System block diagram of YSS241

YSS241 is a synthetic Dolby Pro Logic decoder chip. Its internal processing operations are all digital .
It uses advanced digital signal processing technology to complete Dolby Surround Sound decoding, so it is also called a digital Dolby Pro Logic
decoder .
    Digital Dolby Pro Logic decoder provides higher accuracy and lower distortion. Figure 9-37 is the system
block diagram of YSS241.

38. Several Dolby Pro Logic surround sound decoders introduced above all use special chips, and their circuits are also relatively complex.
  In fact, according to the principle of Dolby Surround decoding, a simple Dolby Surround decoder can also be formed using an operational amplifier.
    The schematic diagram of this decoder made with an operational amplifier is shown in Figure 9-38. It can be seen that the circuit is very simple, using only
  blue chip dual operational amplifiers.
    The left and right channel composite stereo signals pass through the coupling capacitors cl and C2 to the potentiometer RPt for volume adjustment, which is the main volume control of
  this decoder. For standard decoders, considering the signal-to-noise ratio, the volume potentiometer should generally be used after the decoder.
  potentiometer, but it must be a four-way or five-way potentiometer, which will inevitably increase the cost of the decoder. Here we connect the volume potentiometer to
  the signal input end.
    The main channel signal passes through a buffer amplifier with a gain of 1 composed of Icl, and is output through Rl l and R12. IC2A forms a
  subtractor circuit, which subtracts the left and right channel signals to generate the LR rear surround S channel signal. R7 and C4
  form a low-pass filter with a frequency of 7kH to prevent the high-frequency signals of the surround channels from affecting
  the directionality . IC2B is the buffer stage for surround sound signal output.
    The adder circuit composed of Rl, R2 and IC3A adds the left and right channel signals to obtain the L+R center channel
  signal. Min~Rio, c5~C7 and IC3B are a third-order low-pass filter with a turning frequency of about 100Hz, which
  is output as a subwoofer signal.
    This circuit uses a ±15v dual power supply.
    When making the circuit, pay attention to the quality of the components. After welding, the circuit can work normally without debugging. It should
  be noted that this circuit is a simple decoder . The separation is not high, but its circuit is simple and can be used in situations
  with low requirements .
    Above we have introduced several application circuits of Dolby Pro Logic surround sound decoders . It can be seen that computer control and digital signal processing technology are widely used in the circuits of audio and video equipment. The application of these technologies improves   the performance
  of all aspects of the equipment.
A substantial increase. It can be said that the digital era of home theater has arrived.