JPH0316155Y2 - - Google Patents

Description

[Detailed explanation of the invention] (a) Industrial application field This invention incorporates a radio receiving circuit for receiving radio broadcasts and a tape recorder for reproducing signals recorded on magnetic tape into the same cabinet. This invention relates to a control circuit for a tape recorder with radio. (b) Prior Art Audio equipment called a tape recorder with radio, which is a combination of a radio receiving circuit and a tape recorder, has become widespread. Such a tape recorder with a radio is equipped with a selection switch for switching between radio use and tape recorder use, and generally the selection switch is used to supply power to the radio receiving circuit and tape recorder and to switch the signal path. It is composed of A technique of such a configuration is disclosed, for example, in Japanese Utility Model Application Laid-Open No. 58-84690. (c) Problems to be solved by the invention In the technology disclosed in the above-mentioned gazette, reproduced signals and radio broadcasts are transmitted up to the position of the switching contact built into the selection switch provided to switch the signal path. Since it is necessary to guide a signal, there is a problem that not only is the selection switch susceptible to the influence of induced noise, but also that the mounting position of the selection switch is restricted.
One method for solving this problem is to selectively supply power to the radio receiving circuit and the tape recorder circuit using a selection switch. In this method of switching between radio use and tape recorder use by selectively supplying power, the signal path of the radio broadcast signal and the signal path of the reproduced signal are always connected. The output signal path of the radio receiving circuit that receives the radio broadcast signal is equipped with a de-emphasis circuit that improves the signal-to-noise ratio of the FM broadcast signal by lowering the signal level of high frequencies. There is a problem in that when the recorder is used, the level of the high frequency signal of the reproduced signal is lowered by the de-emphasis circuit. This idea is
The present invention aims to provide a control circuit that solves this problem. (d) Means for Solving Problems The present invention includes a selection switch for switching between use of a tape recorder and use of a radio, a playback head for reproducing signals recorded on a magnetic tape, and a selection switch that allows the selection switch to use a tape recorder. a preamplifier circuit that amplifies the signal reproduced by the playback head while being supplied with power and in operation when the selection switch is on the radio use side; and a preamplifier circuit that is supplied with power and becomes in operation when the selection switch is on the radio use side a radio receiving circuit, a de-emphasis circuit inserted and connected to the output signal path of the radio receiving circuit and comprising a resistor and a capacitor, and a reproduced signal amplified by the preamplifier circuit and a radio broadcast that has passed through the de-emphasis circuit. a variable resistor to which a signal is applied and adjusts the level of the signal;
a main amplifier circuit to which a signal whose level has been adjusted by the variable resistor is applied and which amplifies the signal;
A switch whose collector is connected to the signal path on the output side of the de-emphasis circuit via a control resistor and whose emitter is grounded, and which is supplied with a base current and becomes conductive when the selection switch is on the tape recorder use side. It consists of a switching transistor. (e) Effect This invention connects a control resistor when using a tape recorder by conducting a switching transistor between the signal path on the output side of a de-emphasis circuit provided to improve the S/N ratio of an FM broadcast signal and the ground. This eliminates the influence of the de-emphasis circuit on the reproduction signal of the tape recorder. (F) Embodiment The illustrated circuit is an embodiment of the control circuit of the present invention. In the figure, 1 is a reproduction head that reproduces signals recorded on a magnetic tape, 2 is a preamplifier circuit to which a signal reproduced by the reproduction head 1 is applied and amplified, and 3 is a tape This is a selection switch for switching between recorder use and radio use, and includes a common terminal B connected to a power source, a tape terminal T, and a radio terminal R. 4 is a radio receiving circuit that is supplied with power and becomes operational when the selection switch 3 is on the radio use side;
5 is a de-emphasis circuit inserted and connected to the output signal path of the radio receiving circuit 4, and a resistor 6
and a capacitor 7. 8, a reproduction signal from the preamplifier circuit 2 is applied via a resistor 9, and a radio broadcast signal from the radio receiving circuit 4 is applied via a de-emphasis circuit 5 and a resistor 10, and the level of the signal is adjusted. 11 is a main amplifier circuit into which the signal level-adjusted by the variable resistor 8 is input; 1
Reference numeral 2 designates a headphone jack into which a headphone plug is inserted, and is provided with a signal terminal 13 to which the output signal of the main amplifier circuit 11 is applied, and a ground terminal 14 which is grounded. 15 is a switching transistor whose collector is connected to the signal path 16 on the output side of the de-emphasis circuit 5 via a control resistor 17 and whose emitter is grounded; its base is connected to the selection switch via a resistor 18; It is connected to the tape terminal T of No.3. In this configuration, the resistance value of the control resistor 17 is set to be smaller than the impedance of the capacitor 7 constituting the de-emphasis circuit 5 in the audio band. The control circuit of the present invention is constructed as described above, and its operation will be explained next. First, the operation when the tape recorder is in use with the selection switch 3 in the state shown in the figure will be described. When the tape recorder is in use, power is supplied to the preamplifier circuit 2 through the selection switch 3, so the preamplifier circuit 2 is in operation and the switching transistor 15 is supplied with base current and is in a conductive state. . In such a state, when a playback operation is performed, the tape recorder enters the playback mode and the signal recorded on the magnetic tape is transferred to playback head 1.
played by. The reproduction signal reproduced by the reproduction head 1 is input to a preamplifier circuit 2, amplified, and then applied to a variable resistor 8 through a resistor 9. The reproduced signal applied to the variable resistor 8 is level-adjusted and then input to the main amplifier circuit 11. The reproduced signal input to the main amplifier circuit 11 is amplified and then applied to a signal terminal 13 constituting the headphone jack 12. Therefore, by inserting a head-on plug into the head-on jack 12 , it is possible to listen to the reproduction sound of the magnetic tape through the head-on. Although the tape recorder reproduces in this manner, in the reproduction state, the radio receiving circuit 4 is in an inoperative state because no power is supplied to it. In addition, switching transistor 1
Since a base current is supplied to the base of transistor 5 through selection switch 3 and resistor 18, switching transistor 15 is in a conductive state. Therefore, due to the conduction of the switching transistor 15, the control resistor 17 is connected between the signal path 16 and ground. Since the resistance value of the control resistor 17 is set to a value smaller than the impedance in the audio frequency band of the capacitor 7 constituting the de-emphasis circuit 5 , the level of the reproduced signal is lowered by the control resistor 17. It turns out. Therefore, the level of the reproduced signal is lowered over the entire range from low frequencies to high frequencies, and since it is not affected by the capacitor 7, the reproduced sound with flat frequency characteristics can be heard. I can do it. The reproduction operation of the tape recorder is performed as described above, but next, the operation of listening to radio broadcasting will be explained. Select switch 3 to listen to radio broadcasts
This is done by switching the radio to the side opposite to the state shown, which is the radio use side. Selection switch 3
When the switch is switched to the opposite side of the illustrated state, power is supplied to the radio receiving circuit 4 and the radio receiving circuit 4 enters the operating state. When the selection switch 3 is switched to the radio use side, the preamplifier circuit 2 becomes inactive and the switching transistor 15 becomes non-conductive. When the radio is in use, the broadcast signal received by the radio receiving circuit 4 is applied to the variable resistor 8 through the de-emphasis circuit 5 and the resistor 10. The broadcast signal applied to the variable resistor 8 is level-adjusted and then input to the main amplifier circuit 11 where it is amplified. The broadcast signal amplified by the main amplifier circuit 11 is sent to a headphone jack 12.
Since the signal is applied to the signal terminal 13 of the headphone, the user can listen to the radio broadcast through the headphone. In this embodiment, the tape playback signal and the radio broadcast signal are listened to through a headphone, but they can also be configured to be listened to through a speaker. Further, although the case has been described in which the present invention is applied to a monaural type radio tape recorder, it is of course possible to implement the present invention to a stereo type radio tape recorder having left and right channels. (g) Effects of the invention The control circuit of the invention controls the power supply to the preamplifier circuit that amplifies the signal reproduced by the reproduction head and the radio reception circuit that receives the radio broadcast signal by the switching operation of the selection switch. By selectively switching between radio use and tape recorder use, there is no need to lead the radio broadcast signal and playback signal to the switching contact of the selection switch, and the generation of induced noise can be suppressed as much as possible. Since it is possible to use a switch with a small number of switching contacts, it has the advantage that a small and inexpensive switch can be used. In addition, during the playback operation of the tape recorder, the de-emphasis circuit installed in the output signal path of the radio receiving circuit has no effect on the playback signal, so you can listen to playback sound with a flat frequency response. The idea is ideal for a control circuit for a tape recorder with a radio.

[Brief explanation of drawings]

The illustrated circuit is one embodiment of the control circuit of the present invention. Explanation of main drawing numbers: 1... Reproduction head, 2... Preamplifier circuit, 3... Selection switch, 4... Radio receiving circuit, 5 ... De-emphasis circuit, 11...
...Main amplifier circuit, 15...Switching transistor, 17...Control resistor.

Claims (1)

[Scope of utility model registration request] a selection switch for switching between tape recorder use and radio use; a playback head for reproducing signals recorded on the magnetic tape; when the selection switch is on the tape recorder use side, power is supplied and the device is in operation; a preamplifier circuit that amplifies the signal reproduced by the reproduction head; a radio receiving circuit that is supplied with power and becomes operational when the selection switch is on the radio use side; and inserted into the output signal path of the radio receiving circuit. A de-emphasis circuit includes a connected resistor and a capacitor connected between the output signal path and ground, and the playback signal amplified by the preamplifier circuit and the radio broadcast signal passed through the de-emphasis circuit are transmitted without going through a switch. a variable resistor that adjusts the level of the signal as it is applied; a main amplifier circuit that amplifies the signal that is applied with the level adjusted by the variable resistor; and an output side of the de-emphasis circuit. a switching transistor whose collector is connected to the signal path via a control resistor and whose emitter is grounded, and which is supplied with a base current and becomes conductive when the selection switch is on the tape recorder use side; A tape with a radio, characterized in that the resistance value of the control resistor is made smaller than the impedance in the audio frequency band of the capacitor constituting the de-emphasis circuit, thereby eliminating the influence of the capacitor on the frequency characteristics of the reproduced signal when using a tape recorder. Recorder control circuit.