JPH0132567B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording/reproducing device such as an audio tape recorder which requires switching of an equalizer time constant and a bias alternating current signal.

Conventional configuration and its problems In audio tape recorders, the time constant of the equalizer amplifier during playback is switched depending on whether a normal tape is used or a metal tape is used, and the bias AC signal during recording is changed. It is necessary to switch the frequency or frequency.

First, FIG. 1 shows a circuit diagram of a main part of an example of a conventional audio tape recorder having such a switching means. Here, 1 is a magnetic head for recording and reproduction, 2 is an equalizer amplifier for reproduction, 3 is its time constant circuit, 4 is an input terminal for recording signals, 5,
6 is an amplifier for the recording signal, 7 is a high frequency compensation circuit,
8 is a bias AC signal generation circuit during recording; 9a;
9b, 9c, 9d are interlocking switches for recording/reproducing switching;
10a and 10b are interlocking switches for switching between normal tape and metal tape.

During reproduction, the switches 9a to 9d are switched to the P side. As a result, one end of the magnetic head 1 is grounded via the switch 9b, and the reproduced signal from the magnetic head 1 is applied to the equalizer amplifier 2 via the switch 9a, amplified by the transistors 11 and 12, and transmitted via the switch 9d. Output. At this time, since the switch 9c is opened, the power supply to the bias AC signal generating circuit 8 is cut off, and no bias AC signal is generated.

Next, during recording, the switches 9a to 9d are switched to the R side. As a result, one end of the magnetic head 1 is grounded via the switch 9a. On the other hand, an input signal from a microphone or the like applied to the input terminal 4 is amplified by amplifiers 5 and 6, then compensated for the high frequency by a high frequency compensation circuit 7, and then applied to the magnetic head 1. Furthermore, since power is supplied to the bias AC signal generation circuit 8 via the switch 9c, the transistor 13, the transformer 14, and the capacitor 1
5. An oscillation circuit composed of resistors 16 and 17 oscillates, and the generated alternating current signal is applied to the magnetic head from the transformer 14 as a recording bias signal. As a result, the input signal is recorded from the magnetic head 1 onto the tape. At this time, the input signal is outputted from the amplifier 5 via the switch 9d and monitored.

Next, a description will be given of a portion of this apparatus in which the equalizer time constant and the magnitude of the bias AC signal are switched depending on the type of tape. When the tape used is normal tape, switch 1
0a and 10b are switched to the N side, and the feedback time constant circuit 3 of the equalizer amplifier 2 is switched to the switch 10a.
is open, so resistor 18 and capacitor 19
The collector output signal of the transistor 12 is fed back to the emitter of the transistor 11 according to the time constant determined by , and equalizer compensation is performed using the time constant for normal tape. Also, at this time, since the switch 10b is also open, the bias voltage determined by the resistors 16 and 17 is applied to the base of the transistor 13, and a bias AC signal of a magnitude for normal tape is generated, and the bias voltage determined by the resistors 16 and 17 is applied to the magnetic tape 1. Supplied.

On the other hand, when a metal tape is used, the switches 10a and 10b are switched to the M side. Then, in the equalizer amplifier 2, the resistor 20 is connected in parallel with the resistor 18 via the switch 10a in the feedback time constant circuit 3, and equalizer compensation is performed using a time constant for the metal tape that is smaller than that for the normal tape. Also, in the bias AC signal generation circuit 8, the resistor 21 is connected in parallel with the resistor 17 via the switch 10b, and as a result, the bias voltage to the base of the transistor 13 becomes larger than when using the normal tape. A bias alternating current signal for the metal tape having a larger amplitude is generated and supplied to the magnetic head 1.

In this way, the switches 10a and 10b are used to switch between the use of normal tape and the use of metal tape.In the conventional audio tape recorder shown in Fig. 1, two interlocking switches are used to make the switch. 10a, 10b
Since a two-circuit switch is required, the size inevitably becomes large, which is a major obstacle to miniaturization. In addition, the wiring for the switch 10b is troublesome because two lead wires must be routed to the switch 10b, which is remote from the printed circuit board in which the bias AC generating circuit 8 is installed. The drawback is that it requires a lot of money.

Purpose of the Invention The present invention solves such conventional drawbacks by changing the equalizer time constant for reproduction according to the type of magnetic recording medium such as normal tape and metal tape, and adjusting the magnitude or the bias AC signal for recording. It is an object of the present invention to provide a device which can perform frequency switching with only one switch and can reduce the number of wirings.

Structure of the Invention In the present invention, in an equalizer amplifier, a time constant circuit including a resistor and a capacitor is connected to its collector with the resistor facing the amplification transistor side, and a switch is provided to change the resistance of the time constant circuit. switches the resistor and causes different voltages to be generated at its terminals by switching the switch. On the other hand, a switching transistor that switches the magnitude or frequency of the generated bias AC signal is connected to the bias AC signal generation circuit, and the voltage from the terminal of the switch for changing the equalizer time constant is switched to the switching transistor. By switching, one switch is used to change the equalizer time constant and to change the magnitude of the bias AC signal via the switching transistor.

DESCRIPTION OF THE EMBODIMENTS An embodiment in which the present invention is implemented in an audio tape recorder will be described below with reference to FIG. In addition, in Fig. 2, the same parts as the conventional one are
The same reference numerals as in the figure are used to omit the explanation. In this device, the feedback time constant circuit 3 of the equalizer amplifier 2 has its resistors 18 and 20 connected to the transistor 12 side and its collector, and when the switch 10a is switched to the N side, the feedback time constant circuit 3 has approximately +B at its N side terminal. /2 voltage is generated. The bias AC signal generation circuit 8 also includes a resistor 1 for base biasing the transistor 13.
A series circuit consisting of a resistor 22 and a switching transistor 23 is provided between the connection point of switches 6 and 17 and the ground, and the base of the switching transistor 23 is connected to the N-side terminal of the switch 10a.

With this configuration, when a normal tape is first used, the switch 10a is switched to the N side. Then, the feedback time constant circuit 3 of the equalizer amplifier 2 becomes a time constant for normal tape using the resistor 18 and the capacitor 19, and at this time, +B/2 is applied to the N-side terminal of the switch 10a.
Since a voltage of The bias voltage is reduced, and a small bias AC signal for the normal tape is generated and supplied to the magnetic head 1. Conversely, when a metal tape is used, the switch 10a is switched to the M side. As a result, the feedback time constant circuit 3 has resistors 18 and 20 connected in parallel, and has a small time constant for the metal tape. At this time, since no voltage is generated at the N-side terminal of the switch 10a, the switching transistor 23 is cut off, and the base bias voltage of the transistor 13 of the bias AC generating circuit 8 increases, causing a large amplitude signal passed through the metal tape. A bias AC signal is generated and supplied to the magnetic head 1.

Thus, according to this circuit configuration, one
By using two switches 10a, it is possible to switch the equalizer time constant and the magnitude of the bias AC signal when using a normal tape and when using a metal tape, and a small switch can be used. This can greatly contribute to downsizing the entire device. Moreover, the switching transistors 23 can be attached to the printed circuit board of the bias AC signal generation circuit 8 all together, and the wiring between the switching transistors 23 and the switch 10a can be done with only one lead wire, making wiring easy. This allows for a simple configuration with only a minimum number of lead wires.

In addition, in the above embodiment, the switch 10a
is connected to the resistor 20, but it may also be provided at a portion where different voltages are generated at the terminals by switching the equalizer time constant.Furthermore, the switching transistor 23 may also be connected to the bias AC signal generating circuit 8. It may be provided at any position where the magnitude or frequency of the bias AC signal inside can be switched.

Effects of the Invention As described above, according to the present invention, in a magnetic recording and reproducing apparatus that uses magnetic recording media with different characteristics such as a normal tape and a metal tape, the equalizer time constant for reproduction can be changed using only one switch. The bias alternating current signal for recording can be switched, the configuration can be simplified, and this can greatly contribute to miniaturization and ease of assembly.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a main part of a conventional magnetic recording and reproducing apparatus, and FIG. 2 is a circuit diagram of a main part of a magnetic recording and reproducing apparatus according to an embodiment of the present invention. 1... Magnetic head, 2... Equalizer amplifier, 3... Feedback time constant circuit, 8... Bias AC signal generation circuit, 10a... Switch, 16, 1
7...Resistor, 18...Resistor, 19...Capacitor, 20...Resistor, 22...Resistor, 23...Switching transistor.

Claims (1)

[Claims] 1. A magnetic head, an equalizer amplifier that corrects and amplifies the frequency characteristics of the reproduced signal from the magnetic head during reproduction, a bias AC signal generation circuit that supplies a bias AC signal to the magnetic head during recording, and the equalizer amplifier. A time constant circuit including a first resistor and a capacitor for feeding back the output signal of the amplifying transistor to the previous stage circuit, and a second resistor connected to the collector side of the amplifying transistor to be connected to the time constant circuit. a switch for changing the time constant of the time constant circuit;
Fixing of the switch, which is provided in the bias AC signal generation circuit to switch the magnitude or frequency of the bias AC signal supplied to the magnetic head, and disconnects the second resistor from the time constant circuit. a switching transistor having a base connected to a terminal, and configured to apply a voltage appearing at the fixed terminal when the second resistor is disconnected by the switch as a switching voltage to the base of the switching transistor. Features of magnetic recording and reproducing device.