JPH0328639Y2 - - Google Patents

Description

[Detailed explanation of the idea]

B. Field of Industrial Application The present invention relates to a surround circuit. B. Prior Art Recently, a four-speaker drive circuit called a surround circuit (a circuit that uses four speakers placed in front and rear to surround the device with sound from all sides to create a sense of presence) has been attracting attention. This surround circuit was published in the May 1985 issue of Radio Technology, pages 103 to 107.
It is introduced on page. However, there has been no simple and functional circuit configuration that can efficiently produce surround effects during monaural or stereo reproduction of sound sources. C. Problems that the invention aims to solve The present invention has been made in view of the above-mentioned points, and has a simple and functional circuit configuration that can efficiently obtain a surround effect during monaural or stereo reproduction of a sound source. This is what we do. D. Means for Solving the Problems The present invention includes a main left channel input signal terminal, a main right channel input signal terminal, a surround processor, and the surround processor mixes or processes both signals from both input signal terminals. A stereo/monaural switch that selectively supplies signals;
The surround switch is configured to supply the output of the surround processor to the main and sub channel output signal terminals. E. Effects According to the surround circuit of the present invention, when the surround switch is turned on when switching to stereo, a stereo surround effect can be obtained, and when the surround switch is turned on when switching to monaural, a pseudo-stereo surround effect can be obtained. Embodiment Fig. 1 is a circuit diagram of a surround circuit according to an embodiment of the present invention, where 1 is the main left channel input signal terminal, 2 is the main right channel input signal terminal, and the signal is input from the stereo multiplex circuit (not shown). Supplied. 3 and 4 are buffer amplifiers, 5 is a differential amplifier,
A buffer amplifier 3 is connected to the inverting input terminal, while a non-inverting input terminal is connected to the buffer amplifier 4 when switching to stereo by a stereo/monaural changeover switch _S1-2 . _S1-1 is a stereo/monaural changeover switch linked to _S1-2 , which mixes the main left channel input signal L and the main right channel input signal R when switching to monaural. 6 is a surround processor that mainly creates primary reflected sound, and a low-pass filter 7 whose cutoff frequency is 4KHz;
a delay circuit 8 that delays the output of the circuit to create a primary reflected sound, and a delay circuit 8 that removes noise in the output of this delay circuit 8.
A low-pass filter 9 that cuts off frequency signal components of 4KHz or more, a high-pass filter 10 that has a cutoff frequency of 4KHz, and a variable filter that adjusts the output of the high-pass filter 10 and the output of the low-pass filter 9. Resistor 1
It consists of 1 and 12. Note that the cutoff frequency may be selected to be 4 KHz or less, since the primary reflected sound is created with a greater delay effect as the lower frequency components of the signal are applied. S _2-1 and S _2-2 are surround switches that lead the output of the surround processor 6 to a subsequent stage, and their movable contacts are connected to variable resistors 11 and 12, respectively, when ON, and to ground when OFF. Reference numeral 13 denotes an adder that adds the outputs of the surround processor 6 (the outputs of the low-pass filter 9 and the high-pass filter 10) when the surround switches S _2-1 and S _2-2 are turned on. The output of this adder 13 is sent to the sub-left channel output signal terminal 14.
is used as the sub-left channel output signal (first sub-channel output signal). Reference numeral 15 denotes a phase shifter, which shifts the sub-left channel output signal by a phase angle to obtain the effect of shifting the sound source. The output of this phase shifter 15 is guided to a sub-right channel output signal terminal 16 and used as a sub-right channel output signal (second sub-channel output signal).
17 is an adder connected to the transmission line of the buffer amplifier 3, which adds the main left channel signal L and the output signal of the adder 13, and outputs the main left channel output signal terminal 18.
is used as the main left channel output signal. A differential amplifier 19 differentially amplifies the outputs of the adder 13 and the buffer amplifier 4, and outputs it to the main right channel output signal terminal 20 as a main right channel output signal. The operation of the present invention having the above-mentioned configuration will be explained. [] Stereo/monaural switch S _1-1 ,
When S _1-2 is switched to stereo and surround switches S _2-1 and S _2-2 are ON, the main left channel input signal L and the main right channel input signal R are input to the differential amplifier 5. Since the amplification factor is 1, the R-L signal is supplied to the surround processor 6. The R-L signal is processed by the surround processor 6, where the frequency signal components below 4KHz are delayed and the primary reflected sound (r-l)' (main left channel signal L and main right channel signal R of the original signal) is processed.
Since the frequency signal components are different from that of
is separated into a frequency signal component (r-l)'' of 4KHz or higher. Then, the adder 13 adds both signals ((r-l)' and (r-l)''), and Channel output signal (r-l) (=(r-l)'+(r
This sub-left channel output signal is phase-shifted by the phase angle at the phase shifter 15 (signal (r-l)), creating a feeling that it is not localized as a sound source. The output becomes the sub-right channel output signal.Similarly, the adder 17 and the differential amplifier 19 output the main left channel output signal L+(r-l) and the main right channel output signal R-(r-l), respectively. A signal with a sense of spaciousness can be obtained. [] When switching to stereo, the surround switch
When S _2-1 and S _2-2 are OFF In this case, the non-inverting input terminal of the adder 13 is disconnected from the surround processor 6 and grounded, so the sub-left channel output signal and sub-right channel output signal are zero. becomes. Therefore, the main left channel output signal is the same as the main left channel input signal L, and the main right channel output signal is the same as the main right channel input signal R. [] Surround switch when switching to monaural
When S _2-1 and S _2-2 are ON In this case, the input signal of the differential amplifier 5 is the sum of the main left channel input signal L and the main right channel input signal R. Therefore, this sum signal (L+R)
is the surround processor 6, the low pass filter 7,
9. The delay circuit 8 creates a first-order reflected sound (r+l)' signal, and the high-pass filter 8 extracts the high-frequency component (r+l). Therefore, the adder 1
The output of 3 is (r+l)=(r+l)′+(r+l)″
This becomes the sub-left channel output signal (first sub-channel output signal). In addition, the phase shifter 15
The sub-right channel, which is the signal of (r+l),

【table】

Claims (1)

[Scope of utility model registration request] a main left channel input signal terminal, a main right channel input signal terminal, and a surround processor that delays at least the input signal to generate reflected sound;
a stereo/monaural changeover switch that switches between monaural and stereo and selectively supplies a signal obtained by adding or subtracting both signals of both input signal terminals to the surround processor according to the switching; A surround circuit comprising a surround switch that supplies output to main and sub channel output signal terminals.