JPS647423B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for preventing the generation of harsh noise. 2. Description of the Related Art There is a known device that mixes music obtained from a music source such as a magnetic tape or record with a singing voice blown into a microphone, and emits the sound from a speaker. This is usually called a karaoke device, and it is currently very popular because it allows people to sing easily without the need for live music. However, such karaoke devices are equipped with various tricks so that the singing voice can be heard well, and for example, they have built-in echo circuits to apply an echo to the singing voice. The echo circuit is usually
Those that use BBD (Bucketed Brigade Device) are often used. The BBD has a plurality of MOS transistors and a plurality of capacitors connected in series in several thousand stages, and delays an input signal at each stage to generate an echoed signal at the output terminal. This BBD is extremely superior in terms of echoing and is easy to handle, so it has replaced conventional spring-type or acoustic pipe-type echo devices. Noise caused by the clock signal (usually several KHz) used to drive the
Since several thousand stages of MOS transistors are connected, the MOS transistor itself has the disadvantage that the noise generated (over the entire frequency band) is extremely large. The noise generated from the BBD is not very noticeable due to the masking effect when the signal from the music source or the signal from the microphone is present, but when both of the above signals are absent, it becomes harsh, and the quality of the karaoke equipment increases. This was a serious loss. The present invention has been made in view of the above points, and will be described below based on embodiments with reference to the drawings. FIG. 1 shows an embodiment of the present invention, in which numeral 1 is a magnetic head for picking up music recorded on a magnetic tape, numeral 2 includes an amplification stage 3 and a variable resistor 4; The first transmitting signal
A signal path, 5 is a microphone into which the singing voice is blown, 6 is an amplification stage that amplifies the signal from the microphone 5, 7 is a second transmission path that transmits the output signal of the amplification stage 6, 8 is a BBD 9 and a variable resistor. 10, a third signal path for generating an echoed signal based on the output signal of the amplification stage 6; 11 , an output signal of the second signal path 7 and an output signal of the third signal path 8 ; 12 is a second mixing circuit that mixes the output signal of the first signal path 2 and the output signal of the mixing circuit 11 , and 13 amplifies the output signal of the second mixing circuit 12. Main amplifier circuit, 1
4 is a speaker that generates sound according to the output signal of the main amplifier circuit 13; 15 is a detection circuit for detecting whether or not a signal is present in the first signal path 2 ;
Reference numeral 6 denotes a signal cutoff circuit for short-circuiting the output end of the third signal path 8 to ground in response to the output signal of the detection circuit 15 . The music signal picked up by the magnetic head 1 is applied to a second mixing circuit 12 via a first signal path 2 . Further, the singing voice blown into the microphone 5 is applied to the first mixing circuit 11 via the second signal path 7 and the third signal path 8 including the BBD 9. Therefore, in the first mixing circuit 11 , the singing voice signal and the echoed singing voice signal are mixed, and in the second mixing circuit 12, the music signal and the output mixed signal of the first mixing circuit 11 are mixed, and the whole The mixed signal is amplified by the main amplifier 13 and then applied to the speaker 14. Now, the magnetic tape is stopped and magnetic head 1
If no music signal is generated from the detection circuit 1
Transistor 17 of No. 5 is off, so transistor 18 of cutoff circuit 16 is off and transistor 19 is on. Therefore, the output end of the third signal path 8 is grounded by the collector-emitter path of the transistor 19, and the generation of noise due to the BBD 9 is prevented. In that case, since the second signal path 7 is normally connected, the signal injected into the microphone 5 passes through the second signal path 7 , the first mixing circuit 11 , and the second mixing circuit 12. The voltage is applied to the main amplifier circuit 13, and the function of the microphone 5 can be maintained. Next, when the magnetic tape runs and a music signal is generated from the magnetic head 1, the music signal is applied to the second mixing circuit 4 through the first signal path 2. At the same time, the music signal is transmitted to the detection circuit 1 via the capacitor 20.
The voltage is applied to the base of the transistor 17 of No. 5 to turn on the transistor 17. Therefore, the capacitor 22 is charged via the diode 21, the transistor 18 of the cutoff circuit 16 is turned on, and the transistor 19 is turned off, so the cutoff circuit 16 has no effect on the third signal path 8 , and the microphone The output signal of 5 is applied to the first mixing circuit 11 through a second signal path 7 and is applied to the first mixing circuit 11 through a third signal path 8 comprising a BBD 9 .
is applied to Therefore, the speaker 14 generates a sound corresponding to the mixed signal of the music signal and the echoed singing voice signal. The capacitor 22 of the detection circuit 15 is arranged to prevent the cutoff circuit 16 from operating when there is a pause in the music or when the level drops (for example, in the case of pianissimo). Third
This prevents the signal path 8 from being turned on and off when unnecessary. Therefore, according to the embodiment shown in FIG. 1, when a music signal is present, an echoed singing voice signal can be mixed with the music signal, so that there is an advantage that the user can sing in a good mood, and This has the advantage that noise generated from the BBD can be reliably prevented when no music signal is present. FIG. 2 shows another embodiment of the invention, in which only when the output signal of the microphone 5 is present;
The third signal path 8 is configured to generate an output signal. In FIG. 2, the circuit configuration is exactly the same as in FIG. 1 , except that the input end of the detection circuit 15 is connected to the second signal path 7 instead of the first signal path 2, so the details are as follows. Further explanation will be omitted. In FIG. 2, since the input end of the detection circuit 15 is connected to the second signal path 7 , the BBD 9 is included only when the singing signal from the microphone 5 is present in the second signal path 7 . The output signal of the third signal path 8 is generated. Therefore, since the output of the third signal path 8 is generated only when the original function of the BBD 9, that is, the function of applying an echo to the output signal of the microphone 5, is required, the circuit of FIG. In particular, the speaker 14 allows music signals to be heard without noise.
This has the advantage that it is possible to transmit echoes to audio signals only when necessary, regardless of the presence or absence of music signals. As described above, the noise prevention device according to the present invention can effectively remove noise generated from a harsh BBD, and is particularly effective when used in a karaoke device.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the invention, and FIG. 2 is a circuit diagram showing another embodiment of the invention. Explanation of main drawing numbers, 2 ...First signal path, 7 ...Second signal path, 8 ...Third signal path, 9...BBD, 1
1...First mixing circuit, 12...Second mixing circuit, 1
5...detection circuit, 16 ...cutoff circuit.

Claims (1)

[Claims] 1. In a device that generates a mixed signal of a signal from a music source and a signal from a microphone,
a first signal path for transmitting a signal from the music source, a second signal path for transmitting a signal from the microphone, and a third signal path including a BBD for echoing the signal from the microphone. a signal path; a mixing circuit for mixing the output signals of the first to third signal paths; a detection circuit for detecting the presence of a signal from the music source or the presence of a signal from the microphone; a signal cutoff circuit for cutting off the generation of the output signal of the third signal path according to the output signal of the circuit, and the BBD
A noise prevention device characterized in that it is designed to block harsh noises generated from.