JPS63285706A - Pcm recording and reproducing device - Google Patents

Abstract

PURPOSE:To correctly set a recording level even if the width of a rotary head is different from that of a recording track, by running a magnetic tape at a fixed speed in both recording and reproducing times and automatically setting the optimum recording level by reproducing test signals after the test signals are recorded by making the level variable. CONSTITUTION:A recording level is set by means of a switch which is not shown in the figure and the signal of a test signal generating circuit 1 is amplified at a gain control amplifier circuit 2. ATF signals are added to RF signals from the circuit 2 while the output increasing by gain control signals from a controller 8 and the RF signals, to which the ATF signals are added, are supplied to heads A and B through switches 4 and 5. Outputs of the heads A and B are alternately recorded on a magnetic tape. When the switch 4 is switched to the reproduction side thereafter, the RF signals, on which tracking is performed by the AFT signals, are subject to peak level detection at a level detecting circuit 7 through a band-pass filter 9. Then the controller 8 detects the optimum level from the number of reproduced RF signals detected by a counter 10 and the output of the level detecting circuit 7. Therefore, the optimum recording levels can be set automatically to the heads A and B.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a PCM recording and reproducing apparatus that converts information signals such as audio signals into digital signals and records them on a magnetic tape. The present invention relates to a recording/reproducing device.

[Conventional technology]

In a PCM recording/reproducing device in which a magnetic tape is wound around a rotating drum in which two rotating heads A and B are arranged facing each other at a 180 degree interval, an error in setting the signal recording level can cause PCM.
Leading to an increase in data error rate! & Setting the signal recording level is essential. This optimal signal recording level is determined by the magnetic head and magnetic tape, and especially in the current situation where there are many types of magnetic tapes with different magnetic materials and different characteristics, it is necessary to set an A suitable level between the head and tape. There is a need. Therefore, a PCM recording/reproducing apparatus employing a rotating head is equipped with a means for setting an optimum signal recording level, and a typical configuration thereof is shown in FIG.
Reference numeral 1 denotes a test signal generation circuit that generates a test signal, and supplies a test signal of a constant frequency to the gain control amplifier circuit 2. A gain control signal Sc is supplied from the controller 8 to the gain control amplifier circuit 2, and the gain is linearly varied from a low value to a high value within a 180 degree angle range period in which the rotary head A scans the magnetic tape. Ru. The signal S Rec whose recording level has been changed is switched by the switch circuit 4 via the amplifier 3, and is supplied to the rotating head A during the period TA of the switching pulse SWP of the head switching signal shown in FIG. recorded on tape. At this time, the magnetic tape is stopped with its magnetic surface in contact with the rotating head. Then, during the next period TA2 during which the rotary head A scans the magnetic tape, the switch circuit 4 is switched to the opposite relationship to enter the reproduction state, and the reproduction signal SPB of the recording signal S REC is
get. The reproduced signal SPB is supplied to the level detection circuit 7 via the reproduction amplifier 6, and the level is detected. The detection level of the reproduced signal SPB obtained by the level detection circuit B7 is then supplied to the controller 8, and the recording and reproduction of the test signal every rotation is performed, for example, ten times, until the detection level reaches a certain set value. is detected, and the gain control signal Sc is set to correspond to that point. Further, the switch circuit 5 is also controlled by the controller 8 for the rotary head B, and similarly for the magnetic tape!
& The recording level is set. In this way, a maximum of 11 recording levels are set for the rotary heads A and B.

[Problems to be solved by the invention]

Since the conventional PCM recording/reproducing apparatus having a recording level setting means is configured as described above, the recording level is set while the magnetic tape is stopped, so that the width of the rotating head and the recording track width of the magnetic tape are It is difficult to set an accurate recording level when the recording level is different. That is, in a digital audio tape recorder (DAT), overwriting is performed using a rotating head with a head width of 20 μm to form a recording track width of 13.5 μm. In this case, if the conventional configuration described above is adopted, , the recording track width was 20 μm, and the recording level could not be set under accurate recording and reproduction conditions. This invention was made in order to solve the problems of the conventional PCM recording and reproducing device described above.In the PCM recording and reproducing device having a rotating head, by running a magnetic tape to record and reproduce, accurate An object of the present invention is to provide a PCM recording and reproducing device that sets a recording level.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a PC that uses a rotary head to record and reproduce recording signals on a magnetic tape.
The M recording and reproducing apparatus is provided with means for recording a test signal with a variable level and then reproducing it to automatically set an optimal recording level, and configured to run the magnetic tape at a constant speed during the recording and reproducing. It is characterized by this.

【Example】

An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing the configuration of a PCM recording and reproducing apparatus according to the present invention, which takes as an example a digital audio tape recorder (DAT) in which a magnetic tape is wound at 90 degrees around a rotating drum. In the figure, numeral 1 is a test signal generation circuit, 2 is a gain control amplifier circuit, 3 is a recording amplifier, and 4 is a recording circuit. A switch circuit that is switched according to reproduction, 5 a switch circuit that selects rotary heads A and B, 6 a regenerative amplifier, 7
8 is a level detection circuit that detects the peak level; 8 is a controller that supplies a gain control signal Sc to the gain control amplifier circuit 2 and sends a control signal to the switch circuits 4 and 5;
9 is a band pass filter, 10 is the number of RF signals to be reproduced or a switching pulse SW for switching heads.
A counter 11 counts the number of P and an ATF signal generating circuit 11 generates an ATF signal to be recorded together with the test I signal. The recording level setting operation is performed by operating a switch (not shown), and when this switch operation is performed, the test signal generation port F! ! The test signal from 11 is made into a constant frequency and input to the gain control amplifier circuit 2. A gain control signal Sc is supplied from the controller 8 to the gain control amplifier circuit 2, and the RF recording signal obtained by adding the ATF signal to the test signal is sent to the recording amplifier 3. Since the magnetic tape recorded by the nine rotary heads A and B supplied to the rotary heads A and B via the switch circuits 4 and 5 is running in one direction at a constant speed (normal recording speed), the magnetic tape A track pattern of 13.5 μm in accordance with the DAT format is formed thereon by rotary heads A and B with a head width of 20 μm. The switching pulses TA, TB indicate the periods recorded on the rotary heads A and B, respectively, and the switching pulses TA2, TB2 and TA3, TB3
The same applies to... During the periods of the switching pulses TA, TB, recording signals of the same level are generated, and the recording level gradually increases (see FIG. 2). The magnetic tape on which test signals of different levels have been recorded in this manner is then set for reverse playback. This reverse playback is performed by rotating the rotating drum in the same direction as during recording while reversing the running direction of the magnetic tape and switching the switch circuit 4 to the playback side. As shown in FIG. 3, the reproduced RF signal tracked by the ATF signal passes through a regenerative amplifier 6° band-pass filter 9 to detect only the necessary frequencies, and the level detection circuit 7 detects the peak level. This detection information is output to the controller 8. At the same time, the counter 10 counts the number of reproduced RF multiplied signals or the number of switching pulses SWP, and outputs the count information to the controller 8. The controller 8 can detect the I&PL replay level position based on the information from the level detection circuit 7 and the counter 10, and sets the recording level accordingly. As a result, a recording level of iIk weeks is automatically set for the rotary heads A and B. Note that in the above embodiment, after recording the test signal, the optimum recording level can be detected in a short time by performing reverse playback and detecting the playback level. It may also be possible to play it back. Further, in the above embodiment, the test signal was explained as having one frequency, but for example, in the case of DAT, it is 130KHz and 1.5KHz.
Since it is necessary to set the recording level for each frequency of 7HIIZ, if you use a test signal generation circuit that superimposes two signals of 130KIIZ and 1.57MHz, and prepare two systems of bandpass filters and level detection circuits during playback,
Automatic setting of each recording level can be made possible at the same time.

【Effect of the invention】

As is clear from the above description, the PCM recording and reproducing apparatus of the present invention includes a means for recording a test signal by varying the level and then reproducing it to automatically set an optimum recording level, and for the recording and reproducing apparatus. Since the magnetic tape is configured to run at a constant speed at the same time, it is possible to accurately set the level even with a recording/reproducing device that has a different rotating head head capacity and magnetic tape recording track width. Effects such as reducing the influence of scratches, dropouts, etc. on the magnetic tape, automatically correcting variations in magnetic tape sensitivity, and obtaining a predetermined reproduction level can be obtained. Furthermore, when playing back after recording, reverse playback is performed to automatically return to the recording start position, making it possible to set the level in a short time.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a PCM recording and reproducing apparatus according to the present invention, and FIGS. 2 and 3 are diagrams showing <RF multiplied signals based on recording and reproduction by the PCM recording and reproducing apparatus according to the present invention, respectively.
FIG. 4 is a diagram showing the configuration of a conventional PCM recording and reproducing device, and FIG. 5 is a diagram showing an RF multiplied signal based on recording and reproduction by the conventional PCM recording and reproducing device. 1... Test signal generation circuit , 2... Gain control amplifier circuit, 3... Recording amplifier, 4, 5... Switch circuit,
6... Regenerative amplifier, 7... Level detection circuit, 8...
・Controller, 9...Band pass filter, 10・
...Counter, 11...ATF signal generation circuit Fig. 3 Fig. 4 Fig. 5

Claims (1)

[Claims] A recording signal is recorded on a magnetic tape using a rotating head,
A PCM recording and reproducing device for reproducing is provided with a means for recording a test signal with a variable level and then reproducing it to automatically set an optimum recording level, so that the magnetic tape is run at a constant speed during the recording and reproducing. A PCM recording and reproducing device characterized by the following configurations.