JPH0356914Y2 - - Google Patents

Description

[Detailed Description of the Invention] (A) Technical Field The present invention relates to a tape recorder, and particularly to a muting circuit for a tape recorder in which two tape recorders are incorporated.

(B) Background Art Recently, tape recorders in which two tape recorders that can each operate independently are built into one device have become widespread, but in such tape recorders, the output operation of the playback signal of each tape recorder is difficult. need to be controlled.

(c) Purpose of the invention The present invention is intended to provide a circuit suitable for a muting circuit that controls the output operation of a playback signal of a tape recorder incorporating two tape recorders.

(d) Embodiment of the invention The illustrated circuit is an embodiment of the muting circuit of the invention. In the figure, numeral 1 constitutes a first tape recorder and a first magnetic head that reproduces signals recorded on the first tape; numeral 2 denotes a first magnetic head to which the signals reproduced by the first magnetic head 1 are input; First preamplifier circuits 3 and 4 amplify the signal, to which the signal amplified by the first preamplifier circuit 2 is applied, and first and second variable circuits that adjust the level of the signal. A resistor 5 is a first main amplification circuit into which the signal level-adjusted by the first variable resistor 3 is inputted and amplifies the signal; 6 is a first main amplification circuit amplified by the first main amplification circuit 5; This is the first output terminal to which a signal is applied. A second magnetic head 7 constitutes a second tape recorder and reproduces the signal recorded on the second tape; 8 receives the signal reproduced by the second magnetic head 7 and amplifies the signal; 9 is a third variable resistor to which the signal amplified by the second preamplifier circuit 8 is applied and adjusts the level of the signal; 10 is the second variable resistor; The playback signal from the first tape whose level has been adjusted by the variable resistor 4 and the playback signal from the second tape whose level has been adjusted by the third variable resistor 9 are input, and the second tape amplifies the signal. The main amplifier circuit 11 is a second output terminal to which the signal amplified by the second main amplifier circuit 10 is applied. 12
is a first muting transistor whose collector is connected to the output signal path 13 of the first preamplifier circuit 2 and whose emitter is grounded; It has the effect of channeling. 14 is a second muting transistor whose collector is connected to the output signal path 15 of the first main amplifier circuit 5 and whose emitter is grounded; when in a conductive state, the second muting transistor receives the signal from the output signal path 15; It has the effect of channeling. Reference numeral 16 denotes a third muting transistor whose collector is connected to the output signal path 17 of the second preamplifier circuit 8 and whose emitter is grounded. It has the effect of bypassing. 18 is a fourth muting transistor whose collector is connected to the output signal path 19 of the second main amplifier circuit 10 and whose emitter is grounded; when in a conductive state, the output signal path 1
It has the effect of bypassing the signal of 9. 20 is a first switch that is closed when the first tape recorder is in a stopped state and opened when it is in a playing state; 21 is a first switch that is closed when the second tape recorder is in a stopped state and is in a playing state. This is a second switch that is opened at certain times. 22 is a first switch whose emitter is connected to the power supply and whose base is grounded via the resistor 23 and the first switch 20;
A control transistor whose collector is connected to the bases of the first mutating transistor 12 and the second muting transistor 14 via resistors 24 and 25. 26 is a first switch connected in parallel to the first switch 20;
It is a capacitor, and together with the resistor 23 constitutes a first time constant circuit. 27 is a second control transistor whose emitter is connected to the power supply and whose base is grounded via the resistor 28 and the second switch 21, and whose collector is connected to the resistor 29.
It is connected to the base of the third muting transistor 16 via. 30 is a third control transistor whose emitter is connected to the collector of the first control transistor 22 and whose base is grounded via the resistor 31 and the second switch 21; Fourth mutating transistor 1
It is connected to the base of 8. A second capacitor 33 is connected in parallel to the second switch 21, and together with the resistors 28 and 31 constitutes a second time constant circuit. The time constant of the second time constant circuit is determined by the time constant of the first control transistor 22.
The time constant is set to be smaller than the time constant of the first time constant circuit provided to control the operation of the first time constant circuit.

The present invention is constructed as described above, and its operation will be explained next. When the power switch (not shown) is closed when the first tape recorder and the second tape recorder are in a stopped state, the first preamplifier circuit 2, the first main amplifier circuit 5, and the second preamplifier circuit 8 When power is supplied to the second main amplifier circuit 10 and the second main amplifier circuit 10 becomes operational, the first control transistor 22
Power is supplied to the emitter of the second control transistor 27. In the stopped state, the first switch 20
Since the second switch 21 is in the closed state, the first control transistor 22 and the second control transistor 27 are both biased and conductive. Furthermore, when the first control transistor 22 becomes conductive, power is supplied to the emitter of the third control transistor 30, so that the third control transistor 30 becomes conductive. When the first control transistor 22 becomes conductive, a bias current is supplied to the bases of the first mutating transistor 12 and the second mutating transistor 14 through its emitter-collector path.
Muting transistor 14 becomes conductive. When the second control transistor 27 becomes conductive, a bias current is supplied to the base of the third muting transistor 16 through its emitter-collector path, so that the third muting transistor 16 becomes conductive.
When the third control transistor 30 becomes conductive, a bias current is supplied to the base of the fourth muting transistor 18 through its emitter-collector path, so that the fourth muting transistor 18 becomes conductive. In this way, when the power switch is closed to supply power when the first tape recorder and the second tape recorder are in a stopped state, the first mutating transistor 12, the second mutating transistor 14, and the third mutating transistor are 16 and the fourth mutating transistor 18
becomes conductive, so each output signal path 13, 15,
The signals 17 and 19 are bypassed, and noise generated from the amplifier circuit etc. is not outputted from the first output terminal 6 and the second output terminal 11. Therefore, no noise signal is emitted from the speaker connected to the amplifier into which the signals from the first output terminal 6 and the second output terminal 11 are input, and the user will not feel uncomfortable. When the first and second tape recorders are in a stopped state, the first muting transistor 12, the second muting transistor 14, the third mutating transistor 16, and the fourth muting transistor 18 are in a conductive state.

In this state, when the first tape recorder is operated for reproduction, the magnetic tape drive mechanism enters a constant speed drive state for reproduction operation and the first switch 20 is opened. When the first switch 20 is opened, a charging current flows through the first capacitor 26 for a predetermined period of time, during which time the first control transistor 22 is maintained in a conductive state.
When the charging current to the first control transistor 22 is removed, the first control transistor 22 is inverted to a non-conducting state. When the first control transistor 22 is reversed to a non-conducting state, the first
Since the bias current to the bases of the mutating transistor 12 and the second mutating transistor 14 is cut off, the first muting transistor 12 and the second muting transistor 14 are reversed to a non-conducting state. Further, when the first control transistor 22 is reversed to a non-conducting state, the third control transistor 30 whose emitter is connected to the collector of the first control transistor 22 is reversed to a non-conducting state, so that a bias voltage is applied through the third control transistor 30. 4th muting transistor 1 to which current was supplied
8 is reversed to a non-conducting state. Therefore, in the playback operating state of the first tape recorder, the first mutating transistor 12, the second muting transistor 14 and the fourth muting transistor 18 are in a non-conducting state, and the third mutating transistor 16 is in a conducting state. It is in. The reproduction signal from the first tape reproduced by the first magnetic head 1 is input to the first preamplifier circuit 2, where it is amplified and then applied to the first variable resistor 3 and the second variable resistor 4. Ru. The first variable resistor 3
The reproduction signal applied to the first
The signal is input to the main amplifier circuit 5, amplified, and output to the first output terminal 6. Further, the reproduced signal applied to the second variable resistor 4 is level-adjusted and then input to the second main amplifier circuit 10 and amplified.
1 is output. Therefore, in such a state, the playback signal from the first tape is output to the first output terminal 6 and the second output terminal 11, and the input terminal is connected to the first output terminal 6 and the second output terminal 11. The reproduced signal can be heard by the sound emitting operation of a speaker connected to the amplifier. Further, in such a state, since the output signal path 17 of the second preamplifier circuit 8 is grounded by the third muting transistor 16, the induced noise signal etc. from the second preamplifier circuit 8 is transmitted to the second preamplifier circuit 8. It is not input to the main amplifier circuit 10, and the second output terminal 1
SN of the playback signal from the first tape output to 1
There will be no negative impact on the ratio. When a stop operation is performed in such a reproducing operation state, the reproducing operation state is canceled and the first switch 20 is closed. When the first switch 20 is closed, the charge stored in the first capacitor 26 is immediately discharged, and the first control transistor 22 is turned on. When the first control transistor 22 is turned on, the first mutating transistor 12 and the second muting transistor 14 are turned on, and as the third control transistor 30 is turned on, the fourth mutating transistor 18 is turned on. The state is reversed to a conductive state, and the above-mentioned stopped state is established.

The reproduction operation of the first tape recorder is performed as described above, and next, the reproduction operation of the second tape recorder will be explained. When the second tape recorder is operated for reproduction, the magnetic tape drive mechanism enters a constant speed drive state for reproduction operation, and the second switch 21 is opened. When the second switch 21 is opened, a charging current flows through the second capacitor 33 for a predetermined period of time, during which time the second control transistor 27 and the third control transistor 30 are maintained in a conductive state, but the second capacitor 33 is not charged. When the current disappears, the second control transistor 27 and the third control transistor 30 are reversed to a non-conducting state. When the second control transistor 27 is inverted to a non-conducting state, the bias current to the third muting transistor 16 is cut off, so that the third muting transistor 16 is inverted to a non-conducting state. Further, the third control transistor 30
When is reversed to a non-conducting state, the bias current to the fourth muting transistor 18 is cut off, so that the fourth muting transistor 18 is reversed to a non-conducting state. Therefore, in the playback operation state of the second tape recorder, the first mutating transistor 12 and the second muting transistor 14 are in a conductive state, and the third mutating transistor 16 and the fourth mutating transistor 18 are in a non-conducting state. be. Second
The reproduction signal from the second tape reproduced by the magnetic head 7 is input to the second preamplifier circuit 8, amplified, and then applied to the third variable resistor 9. The reproduced signal applied to the third variable resistor 9 is level-adjusted, then inputted to the second main amplifier circuit 10, amplified, and outputted to the second output terminal 11. Therefore, in such a state, the playback signal from the second tape will be output to the second output terminal 11, and the output of the speaker connected to the amplifier whose input terminal is connected to the second output terminal 11 will be output. The reproduced signal can be heard through sound motion. In addition, in such a state, the output signal path 13 of the first preamplifier circuit 2 is grounded by the first muting transistor 12, so that the induced noise signal etc. from the first preamplifier circuit 2 is transmitted to the second main amplifier circuit 2. The second signal is not input to the amplifier circuit 10 and is output to the second output terminal 11.
It does not adversely affect the signal to noise ratio of the reproduced signal from the tape. Furthermore, in such a state, since the output signal path 15 of the first main amplifier circuit 5 is grounded by the second muting transistor 14, noise signals etc. are transmitted to the amplifier whose input terminal is connected to the first output terminal 6. is never applied. When a stop operation is performed in such a reproducing operation state, the reproducing operation state is canceled and the second switch 21 is closed. When the second switch 21 is closed, the second
The electric charge stored in the capacitor 33 is immediately discharged, and the second control transistor 27 and the third control transistor 30 are turned on. the second control transistor 27
and when the third control transistor 30 is turned on, the third mutating transistor 16
Then, the fourth muting transistor 18 is inverted to a conductive state, and the above-mentioned stopped state is established.

As described above, the operation is performed when the first tape recorder and the second tape recorder are individually operated. Next, the operation when the two tape recorders are operated will be explained. When each tape recorder is operated for reproduction, the drive mechanism of each tape recorder is brought into a state for reproduction operation, and both the first switch 20 and the second switch 21 are opened. When the first switch 20 and the second switch 21 are opened, the first control transistor 22, the second control transistor 27, and the third control transistor 30 are inverted to a non-conducting state, so that the first mutating transistor 12 and the second Teing transistor 1
4. The third muting transistor 16 and the fourth muting transistor 18 are inverted to a non-conducting state. In such a situation,
The reproduction signal from the first tape reproduced by the first magnetic head 1 is input to the first preamplifier circuit 2, where it is amplified and then applied to the first variable resistor 3 and the second variable resistor 4. The level will be adjusted accordingly. Also the second
The reproduced signal from the second tape reproduced by the magnetic head 7 is input to the second preamplifier circuit 8, amplified, and then applied to the third variable resistor 9 for level adjustment. The reproduction signal from the first tape whose level has been adjusted by the first variable resistor 3 is input to the first main amplifier circuit 5, amplified, and then output to the first output terminal 6. The playback signal from the first tape whose level has been adjusted by the second variable resistor 4 and the playback signal from the second tape whose level has been adjusted by the third variable resistor 9 are mixed and sent to the second main amplification. It is input to the circuit 10. The mixed reproduction signal from the first tape and the second tape input to the second main amplifier circuit 10 is amplified and then output to the second output terminal 11. Therefore, the reproduction signal of the first tape is emitted from the speaker connected to the amplifier to which the signal from the first output terminal 6 is input, and the speaker is connected to the amplifier to which the signal from the second output terminal 11 is input. A signal in which the reproduction signal of the first tape and the reproduction signal of the second tape are mixed is emitted from the speakers. When each tape recorder is stopped in such a state, the above-mentioned operation is performed and a stopped state is established.

The reproduction operation of the tape recorder is performed as described above, but the muting operation when the power is turned on will now be explained. First, a case will be described in which power is supplied by a timer or the like while the first tape recorder is set in the reproduction operation state. When the first tape recorder is set to playback mode, the first switch 20 is open and the second switch 21 is closed. When power is supplied in such a state, a charging current flows through the first capacitor 26, and while the charging current is flowing, the first control transistor 22 becomes conductive. Therefore, the first mutating transistor 12,
The second mutating transistor 14, the third control transistor 30, and the fourth mutating transistor 18 are in a conductive state. Then, after a predetermined period of time has elapsed, the first control transistor 22 is inverted to a non-conducting state, and with the inversion, the first muting transistor 12, the second muting transistor 14, the third control transistor 30, and the fourth mutating transistor 1 are turned off.
8 is reversed to a non-conducting state. On the other hand, the second control transistor 27 becomes conductive as soon as the power is supplied and maintains that state.
The muting transistor 16 is in a conductive state, and the above-described reproduction operation state of the first tape recorder is established. In this manner, when power is supplied to the first tape recorder in the playback mode, the first mutating transistor 12, the second mutating transistor 14, and the fourth mutating transistor 18 become conductive for a predetermined period of time, and the first mutating transistor 3. Since the muting transistor 16 becomes conductive, the noise generated when the power is turned on is transmitted to the first output terminal 6 and the second output terminal 1.
1 and does not cause discomfort to the user.

As described above, if power is supplied when the first tape recorder is set to the playback operation state, the operation will be performed, but then power is supplied when the second tape recorder is set to the playback operation state. Let me explain the case. When the second tape recorder is set to playback mode, the second switch 21 is open and the first switch 20 is closed.
When power is supplied in such a state, the first
The control transistor 22 is biased immediately into a conductive state, and the first muting transistor 12 and the second muting transistor 14 are reversed into a conductive state. Further, when power is supplied to the emitters of the second control transistor 27 and the third control transistor 30, the second control transistor 27 and the third control transistor 30
A charging current flows through the capacitor 33, and while the charging current is flowing, the second control transistor 27 and the third control transistor 30 are in a conductive state. Therefore, during that time, the first muting transistor 12, the second muting transistor 14, the third muting transistor 16, and the fourth muting transistor 18 are in a conductive state. Then, after a predetermined period of time has elapsed, the second control transistor 27 and the third control transistor 30 are reversed to a non-conductive state, and along with the reversal operation, the third mutating transistor 16 and the fourth mutating transistor 18 are reversed to a non-conductive state. Then, the above-described reproduction operation state of the second tape recorder is configured. In this way, when power is supplied while the second tape recorder is in the playback mode, the first mutating transistor 12 and the second mutating transistor 14 are activated.
becomes conductive, and the third mutating transistor 16 and fourth mutating transistor 18 also become conductive for a predetermined period of time, so that the noise generated when the power is turned on is output to the first output terminal 6 and the second output terminal 11. There is no discomfort to the user.

As described above, if power is supplied while the first tape recorder or the second tape recorder is set to the playback operation state, the operation will be performed, but next, both the first tape recorder and the second tape recorder will playback. A case in which power is supplied while the device is set in this state will be explained. When power is supplied in such a state, a charging current flows through the first capacitor 26 and the second capacitor 33, during which time the first control transistor 22,
The second control transistor 27 and the third control transistor 30 become conductive, but after a predetermined time, that is, the time set by the second time constant circuit, the second control transistor 27 and the third control transistor 30 become non-conductive. The first control transistor 22 is then inverted to a non-conducting state after a period of time set by the first time constant circuit has elapsed. Therefore, the first tape recorder and the second
When power is supplied while the tape recorder is set to the playback state, the first mutating transistor 12, the second muting transistor 14, the third mutating transistor 16, and the fourth mutating transistor 1 are activated.
8 are in a conductive state for a predetermined time set by the time constant circuit, the noise generated when the power is turned on is not output to the first output terminal 6 and the second output terminal 11, and the user It doesn't cause any discomfort.

In this embodiment, the time constant of the second time constant circuit was set to be smaller than the time constant of the first time constant circuit, but conversely, the time constant of the second time constant circuit was set to be smaller than the time constant of the first time constant circuit. It can also be set larger than the time constant of the circuit. In such a case, the third
The conduction time of the control transistor 30 when the power is turned on, that is, the fourth mutating transistor 18
The conduction time of is determined by the time constant of the first time constant circuit.

(E) Application example of the invention In this embodiment, the first muting transistor 12, the second muting transistor 14,
The third mutating transistor 16 and the fourth
NPN as a mutating transistor 18
Although a type transistor was used, a PNP type transistor can also be used. Also, as the first control transistor 22, the second control transistor 27, and the third control transistor 30.
Although a PNP type transistor was used, an NPN type transistor can also be used.

(F) Effect The muting circuit of the present invention includes first and second switches that are opened and closed by switching the first tape recorder and the second tape recorder between the stop state and the playback state, and the opening and closing operations of the switches. Three control transistors whose operations are controlled by the three control transistors are provided, and these three control transistors control the operations of the four muting transistors, thereby controlling the output operations of the amplifier circuits constituting the two tape recorders. By doing so, the outputting operation and mixing operation of the reproduction signals reproduced from each tape recorder can be performed accurately and favorably. In addition, when power is supplied to each tape recorder while it is set for playback operation, the muting transistor is made conductive for a predetermined period of time by the action of a time constant circuit, so that when the power is turned on, It is possible to prevent the output operation of the generated noise signal, and since the muting transistor is also used as the muting transistor that controls the output operation of the reproduced signal, the circuit configuration is simplified, and the practical value of the present invention is extremely high. It is expensive.

[Brief explanation of the drawing]

The illustrated circuit is one embodiment of the muting circuit of the present invention. Explanation of main drawing numbers, 1...first magnetic head, 2...
...First preamplifier circuit, 5...First main amplifier circuit, 7
...Second magnetic head, 8...Second preamplifier circuit,
10...Second main amplifier circuit, 12...First mutating transistor, 14...Second mutating transistor, 16...Third mutating transistor, 18...Fourth mutating transistor, 20...First mutating transistor Switch, 21...
...Second switch, 22...First control transistor, 27...Second control transistor, 30...
Third control transistor.

Claims (1)

[Scope of utility model registration request] A first tape recorder including a drive mechanism for driving a first tape and a first magnetic head for reproducing signals recorded on the first tape; a drive mechanism for driving a second tape; and a drive mechanism for recording signals on the second tape. A tape recorder is equipped with a second tape recorder having a second magnetic head for reproducing a signal played back by the first magnetic head. a preamplifier circuit, a first main amplifier circuit to which the signal amplified by the first preamplifier circuit is input, and a first main amplifier circuit which amplifies the signal; and a signal reproduced by the second magnetic head to which the signal is input. a second preamplifier circuit that receives and amplifies the signal; and a second main amplifier that receives the signal amplified by the first preamplifier circuit and the second preamplifier circuit and amplifies the signal. a first muting transistor having a collector-emitter path connected between the output signal path of the first preamplifier circuit and ground and for shunting a signal flowing through the output signal path when in a conductive state; , a second muting transistor having a collector-emitter path connected between the output signal path of the first main amplifier circuit and ground, and bypassing a signal flowing through the output signal path when in a conductive state; a third mutating transistor having a collector-emitter path connected between the output signal path of the second preamplifier circuit and ground, and bypassing a signal flowing through the output signal path when in a conductive state; A collector-emitter path is connected between the output signal path of the amplifier circuit and ground, and a fourth muting transistor bypasses a signal flowing through the output signal path when in a conductive state, and the first tape recorder is in a stopped state. a first switch that is closed when the tape recorder is in the stopped state and opened when the second tape recorder is in the playback state, and a second switch that is closed when the second tape recorder is in the stop state and opened when the second tape recorder is in the playback state. , a first control transistor that is conductive when the first switch is in a closed state and causes the first muting transistor and the second muting transistor to be conductive when the first switch is in the conductive state; a second control transistor that is conductive when in a closed state and causes the third mutating transistor to be conductive when in a conductive state; and a second control transistor that is conductive when the first control transistor is in a conductive state; a third control for making the fourth muting transistor conductive when the second switch is in the closed state and conductive when the second switch is supplied with operating power through the emitter-collector path; a transistor, a first time constant circuit provided to make the first control transistor conductive for a predetermined period of time when power is supplied when the first switch is in an open state, and a first time constant circuit in which the second switch is in an open state. in order to cause the second control transistor to conduct for a predetermined period of time when power is supplied, and to cause the second control transistor to conduct for a predetermined period of time when power is supplied when the first switch and the second switch are open; a second time constant circuit provided to keep the third control transistor in a conductive state for a predetermined time;
The conduction time of the muting transistor is determined by the first time constant circuit, and the conduction time of the mutating transistor is determined by the first time constant circuit.
The conduction time of the mutating transistor is determined by the second time constant circuit, and the conduction time of the fourth mutating transistor is determined by the first time constant circuit or the second time constant circuit. A tape recorder muting circuit characterized by: