adopts Q-SurroundTM, the top virtual surround sound technology of Canada QSound company, and is certified by QSound laboratory. The chip can perform 3D stereo enhancement processing and 3D virtual surround sound processing. It can decode the mixed signal of Dolby directional logic or Dolby Digital AC-3 and perform three-dimensional virtual surround sound processing. Only two two-channel power amplifiers are used. The speaker can produce a three-dimensional virtual surround sound field that is comparable to Dolby multichannel.

Figure 1 is the internal circuit structure diagram of QS7779, which is composed of surround sound decoder, 3D virtual surround sound processor, mixer, data input circuit, working mode control circuit, etc .; Figure 2 is the author's application information according to the chip The designed application circuit, the center signal can be adjusted through RP1, which can properly adjust the vocal dialogue. The circuit is equipped with reverse power protection and three-terminal voltage regulator, which is very convenient to add into the power amplifier, DVD player, active Speakers, multimedia computers, car audio, etc., because of the three-terminal voltage regulator, the DC power supply can be taken from the DC power supply (+ 10V-24V) in the machine to be installed. If there is no suitable power supply, a transformer and bridge rectifier filter circuit can be added , But one more transformer will cause one more electromagnetic field to interfere with the audio.

In Figure 2, pins 4 and 5 of QS7779 are the signal input, pins 17 and 18 are the signal output, pin 6 is the center signal output (you can connect the amplifier to drive the center speaker), and pin 7 is the center channel signal. The input terminal (Figure 2 inputs the 6-pin neutral signal by RP1), 23 pin is the positive power terminal, 11 pin is the power ground, and the capacitance of 1-3 pin, 19-22 pin and 24 pin is the external connection of the 3D enhancement circuit Capacitor, pin 15 is the digital control power supply, pin 16 is the mute control terminal, the mute is effective at high level, pin 13 is the control terminal for switching between the pass-through and 3D virtual surround sound processing, pass-through at high level, and 3-D virtual surround sound at low level Processing status, pin 12 is the control terminal of the processing effect. When the level is low, the effect is weak, and when the level is high, the effect is strong.

The basic characteristics and parameters of QS7779CM / PM: ① can decode Dolby directional logic or Dolby Digital AC-3 mixed signal and realize three-dimensional virtual sound processing; ② can also perform three-dimensional stereo enhancement processing on ordinary stereo sound sources (this kind of The three-dimensional enhancement effect is better than that of SRS); ③Working voltage (23) feet: 5 to 13V (typical application 9V); ④Signal to noise ratio dynamic range: 110dB; ⑤24-foot SSOP (patch) package; ⑥Input impedance 20KΩ; ⑦ Working current (at 9V): 5mA.

QS7779 has the advantages of simple peripheral components and good surround effect. It is widely used in power amplifiers, car stereos, large-screen TVs, active speakers, multimedia computers, VCD players, etc. Interested enthusiasts can add the finished board of Figure 2 You can upgrade it to a two-speaker home theater in your own audio system (installed between the audio source and power amplifier) ​​and enjoy the same virtual surround sound as Dolby multi-channel surround!

To play the best scene of QS7779, material selection is also very important! The author's design —————— ①The input and output coupling capacitors use Japanese ruby, black diamond and other capacitors with excellent performance; ②The electrodeless capacitors should use Japanese music sound metalized non-inductive capacitors, or MKP capacitors; ③The circuit board uses epoxy The circuit board is silver-plated; ④ The resistance is made of five-color ring metal film with low noise, and the potentiometer is imported W · L genuine goods; ⑤ Other capacitors are made of Japanese rubies, black diamonds, etc. I believe that the material selection of the author is impossible for the master of the motorcycle!

Speaking is without proof, and hearing is true. The author assembled a set of value-added home theater combinations with the circuit of FIG. 2 and related circuits and conducted a trial listening. The configuration is as follows: Sound source (Xianke AL-P700K Super VCD) → QS7779 → LM4610N (with volume, tone, balance, equal loudness control and 3D processing circuit) → power amplifier circuit (TDA7294 current feedback DC servo type). A Dolby disc "Operation Broken Arrow" was put into the Yushchenko Super VCD. With the development of the plot, the sense of three-dimensional space and surrounding is very strong. With the appearance of the aircraft, wow! A very realistic sense of presence emerged: I heard the plane flying from my right front to my left rear, and felt the sound of the plane flying overhead, so I felt like being there! I didn't believe it at first, so I pressed the repeat button and listened several times, and then connected the QS7779 to the through state. I only heard the sound of the aircraft. The right speaker moved to the left speaker, and the sound effect was very monotonous. Then QS7779 was connected to the three-dimensional virtual surround sound processing state and continued to listen ... The whole viewing process is very realistic, the sound image positioning is accurate, and the experience is immersive. Later, when I added the BBE circuit (XR1071) between QS7779 and LM4610N, I found that the sound positioning is more accurate, and it is very clear, and the sense of presence is better!

The author tried to play a common stereo CD. After QS7779 processing, the clarity and transparency of its sound quality have been significantly improved, and its three-dimensional spatial sense is very good, which is better than the three-dimensional spatial sense of SRS: because SRS is about two The difference and sum of the channel signals and the characteristics of the filter are used. The enhanced stereo will completely lose directionality in hearing and become a stereo mono sound. The QS7779's three-dimensional stereo enhancement processing is QSound. —— Separate the left and right channels, and use the characteristics of the phase difference filter to enhance the three-dimensional stereo effect. The three-dimensional stereo enhancement technology in QSound mode makes the left and right channels highly independent, and there is no added component of the left and right channel signals. Therefore, it can faithfully reproduce the three-dimensional stereo effect of the recording scene.

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