JPS5822817B2 - magnetic recording and reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing device equipped with a device that automatically adjusts the amount of recording compensation or recording compensation characteristics, and its purpose is to reduce the adjustment time required for the automatic adjustment. The aim is to shorten the

In general, magnetic tapes used in tape recorders have different recording and reproducing frequency characteristics, mainly in the high range, as shown in A, B, and C in FIG. 1, depending on their magnetic properties.

For this reason, conventional tape recorders deal with this by switching between two or three types of recording compensation characteristics using a switch, or by interlocking variable resistance using a variable resistor. It had the disadvantage that only tape could adjust the frequency characteristics to be flat.

Recently, in order to eliminate these drawbacks, devices that automate this adjustment have been proposed (Japanese Patent Publication No. 45-34225, Japanese Patent Application Laid-Open No. 51-9410).

However, these devices have disadvantages in that the time required for adjustment is long and that adjustments cannot be made with a sufficiently high degree of precision, so that sufficient performance cannot always be obtained for practical use.

FIG. 2 shows a change in the recording compensation characteristic of a conventional device, and FIG. 3 shows a change in the recording/playback frequency characteristic accompanying the change in the recording compensation characteristic.

Moreover, FIG. 4 shows the time change of the 20 KHz level at this time.

In FIG. 4, the solid line shows the output of the recording compensation circuit, and the broken line shows the change in the playback output.

As you will see, there is a tape running time τd = L/V 1 second between the recording head and the playback head (L: distance between the recording and playback heads, vl: tape speed), so the playback output is always 16 seconds earlier. It is recorded, and therefore each change is always accompanied by a time difference of τd.

In conventional devices, automatic adjustment is performed in such a state, so the recording compensation characteristic is not at the optimal point at the time the optimal point is detected (for the unit time increase ΔA/Δt of the high frequency level, ΔV8−τd・Causes an adjustment error of ΔA/Δt.

For this reason, it is not desirable to increase the rate of change of the recording compensation characteristic in order to shorten the adjustment time because this increases the adjustment error.

The present invention eliminates the above-mentioned conventional drawbacks and provides a device that can automatically set the recording bias to an optimal value in a short time, with high precision.

An embodiment of the present invention will be described below with reference to the block diagram of FIG. 5 and the time chart of FIG. 6.

In FIG. 5, Sl and S2 are contacts of relay 1, which are connected as shown by broken lines in normal recording and playback conditions.

The recording equalizer automatic adjustment is started by instantaneously switching the switch S3 (FIG. 6A).

As a result, the flip-flop 2 is inverted as shown in FIG. 6B, and a pulse is sent to the triangular wave generator 3.

This pulse resets the triangular wave generator 3 and immediately starts generating a triangular wave.

As shown in FIG. 6C, the generated triangular wave is inputted to the control voltage terminal Q of the voltage variable recording equalizer 50 through the analog memory 4.

As a result, the recording high frequency compensation characteristic changes continuously as shown in FIG.

On the other hand, the previous reversal of flip roller 120 turns on relay 1 at the same time, and its contacts S1. S2 is connected as shown by the solid line.

This allows two different frequency reference signal generators (i
(400 Hz) and 7 (20 KHz) are compensated for the recording high frequency range by the voltage variable recording equalizer 5, mixed with the bias output of the recording bias oscillator 9 through the recording amplifier 8, and are recorded with high frequency bias from the recording head 10 onto the magnetic tape 11. be done.

The reference signal recorded on the magnetic tape 11 in this way is
The signal passes through the playback head 12 and the playback equalizer 13 and reaches the contact point S1.

The contact S1 is connected to the solid line as described above, and the reproduction reference signal is sent to the optimum point detection circuit 14.

The optimal point detection circuit 14 TE reference signal is separated into two original frequency reference signals by a band pass filter 15 and a band pass filter 16, and converted to a DC level by a rectifier 17, a rectifier 18, a smoothing circuit 19, and a smoothing circuit 20, respectively. be done.

These two DC levels are further input to the inverting input and non-inverting input of the comparator 210 for level comparison.

The DC levels of the two signals here change over time as shown in FIG. 6 because the recording/playback frequency characteristics change as shown in FIG. 3 due to the time change of the voltage variable recording equalizer 5.

Therefore, the output of the comparator 21 changes as shown in FIG.
The time constant of the voltage variable time constant circuit is varied.

The point at which the output of the comparator 21 becomes O is the optimal point, that is, the flat point of the recording/playback frequency characteristic.

The voltage variable time constant circuit 22 has a configuration as shown in FIG. 7, and its time constant CR varies in voltage as shown in FIG.

In FIG. 7, 29 is a field effect transistor,
The output of the comparator 21 is applied to the gate of this field effect transistor 29.

The triangular wave generator 3 has a voltage rising speed of the triangular wave that is variable in proportion to the time constant CR of the voltage variable time constant circuit 220, and therefore, as shown in FIG. is shown in FIG. 6C (changes from a solid line to a broken line).

In other words, immediately after the start of adjustment, the output of the comparator 21 is thick (,
Therefore, the time constant of the time constant circuit 220 is small, the voltage rise speed of the triangular wave is fast (it reaches near the optimum point in a short time, and the frequency characteristic approaches flat near the optimum point, so the output of the comparator 21 is small. Therefore, the rising speed of the triangular wave is suppressed so that the adjustment error becomes sufficiently small.

On the other hand, the output of the comparator 21 is simultaneously output from the Schmitt trigger 23.
is connected to the Schmitt trigger 2 at the optimum point (0 voltage point).
Turn 3 off.

The output of the Schmitt trigger 23 triggers the flip-flop 2 through the inverter 24 and inverts it, causing the analog memory 4 to retain the memory, while also releasing the relay 1 and connecting Sl and S2 as shown by the solid line.

The recording equalizer automatic adjustment is now complete, and normal recording and playback is possible using the optimal recording equalizer.

The analog memory 4 includes a reed relay 25, a field effect transistor 26, a capacitor CA as shown in FIG.
, resistors R,, R2, and a capacitor c
The electric charge stored in A is leaked and blocked by a reed relay 25 and a field effect transistor 26, and storage is performed.

Therefore, the memory is retained even after the power is turned off, and the memory time is at least 1000 hours, which is sufficient for normal use.

The variable voltage recording equalizer 5 has a configuration as shown in FIG. 10, and is composed of a transistor 27, a field effect transistor 28, a resistor, a capacitor, etc., and controls the amount of high frequency compensation.

The magnetic recording/reproducing device of the present invention has the above configuration,
According to the present invention, the following effects can be obtained.

(1) Recording compensation is automatically performed on any type of magnetic tape, making it possible to record and play back with always flat frequency characteristics.

(2) Recording compensation adjustment can be done quickly and accurately.

(3) It is also effective against changes in frequency characteristics caused by aging or replacement of recording heads and playback heads.

(4) Can be realized by simply adding a simple circuit.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the recording and reproducing frequency characteristics of different magnetic tapes A, B, and C. Fig. 2 is a diagram showing the high frequency compensation characteristics of the magnetic recording and reproducing device. Fig. 3 is a diagram showing the high frequency compensation characteristic of the magnetic recording and reproducing device. FIG. 4 is a diagram illustrating the causes of adjustment errors in recording compensation in a conventional magnetic recording and reproducing device. FIG. A block diagram of the recording/reproducing device, FIGS. 6A to 6F are diagrams showing changes in voltage at each part of the device of the present invention, FIG. 7 is an electric circuit diagram of the voltage variable time constant circuit of the device of the present invention, and FIG. 8 is the same. FIG. 9 is an electric circuit diagram of the analog memory of the device of the present invention, and FIG. 10 is an electric circuit diagram of the voltage variable equalizer of the device of the present invention. 1...Relay, 2...Flip-flop, 3°°. ... Triangle wave generator, 4 ... Analog memory,
5...Voltage variable recording equalizer, 6,7...
... Reference signal generator, 8 ... Recording amplifier, 9
... Recording bias oscillator, 10 ... Recording head, 11 ... Magnetic tape, 12 ...
...Playback head, 13...Playback equalizer, 1
4...Optimum point detection circuit, 15, 16...
・Band pass filter, 17, 18... Rectifier, 19°20... Smoothing circuit, 21...
Comparator, 22... Voltage variable time constant circuit, 23.
...Schmitt trigger, 24...Inverter.

Claims (1)

[Claims] 1 means for generating reference signals of different frequencies; means for varying recording high frequency compensation characteristics; means for mixing and recording the reference signals while varying the recording high frequency compensation characteristics; In the magnetic recording and reproducing apparatus, the above-mentioned magnetic recording and reproducing apparatus is provided with a means for separating and reproducing the signal into a reference signal frequency, a means for comparing the separated signals, and a means for stopping the variation of the recording high frequency compensation characteristic by the output signal from the comparing means. A magnetic recording/reproducing apparatus comprising means for controlling the variable speed of the recording high frequency compensation characteristic according to the output signal level from the comparing means.