JPS5850493Y2 - Frequency characteristic adjustment circuit for tape recorder - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a frequency characteristic adjustment circuit for a tape recorder.

Recently, high-grade tape recorders called tape decks have become popular, but such tape recorders are required to have flat frequency characteristics over a wide frequency band.

Therefore, such tape recorders are equipped with a frequency characteristic adjustment circuit to flatten the frequency characteristics.

FIG. 1 shows a generally used circuit, in which 1 is a reproducing magnetic head, 2 is an amplifier circuit for amplifying the signal reproduced by the magnetic head 1, and 3 is an output terminal.

i is a frequency adjustment circuit consisting of a variable resistor 5, a resistor 6, and a capacitor 7, and by varying the variable resistor 5, the reproduced frequency characteristics are adjusted.

Reference numeral 8 denotes a main switch provided in the tape recorder, and when it is closed, power is supplied not only to the amplifier circuit 2 but also to the electric motor (not shown). By performing operations such as recording, playback, and fast forwarding, the drive mechanism becomes operational and various operations are performed.

Such a circuit can also obtain good frequency characteristics, but if the reproduction magnetic head 1 has poor high frequency characteristics, it cannot obtain satisfactory characteristics at high frequencies.

Therefore, in order to improve this point, a circuit as shown in FIG. 2 is generally used.

That is, in addition to the frequency adjustment circuit 4 shown in the circuit of FIG. 1, a frequency adjustment circuit 11 consisting of a capacitor 9 and a variable resistor 10 is connected in parallel to the reproducing magnetic head 1.

In such a circuit, the middle frequency can be adjusted by varying the variable resistor 5 of the frequency adjustment circuit 4 connected to the amplifier circuit 2, and the high frequency can be adjusted by changing the variable resistor 10 at the frequency adjustment circuit. This is done by changing.

Although such a circuit can flatten the frequency characteristics in a wide frequency band, noise is generated when the variable resistor 10 that constitutes the frequency adjustment circuit U that adjusts the high frequency is varied, and the reproduction magnetic field is There is a problem in that the head 1 is magnetized.

In order to eliminate such magnetization, adjustment can be made with the main switch 8 open, that is, without power being supplied. , it is necessary to repeat the operations of closing the main switch 8, regenerating operation, stopping operation, and opening the main switch 8 several times, so it not only has the disadvantage that adjustment operations take time, but also when the main switch 8 is opened. Therefore, the amplifier circuit 2, the flywheel, etc. are repeatedly inoperative and inoperable, which has the disadvantage that it takes time for the operation to reach a steady state.

The present invention has been developed in view of these points, and one embodiment shown in FIG. 3 will be described below.

In the figure, 12 is a reproducing magnetic head, 13 is an amplifier circuit for amplifying the signal reproduced by the magnetic head 12, and 1
4 is the output terminal of the amplifier circuit 13; 15 is the output terminal of the amplifier circuit 1;
3 and a main switch that supplies power to an electric motor (not shown).

U is a first frequency adjustment circuit connected to the amplifier circuit 13, and includes a variable resistor 17, a resistor 18, and a capacitor 19.
It is composed of

(3) is a second magnetic head connected in parallel to the reproducing magnetic head 12;
It is a frequency adjustment circuit, and includes a capacitor 21. It is composed of a switching transistor 22 and a variable resistor 23.

Reference numeral 24 denotes an adjustment switch which is switched to the opposite side from the state shown in the figure by a regeneration operation and inverts the switching transistor 22 to a conductive state.

The present invention is constructed as described above, and the adjustment operation of such a circuit will now be explained.

The main switch 15 is closed to supply power to the amplifier circuit 13 and the electric motor, thereby bringing the flywheel rotated by the amplifier circuit 13 and the electric motor into a steady operating state.

If you perform playback operations in this state, adjustment switch 2
4 is switched, the drive mechanism is switched, the magnetic tape for adjustment is made to run for reproduction, and the tape recorder is placed in the reproduction state.

Then, in this reproduction state, the first frequency adjustment circuit 16
The mid-range frequency is adjusted by varying the variable resistor 17 that constitutes the.

Furthermore, the adjustment of the high frequency is performed by switching the adjustment switch 24 to the state shown in the figure by a stop operation to make the switching transistor 22 non-conductive, then varying the variable resistor 23, and by switching the switch 24 again by a regeneration operation to turn off the switching transistor 22. 22 is made conductive and the frequency characteristics are measured.

At this time, if the frequency characteristics are not good, the above-described operation is repeated to perform adjustment.

The variable resistor 23 is controlled by the switching transistor 2.
Since this is done when the variable resistor 23 is in a non-conductive state, the reproducing magnetic head 12 will not be magnetized even if noise is generated from the variable resistor 23.

In this embodiment, the adjustment switch 24 is switched by a regeneration operation, but it can also be switched only when frequency characteristics are adjusted at the factory.

Further, although the case where a transistor is used as the switching means has been described, it is of course possible to use an element such as a field effect transistor.

As explained above, according to the present invention, it is possible not only to solve the problem of the magnetic head being magnetized by the noise generated by the variable resistor that is changed when adjusting the frequency characteristics, but also to make the adjustment operation easy and It can be done quickly.

[Brief explanation of the drawing]

FIGS. 1 and 2 show an embodiment of a conventional frequency characteristic adjustment circuit, and FIG. 3 shows a circuit embodiment of the present invention. Explanation of main figure numbers, 12...Magnetic head for reproduction,
13...Amplification circuit, 15...Main switch, 16...First frequency adjustment circuit, 20...
... Second frequency adjustment circuit, 22 ... Switching transistor, 24 ... Adjustment switch.

Claims (1)

[Scope of utility model registration request] a reproducing magnetic head, an amplifying circuit for amplifying the signal reproduced by the magnetic head, and a first amplifying circuit connected to the amplifying circuit.
A frequency adjustment circuit, a second frequency adjustment circuit connected in parallel to the reproducing magnetic head, and an adjustment switch connected to the second frequency adjustment circuit and switched during a frequency characteristic adjustment operation are brought into conduction. 1. A frequency characteristic adjustment circuit for a tape recorder, comprising an inverting switching transistor, and adjusting the second frequency adjustment circuit while keeping the switching transistor in a non-conducting state.