JP2683119B2 - Multiplex signal recording method and recording / reproducing apparatus thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a signal multiplex recording method suitable for use in, for example, a video tape recorder and a recording / reproducing apparatus for the same, and particularly while maintaining compatibility with existing systems. The present invention relates to a method of multiplex recording a PCM audio signal of higher quality and a recording / reproducing apparatus thereof.

[Conventional technology]

A conventional video tape recorder for performing such kind of multiplex recording is
For example, as described in Japanese Patent Laid-Open No. 63-171403, a video signal, a PCM (Pulse Coded Modulation) audio signal, and a frequency modulated (FM: Frequency Modulation) audio signal have different azimuth angles. A dedicated magnetic head is used to record three layers on the same track.

[Problems to be solved by the invention]

However, in the above-mentioned conventional technique, no consideration is given to the recording level of each of the video signal, the PCM audio signal and the FM audio signal, and the magnetic gap length of the magnetic head for PCM audio, and the reproduction output level of the PCM audio signal is not considered. There was a problem in terms of securing and obstructing the video signal.

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art,
An object of the present invention is to provide a signal multiplex recording method and a recording / reproducing apparatus for the same, which secures a reproduction level of an audio signal and eliminates interference with a video signal.

[Means for solving the problem]

In order to achieve the above object, the present invention sets the recording current of the video signal slightly lower than the optimum recording current value at which the maximum reproduction output level is obtained. Furthermore, the magnetic gear length of the magnetic head for PCM audio is shortened to about the same as the magnetic gear length of the magnetic head for video, and the recording current of the PCM audio signal is set slightly lower than the optimum recording current value. The signal recording current is set to be considerably lower than the optimum recording current value.

[Action]

The PCM audio signal is erased by the video signal that is over-recorded later, and its reproduction output level is attenuated, but this amount of erasure, in other words, the reproduction output level of the PCM audio signal greatly changes depending on the recording current of the video signal. . Therefore, lowering the recording current of the video signal increases the reproduction output level of the PCM audio signal. Since the recording current is only slightly decreased, the reproduction output level of the video signal itself is hardly decreased, and the reproduction output level of the PCM audio signal can be secured.

Similarly, the FM audio signal is also erased by the PCM audio signal recorded later. Therefore, the recording current of the PCM audio signal is also lowered slightly within a range in which the reproduction output level of itself can be secured. Also, by reducing the magnetic gear length of the magnetic head for PCM audio, the amount of FM audio signal erased can be reduced. With these, the reproduction output level of the FM audio signal can be secured.

Also, shortening the magnetic gear length of the magnetic head for PCM audio can reduce the distortion generated in the recording / reproducing process, and as a result, the low-side side lobe of the PCM audio reproduction signal that has been phase-modulated by four phases. The components can be reduced. This reduced side lobe component is not only necessary for demodulation of the PCM audio signal, but is also a low-frequency component with no azimuth effect, so it is reproduced even in the video head and interferes with the color signal. Therefore, shortening the magnetic gear length of the magnetic head for PCM audio reduces interference with the video signal.

Finally, by reducing the recording current of the FM audio signal within the range where the reproduction output level of the FM audio signal is secured, the interference from the FM audio signal to the video signal can be reduced.

〔Example〕

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

FIG. 1 is a schematic explanatory view showing the principle of the present invention, which schematically shows the magnetization pattern in the magnetic layer depth direction of the magnetic recording medium. In FIG. 1, 1 is an FM audio head, 2 is a PCM audio head, 3 is a video head, and 8 is a video head.
Indicates a magnetic tape comprising a magnetic layer 8a and a base film 8b.

FIG. 2 is a diagram showing an example of frequency allocation of recording signals in the present invention. In FIG. 2, (a) shows the frequency arrangement of the video signal recorded by the video head 3, and the luminance signal FM-modulated (frequency deviation is 5.4 MHz to 7 MHz) and low frequency conversion (conversion). Subsequent color subcarrier frequency fsc is about 629K H
z) The color signals are frequency-multiplexed.
(B) shows the frequency allocation of the PCM audio signal recorded by the PCM audio head 2, which is a 4-MHz differential PSK (O-QDPSK; Offset Quadrature Differential Ph
ase Shift Keying) Modulated. (C) is FM
The frequency arrangement of the FM audio signal recorded by the audio head 1 is shown, and the audio signals of the two channels (left / right or main / sub) are independently FM-modulated by a carrier of 1.3MHz and 1.7MHz and frequency-multiplexed. It was done.

 Hereinafter, the operation will be described.

In FIG. 1, first, the FM audio signal shown in FIG. 2C is recorded on the magnetic tape 8 by the FM audio head 1. Next, the PCM audio signal shown in FIG. 2 (b) is recorded over the same track by the PCM audio head 2. Finally, the video signal shown in FIG. 2A is recorded on the same track by the video head 3 in the same manner. At this time, the FM voice signal has the lowest recording frequency, in other words, the longest recording wavelength, and the magnetic gear length G ₁ of the FM voice head 1 is also the longest correspondingly (about 1 μm-
1.2 μm), the magnetic layer 8 of the magnetic tape 8
It is recorded up to the deep part of a. The recording frequency of PCM audio signals is higher than that of FM audio signals, in other words, the recording wavelength is short, and the magnetic gear length G ₂ of the PCM audio head 2 is set shorter than G ₁ to match it, so the recording depth is high. It reaches only the middle layer of the magnetic layer 8a. Therefore, the FM recorded earlier
The voice signal is overwritten and erased by the PCM voice signal recorded later, but a part of it remains in the deep portion of the magnetic layer 8a. C in FIG. 1 is a simulation of the residual magnetization pattern of the FM voice signal.

The video signal has the highest recording frequency, in other words, the shortest recording wavelength, and the magnetic head length G _{3 of the} video head 3 is also the shortest correspondingly (about 0.3 μm to 0.4 μm).
Since it is set, only the shallow layer portion of the magnetic layer 8a is recorded. Therefore, the PCM audio signal is also erased by the video signal which is overlaid and recorded later, but a part thereof remains in the intermediate layer portion of the magnetic layer. In FIG. 1, A is a simulated pattern of a video signal, and B is a simulated pattern of a PCM audio signal remaining in the intermediate layer.

In this way, the video signal, the PCM audio signal and the FM audio signal are multiplexed and recorded layer by layer in the magnetic layer depth direction of the magnetic tape 8.

Next, for reproduction, the azimuth angles of the FM audio head 1, the PCM audio head 2 and the video head 3 are different from each other (for example, FM audio head 1 is 30 degrees, PCM audio head 2 is 20 degrees). , The video head 3 is set to 6 degrees and recorded, and each is reproduced at the same head as the recording. At this time, the signals having different azimuth angles are attenuated by the azimuth loss, so that the respective signals can be separated and reproduced.

As is well known, this azimuth loss increases in proportion to the frequency. Conversely, in the low frequency region, the azimuth loss is small and separation and reproduction cannot be performed. This is the reason why the PCM audio signal is further O-QDPSK modulated with a carrier of 2.5 MHz and attenuation is recorded.

The present invention defines the recording currents to flow to the heads of video, PCM audio, and FM audio in the multiplex recording system. The present invention further defines the magnetic gear length G ₂ of the PCM audio head 2.

 Hereinafter, this will be described in detail.

FIG. 3 is a diagram showing reproduction output characteristics of a video signal and a PCM audio signal with respect to a recording current supplied to the video head 3. The video recording current on the horizontal axis is the optimum recording current (ORC; Optimum Recording Curren) at which the maximum playback output level is obtained.
t) is normalized as 1. Also, a single signal of 5.4 MHz is used as the video signal and 2.5 MHz as the PCM audio signal.
Is a single signal recorded and reproduced. In FIG. 3, (a) shows the reproduction output characteristic of the video signal as a relative value with the maximum reproduction output level in the ORC as a reference (0 dB). (B) shows the reproduction output characteristics of the PCM audio signal as a relative value with the reproduction output level when no video signal is recorded as the reference (0 dB).
It was recorded and played back in.

Thus, as is well known, the video signal reproduction output characteristic of (a) shows a mountainous characteristic around the ORC, and there is almost no change in the reproduction output level near the ORC. For example, the reproduction output level at a recording current of ORC ± 10% is about −0.2 dB to −0.3 dB. On the other hand, in the reproduction output characteristic of the PCM audio signal, as shown in (b), the reproduction output level greatly decreases as the video recording current increases.
For example, when the video recording current is ORC, the playback output level of the PCM audio signal is about -15 dB, and the video recording current is ± 1 dB from the ORC.
When it fluctuates by 0%, the playback output level of the PCM audio signal increases or decreases by about 3 dB.

Normally, the video recording current is set to ORC, but the value naturally varies. Although there is no problem in that the video recording current varies in the decreasing direction, if it conversely increases, the playback output level of the PCM audio signal is greatly reduced, which causes the S / N (signal pair) of the PCM audio signal to decrease. Noise ratio)
May decrease and the code error rate after demodulation may increase.

Therefore, in the present invention, the variation width S of the video recording current
It is characterized in that it is set slightly lower than the ORC in consideration of the minimum required level L min of the PCM audio signal reproduction output. That is, as shown in FIG. 3, the standard of the video recording current is set so that the reproduction output level of the PCM audio signal does not fall below the minimum required level L min even if the video recording current varies in the maximum direction. Setting) Value I vid is set lower than ORC. As a result, the reproduction output level of the PCM audio signal can be ensured, and as a result, the quality of the reproduced and demodulated PCM audio signal can be ensured. It should be noted that the reproduction output level of the video signal is slightly lower than that of the conventional setting method, especially when the video recording current is varied in the decreasing direction, but the quality of the reproduced image is hardly affected.

Next, the magnetic gear length G ₂ of the PCM audio head 2 which is another feature of the present invention will be described.

FIG. 4 is a diagram showing the relationship between the recording frequency and the length of the magnetic gear of each head. Normally, the magnetic gear length G ₁ of the FM audio head 1 is 1.3 MHz to 1.7 MHz as shown in FIG.
It is set to 1.0 μm to 1.2 μm for the recording frequency of M Hz. On the other hand, the magnetic gap length G ₃ of the video head 3 is set to 0.3 μm to 0.4 μm for the recording frequency of 5.4 MHz to 7 MHz, as shown in FIG. From the relationship between the recording frequency of the FM audio head 1 and the video head 3 and the magnetic gear length, G ₂ is arithmetically calculated and the magnetic gear length G ₂ of the PCM audio head 2 with a recording frequency of 2.5 MHz is calculated. Is 0.6 μm to 0.9 μm. However, in the present invention, the magnetic gear length G ₂ of the PCM audio head 2 is shorter than the above calculated value, and is 0.4 μm or less as shown in FIG. It is characterized by shortening to about the same as ₃ .

 Hereinafter, this effect will be described.

FIG. 5 is a diagram showing a recording and reproducing spectrum of a PCM audio signal. In Fig. 5, (a) shows the spectrum at the time of recording, which has a code transmission rate of about 2.6M bps.
PCM voice signal is further O-QDPSK modulated with a carrier of 2.5MHz. The above-mentioned code transmission rate of 2.6 Mbps is a value after adding a synchronizing signal, an error correction code, etc. to a digital audio signal of standardized frequency 48 KHz, quantization bit number 16 bits, stereo 2 channel. Fifth
(B), (c) and (d) of the figure show that the signal of the spectrum shown in (a) above has a magnetic gear length G ₂ of 0.
This is the spectrum when recording and reproducing with PCM audio head 2 of 7 μm, 0.5 μm and 0.35 μm. In addition, (b),
(C) and (d) show the reproduction spectrum when the PCM audio signal is not recorded, that is, the noise spectrum in comparison.

In this way, 1.2 MH should have been sufficiently attenuated during recording.
There is a phenomenon that low-side lobe components below z are restored during playback. It is considered that this is because the signal is distorted due to the non-linearity of the magnetic recording, but as shown in the figure, it is understood that the shorter the magnetic gear length G ₂ is, the less the low frequency side lobe component is. Since this low-frequency side lobe component interferes with the color signal of the image recorded on the surface layer (the frequency fsc of the color sub-carrier whose frequency is low-frequency converted is about 629 KHz), it is better to reduce it as much as possible. This is because the separation effect (azimuth effect) due to the azimuth angle difference between the PCM audio head 2 and the video head 3 cannot be expected in the frequency domain as described above.

As shown in FIG. 5 (b), the magnetic gear length G ₂ of the PCM voice head 2 calculated from the magnetic gear lengths G ₁ and G _{3 of the} conventional FM voice head 1 and video head 3 is as shown in FIG. This low side lobe component is large, and the interference with the color signal is large accordingly. On the other hand, in the present invention, as shown in FIG. 5 (d), the low side lobe component is small, and the interference with the color signal is greatly reduced.

The effect of reducing interference with the video color signals by shortening the magnetic gear length G ₂ of the PCM audio head 2 has been described above. In addition to this effect, the playback output level of the FM audio signal is improved. Is also effective. This will be described below.

Figure 6 shows P for the recording current sent to the PCM audio head 2.
It is a figure which shows the reproduction output characteristic of CM audio signal and FM audio signal. The PCM voice recording current on the horizontal axis is normalized with ORC set to 1 as in FIG. 2.5M Hz for PCM audio signal
Is recorded and reproduced, and the reproduction output level on the vertical axis is based on the maximum reproduction output level in the ORC (0d
B) shows the relative value. Also, as the FM audio signal, a single signal of 1.7MHz was recorded and reproduced,
The reproduction output level on the vertical axis is shown as a relative value with the reproduction output level when no PCM audio signal is recorded as a reference (0 dB). The recording current of the FM voice signal itself is ORC.

In FIG. 6, (a) and (b) are PCM audio and FM audio signal reproduction output characteristics when recording and reproducing are performed using the PCM audio head 2 having a magnetic gear length G ₂ of 0.7 μm. ) And (d), the magnetic gear length G ₂ is 0.35μ
PCM when recording / reproducing using PCM audio head 2
These are the output characteristics of the audio and FM audio signals. The length G ₁ of the magnetic gear of the FM audio head 1 is the same as described above.
As shown in (a) and (c), the reproduction output characteristics of the PCM audio signal show almost the same characteristics regardless of the magnetic gear length G ₂ . The absolute level of playback output is 0.7μm and 0.35μ.
m is almost the same. On the other hand, as shown in (b) and (d), the reproduction output characteristic of the FM audio signal is larger when the magnetic gear length G ₂ of the PCM audio head 2 is shortened to 0.35 μm. Become. This is achieved by shortening the magnetic gear length G ₂ of the PCM audio head 2
The recording depth of the M signal becomes shallower, and only that much
This is because the erasing rate of the M audio signal decreases.

Thus, the magnetic gear length G ₂ of the PCM audio head 2 is
By shortening, there is not only the effect of reducing the interference with the color signal described above, but also the effect of improving the reproduction output level of the FM audio signal.

By the way, the first feature of the present invention is to define the recording current, which defines not only the recording current of the video signal described above but also the recording current of each of the PCM audio signal and the FM audio signal. Is. That is, the recording current of the PCM audio signal is slightly smaller than the ORC (1 dB to 2 dB), and the recording current of the FM audio signal is considerably smaller than the ORC (3 dB to 6 dB). is there.

As shown in FIG. 6, by slightly reducing the recording current of the PCM audio signal, the reproduction output level of the FM audio signal can be improved with almost no decrease in the reproduction output level of the PCM audio signal itself. To improve the reproduction output level of the FM voice signal, from the opposite viewpoint, if the absolute level has a margin, the recording current of the FM voice signal itself can be reduced. Then, reducing the recording current of the FM audio signal has the effect of reducing interference with the video signal.

FIG. 7 is a block diagram showing an embodiment of the recording / reproducing apparatus according to the present invention. First, the operation during recording will be described.

The audio signal for FM recording is input from the FM audio signal input terminal 37, FM modulation processing is performed by the FM audio recording processing circuit 38, the recording current is set by the FM audio signal level adjuster 63, and the FM audio signal recording amplifier 39 FM audio signal recording / playback switcher 40
To the tape 8 with the FM audio heads 1a and 1b.

The audio signal for PCM recording is input from the PCM audio signal input terminal 41, converted into a digital signal by the PCM audio signal recording processing circuit 42, and further subjected to O-QDPSK modulation processing. The output of the processing circuit 42 sets the recording current with the PCM audio signal level adjuster 62, amplifies it with the PCM audio signal recording amplifier 43, inputs it to the PCM audio signal recording / playback switch 44, and outputs it to the PCM audio head 2a, Record on tape 8 with 2b.

The video signal is input from the video signal input terminal 45, the video signal recording processing circuit 46 performs the recording signal conversion process, the video signal level adjuster 61 sets the recording current, and the video signal amplifier
The signal is amplified at 47, input to the video signal recording / reproducing switch 48, and recorded on the tape 8 by the video heads 3a and 3b.

At the time of reproduction, the signal recorded on the tape 8 is recorded on the head 1a, 1
b, 2a, 2b, 3a, 3b are read, and the head output is input to the recording / playback switching devices 40, 44, 48, and the FM audio playback amplifier 49, PCM audio signal playback amplifier 50, and video signal playback amplifier 51 are input. Input and amplify. The outputs of the amplifiers 49, 50 and 51 are subjected to reproduction processing by an FM audio reproduction processing circuit 52, a PCM audio reproduction processing circuit 53 and a video signal processing circuit 54, respectively.
The outputs of 52, 53 and 54 are FM audio signal output terminals 5 respectively.
5, PCM audio signal output terminal 56, and video signal output terminal 57
Output from

Here, the recording current of each of the video signal, the PCM audio signal and the FM audio signal is set to a value smaller than the ORC as described above by the level adjusters 61, 62 and 63, and further, the PCM audio head 2a, 2b magnetic gear length is 0.4μ
It goes without saying that the length is set to m or less, which is as short as the magnetic gear length of the video heads 3a and 3b.

This secures the playback output level of each of the video signal, PCM audio signal, and FM audio signal, and
This has the effect of reducing interference from audio signals and FM audio signals to video signals.

In the embodiment shown in FIG. 7, level adjusters 61, 62 and 63 are used.
Although the recording current of each of the video signal, the PCM audio signal and the FM audio signal is set by the above, the present invention is not limited to this.For example, instead of the level adjusters 61, 62 and 63, the recording amplifier 47, The amplification degree of each of 43 and 39 may be adjusted. Also, recording amplifiers 47, 43 and 3
9 If the automatic gain control function is added to each of them, the level adjusters 61, 62 and 63 become unnecessary. The point is that the standard recording current for each of the video signal, the PCM audio signal and the FM audio signal can be set as described above, and any means therefor is not limited.

〔The invention's effect〕

As described above, according to the present invention, it is possible to multiplex-record a higher quality PCM audio signal on a conventional video tape recorder without interfering with the video signal, which is a great effect on the performance improvement. There is.

[Brief description of the drawings]

Each of the drawings relates to an embodiment of the present invention, FIG. 1 is an explanatory view schematically showing a magnetization pattern in the magnetic layer depth direction, FIG. 2 is an explanatory view showing an example of frequency arrangement of recording signals, and FIG.
FIG. 4 is an explanatory diagram showing reproduction output characteristics of a video signal and a PCM audio signal with respect to a recording current applied to the video head, and FIG. 4 is an explanatory diagram showing a relationship between the frequency of the recording signal and the magnetic gear length of each recording head. FIG. 5 is an explanatory diagram showing the recording and reproducing spectrum of the PCM audio signal, FIG. 6 is an explanatory diagram showing the reproduction output characteristics of the PCM audio signal and the FM audio signal with respect to the recording current sent to the PCM audio head, and FIG. 7 is the recording and reproducing. It is a block diagram which shows an example of an apparatus. 1,1a, 1b …… FM audio head, 2,2a, 2b …… PCM audio head, 3,3a, 3b …… Video head, 8 …… Magnetic tape, 6
1,62,63 …… Level adjuster.

Claims (7)

(57) [Claims] 1. A first information signal having the lowest recording frequency is recorded on a magnetic recording medium by using a first magnetic head, and then a second information signal having an intermediate recording frequency is used as a second magnetic signal. A head is used to perform overwriting on the track on which the first information signal is recorded, and finally, a third information signal having the highest recording frequency is used for the first and second information signals using a third magnetic head. Is recorded on the track, the reference value of the recording current of the first information signal is equal to or less than an optimum recording current value at which a maximum reproduction output level is obtained, and the first information is recorded. The reference value of the recording current of the second information signal is set to a value such that the reproduction output level of the first information signal is equal to or higher than the necessary minimum level even if the recording current of the signal varies maximum in the decreasing direction. Optimal for maximum playback output level It is set to a value that is equal to or lower than the recording current value and that the reproduction output level of the first information signal is equal to or higher than the required minimum level even if the recording current of the second information signal varies in the maximum direction. The reference value of the recording current of the third information signal is less than or equal to the optimum recording current value at which the maximum reproduction output level is obtained, and even if the recording current of the third information signal varies maximum in the increasing direction. 2. A signal multiplex recording method, characterized in that the reproduction output level of the information signal 2 is set to a value higher than a required minimum level. 2. The audio signal, which has been frequency-modulated as the first information signal, is recorded as the first information signal, and the digitized audio signal and / or digital data is further quadrature phase-modulated as the second information signal. And a frequency-modulated video luminance signal and a low-frequency-converted video color signal are frequency-multiplexed and recorded as the third information signal. 3. A first information signal having the lowest recording frequency is recorded on a magnetic recording medium by using a first magnetic head having a relatively long magnetic gap length, and then the first recording signal having the recording frequency located in the middle is recorded. The second information signal is recorded on the track on which the first information signal is recorded by using the second magnetic head,
Finally, a method of overwriting the third information signal having the highest recording frequency on the track on which the first and second information signals are recorded by using a third magnetic head having a relatively short magnetic gap length. And the magnetic gap length of the second magnetic head is set to
A signal multiplex recording method characterized in that the recording frequency of each of the second and third information signals and the magnetic gap length of each of the first and third magnetic heads is made shorter than a value arithmetically calculated. 4. The method according to claim 3, wherein a frequency-modulated voice signal is recorded as the first information signal, and a digitized voice signal and / or digital data is further quadrature phase-modulated as the second information signal. And a frequency-modulated video luminance signal and a low-frequency-converted video color signal are frequency-multiplexed and recorded as the third information signal. 5. The method according to claim 4, wherein the reference value of the recording current of the first information signal is less than or equal to the optimum current value at which the maximum reproduction output level is obtained, and the first
Is set to a value such that the reproduction output level of the first information signal is equal to or higher than the required minimum level even if the recording current of the information signal varies in the maximum direction. The reference value is equal to or less than the optimum current value at which the maximum reproduction output level is obtained, and the reproduction output level of the first information signal is the minimum required even if the recording current of the second information signal varies in the maximum direction. Is set to a value equal to or higher than the level of, and the reference value of the recording current of the third information signal is
The maximum reproduction output level is less than or equal to the optimum current value, and the reproduction output level of the second information signal is not less than the required minimum level even if the recording current of the third information signal varies in the maximum direction. The signal multiplex recording method is characterized in that it is set to such a value. 6. A first information signal having the lowest recording frequency is recorded on a magnetic recording medium by using a first magnetic head, and then a second information signal having a recording frequency in the middle is recorded on the second magnetic signal. A head is used to perform overwriting on the track on which the first information signal is recorded, and finally, a third information signal having the highest recording frequency is used for the first and second information signals using a third magnetic head. Is a signal multiplex recording / reproducing apparatus adapted to perform over-recording on the track on which is recorded, a reference value of a recording current of the first information signal being equal to or less than an optimum current value at which a maximum reproduction output level is obtained, and , The first
Is set to a value such that the reproduction output level of the first information signal is equal to or higher than the required minimum level even if the recording current of the information signal varies in the maximum direction. The reference value is equal to or less than the optimum current value at which the maximum reproduction output level is obtained, and the reproduction output level of the first information signal is the minimum required even if the recording current of the second information signal varies in the maximum direction. Is set to a value equal to or higher than the level of, and the reference value of the recording current of the third information signal is
The maximum reproduction output level is less than or equal to the optimum current value, and the reproduction output level of the second information signal is not less than the required minimum level even if the recording current of the third information signal varies in the maximum direction. A signal multiplex recording / reproducing apparatus characterized by being set to such a value. 7. A first information signal having the lowest recording frequency is recorded on a magnetic recording medium by using a first magnetic head having a relatively long magnetic gap length, and then the first recording medium is positioned at an intermediate recording frequency. The second information signal is recorded on the track on which the first information signal is recorded by using the second magnetic head,
Finally, the third information signal having the highest recording frequency is recorded on the track on which the first and second information signals are recorded by using the third magnetic head having a relatively short magnetic gap length. And a magnetic gap length of the second magnetic head, wherein
A signal multiplex recording / reproducing apparatus characterized in that it is shorter than a value arithmetically calculated from the recording frequency of each of the second and third information signals and the magnetic gap length of each of the first and third magnetic heads. .