JPS6118243B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION An object of the present invention is to provide a magnetic recording/reproducing device such as a tape recorder, which can always record at an optimal bias current value depending on the type and characteristics of the tape used.
The purpose is to automatically determine the amount of recording compensation so that the frequency characteristics become flat at that bias current value.

First, a conventional magnetic recording/reproducing device will be explained.

FIG. 1 shows an example of a conventional recording head drive circuit. As shown in FIG. 1, the amount of current from the bias oscillator is adjusted and fixed by a variable resistor. On the other hand, the recording compensation amount is structured so that LC resonance is obtained in the emitter circuit of the transistor in the drive stage, and the resonance frequency is selected and used according to the tape speed. In the example shown in FIG. 1, the characteristics of the magnetic tape to be used are preset. However, the recent development of magnetic tape has produced various types of magnetic tape, and their operating bias and MOL
(maximum operating level) are also different, so when presetting the bias and equalizer (recording compensation) as in the conventional case, it cannot be handled with one position.In recent tape recorders, the tape selector has three bias stages and three equalizer stages. There is even an example of a total of 9 positions. Therefore, the operation is complicated and error-prone, and there are still some tapes whose characteristics cannot be fully covered.

The present invention eliminates the above-mentioned drawbacks and uses a constantly used magnetic tape with the best bias and equalizer.One embodiment of the present invention will be described below with reference to FIG. 2.

In Fig. 2, 1 is the starting circuit ST, 2 is the first
Flip-flop FF ₁ , 3 is monostable multivibrator MM, 4 is second flip-flop
FF2 and 5 are the third flip-flop FF ₃ , 6 is the fourth flip-flop FF ₄ , and 7 is the first AND gate
AND1 and 8 are the first relay K1, 9 is the second AND gate AND2, 10 is the second relay K2, 11 is the third relay K3, 12 is the first triangular wave generator OS
1 and 13 are the first electronic volume EVR1, 14 is the D/C amplifier, 15 is the second triangular wave generator OS2,
16 is the second electronic volume EVR2, 17 is D.
C amplifier, 18 input terminals, 19 input amplifier, 2
0 is a voltage controlled impedance element, 21 is a recording compensation circuit, 22 is a recording head, 23 is a voltage controlled AC bias oscillator VC0, 24 is a magnetic tape, 25 is a playback head, 26 is a playback equalizer amplifier, 2
7 is a reproduction equalizer time constant circuit, 28 is a band pass filter BPF1, and the center frequency is 〓 ₁ , 29
is an analog delay element, and the delay time τ is infinitely 0.
It is set close to [sec]. 30 is band pass filter BPF2, 31 is contact A of relay K3,
32 is contact B of relay K3, 33 is contact A of relay K2, 34 is contact B of relay K2, 35 is contact A of relay K1, 36 is a comparison amplifier, 37 is a Schmitt trigger SH, and 38 is an oscillator. The oscillation frequency is ₁ , 39 is an oscillator and the oscillation frequency is ₂ ,
40 is a line amplifier, and 41 is an output terminal.
As a definition, each FF and MM is divided into A and B, and the state of 1 is defined as H (high level). Furthermore, the signals of each FF and MM are inverted from H to L (low level) when a positive pulse is input.

Figure 4 shows a time chart for the circuit shown in Figure 2. Based on this time chart, the second
The operation of the circuit shown in the figure will be explained. 1 starting circuit
2, 4, 5, 6 by ST start pulse
All flip-flop FFs of FF enter the reset state.

At that time, the 12th triangular wave generator OS1 starts to rise, and the relay K1 is activated by AND ₁ which inputs the inverted outputs of the 2nd and 5th flip-flops FF ₁ and FF ₃ .
It turns on, and relay K3 of 11 also turns on. 3
Signal from oscillator 8 = ₁ passes through a recording compensation circuit 21 to a recording head 22, and records an analog signal on a magnetic tape 24.

At this time, the voltage from OS1 of 12 supplies a current in the H state of flip-flop FF ₄ (B) of 6, the switch is opened by the L state, and the voltage is stored in analog form by the first electronic volume EVR1 of 13, and the D of 14 is stored.・23 bias oscillators by C amplifier
Control the VCO (Figure 6 shows the time changes of the 12 triangular wave generators, that is, the time changes of the bias current ib,
FIG. 5 shows an example of changes in reproduction voltage V _h with respect to changes in bias current ib. ). Signals recorded on 24 magnetic tapes = ₁ is converted into 2 by 25 playback heads
It passes through 6 equalizer amplifiers, 28 filters, 32 K3Bs, is rectified by diode _D1 , and is led to the (+) input terminal of 36 operational amplifiers. On the other hand, the signal passed through 28 bandpass filters = ₁ passes through 29 delay elements, is delayed by real time τ, passes through 35 K ₁ A, is rectified by diode D ₁ , and is the (-) input of 36 operational amplifiers. When the slope of the signal ₁ due to the time difference guided to the terminal is detected (corresponding to ΔV _h /Δib in Fig. 5) and becomes below the threshold value (when the peak is detected), the Schmitt trigger SH of 37 is activated. Trigger and trigger 6's FF ₄ . At the same time, 5's FF ₃ , then 2's
Trigger FF ₁ . Since the switch of EVR1 of 13 which was closed by FF ₄ of 6 is opened, the output voltage of VCO 23 is fixed, and the peak bias current value at that time is memorized and held by EVR1 of 13.

Next, with the inverted output of the A side of MM 3, FF ₃ of 5 is 3
When the MM specified time has passed, it will return to its original state. The voltage of MM triggers the second triangular wave generator OS2 of 15, and the OS2 of 15 starts generating a triangular wave. As shown in Figure 4, the gate at that time opens 16 as AND2 of 9 turns on.
Supplies voltage to EVR2. The control signal voltage V _D from the EVR 2 (16) gives a control signal to the voltage controlled impedance element (20) to control the frequency characteristics of the recording compensation circuit (21). This situation is shown in FIG. That is, as the control voltage V _D changes in FIG. 9, the frequency characteristics of the recording compensation circuit shown in FIG. 21 change continuously from a to e. Therefore, the integrated frequency response obtained by the circuit shown in FIG. 2 changes as shown by the shaded area in FIG. At this time, 38 oscillation signals are generated by 31 K3A and 33 K2A.
Oscillation signals of ₁ and 39 = ₂ are mixed and led to the recording head of 22 through the recording compensation circuit of 21,
It is recorded on magnetic tape No. 4, picked up by playback head No. 25, amplified by playback equalizer circuit No. 26, and then returned to the original level by filter No. 28 _.
and 30 filters into the original 〓 ₂ signals, which pass through the contacts of 32 K3B and 34 K2B and are converted to DC by diodes D ₁ and D ₂ .
It is led to both the (+) and (-) input terminals of the operational amplifier No. 6. When there is no difference in the reproduction output level of signals ₁ and _2, that is, when there is no difference in frequency characteristics between low and high frequencies as shown in Figure 7 (indicating that a flat characteristic has been obtained), 37. The Schmidt trigger SH flips again and triggers 5's FF ₃ . At this time 5
FF ₃ has already been returned to standby by 3's MM. The switch of EVR2 of 16 is first opened by the signal obtained by _FF3 of 5 triggered by the second reversal of Schmitt trigger SH, and the predetermined voltage (synthesized frequency) given by OS2 of 15 is opened. The frequency characteristics of the recording compensation circuit 21 are fixed at a voltage at which the characteristics become flat. In addition, relay K3 of No. 11 is turned off by reversal of Schmitt trigger SH and FF of No. 5 is turned off by reversal of _{No. 3} .
Therefore, 31, 32K3A and K3B are turned OFF and the automatic adjustment signal circuit is opened.

Next, the “electronic volume” used in Figure 2
The internal configuration of EVR will be explained. Figure 3 is
This shows a circuit that uses EVR to control a recording compensation circuit. In Figure 3, 45 is an input terminal, 46 is a reed relay, and 47 is plastic molded.
The entire EVR, 48 is a control terminal, 49 is an analog storage capacitor, 50 is FET, 51 is a resistor,
52 is an output terminal, 53 is a signal input terminal, 54 is a variable impedance transistor, 55 is a capacitor as an impedance element, 56 is a resistor, 57 is a resistor for negative feedback circuit configuration, 58 is a signal amplifier, 59 is a signal output terminal.

As shown in FIG. 3, the EVR used in the present invention has a function of being able to be turned on and off by an external voltage and a function of holding the input voltage for a long period of time.

Next, the function of the recording compensation circuit shown in FIG. 3 will be explained. Transistor 54 functions as a voltage-controlled resistance element, and together with capacitor 55 determines the rise time constant of the high-frequency boost. (The impedance of the negative feedback circuit is voltage-controlled in relation to R1 of 57.) Therefore, as described above, continuous control as shown in a and e of FIG. 9 is possible.

As shown in FIG. 5, the output voltage V _h varies depending on ib and has a certain peak. That is, if the optimum recording/reproducing sensitivity varies depending on the bias current ib, this is a characteristic unique to the magnetic tape. Therefore, depending on the type of tape, there will be as many characteristic diagrams as there are types of tape, as shown in FIG. Furthermore, when the bias position is selected from any one of 1 to 5 in FIG. 5, the frequency characteristics also change as shown in FIG. The harmonic distortion rate generated at this time also changes, but as shown in FIG. 5, generally the minimum point of the distortion rate and the minimum point of the recording sensitivity may not coincide. In general, if point 4 or 5 shown in Figure 5 is detected as the optimum value and the recording compensation amount is determined so that the frequency characteristics become flat at this point, it will be at the center of the change range shown in Figure 7. Flat characteristics as shown by the solid line shown are obtained. The magnetic recording/reproducing apparatus of the present invention detects point 5 shown in FIG. 5 as the optimum value and flattens the frequency characteristics at this point, so that the following effects can be obtained.

(i) The tape recorder can always be used at the optimum bias point.

(ii) The user does not need to select and set the tape selector (bias position or equalizer position) according to the type of magnetic tape.

(iii) By automating equalizer adjustment, even frequency characteristics can always be obtained.

(iv) The tape recorder's characteristics allow it to always record in its best condition.

(v) Even if the type of magnetic tape is unknown, completely compatible recordings can be made without any problems.

(vi) It is a simple device and the entire device is processed electronically, so it is inexpensive and industrially advantageous.

(vii) Bias equalizer circuit becomes simpler.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram of a recording head drive circuit of a conventional magnetic recording and reproducing device, and FIG. 2 is a block diagram of a magnetic recording and reproducing device according to an embodiment of the present invention.
Fig. 3 is an electrical circuit diagram of the electronic volume of the device, Fig. 4 is a time chart of the device, Fig. 5 is a bias and distortion characteristic diagram in magnetic recording, Fig. 6 is a characteristic diagram of the triangular wave voltage generator, and Fig. 7 is a diagram of the characteristics of the triangular wave voltage generator. The figure is an explanatory diagram of frequency chart characteristic flattening of the recording compensation circuit of the device of the present invention, FIG. 8 is a diagram showing changes in the overall frequency characteristic due to bias current of the device, and FIG. FIG. 3 is a diagram showing changes in frequency characteristics. 1... Starting circuit, 2, 4, 5, 6... Flip-flop, 3... Monostable multivibrator, 7, 9... AND gate, 8, 10, 11
...Relay, 12,15...Triangle generator, 13,
16...Electronic volume, 14, 17...DC amplifier, 18...Input terminal, 19...Input amplifier,
20... Voltage controlled impedance element, 21...
Recording compensation circuit, 22... Recording head, 23... AC bias oscillator, 24... Magnetic tape, 25...
...Reproduction head, 26...Reproduction equalizer amplifier, 27...Reproduction equalizer time constant circuit, 2
8, 30... Band pass filter, 29... Delay element, 36... Comparison operational amplifier, 37... Schmitt trigger, 38, 39... Oscillator, 40...
...Line amplifier, 41...Output terminal.

Claims (1)

[Claims] 1. A means for recording a signal on a magnetic tape, a means for reproducing the recorded signal, a plurality of reference signal generation circuits with different frequencies, an AC bias current generation circuit, and an AC bias current value of the AC bias generation circuit. means for changing the AC bias current value according to time; means for detecting the maximum value of the reproduction voltage of one reference signal recorded on the magnetic tape and fixing the AC bias current value; and means for changing the frequency characteristic according to time. a recording compensation circuit; means for detecting reproduction voltages of a plurality of reference signals recorded on a magnetic tape via the recording compensation circuit; A magnetic recording/reproducing device comprising means for fixing frequency characteristics of a circuit.