JPS6051165B2 - magnetic recording circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording circuit that continuously performs optimal frequency compensation for each magnetic tape used to obtain even recording and playback frequency characteristics.

First, as shown in FIG. 1, the overall recording and reproducing frequency characteristics of the magnetic tape deviate greatly in the short wavelength region from the ideal curve shown by a straight line of 6 dB/OCT due to various losses.

Here, Le is the eddy current loss of the recording head, Moon is the recording demagnetization loss, Lt is the thickness loss, and the sum of these is the recording time loss LR. Also, L is the spacing loss, Le'
is the eddy current loss of the reproducing head, Lg is the gap loss, and the sum of these is the reproducing time loss Lp. As mentioned above, the overall magnetic recording/reproducing frequency characteristics are quite distorted, so in order to obtain even characteristics, it is necessary to equalize the characteristics.
must be compensated. Therefore, in order to compensate for this characteristic, conventionally LC peaking as shown in FIG. 2 has been performed. That is, by inserting a series circuit of a reactance 2 and a capacitor 3 on the emitter side of the final stage output transistor 1 and applying negative feedback, peaking is performed, and then a resistor 4 and a capacitor 5, 6 are connected. The configuration was such that a recording signal was supplied to the recording head 7 via a coupling circuit. By appropriately selecting the values of reactance 2 and capacitor 3 for performing LC peaking, and by adjusting the resistance value of resistor 8, the optimum overall magnetic recording and reproducing characteristics can only be obtained. . That is, in conventional magnetic recording circuits, LC peaking is mainly used to compensate for recording loss LR in the overall recording and playback frequency characteristics of magnetic tape, or for the purpose of compensating for various losses and regulating the overall recording and playback frequency characteristics. A recording compensation curve was determined and K-seeking was performed. In addition, with the recent trend toward high-density recording, recording and playback in the short wavelength range has become increasingly important, and in response to this trend, the number of types of magnetic tape on the market has increased, so recording compensation is a typical A preset peaking method has been adopted that creates peaking in the frequency characteristics with magnetic tape in mind.

However, if a magnetic tape that matches the preset peaking characteristics is used, the frequency characteristics will be flat, but other magnetic tapes will not have flat characteristics.
Furthermore, the preset peaking method cannot cope with changes in the characteristics of the magnetic tape itself or the head, and therefore users of tape recorders are always in a state of anxiety. The present invention aims to eliminate the drawbacks of the conventional frequency compensation circuit described above, and to provide a magnetic recording circuit that can perform compensation that matches the characteristics of the magnetic tape that is always used, and can obtain flat frequency characteristics. purpose.

Next, embodiments of the invention will be described with reference to the drawings.

In FIG. 3, 9 is a magnetic tape, 10 is a recording head, 11 is a bias oscillator, 12 is a reference signal generator, and the oscillation frequency is f1. 13 is a comparison signal generator whose oscillation frequency is F2.

14 is contact piece A of relay 5-K, l5 is recording compensation amplifier, 1
6 is a negative feedback impedance element of the recording compensation amplifier, 17
is the negative feedback variable impedance element of the recording compensation amplifier, 1
8 is a recording line amplifier, 19 is an input terminal, 20 is a voltage storage element, 21 is a triangular wave generator, 221 is a start circuit,
23 is a playback head, 24 is a playback preamplifier, 25 is contact piece B of relay K, 26 and 27 are bandpass filters,
The respective center frequencies are Fl, f2, 28 is a comparator, 29 is a Schmitt trigger, 30 is a flip-flop, 31 is a relay Kl32 is an output amplifier, and 33 is an output terminal.

Next, the operation of this circuit will be explained.

Now, the frequency f1 of the output signal F1 of the reference signal generator 12 and the frequency F2 of the output signal F2 of the comparison signal generator 13 are set to represent the recording and playback frequency characteristics of the entire recording and playback system (for example, f1 =1kHz, f2=10k pressure),
These are mixed and supplied to the contact α of the relay contact A. When a start pulse is then generated by the start circuit 22, a triangular wave voltage is generated from the triangular wave generator 21, and at the same time, the flip-flop 30 is also inverted and the relay K3l is activated.
becomes 0N and each contact piece A, B enters the adjustment side as shown in the figure, so the output signal F1 of the reference signal generator 12 and the output signal F2 of the comparison signal generator 13 are mixed. The data is recorded on the magnetic tape 9 by the recording head 10 through the recording compensation amplifier 15. These recorded signals are reproduced and detected by the reproduction head 23, amplified by the reproduction amplifier 24, and then passed through the contact piece B of the relay to the bandpass filter 26.
, 27 into two signals F″1 and F″2, which are input to the respective input terminals A and b of the comparator 28. On the other hand,
The voltage of the triangular wave generator 21 changes over time as shown in FIG.
As a result, the frequency characteristics of the recording compensation amplifier 15 change, and as a result, at a certain point in time, the frequency characteristic of the recording compensation amplifier 15 changes.
The recording and reproduction levels of the two signals F″1 and F″2 match. If the trigger level of the Schmitt trigger 29 is set to a point where these two signals match, the Schmitt trigger 29 is inverted when the two signals match, and the flip-flop 3
0 is triggered to invert this flip-flop, and at this time, the voltage acting on the negative feedback variable impedance element 17 is stored and held in the voltage storage element 20,
Since the relay K is also activated to reverse the contacts A and B and switch the magnetic recording circuit to the signal recording/reproducing side, normal recording/reproducing is possible. Next, with reference to FIG. 5, the recording compensation circuit section shown surrounded by a dashed line in FIG. 3 will be explained in more detail.

34 is a control signal input terminal, 35 is a contact piece for controlling the capacitor 36 which is a voltage storage element, 36 is a capacitor forming the voltage storage element, and 37 is a voltage storage circuit FE.
T, 38 is a transistor, 39 is a capacitor, 40 is a resistor R2, 4l is a resistor Rl, 42 is a recording compensation amplifier, 4
3 is an AC signal input terminal, 44 is an AC signal output terminal, 45
46 is a command voltage input terminal, and 46 is a terminal for controlling the opening and closing of the contact piece 35. 47 is a load resistance of the FET, and 48 is a power supply terminal.

Next, the operation of this will be explained. Now, a triangular wave voltage whose voltage changes with time as shown in FIG. 4 is applied to the control signal input terminal 34, and a voltage is also applied from the flip-flop 30 of FIG.
When the contact piece 35 is closed by 6, a triangular wave voltage is applied to the capacitor 36 and charge is accumulated, so that the terminal voltage thereof increases.

When this terminal voltage is applied to the transistor 38 through the FET 37, the impedance also changes according to the voltage as shown in FIG. Therefore, the feedback constant of the recording compensation amplifier 42 composed of the transistor 38, the capacitor 39, and the resistor 40, that is, the output frequency characteristic of the recording compensation amplifier 42, can be arbitrarily determined by the terminal voltage of the capacitor 36, which is a voltage storage element. As a result, it is possible to continuously control the operating point of the high frequency boost. Further, in the normal recording/reproducing state, the contact piece 35 is in an open state, so that the charge of the capacitor 36, which is a voltage recording element, is retained for a long time. As explained above, according to the configuration of the present invention, the impedance 4 of the variable impedance element 17 changes as shown in FIG. 7 with respect to the voltage of the voltage storage element 20, and the high frequency characteristics also change accordingly. ,
It is now possible to record and play for long periods of time with flat frequency characteristics, and since the frequency characteristics are detected and compensated when recording each individual magnetic tape, even if the characteristics of the magnetic head or magnetic tape change, This has the effect of allowing you to record under optimal conditions.

Furthermore, since the configuration itself is simple, it is also practical.

[Brief explanation of the drawings] Figure 1 shows tape speed 19C77! Figure 2 is a diagram showing an example of the overall magnetic recording/reproducing frequency characteristics in SeC.
Fig. 3 is a block diagram showing an embodiment of the present invention, Fig. 4 is an output waveform diagram of the triangular wave voltage generator, and Fig. 5 shows the recording compensation circuit section surrounded by the dashed line in Fig. 3 in more detail. FIG. 6 is a diagram showing an example of voltage variable impedance change, and FIG. 7 is a diagram showing changes in the overall magnetic recording/reproducing frequency characteristic corresponding to points V1 to V5 in FIG. 6. 9...Magnetic tape, 10...Magnetic head, 11...Bias oscillator, 12...Reference signal generator, 13...Comparison signal generation vessel, 14
...Relay K contact piece All5...Recording compensation amplifier, 16...Impedance element, 17
...Variable impedance element, 18...
・Recording line amplifier, 19... Input terminal, 20
... Voltage storage element, 21 ... Triangular wave generator, 22 ... Start circuit, 23 ... Playback head, 24 ... Playback preamplifier, 25 ...・・・
・Relay K contact piece Bl26, 27...Band pass filter 7-, 29...Schmitt trigger,
30...Flip-flop, 31...Relay Kl35...Output amplifier, 33...
・Output terminal, 34... Control signal input terminal, 35.
... Contact piece, 36 ... Capacitor constituting the voltage storage element, 37 ... FET138 ...
... Transistor, 39 ... Capacitor, 4
0,41...Resistor, 42...Recording compensation amplifier, 43...AC signal output terminal, 45...
Command voltage input terminal, 46... Coil that controls opening/closing of contact piece 35, 47... Resistor, 48...
...Power terminal.

Claims (1)

[Claims] 1. In a recording/playback circuit of an AC bias type tape recorder, a negative feedback amplifier for compensating recording/playback frequency characteristics and a voltage acting on a negative feedback variable impedance element of the negative feedback amplifier are connected via a first switch. a voltage storage element for storing memory; a triangular wave voltage generator for generating a triangular wave voltage acting on the voltage storage element;
a first signal generator that generates an adjustment high frequency signal to be recorded on a recording medium; a second signal generator that generates an adjustment low frequency signal to be recorded on the recording medium; and a second signal generator that generates an adjustment low frequency signal to be recorded on the recording medium; A Schmitt trigger whose trigger level is set to the point where the recording and playback levels of the adjustment high-frequency signal and the adjustment high-frequency signal match, a flip-flop that is inverted by the trigger output of the Schmitt trigger, and adjustment according to the inversion state of the flip-flop. a second relay means for switching between the output signals of the first and second signal generators and the recording signal according to the adjustment state or the signal recording and reproducing state of the relay means; switch and the second
and a third switch that switches the reproduction signal from the recording medium to an adjustment system or a signal recording and reproduction state in conjunction with the switch, and continuously adjusts the amount of compensation using the triangular wave voltage to achieve a flat recording and reproduction frequency. What is claimed is: 1. A magnetic recording circuit configured to obtain characteristics, and configured to store and hold the adjusted compensation amount in the voltage storage element by turning off a first switch.