JPH0328631Y2 - - Google Patents

Description

[Detailed Description of the Invention] (A) Field of Industrial Application The present invention relates to an audio device such as a tape recorder, and more particularly to a signal control circuit for a stereo audio device having left and right channels.

(B) Prior Art Recently, sound devices called so-called radio tape recorders, which are a combination of a radio receiver and a tape recorder, have become popular, but such sound devices are generally of a stereo type with left and right channels. be. Some of these audio devices change the sound quality by changing the frequency characteristics of the signal by switching a switch.
In order to switch the sound quality, switching transistors that act on signals passing through the left and right channel signal paths are generally provided, and a switch is provided to control the operation of the two switching transistors.

(c) Purpose of the invention The present invention aims to provide a signal control circuit that can change the frequency characteristics of left and right channel signals using a simple circuit configuration.

(d) Structure of the invention The invention is based on the first channel through which the left channel signal passes.
signal path, and a second signal path through which the right channel signal passes.
a collector is connected to the first signal path in order to change the frequency characteristics or level of the signal passing through the first signal path, the emitter is grounded, and the base is connected to a power source. The control switch comprises a switching transistor and a first terminal and a second terminal, the common terminal of which is grounded and which is connected to the common terminal by a switching operation, the first terminal of the control switch being connected to the second terminal. It is connected to the second signal path to change the frequency characteristics or level of the signal passing through the signal path, and its second terminal is connected to the base of the switching transistor to control the operation of the transistor.

(E) Embodiment The illustrated circuit is an embodiment in which the signal control circuit of the present invention is implemented in a stereo tape recorder. In the figure, 1 is a first magnetic head that reproduces the left channel signal recorded on the magnetic tape, and 2 is a first magnetic head that receives the signal reproduced by the first magnetic head 1 and amplifies the signal.
a preamplifier circuit, 3 a first variable resistor to which the signal amplified by the first preamplifier circuit 2 is applied and adjusts the level of the signal; 4 a first variable resistor to which the first variable resistor 3 is applied; A first main amplifier circuit 5 receives the level-adjusted signal and amplifies the signal.
is a first speaker to which the signal amplified by the first main amplifier circuit 4 is applied and which emits the signal. 6 is a second magnetic head that reproduces the right channel signal recorded on the magnetic tape; 7 is a second preamplifier circuit to which the signal reproduced by the second magnetic head 6 is input and which amplifies the signal; , 8 is a second variable resistor to which the signal amplified by the second preamplifier circuit 7 is applied and adjusts the level of the signal; 9 is a second variable resistor that adjusts the level by the second variable resistor 8. a second main amplification circuit to which a signal is applied and which amplifies the signal;
This is a second speaker to which the signal amplified by the main amplifier circuit 9 is applied and also emits the signal. 11 is a switching transistor whose collector is connected to the first signal path 12 through which the signal amplified by the first preamplifier circuit 2 passes through a resistor 13 and a capacitor 14, and whose emitter is grounded. , whose base is connected to the power supply via a resistor 15. 16, the common terminal C is grounded, and a first terminal a and a second terminal are connected to the common terminal C by a switching operation.
The first terminal a is connected to a second signal path 17 through which the signal amplified by the second preamplifier circuit 7 passes through a resistor 18 and a capacitor 19. , the second terminal b is connected to the base of the switching transistor 11. In such a configuration, resistor 1
The resistance values of 3 and 18 and the capacitance values of capacitors 14 and 19 are set to values that change the characteristics of a predetermined frequency in the signals passing through the first signal path 12 and the second signal path 17.

The signal control circuit of the present invention is constructed as described above, and the operation of this circuit will now be described.
When the control switch 16 is in the illustrated state, the base of the switching transistor 11 is grounded by the control switch 16, so that the switching transistor 11 is in a non-conducting state. When the switching transistor 11 is in a non-conducting state, the resistor 13 and the capacitor 14 have no effect on the signal passing through the first signal path 12. Further, since the first terminal a constituting the control switch 16 is not grounded, the resistor 18 and capacitor 19 connected between the first terminal a and the second signal path 17 It has no effect on the signal passing through it. When the tape recorder is operated to play back in such a state, the playback operation state is established, and the signals of the left and right channels recorded on the magnetic tape are played back by the first magnetic head 1 and the second magnetic head 6. . The left channel signal reproduced by the first magnetic head 1 is amplified by a first preamplifier circuit 2 and then applied to a first variable resistor 3 through a first signal path 12. The left channel signal applied to the first variable resistor 3 is input to the level-adjusted first main amplifier circuit 4 and amplified. The signal amplified by the first main amplification circuit 4 is applied to the first speaker 5 to emit sound.
The right channel signal reproduced by the second magnetic head 6 is amplified by the second preamplifier circuit 7 and then applied to the second variable resistor 8 through the second signal path 17. The right channel signal applied to the second variable resistor 8 is level-adjusted and then input to the second main amplifier circuit 9 where it is amplified. The signal amplified by the second main amplification circuit 9 is applied to the second speaker 10 to emit sound. When the tape recorder is operated in this way, the signals of the left and right channels are emitted from the first speaker 5 and the second speaker 10, respectively, so the user can listen to the playback sound of the magnetic tape in stereo. .

As described above, the operation is performed when the control switch 16 is in the state shown in the figure, but next, the operation when the control switch 16 is switched will be explained. When the control switch 16 is switched to the opposite side from the state shown, the first terminal a of the control switch 16 is connected to the common terminal c and grounded.
When the first terminal a is grounded, the first terminal a and the second
A resistor 18 and a capacitor 19 connected between the second signal path 17 act on the signal passing through the second signal path 17. Further, when the control switch 16 is switched to the opposite side from the state shown in the figure, the second terminal b connected to the base of the switching transistor 11 becomes ungrounded, so that a bias voltage is applied to the base of the switching transistor 11 through the resistor 15. Current is supplied and the transistor 11 becomes conductive. When the switching transistor 11 becomes conductive, one end of the resistor 13 is grounded, so that the transistor 1
A resistor 13 and a capacitor 14 connected between the collector of the first signal path 1 and the first signal path 12 act on the signal passing through the first signal path 12 . Therefore, in such a state, when a playback operation is performed, the signals of the left and right channels recorded on the magnetic tape are played back by the first magnetic head 1 and the second magnetic head 6, and then the signals are output to the first speaker. 5 and the second speaker 10 and is heard, the frequency characteristics of the reproduced sound are changed.

As described above, by changing the control switch 16, the frequency characteristics of the reproduced signal can be changed, so that the frequency can be corrected in accordance with the tone quality change or the characteristics of the magnetic tape used. Furthermore, if the capacitors 14 and 19 are removed, the resistors 13 and 18 act on the entire frequency band of the signal passing through the first signal path 12 and the second signal path 17, thereby reducing the level of the signal. and operates as a muting circuit.

In this embodiment, the case where the present invention is applied to a tape recorder has been described, but it can of course be applied to an audio device such as a stereo type radio receiving apparatus.

(f) Effects of the invention The signal control circuit of the invention performs switching transistor control operation and signal control of the signal path by switching one switch when changing the frequency characteristics or level of the signal flowing through the left and right channel signal paths. Since it is configured to operate, the number of transistors can be reduced, which has the advantage of simplifying the circuit configuration and being able to manufacture it at low cost.

[Brief explanation of the drawing]

The illustrated circuit is one embodiment of the signal control circuit of the present invention. Explanation of main drawing numbers, 1...first magnetic head, 2...
...First preamplifier circuit, 4...First main amplifier circuit, 6
...Second magnetic head, 7...Second preamplifier circuit,
9... Second main amplifier circuit, 11... Switching transistor, 12... First signal path, 16... Control switch, 17... Second signal path.

Claims (1)

[Scope of utility model registration request] In a stereo audio device having left and right channels, a first signal path through which a left channel signal flows, a second signal path through which a right channel signal flows, and a frequency characteristic or level of a signal flowing through the first signal path. a switching transistor whose collector is connected to the first signal path via a frequency characteristic or level changing means, whose emitter is grounded, and whose base is connected to a power supply via a resistor; a common terminal connected to the base of the switching transistor, a first terminal connected to the base of the switching transistor, and a frequency characteristic or level changing means in the second signal path for changing the frequency characteristics or level of the signal flowing through the second signal path. and a control switch which is switched from the first terminal side to the second terminal side during a frequency characteristic or level changing operation, and has a second terminal connected to the second terminal through the frequency characteristic or level changing operation. By switching to the second terminal side, the switching transistor is made conductive, and the first signal path and the second signal path are connected by the conduction of the switching transistor and the grounding operation of the second terminal by switching the control switch. 1. A signal control circuit for a stereo sound device, characterized in that the frequency characteristic or level of a flowing signal is changed.