JPH10293903A - Recording circuit for magnetic tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording circuit for magnetic tape for recording a signal on the magnetic tape subjected to saturation magnetization by a DC erase system which has a simple constitution. SOLUTION: The magnetic tape 2, on which an audio signal is recorded, is saturation magnetized by an erase head 5 for erasing the previously recorded signal. The AC bias recording is performed in a sound recording/reproducing circuit 1 by superposing the audio signal with an AC bias signal supplied from an AC bias oscillating circuit 9. In the sound recording/reproducing circuit 1, the DC correction at the time when the signal is recorded on the magnetic tape 2 subjected to saturation magnetization by the DC erase system, is executed by a diod 14 operating as a slice circuit, which is provided between a terminal 4b of coil 4 of a sound recording/reproducing head 3 and the ground.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording circuit for a magnetic tape, and more particularly to a recording circuit for a magnetic tape for recording a signal on a magnetic tape saturated by a DC erasing method.

[0002]

2. Description of the Related Art Conventionally, in a recording apparatus for a magnetic tape, when recording on a magnetic tape, the next new recording is performed after erasing a previously recorded magnetic signal. As a method of erasing such a magnetic signal, a direct current is applied to an erasing head or a magnetic tape is passed through a magnetic field that is equal to or greater than a saturation magnetic field generated by using a permanent magnet, and the magnetic tape is saturated in one direction. There is a direct current elimination method for causing the erasure. For example, in a simple portable tape cassette recording / reproducing apparatus, this DC erasing method is generally used.

[0003] Conventionally, in a magnetic tape recording apparatus,
An AC bias recording method is used in which recording is performed by simultaneously adding a signal current and an AC bias current to a coil of a recording head.

In this AC bias recording method, the frequency of the AC bias current is selected to be, for example, about several times the signal frequency.

When a signal is recorded on a magnetic tape erased by such a DC erasing method, recording is usually performed by applying a DC bias together with the AC bias current to improve the distortion factor.

FIG. 4 shows a recording circuit of a magnetic tape to which a DC bias is applied. A recording circuit 100 for a conventional magnetic tape includes a recording head 101 which is a magnetic head for recording a signal on a magnetic tape 110, an AC bias oscillation circuit 102 for supplying an AC bias current to a coil of the recording head 101, A recording equalizer circuit 103 connected via a coupling capacitor 104 to the other end of the coil 101 to which no AC bias current is supplied.

Further, the recording circuit 100 for this magnetic tape
Includes a DC bias circuit 105 for supplying a DC voltage to the other end of the coil of the recording head 101 to which the AC bias current is not supplied.

Such a recording circuit 100 for a magnetic tape
When recording of an audio signal supplied from a microphone or a line input is started, an audio signal is supplied to the recording equalizer 103, and a recording control signal is supplied from, for example, a controller or the like.

When a recording control signal is supplied from a controller or the like, the AC bias oscillation circuit 102
An AC signal of about 50 to 100 KHz at 50 V (PP) is supplied to the recording head 101.

An audio signal supplied from a microphone or a line input is supplied to the recording equalizer 103 via an amplifier or the like. The recording equalizer 103 performs frequency compensation on the audio signal so as to make the current constant without depending on the frequency, and supplies the current to the recording head 101.

The DC bias circuit 105 includes a resistor 105c
Recording head 1 based on a recording control signal input through
The recording element 101 includes a switching element 105a for switching a DC bias supplied to the coil No. 01, and a current limiting resistor 105b connected in series to the switching element 105a to limit the current supplied to the coil of the recording head 101.

The DC bias circuit 105 applies a DC bias to the recording head 101, and applies a DC bias magnetic field having a reverse polarity to a magnetic tape which has been saturated in advance. That is, if the DC bias is applied to the recording head 10
If it is not added to 1, a signal having a waveform distorted due to the curvature of the hysteresis curve will be recorded, but a proper recording waveform can be obtained by applying this DC bias in an appropriate amount.

After the magnetic tape 110 is saturated magnetized by the erasing head by the DC erasing method, the recording head 1
01, and is magnetized according to the voice signal.

In such a magnetic tape recording circuit 100, by applying a DC bias to both the audio signal and the AC bias current, the magnetization of the tape advances in the DC portion, and the magnetic tape is saturated and magnetized by the DC erasing method. Even so, you can record without distortion.

[0015]

However, in a conventional magnetic tape recording circuit 100 for applying an AC bias current to a recording head by a DC erasing method, a DC bias circuit 105 is provided.
In this case, it is necessary to route control lines and power supply lines. Also, the number of elements is the transistor 105a.
And two resistors 105b and 105c were required.

When the logic of the control line is reversed, the forward / reverse of the logic, such as the necessity of an inverting circuit, must be considered.

The present invention has been made in view of such circumstances, and has as its object to provide a recording circuit of a magnetic tape which records a signal on a magnetic tape which has a simple configuration and which has been subjected to saturation magnetization by a DC erasing method. And

[0018]

In order to solve the above-mentioned problems, a recording circuit for a magnetic tape according to the present invention comprises an AC bias oscillating means for oscillating an AC bias signal, and a recording circuit for generating a recording signal for the magnetic tape. A signal generating means, a recording head in which the recording signal is supplied to one end of a coil and an AC bias signal is supplied to the other end, and a voltage generated in one end of the recording head in which the recording signal is supplied to the magnetic tape. And slicing means for slicing according to the saturation magnetic field.

In this magnetic tape recording circuit, the slicing means cuts the DC component of the signal to be recorded according to the saturation magnetic field of the magnetic tape, and records the signal with an improved distortion factor.

In the recording circuit for a magnetic tape according to the present invention, the slicing means may include a diode having a cathode connected to one end of the coil of the recording head to which a recording signal is supplied and an anode grounded. It is characterized by.

In this magnetic tape recording circuit, the diode cuts the DC component of the signal to be recorded according to the saturation magnetic field of the magnetic tape, and records the signal with an improved distortion factor.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic tape recording / reproducing circuit according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a recording / reproducing circuit for a magnetic tape according to an embodiment of the present invention.

A recording / reproducing circuit 1 includes a recording / reproducing head 3 for recording / reproducing an audio signal on / from a magnetic tape 2 and a magnetic tape 2
And an erasing head 5 for applying a saturation magnetic field to the magnetic field to saturate the magnetic field to erase an already recorded audio signal. This recording / reproducing head 3 has a coil 4 provided with terminals 4a and 4b. The erasing head 5 has a coil 6 provided with terminals 6a and 6b.

The recording / reproducing circuit 1 includes a recording equalizer circuit 8 to which a sound signal is supplied via a recording amplifier 7.
The recording equalizer circuit 8 is connected to a terminal 4b of the recording / reproducing head 3 via a coupling capacitor 8a. The recording / reproducing circuit 1 includes an AC bias oscillation circuit 9 and a reference circuit 10. The AC bias oscillation circuit 9 is connected to a terminal 4a which is the other end of the terminal 4b of the coil 4 of the recording / reproducing head 3 described above. This terminal 4a is hereinafter referred to as a common terminal 4a. The reference circuit 10 is connected to a common terminal 4 a of the coil 4 of the recording / reproducing head 3 via a switching circuit 11.

The recording / playback circuit 1 has a preamplifier 12 for outputting a playback signal. This preamplifier 12 has
The input terminal is connected to the terminal 4b of the coil 4 of the recording / reproducing head 3 and the reference circuit 10.

The recording / reproducing circuit 1 includes a DC bias circuit 15
It has. The DC bias circuit 15 is connected to the terminals 6a and 6b of the coil 6 of the erase head 5.

The recording / reproducing circuit 1 includes a controller 1
3 is provided. The controller 13 supplies a recording control signal to the AC bias oscillation circuit 9, the switching circuit 11, and the DC bias circuit 15.

The recording / reproducing circuit 1 further includes a diode 14 serving as a slice circuit. This diode 1
Reference numeral 4 denotes a cathode connected to the terminal 4b of the coil 4 of the recording / reproducing head 3, and an anode connected to ground.

The recording operation and the reproducing operation of the audio signal of the recording / reproducing circuit 1 having such a configuration will be described.

When the recording / reproducing circuit 1 records an audio signal on the magnetic tape 2, the controller 13 sets the recording control signal to, for example, high and sets the AC bias oscillation circuit 9
Is supplied to the switching circuit 11 and the DC bias circuit 15.

The switching circuit 11 disconnects the connection between the reference circuit 10 and the common terminal 4a of the coil 4 of the recording / reproducing head 3 based on the recording control signal, and supplies the reference voltage output from the reference circuit 10 to the magnetic head 3. Don't do it.

The AC bias oscillation circuit 9 supplies a sine wave signal having a peak-to-peak voltage of about 30 to 50 volts as a bias signal to the common terminal 4a based on the recording control signal. The frequency of the bias signal is, for example, about several times the frequency of the audio signal to be recorded.
Hz to 100 kHz.

The DC bias circuit 15 supplies a DC current to the terminals 6a and 6b of the coil 5 of the erasing head 5 based on the recording control signal. This is because the recording / reproducing circuit 1 applies a saturation magnetic field from the erasing head 5 to the magnetic tape 2 because the next new recording is performed after erasing the previously recorded magnetic signal during recording. In the recording / reproducing circuit 1, a saturation magnetic field may be applied to the magnetic tape 2 by a permanent magnet without using the DC bias circuit 15.

On the other hand, an audio signal supplied from a microphone or a line input during recording is supplied to a recording amplifier 7.

The recording amplifier 7 amplifies the audio signal by a fixed amount and supplies it to the recording equalizer 8. Recording equalizer 8
Performs a frequency correction of the audio signal in accordance with the impedance of the coil 3 of the magnetic head 2 in order to make the current supplied to the recording / reproducing head 3 constant without depending on the frequency. The frequency-corrected audio signal is supplied to the coupling capacitor 8a.
Is supplied to the terminal 4b.

The recording / reproducing head 3 superimposes the audio signal supplied from the recording equalizer 8 on the AC bias signal supplied from the AC bias oscillating circuit 9 and performs AC bias recording on the magnetic tape 2. That is, the recording / reproducing head 3 records an audio signal on the magnetic tape 2 after erasing a signal already recorded by the erasing head 5.

Here, the magnetic tape 2 on which the audio signal is recorded is saturated and magnetized by the erasing head 5 as described above. Therefore, the recording / reproducing head 3 has to record the signal on which the DC correction has been performed for the saturation magnetization on the magnetic tape 2.

In the recording / reproducing circuit 1 of this embodiment, DC correction is performed by the diode 4 serving as a slice circuit provided between the terminal 4b of the coil 4 of the recording / reproducing head 3 and the ground.

FIG. 2A is an equivalent circuit of impedance when the AC bias oscillation circuit 9 is regarded as an AC voltage source. The recording / reproducing circuit 1 includes an impedance Z _H of the magnetic head 3 and an output impedance Z of the equalizer circuit 8.
_EQs are connected in series, during which an AC bias signal is applied. The diode 14 is connected in parallel with the output impedance Z _EQ of the equalizer circuit 8.

Therefore, the voltage generated at the output impedance Z _EQ of the equalizer circuit 8 is equal to the voltage of the diode 1 when the AC bias current is generated in the direction i _{B in} FIG.
Since the impedance of _No. 4 is sufficiently large as compared with the Z _EQ , no distortion occurs in the waveform. On the other hand, when the AC bias current is generated in the opposite direction to i _B , the diode 1
Based on the voltage limit characteristics of 4, the voltage absolute value than the forward voltage V _F is large, it would be cut. That is, the voltage V _P of the reference potential which would occur if there is no diode 14 to a peak value, only a value obtained by subtracting the forward voltage V _F is the slice voltage V _Slice of the diode 14 is removed.

That is, the slice voltage V _Slice is
Appears as a corrected DC bias component when recording an audio signal. That is, the diode 14 functions as a slice circuit, and performs DC correction when recording a signal on the magnetic tape 2 that has been saturated magnetized by the DC erasing method.

In the impedance equivalent circuit shown in FIG. 2A, the coupling capacitor 8a is ignored.

Next, when the recording / reproducing circuit 1 reproduces an audio signal from the magnetic tape 2, the controller 13
Sets the recording control signal to low, for example, and supplies it to the AC bias oscillation circuit 9, the switching circuit 11, and the DC bias circuit 15.

The switching circuit 11 conducts the reference circuit 10 and the common terminal 4a of the coil 4 of the recording / reproducing head 3 based on the recording control signal, and supplies the reference voltage output from the reference circuit 10 to the magnetic head 3. .

The AC bias oscillation circuit 9 does not generate the aforementioned AC bias signal. Here, the reference voltage from the reference circuit 10 is supplied to the AC bias oscillation circuit 9. However, since the input impedance of the AC bias oscillation circuit 9 is very high, it does not affect the reproduction operation.

DC bias circuit 15 and erase head 5
Does not work during playback.

The recording / reproducing head 3 has a coil 4 to which a reference voltage from a reference circuit 10 is applied. The recording / reproducing head 3 converts a magnetic signal recorded on the magnetic tape 2 into an electric signal, and supplies the reproduced signal to the preamplifier 12.

The preamplifier 12 amplifies the reproduced signal reproduced by the recording / reproducing head 3 and outputs the reproduced signal. The reproduced output is output from a speaker or the like via, for example, a noise reduction circuit or the like.

Here, as shown in FIG. 3, the diode 14 hangs in parallel with the input of the preamplifier 12, but the minimum value of the reproducing voltage reproduced by the recording / reproducing head 3 is sufficiently higher than the ground. Since the voltage is high and the voltage is about -70 dB, the reproducing operation is not affected.

As described above, in the magnetic tape recording / reproducing circuit 1 to which the present invention is applied, by providing the diode 14, no special control is required to improve the distortion factor. Magnetic tape 2 with saturation magnetization
Can be recorded. In particular, diode 1
In this way, it is possible to easily improve the distortion rate and perform good recording.

[0052]

In the recording circuit of the magnetic tape according to the present invention, the DC component of the signal to be recorded is cut in accordance with the saturation magnetic field of the magnetic tape, the distortion is improved, and the signal is recorded. The power supply line does not have to be routed, and the circuit configuration can be simplified.

Further, in the recording circuit of the magnetic tape according to the present invention, it is possible to easily improve the distortion factor by one diode and perform good recording.

[Brief description of the drawings]

FIG. 1 is a block diagram of a recording / reproducing circuit to which the present invention is applied.

FIG. 2 is a diagram showing an equivalent circuit of impedance and its voltage waveform.

FIG. 3 is a diagram illustrating the influence of a diode during reproduction by a recording / reproducing circuit to which the present invention is applied.

FIG. 4 is a block diagram of a conventional magnetic tape recording circuit.

[Explanation of symbols]

1 recording and reproducing circuit, 2 magnetic tape, 3 recording and reproducing head, 4 coils, 4a and 4b terminals, 5 erasing head,
6 coil, 6a, 6b terminal, 7 recording amplifier, 8
Recording equalizer, 9 AC bias oscillation circuit, 10 reference circuit, 11 switching circuit, 15 DC
Bias circuit, 13 controller, 14 diode

Claims (2)

[Claims] 1. A recording circuit of a magnetic tape for recording a signal on a magnetic tape saturated by a DC erasing method, comprising: an AC bias oscillating means for oscillating an AC bias signal; and a recording signal generating means for generating a recording signal for the magnetic tape. A recording head in which the recording signal is supplied to one end of the coil and an AC bias signal is supplied to the other end; and a voltage generated at one end of the recording head where the recording signal is supplied is a saturation magnetic field of the magnetic tape. And a slicing means for slicing in accordance with the following conditions: 2. The magnetic device according to claim 1, wherein the slicing means comprises a diode whose cathode is connected to one end of the coil of the recording head to which a recording signal is supplied, and whose anode is grounded. Tape recording circuit.