Surround sound circuit composed of TDA3810

Figure 1-122 is a surround sound circuit composed of a dedicated high-fidelity surround sound processing integrated circuit TDA3810.
The stereo signal is input to pins 2 and 17 via the input coupling capacitor cJ and C2. After being buffered by the internal amplifier, the left and right channel signals
are divided into two channels respectively. One channel is directly output from pins 3 and 16 and is used as the signal of the main speaker . The other channel is sent to an active phase shifter for
phase shifting. At the same time, the active phase shifters of the left and right channels realize the inversion between the two channels through the common resistor R. Phase crosstalk forms
(L one foot) and (R - L) signals. The depth of the crosstalk depends on the ratio of R4 (Rs) and Rg. The larger the Rg, the shallower the crosstalk depth
. The external brain components R3, F, C4, q (Rs, R7, Cii, C12) and the internal operational amplifier and resistors constitute an active phase shifter
. The degree of phase shift can be adjusted by changing the resistance of R (R5). The larger the value, the larger the phase shift. After anti-phase
crosstalk and phase shift, the (L-R) and (R-L) signals pass through the electronic selection switch inside the circuit and are output from pin 613
as the signals of the left and right sub-speakers. . The electronic selector switch is used to select the working state of the circuit. When the switch SA on pin 11
is turned off, pin 11 is high level and the circuit is in surround sound state. When switch SA is closed,
pin 11 is placed at 0 level, and the circuit is in stereo working state, that is, straight-through state. At this time, after the stereo signal
is input from pins 2 and 17, it is directly output from pins 3, 16 and 6 and 13 through the electronic selection switch. The light-emitting diode VDi on pin 7
is used to display the surround sound working status. & is the decoupling capacitor of the internal reference power supply of the integrated circuit, island is the buffer capacitor t of the internal electronic selection switch, which is used to eliminate the switching
noise generated during switch switching , and cs is the power supply decoupling capacitor. Resistor Rz (R6) mixes part of the sub-speaker signal into the main speaker signal to form L+ card (L-R) and R+ string (Chi- L) ​​signals and send them to the main speaker o