JPH0644329B2 - Magnetic recording / playback device - Google Patents

Description

The present invention relates to a magnetic recording / reproducing apparatus in which optimum recording bias current, optimum recording level, and optimum recording equalizer characteristic are automatically set.

A magnetic recording / reproducing apparatus of this kind is disclosed in, for example, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent No. 16206, the recording bias current is varied at an arbitrary time interval, each corresponding reference recording / playback signal is stored, the maximum value among the stored values is detected, and the maximum value is output. Bias current setting means to set the bias current to the time state, and the recording level in the mid range is varied at arbitrary time intervals, and the corresponding reference recording / playback signal is compared with the reference level to obtain the reference recording / playback signal. Recording level setting means for setting the recording level when the reference level is reached, and the recording equalizer characteristics are changed at arbitrary time intervals, and the corresponding reference recording playback signals are compared with the reference level for reference recording. There is provided an equalizer characteristic setting means for setting the recording equalizer characteristic when the reproduction signal reaches the reference level.

For example, in FIG. 1, as shown in FIG. 2, the bias current variable circuit 10 is controlled from the CPC 5 to sequentially increase the bias current from the bias oscillation circuit 1, and, for example, 33
The output of the low-frequency oscillator 2 that oscillates at 3 Hz is switched to the switch 1.
5, output via the recording current variable circuit 12 and the recording equalizer variable circuit 11, recorded on a magnetic tape by superimposing with the output of the bias current variable circuit 10, and the reproduced output reproduced. The reproduction level detection circuit 4 detects the maximum value of the reproduction level accompanying the increase of the bias current, and the bias current variable circuit is set so that the bias current becomes the maximum value (FIG. 2). Steps a, b, c). Next, the CPU 5 changes the recording current variable circuit 1
2 is controlled to sequentially increase the output current of the low-frequency oscillator 2 supplied to the recording head 7 and recorded on the magnetic tape, and the reproduction output of reproducing this is detected by the reproduction level detection circuit 4 and the reproduction level detection circuit. The variable recording current circuit 12 is set so that the recording current becomes when the output of 4 reaches the reference level (steps d and e in FIG. 2). Next, the CPU 15 switches the switch 15 to select the high frequency oscillator 3 side, and controls the recording equalizer variable circuit 11 to sequentially increase the output current of the high frequency oscillator 3 with an oscillation frequency of 10 KHz supplied to the recording head 7. A reproduction output detected by recording on a magnetic tape and reproducing it is detected by the reproduction level detection circuit 4, and the recording equalizer variable circuit 11 is set to the frequency characteristic state when the output of the reproduction level detection circuit 4 reaches the reference level ( Steps g, h, i in FIG. 2).

As described above, according to the conventional magnetic recording / reproducing apparatus, the bias current, the recording level, and the recording equalizer characteristic are set to their respective optimum values, but the oscillation frequency of the low-frequency oscillator 2 for sensitivity detection is fixed, It is impossible to operate the recording head with an operating bias other than the bias current value that gives the maximum sensitivity at this fixed frequency. Therefore, although the recording characteristic is flattened by the operation bias and the frequency characteristic is flattened, there is a drawback that the balance between the middle and low range MOL (maximum output level) and the high range MOL is fixed at a certain ratio.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and it is an optimum bias current that eliminates the above drawbacks and obtains an arbitrary MOL balance.
It is an object of the present invention to provide a magnetic recording / reproducing device capable of adjusting an optimum recording level and an optimum equalizer characteristic.

Hereinafter, the present invention will be described with reference to examples.

FIG. 3 is a block diagram showing an embodiment of the present invention.

In one embodiment of the present invention, a low frequency oscillator 2'having a variable oscillation frequency is provided in place of the low frequency oscillator 2 in the conventional magnetic recording / reproducing apparatus shown in FIG. The oscillator 2'is constructed so that oscillation and oscillation stop are controlled by the output of the CPU 5. Furthermore, the low-frequency oscillator 2'receives the CP that receives the instruction signal from the keyboard 16.
The oscillation frequency is controlled directly by the output of U5 or by an instruction signal from the keyboard 16.

In the embodiment of the present invention configured as described above, the CPU 5 is operated at step a of the flowchart shown in FIG.
To control the bias current variable circuit 10 to sequentially increase the bias current from the bias oscillator 1 and select the output of the low-frequency oscillator 2'via the switches 14 and 15 to change the recording current variable circuit 12 and the recording equalizer variable circuit. 11 is output, and is superimposed on the output of the bias current variable circuit 10 to be recorded on a magnetic tape, and the reproduction output which reproduces this is detected by the reproduction level detection circuit 4, and the maximum reproduction level due to the increase of the bias current is detected. The bias current variable circuit 10 is set so that the value is detected and the bias current becomes the maximum value. In this case, the oscillation frequency of the low band oscillator 2'is set to set the balance between the high band MOL and the low band MOL to a desired value.

For the case where the oscillation frequency F of the low frequency oscillator 2 'for bias sweep was changed as _{f 1, f 2, f 3} , the correlation diagram of 315HzMOL and 10KHzMOL in the bias values and the bias these reproduction output is maximized It is shown in FIG. Now, in FIG. 4 (a), it is assumed that f ₁ <f ₂ <f ₃ .

A bias value (hereinafter referred to as a peak bias value) showing the maximum output by the frequency f ₃ is B ₁ , a peak bias value by the frequency f ₂ is B ₂ , and a peak bias value by the frequency f ₁ is B ₂ .
_If the frequency is ₃ , the sensitivity curve becomes broader and the peak bias becomes deeper as the frequency becomes lower. Therefore, the following relationships are established between the peak biases B _{1 to} B ₃ .

That is, B ₁ <B ₂ <B ₃ .

Here, assuming that B ₂ is a standard bias and O dB is considered, the peak biases B ₁ and B ₃ are −Δb _{1 with} respect to this.
The bias is assumed to differ by dB and + Δb ₃ dB.

Since the sensitivity curve of a general magnetic tape has a pattern as shown in FIG. 4 (b), the peak bias B ₁ (-
Δb ₁ ) dB and B ₃ (+ Δb ₃ ) dB at 315 Hz
MOL and 10 KHz MOL are (−α ₁ dB, + β ₁ dB) and (+ α ₃ dB, −β ₃ dB), respectively, when each value of B ₂ (O) dB is OdB.

That is, the 315 Hz MOL at the peak bias value by the frequency f ₁ is lower than the peak bias value by the frequency f ₂ by α ₁ dB, and the 10 KHz MOL becomes higher by β ₁ dB. In addition, _{3 in the} peak bias value due to the frequency f 3
The 15 Hz MOL is higher than the peak bias value by the frequency f ₂ by α ₃ dB, and the 10 KHz MOL is lower by β ₃ dB.

Therefore, the balance between the high frequency band MOL and the low frequency band MOL centering around the standard bias is set to the oscillation frequency F of the low frequency band oscillator 2 '.
It is possible to arbitrarily set by changing.

Therefore, the oscillation frequency of the low-frequency oscillator 2'is set in order to set the balance between the high-frequency MOL and the medium-low frequency MOL. According to the above description, when f ₁ <f ₂ <f ₃ , the high frequency range MO
When it is desired to increase L, the oscillation frequency F of the low-frequency oscillator 2'is set to f ₁ ≦ F ≦ f ₂ , and when it is desired to increase the mid-low frequency MOL, it is set to F
Is set to f ₂ ≦ F ≦ f ₃ .

As described above, it is possible to adjust the magnetic tape in consideration of the MOL balance by setting the frequency used when detecting the bias value.

In the above embodiment, the oscillation frequency of the low frequency oscillator 2'is set to 3
Although the case of the step is described, if it is continuously changed, a finer MOL balance can be set.

Further, in the above embodiment, the automatic adjustment mechanism for measuring and controlling the bias, the recording sensitivity and the recording compensation amount has been described.
Even if only the automatic bias adjustment mechanism is used, the action and effect are the same.

Further, instead of the peak detection, the same effect can be obtained by detecting the number of peak over dB.

As described above, according to the present invention, the oscillation frequency of the low frequency oscillator for sensitivity detection is made variable, and the oscillation frequency of this low frequency oscillator is selectively set according to the desired MOL balance between the low frequency range and the high frequency range. Since it was done, low range MOL and high range M
It becomes possible to control the balance with OL arbitrarily.
For example, in the case of a source having a large dynamic range between the high-frequency level and the low-frequency level, a high low-frequency is selected, and an excellent effect that the optimum MOL balance according to the type of music can be automatically set is exhibited.

[Brief description of drawings]

FIG. 1 is a block diagram of a conventional magnetic recording / reproducing apparatus, FIG. 2 is a flow chart for explaining the operation of the conventional magnetic recording / reproducing apparatus, FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG. (a), (b) is a characteristic view for explaining the operation of one embodiment of the present invention. 1 ... Bias oscillator, 2 '... low band oscillator, 3 ... high band oscillator, 4 ... reproduction level detection circuit, 5 ... CPU,
7 ... recording head, 8 ... reproduction head, 10 ... bias current variable circuit, 11 ... recording equalizer variable circuit.

Claims (1)

[Claims] 1. A high frequency oscillator for adjusting a high frequency characteristic, a low frequency oscillator for adjusting a low frequency characteristic, and an output of the bias current variable circuit while sequentially changing an output of the bias current variable circuit. An optimum bias current setting for setting the bias current variable circuit to a bias current value at which a signal superposed with the output of the low frequency oscillator is recorded on a magnetic tape and the maximum reproduction output level is exhibited when the magnetic tape is reproduced. An optimum recording level for setting the recording current variable circuit to a value at which the recording output is recorded on the magnetic tape while sequentially changing the oscillation output of the low-frequency oscillator and the maximum reproduction output level is exhibited when the magnetic tape is reproduced. Setting means and an output of the bias current variable circuit and an output of the high frequency oscillator while sequentially changing the frequency characteristics of the recording equalizer variable circuit. Is recorded on a magnetic tape, and the optimum equalizer setting means for setting the recording equalizer variable circuit to the frequency characteristic when the reproduction output exhibits a predetermined reference level when the magnetic tape is reproduced. In the magnetic recording / reproducing apparatus, the oscillation frequency of the low-frequency oscillator is variable, and the oscillation frequency of the low-frequency oscillator is selectively set according to the desired MOL balance between the low frequency range and the high frequency range. Magnetic recording / playback device.