JPS5931766B2 - magnetic recording and reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording/reproducing device such as a tape recorder,
In particular, the present invention provides a magnetic recording and reproducing device that can automatically detect and set the optimum high frequency bias current value according to the characteristics of the magnetic tape in order to maximize the performance of the tape recorder.

FIG. 1 shows an example of the circuit configuration of a general tape recorder.
In Figure 1, 1 is a playback head, 2 is a playback preamplifier, 3 is an output amplifier, 4 is an output terminal, 5 is a recording head, 6 is a signal level adjustment volume, □ is a recording head drive circuit, 8 9 is a recording compensation circuit, 9 is an input level adjustment volume, 10 is an input terminal, 11 is a high frequency bias transmission circuit, and 12 is a high frequency bias current adjustment volume. As shown in the block diagram of FIG. 1, in a tape recorder, it is necessary to supply a high frequency bias current to the recording end.

This high frequency bias current adjustment determines the sensitivity (S/N) and processing efficiency of the system depending on the characteristics of the magnetic tape used.

In the example shown in FIG. 1, an appropriate current value is found and set by comprehensively determining the power consumption, frequency characteristics, sensitivity (recording/playback output characteristics), etc. using the 12 volumes. As an example of a general tape recorder, as shown in Figure 2, magnetic tapes are classified into several types according to their characteristics, such as A, B, and C, and typical current values are preset. is normal. In that case, as shown in the characteristic example shown in Figure 2, A
, B, and C, it seems that there are relatively few problems with the preset method if you can classify them, but as mentioned in the adjustment example, the optimum method depends on which of the magnetic tape characteristics you prioritize. The bias current values are different (as shown in Figure 2, the maximum value of recording sensitivity and the maximum value of processing efficiency are usually different), and the bias current characteristics as shown in Figure 2 are different for magnetic tape. The curves varied between manufacturers, and the preset method could not bring out the maximum potential of the tape. The present invention eliminates the above-mentioned conventional drawbacks, and one embodiment of the present invention will be described below with reference to FIG. 3. In FIG. 3, 21 is a magnetic tape, 2
2 is a reproduction magnetic head, 23 is a preamplifier, 24 is a bandpass filter (fl or f2), 25 is a similar bandpass filter (2f4-f2 or 2f2-f,),
26, 2? is a rectifier circuit, 28, 28″ is a DC amplifier, 2
9 is a differential amplifier, 30 is a differential circuit, 31 is a Schmitt trigger circuit, 32 is a flip-flop circuit, 33 is a start pulse generation circuit, 34 is a relay, 35 is a relay contact for switching the reproduction output, and 36 is also for input switching. relay contacts,
37 is a relay contact for switching the control voltage, 38 is a triangular wave generation circuit, 39 is a DC amplification circuit, 40 is an analog memory circuit, 41 is a bias oscillation circuit, 42 is a recording head drive circuit, 43 is a recording head, and 44 is a Reference signal generator F, 45 is reference signal generator F2, 46 is an output amplifier, 47 is an output terminal, 48 is an input amplifier, and 49 is an input terminal. The operation of the circuit of FIG. 3 according to the present invention will be explained using the time charts of FIGS. 3 and 4. In addition, in FIGS. 4a to 4g, the numbers of each part in FIG. 3 are also written. A pulse from the start pulse generating circuit 33 causes the entire system to enter an automatic bias adjustment state. The reference signals f1 and F2 are generated by reference signal generators 44 and 45, and are supplied as mixed signals to the recording head 43 from the recording drive circuit 42. The analog memory circuit 40 is driven by the DC level from the flip-flop circuit 32, and the output from the triangular wave generation circuit 38 is sent to the DC amplification circuit 3.
9, and the bias oscillation circuit 41 is controlled by this output. That is, as the voltage applied to the bias oscillator circuit 41 increases, the high frequency bias current value of the recording head 43 increases, and the recording and playback characteristics proportional to the magnetic flux on the magnetic tape 21 are converted into voltage by the playback head 22. After being amplified by a preamplifier 23, the reference signal component 1 or F
2 component and the main component of the difference frequency distortion component (2f1-
F2) or (2f2-f1). Each component is converted to an average DC level by the rectifiers 26 and 27, and the difference between the reference signal level and the difference frequency distortion component level is amplified by the differential amplifier 29. The output of the differential circuit 31 inverts the Schmitt trigger circuit 31, and the flip-flop circuit 32 inverts. At this time, the entire system returns to the adjustment completion state by the operation of 34 relays. Therefore, the control voltages of the 40 analog memory circuits are cut off, and the analog memory circuits memorize and hold the voltage value of that state, ie, the point (voltage, ie, bias current) at which the ratio of the difference frequency distortion component to the output voltage is minimum.

FIG. 5 shows bias current versus recording/playback level and difference frequency distortion level for a certain magnetic tape. As shown in Figure 5, the feature of the device of the present invention is that the optimal bias current value is set at the point where the difference between the recording and playback sensitivity and the distortion component is maximum, and the straight line of the recording and playback output at this point Sex is at its best. Conventionally, there was an example of determining the bias current using a simple harmonic distortion factor as shown in Figure 7, but the distribution of harmonic components expands to the high range as shown in the figure, and the influence of frequency characteristics and noise Not only are there cases in which the adjustment is not always accurate due to the influence of Moreover, there are problems in that modulation distortion, which is a major factor in determining tape recorder quality, cannot be taken into account at all.

The difference frequency distortion used here has a frequency distribution as shown in FIG. 8, for example, and typical examples of how to select two frequencies are 8 KHz and 8.1 KHz.

Being able to select two relatively close frequencies like this means that not only are they unaffected by frequency characteristics, but the distribution of distortion components is regular (8, 1-8 KHz) = every 100 Hz, which improves measurement evaluation. Not only is it convenient for have Note that the analog memory circuit 40 used in the above embodiment of the present invention is the sixth analog memory circuit 40.
As shown in the figure, it consists of one reed relay, a voltage storage capacitor, and an FET (field effect transistor) for output extraction, and these parts are sealed in a single case with good insulation. be. Control signal (D.C.
) opens and closes the reed relay, charges the external input voltage to the capacitor, and takes it out using the FET. By using this element, when using several rolls of the same tape, you can use the sample tape. Once adjusted, the memory of the analog voltage remains for a long time even if no voltage is applied, and it can be handled in the same way as a preset system. The device of the present invention has the above-described configuration, and according to the present invention, the following effects can be obtained.

(1) Bias current can be automatically adjusted to fully exhibit the characteristics of any magnetic tape. (2) Even if the characteristics of the tape recorder change (for example, the magnetic head wears out), the bias current value can be set to the optimum value.

(3) There is no need to worry about setting the various knobs of the tape recorder in consideration of the name, type, characteristics, etc. of the magnetic tape to be used.

(4) It is possible to provide an inexpensive device that can be configured with a simple device and allows anyone to use a tape recorder in the best condition.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional magnetic recording/reproducing device, Figure 2 is a diagram showing bias characteristics and distortion rates of various magnetic tapes,
FIG. 3 is a block diagram of a magnetic recording/reproducing apparatus according to an embodiment of the present invention, FIGS. 4 a to 4 g are explanatory diagrams of the operation of the apparatus of the present invention, and FIG. 5 shows output levels and difference frequencies due to bias current of the magnetic tape. FIG. 6 is an electric circuit diagram of the analog memory circuit of the device of the present invention, FIG. 7 is a diagram showing an example of the distribution of harmonic distortion, and FIG. 8 is a diagram showing an example of the distribution of difference frequency distortion. It is. 21...Magnetic tape, 22...Magnetic head (for reproduction), 23...Preamplifier, 24,
25...Band pass filter 1, 26, 27...
... Rectifier circuit, 28, 28'' ... DC amplifier, 29 ... Differential amplifier, 30 ...
Differential circuit, 31... Schmitt trigger circuit,
32...Flip-flop circuit, 33...
...Start pulse generation circuit, 34...Relay, 35, 36, 37...Relay contact, 38...
... Triangle wave generation circuit, 39 ... DC amplifier circuit, 40 ... Analog memory circuit, 41 ...
...Bias oscillation circuit, 42...Drive circuit, 43...Recording head, 44, 45...
... Reference signal generator, 46 ... Output amplifier,
47...Output terminal, 48...Input amplifier, 49...Input terminal.

Claims (1)

[Claims] 1 means for continuously varying the high frequency bias current, means for generating two different reference signals f_1 and f_2, means for supplying the reference signal to the recording head, means for reproducing the reference signal, means for selectively extracting only the reference signal component f_1 or f_2 from a group of signals;
_1); means for comparing the magnitudes of the two extracted signal components; means for detecting the maximum value of the output from the comparing means; and a high-frequency bias current corresponding to the maximum value. 1. A magnetic recording and reproducing device comprising means for storing and retaining values.