JPH0345287Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a tape recorder having a microphone mixing function and a music selection function. (b) Prior Art Conventionally, such a tape recorder has a circuit configuration as shown in FIG. An output path 8 leads the output to the speaker section 7 through the amplifier 6. When an external microphone is connected to the microphone jack 9 and an external microphone is used, the microphone signal from the external microphone is amplified by the amplification transistor 10 and then sent to the input side of the line amplifier 4. The microphone mixing circuit 11 is supplied with power supply voltage (+B) by the music selection switch 12, which is closed during the music selection operation, and is activated.In this activation state, the microphone mixing circuit 11 determines whether or not there is a signal output from the line amplifier 4 and performs the music selection. 13 is a plunger that is driven to cancel the song selection state when the song selection circuit 11 determines that there is no reproduction signal; 14 is its collector;
A muting transistor whose emitter path is connected between the output line 15 of output path 1 and the ground, and the power supply voltage (+B) is applied to the base of the transistor 14 from the recording terminal R side of the recording/playback switch 16 during recording. During the song selection operation, a power supply voltage (+B) is applied from the playback terminal P side of the recording/playback switch 16 through the song selection switch 12. Therefore, during the recording operation and the song selection operation, the mutating transistor 14 becomes conductive and bypasses the signal on the output line 15. And 17 is the radio/
A tape changeover switch 18 is a radio receiving section, and its reception output is input to the line amplifier 4 side of the output path 1 during radio reception when the radio/tape changeover switch 17 is switched to the radio terminal (Ra) side. 19 is a line out terminal connected to the output line 15, and 20 and 21 are diodes for preventing backflow. Note that the broken line portion is for other channels. Therefore, during the song selection operation, the presence or absence of the reproduction signal from the magnetic head 2 taken out from the output side of the line amplifier 4 is determined, and during the microphone mixing operation, the reproduction signal from the magnetic head 2 is detected at the input side of the line amplifier 4. A microphone mixing state is entered in which the reproduced signal is mixed with the microphone signal from the external microphone through the microphone mixing circuit 8 . However, in such a conventional circuit, the microphone jack 9
If a song selection operation is performed while an external microphone is connected to the external microphone, the microphone signal will be superimposed on the playback signal at the input side of the line amplifier 4, so the signal will be extracted from the output side of the line amplifier 4. In the song selection circuit 11, it is determined that the song is continuing based on the microphone signal even though there is no playback signal (that is, between tape songs), and a problem has arisen in which the correct song selection operation is not performed. . (c) Purpose of the invention The present invention has been developed in view of the above points, and is a method for connecting an external microphone when you want to perform so-called "karaoke" in which a microphone signal from an external microphone is mixed with a reproduction signal from a magnetic head. This allows you to accurately select the desired song even when using an external microphone. (d) Structure of the invention In other words, in order to achieve the above-mentioned object, the present invention provides a tape recorder having a microphone mixing function and a song selection function, in which a reproduced signal from a magnetic head is amplified by an amplifier and then output to a speaker section. an output system path, a microphone mixing circuit connected to the output system path at a stage before the amplifier, and when an external microphone is used, a microphone signal from the external microphone is amplified by an amplification transistor and then output to the output system path;
A music selection circuit is connected to the output system at a stage subsequent to the amplifier and determines the presence or absence of a signal on the output system during a music selection operation to locate the beginning of a song, and a control voltage is applied to the base of the amplification transistor during the music selection operation. and a control circuit that changes the amplification transistor from an active state to a saturated state by applying a voltage to the amplification transistor, and prevents a microphone signal from being input to the output path from the microphone mixing circuit during a music selection operation when an external microphone is used. It is composed of (E) Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that parts that are the same as those in the prior art will be given the same drawing numbers and their explanations will be omitted. That is, according to the present invention, during the music selection operation, the amplifying transistor 10 of the microphone mixing circuit 8
A power supply voltage (+B) as a control voltage is applied to the base of the amplifying transistor 10 through the music selection switch 12 and the control circuit 22, thereby changing the amplifying transistor 10 from an active state having an amplifying effect to a saturated state. Therefore, when selecting a song with an external microphone connected to the microphone jack 9, the microphone signal from the external microphone is no longer led to the input side of the line amplifier 4 through the microphone mixing circuit 8, and the music selection circuit 11 is connected to the magnetic head. It is possible to accurately determine the presence or absence of a reproduced signal. (f) Effects As described above, the present invention provides a tape recorder having a microphone mixing function and a song selection function, which allows accurate song selection even when an external microphone is connected to the microphone jack. Therefore, for example, during karaoke, with an external microphone connected, it is possible to select a desired song without any malfunction, and this effect is of extremely high practical value.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional example, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. 1 ... Output system path, 8 ... Microphone mixing circuit, 10... Amplifying transistor, 11... Music selection circuit, 22... Control circuit.

Claims (1)

[Scope of utility model registration request] In a tape recorder that has a microphone mixing function and a song selection function, there is an output system that amplifies the reproduced signal from the magnetic head using an amplifier and then leads it to a speaker section, and a circuit that is connected to the output system at a stage before the amplifier. A microphone mixing circuit that amplifies the microphone signal from the external microphone with an amplification transistor when an external microphone is used and then directs it to an output path; A music selection circuit that determines the presence or absence of a signal on the road and locates the beginning of a song; and a control circuit that applies a control voltage to the base of the amplification transistor to change the amplification transistor from an active state to a saturated state during a music selection operation. A tape recorder characterized in that, during a music selection operation when an external microphone is used, no microphone signal is input from the microphone mixing circuit to the output path.