JPH0366002A - Magnetic tape recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve the S/N of a PCM sound signal and an FM sound signal by providing an FM sound signal carrier selecting means for performing one channel recording of the FM sound signal; the recording of only an L channel having a 1st carrier, at the time of three-layer recording. CONSTITUTION:The L-CH signal and the R-CH signal of an FM system sound signal are added by an adder 53 so as to become an L+R signal. The L+R signal, the L-CH signal and the R-CH signal are selected by a switching circuit 54 and inputted in the FM sound signal processing circuit 8. At the time of the three-layer recording, one of the L-CH signal, the R-CH signal and the L+R signal is inputted in the L side of the processing circuit 8. In the case that the L+R signal is inputted, it is converted to an FMA-L/R signal by the processing circuit 8. And the FMA-L/R signal is selected by the switching circuit 58 and recorded through the FM sound signal recording and amplifying circuit 10. Only the FMA-L/R signal is recorded in this way, so that there is much margin in a recording capacity. Thus, a recording level can be increased, so that the S/N deterioration of the FM sound signal caused by the recording of a PCM sound signal can be prevented.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic tape recording and reproducing device configured to record and reproduce video signals, FM audio signals, and PCM audio signals, and particularly relates to a magnetic tape recording and reproducing device configured to record and reproduce video signals, FM audio signals, and PCM audio signals. It concerns the recording of signals.

[Prior Art] FIG. 5 is a block diagram showing the configuration of a conventional magnetic tape recording and reproducing apparatus of the type that simultaneously records and reproduces a video signal, FM audio signal, and PCM audio signal, and FIG. 6 shows a video signal to be recorded and reproduced. FIG. 10 is a diagram showing spectra of a signal, an FM audio signal, and a PCM audio signal, and these diagrams are, for example, FIG. 1O and FIG. This corresponds to Figure 11.

Note that the video signal and FM audio signal are recorded using a 5-VH3 type magnetic tape recording and reproducing device (hereinafter referred to as 5-VH3 type VT).
R) is recorded and reproduced using the same method as PCM
For example, the signal speed is approximately 2.8 Mbps, as disclosed in the 1986 ICASSP Proceedings "Study on Digitization of Audio Signals in Video Tape Recorders"
PCM signal of offset type 4-phase differential phase modulation (hereinafter referred to as
0-QDPSK) and is recorded and reproduced.

5 and 6, (1) is a video signal recording processing circuit, (2) is a video signal recording amplification circuit, (3) is a rotating drum, and (4) is a video signal magnetic head (hereinafter referred to as video head). , (5) is a magnetic tape, (6) is a video signal reproduction amplification circuit, and (7) is a video signal reproduction processing circuit, which together constitute a video signal recording and reproduction system.

(8) is an FM audio signal recording processing circuit, (8) is an addition circuit, (10) is an FM audio signal recording amplification circuit, (11) is a magnetic head for FM audio signals (hereinafter referred to as FMA head), (12) ) is an FM audio signal reproduction amplification circuit, (13
a) is the L-channel of the FM audio signal (hereinafter referred to as "L-channel").

(13b) is a band pass filter that separates the R-channel (hereinafter referred to as R-CH) component of the FM audio signal; (Hereinafter referred to as BPF-R)
, (14) is an FM audio signal reproduction processing circuit, which constitutes an FM audio signal recording and reproduction system.

(15) is an analog-to-digital conversion circuit (hereinafter referred to as ADC).
), (1B) is a digital audio recording processing circuit, (17) is an offset type 4-phase differential phase modulation circuit (hereinafter referred to as 4-phase phase modulation circuit), (18) is a PCM
Audio signal recording amplification circuit, (18) is a PCM audio signal magnetic head (hereinafter referred to as PCM head), (20)
(21) is an offset type 4-phase differential phase modulation signal demodulation circuit (hereinafter referred to as 4-phase phase demodulation circuit), (22) is a digital audio/reproduction processing circuit, and (23) is a digital audio/reproduction processing circuit. , digital-to-analog conversion circuit (
One or more DACs (hereinafter referred to as DACs) constitute a recording and reproducing system for PCM audio signals.

In FIG. 6(a), (30) is the spectrum of the FM-modulated luminance signal (hereinafter referred to as Y-FM signal), (3
1) is a spectrum of a low-pass converted color signal (hereinafter referred to as a C(L) signal). In addition, in FIG. 6(b), (32) is the spectrum of the FM-modulated L-CH side audio signal (hereinafter referred to as FMA-L signal), and (33) is the FM-modulated R-CH side spectrum. audio signal (hereinafter referred to as FMA-
R signal).

Furthermore, in FIG. 6(C), (30 is a four-phase phase modulated PCM audio signal (hereinafter referred to as a QDPSK signal)
This is the spectrum of

FIG. 7 shows a cross-sectional view of a magnetic tape (5) that performs two-layer recording, in which (35) is the base film of the magnetic tape (5), (36) is the magnetic layer of the magnetic tape (5), (37) and (38) are recording layers for FM audio signals and video signals recorded on the magnetic layer (3B).

Next, the operation of the above configuration will be explained.

The baseband video signal is processed by the video signal recording processing circuit (1)
Here, the luminance signal acid component of the baseband video signal is FM-modulated into a Y-FM signal so that the synchronization tip level is 5.4 MHz and the white peak level is 7.0 MHz. , the color signal component has a carrier frequency of approximately 62
After being low frequency converted to 9 KHz and converted into a C(L) signal, the above Y-FM signal and C(L) signal are added to produce an RF video signal with the spectrum shown in Figure 6(a). as video signal recording amplification circuit (2), rotating drum (3)
) Recorded on a magnetic tape (5) via a built-in rotary transformer (not shown) and a video head (4).

Further, the RF video signal reproduced by the video head (4) is amplified by a video signal reproduction amplification circuit (8), and restored to a baseband video signal by a video signal reproduction processing circuit (7).

On the other hand, the FM audio signal is processed by the FM audio signal recording processing circuit (8
), and after being subjected to noise reduction processing, the L-CH
is frequency modulated by a carrier wave of 1.3 MHz and R-CH is frequency modulated by a carrier wave of 1.7 MHz, as shown in (32) in Fig. 6(b).
, (33) are converted into FMA-L and FMA-R signals having spectra shown in (33), and then sent to an adder circuit (9
) and recorded as an FMA signal on the magnetic tape (5) via the FM audio recording amplifier circuit (lO), the rotary transformer (not shown) built in the rotating drum (3), and the FMA head (11). be done.

Also, the FM reproduced by the FMA head (11)
After the A signal is amplified by the FM audio signal reproducing amplifier circuit (12),
FMA-L signal and FM by P F -R (13b)
The A-R signal is separated into FM audio signal reproduction processing circuit (1
4) After frequency demodulation and noise reduction processing are performed,
Restored to audio signal.

As shown in FIG. 7, an FMA signal is recorded on the magnetic layer (3B) of the magnetic tape (5) to form an FM audio signal recording layer (37), and then an RF video signal is recorded on the magnetic layer (3B).
), and a video signal recording layer (38) is formed on the surface side of the FM audio signal recording layer (37).

The method in which the RF video signal is recorded on the surface layer and the FM audio signal is recorded on the deeper layer is called the dual-layer recording method. In this dual-layer recording method, two types of signals are recorded on essentially the same recording track. Therefore, the video head 0) reproduces the FMA signal, and the FMA head (11) reproduces the RF video signal as a noise component.

Therefore, the azimuth angle of the FMA head (11) is set to ±30' while the azimuth angle of the video head (0) is ±66. The combination of the above azimuth angles is as shown in FIG. 8, tape speed standard mode (sp mode) and 1/
The operations of 0 or more that differ in the three modes (EP mode) are the same as in the 5-VH3 system VTR.

On the other hand, the PCM audio signal is converted into a digital signal by the ADC (15), and then added with an error correction code etc. by the digital audio recording processing circuit (IB), pulse code modulated, and converted into a PCM signal at approximately 2.8 Mbps. It is converted into a signal and subjected to offset type four-phase differential phase modulation by the four-phase phase modulation circuit (17), and ±
It is converted to a QDPSK signal with a bandwidth of 0.85 MHz, and is connected to a PCM audio recording amplifier circuit (18) and a rotating drum (
3) Built-in rotary transformer (not shown), PC
It is recorded on the magnetic tape (5) via the M head (18).

In addition, the QDPS reproduced by the above PCM head (18)
The K signal is amplified by the PCM audio signal regeneration amplifier circuit (20), and then converted to PCM by the 4-phase phase demodulation circuit (21).
The digital audio signal reproduction processing circuit (2
2) performs processing such as error correction and restores it to a digital signal, and the DAC (23) restores it to an audio signal. Note that the carrier frequency of the QDPSK signal is the R
2.0 to 2.5 MH considering interference with F video signal
The area around z is 2.8 if we take into account the interference with the FMA signal mentioned above.
MHz or higher is desirable.

On the other hand, if the QDPSK signal is recorded in a deeper layer than the RF multiplied signal, it will be partially erased compared to the RF multiplied signal, but the carrier frequency of the QDPSK signal will be The carrier frequency of the QDPSK signal is set to 2.5 MHz due to the frequency being 0 or more, the lower the frequency, the better. The spectrum of the QDPSK signal in this case is shown in FIG. 6(c).

As shown in Figure 6, the carrier frequency is FMA signal, QDP
Since the SKi number and the RF video signal are in that order, the recording order is also as shown in FIG.

The order is FMA signal, QDPSK signal, and RF video signal, and the FM audio signal recording layer (3B) is placed from the deep side of the magnetic layer (3B).
7), P CM audio signal recording J'i! ' (39) and a video signal recording layer (38) are formed. This type of recording method is called three-layer recording. In this three-layer recording method, three types of signals are recorded on almost the same recording track, so the video head (4), FMA head (11), and PCM head ( 19) each reproduces two types of signals as noise in addition to the signal to be reproduced.

Since the azimuth angles of ±6° and ±30° have already been set for the video head 0) and the FMA head (11), the azimuth angle of the PCM head (19) is as shown in Figure 10. Azimuth angle with head 0) ±12°
For the above reason, it is set to ±20'.

As described above, it has become possible to add the PCM audio recording and playback function to the 5-VH5 system VTR system.
C(L) of MA signal, QDPSK signal and RF video signal
) signals have relatively low frequencies, so the separation of the signals by azimuth loss is not sufficient, and as shown in FIG. 11, they interfere with each other as noise.

FIGS. 11(a), (b), and (c) show examples of signal spectra reproduced by the video heads (0PCM head (19) and FMA head (11), respectively. For example, the C(L) signal (31 ) is the PCM head (18
), (40), (41) for FMA head (11)
) will result in a noise as shown in Similarly, the FMA-L signal (
32), FMA-R signal (33) is the video head (4)
, 02), 00 and 0 for PCM head (19)
3), (45), and QDPSK
The signal (30 corresponds to the video head (4) and the FMA head (1) produces noise as shown in (4B) and (47)).

Of these, the FMA-R signal (33
) and the QDPSK signal (30 interferences).

If the signal level of FMA-R signal (33) is high, QDP
The S/N deterioration of the SK signal (30) is large and the PCM block error rate (B, E, R) becomes worse, and conversely, the QDPS
Increasing the signal level of the K signal (30) not only increases the noise level of the FMA-R signal (33) but also increases the
K signal (FMA by increasing the recording level of 30)
A decrease in the signal level due to an increase in the erasure rate of the -R signal (33) and the FMA-L signal (32) also poses a problem. 12th
Figure (a) shows this situation, and the spectrum marked O in the figure is the spectrum of the FM audio signal when the QDPSK signal (30) is not recorded. This shows that more of the FMA-R signal (33) is erased. Therefore, in order to ensure the S/N of the FM audio signal, the recording of the FM audio signal must be strengthened.

However, the FM audio signal is the FMA-L signal (32) and the FM
The above F
1.3 MH2 power component MA- of MA-L signal (32)
R signal (33) - 0.5 in addition to 1.7 MHzdc
MHz, 0.9 MHz, 2.1 MHz,
High frequency components such as 2.5 MHz, that is, distortion.
Moreover, even if the recording level is increased, the fundamental wave components of 1.3 M) lz and 1.7 M) lz only increase slightly, and conversely, the fundamental wave components of 1.3 M) lz and 1.7 M) lz
．． 5 MHz, OJ MHz, 2.1 MHz,
Distortion components at frequencies such as 2.5 MHz increase significantly. 12th
Figure (b) shows this situation, in which the O mark is a spectrum for a normal recording level, and the x mark is a spectrum when the recording level is increased. Above 0.
The distortion components at 5 MHz and 0.9 MHz are the C(L) signal (
Since the frequency is within the signal band of 31), it interferes with the color signal.

As mentioned above, in conventional three-layer recording type magnetic tape recording and reproducing devices, there is mutual interference between FM audio signals, PCM audio signals, and low-frequency conversion color signals, and the signal track width is generally narrow, especially in EP mode. A record with no guard band.

This poses a particular problem because signals from adjacent tracks are also reproduced as noise.

[Problems to be Solved by the Invention] Since the conventional three-layer recording type magnetic tape recording and reproducing device is configured as described above, it is possible to erase the FM audio signal by recording the PCM audio signal and to erase the PCM audio signal and the FM audio. There have been problems such as deterioration of S/H due to mutual interference of signals and interference with RF video signals.

This invention was made in order to solve the above-mentioned problems, and it is possible to perform S// of PCM audio signals and FM audio signals without changing the configuration of the conventional three-layer recording type magnetic tape recording/reproducing device. It is an object of the present invention to provide a magnetic tape recording and reproducing device with high image quality and high sound quality, which can improve N and is compatible with a conventional two-layer recording type magnetic tape recording and reproducing device.

[Means for Solving the Problems] The magnetic tape recording and reproducing apparatus according to the present invention has two-layer recording mode and three-layer recording mode, and in the two-layer recording mode, the FM audio signal is transmitted to the L channel having the first carrier wave. , a two-channel recording of the R channel with a second carrier wave, and PCM
In the three-layer recording mode in which audio signals are recorded, the present invention is characterized by comprising carrier wave selection means for the FM audio signal, which records the FM audio signal in one channel of only the L channel having the first carrier wave.

[Function] According to the present invention, since the FM audio signal carrier wave selection means records only the L channel having the first carrier wave at the time of three-layer recording, a certain bandwidth centering on the carrier wave frequency of the PCM audio signal is recorded. PCM audio signal and FM with
Mutual interference with audio signals can be reduced, and S/N can be improved by increasing the FM audio recording level, making it possible to achieve higher sound quality.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the configuration of an FM audio signal recording system of a magnetic tape recording and reproducing apparatus according to an embodiment of the invention, FIG. 2 is a block diagram showing the configuration of an FM audio signal reproducing system, and FIG. 3 is a block diagram showing the configuration of an FM audio signal reproducing system. FIG. 3 is a diagram showing spectra of a video signal, a QDPSK signal (PCM audio signal), and an FMA signal.

In FIG. 1, (8) is an FM audio signal recording processing circuit;
(9), (53) are adder circuits, (50, (58)
1 is a switching circuit, (55) is a control circuit, and (10) is an FM audio signal recording amplification circuit.

The FM audio signal recording processing circuit (8) is an L-CH8 and R-CH noise reduction circuit (hereinafter referred to as a noise reduction circuit).

N, C) (511a), (58b) and voltage controlled oscillation circuit (hereinafter referred to as VCO) (57a),
(5?b).

In FIG. 2, (12) is a gain controllable FM audio signal reproduction processing circuit, (13a) is a BPF-L, (13b is
) is BPF-R1 (13c) is BPF-L/C1 (14
) is an FM audio signal reproduction processing circuit, (53) is a comparison circuit,
(60) is a switching circuit.

The FM audio signal reproduction processing circuit (14) is an L-CH and R-CH noise reduction circuit (hereinafter referred to as N and C).
(58al), (58bl) and voltage controlled oscillator circuit (hereinafter referred to as VCO) (5?al), (5?bl) and phase comparison circuit (hereinafter referred to as P and D) (81a) (e
tb).

In Figure 3, (30) is the Y-FM signal, (31) is the C(L) signal, (30 is the QDPSK@ signal, and (50) is the F
This is an FM-modulated audio signal having a different carrier wave from the MA-Lm signal (32) and the FMA-R signal (33).

Also, in Figure 4, (4G) and (41) are C(L)
Noise components due to signal (31), (4B) and (47) are Q
DPSK signal (noise component due to 30, (5D, (52
) is a noise component due to the FMA-L/R signal (50).

Next, the operation of the magnetic tape recording/reproducing apparatus having the above configuration will be explained.

In Figure 1, the L-CH of the input FM audio signal
A (L+R) signal is obtained by adding the double signal R-CH in the double signal addition circuit (53).

This (L+R) signal, the L-CH multiplied signal, and the R-CH multiplied signal are inputted to the R and LR terminals of a switching circuit (54), respectively, and are selected by a control signal inputted from a control circuit (55).

In the two-layer recording mode, the L side and R bias inputs of the FM audio signal recording processing circuit (8) are L-CH9,
There is an R-CH double signal, and in three-layer recording mode, there is an L
The eccentric input becomes either the L-CH multiplied signal or the R-CH multiplied signal (L+R) signal. Below, to simplify the explanation, FM
The case where the (L+R)@ sign is input to the audio signal recording processing circuit (8) will be explained.

The (L + R) signal is adjusted to an appropriate level and input to the L side of the recording processing circuit (8), subjected to noise reduction processing at N and C (56a), and then sent to V CO (57a).
For example, the signal is converted into an FM signal having a carrier wave of 1.5 MHz, that is, an FMA-L/R signal. The switching circuit (58) is set to No. by the control signal from the control circuit (55).
and therefore the above FMA-L/R
The signal is recorded via an FM audio signal recording amplification circuit (10). Therefore, the video signal recording layer (3B
), the spectrum of each signal recorded on the PCM audio signal recording layer (38) and the FM audio signal recording layer (37) is
The result is as shown in Figures (a) to (C).

The signals recorded in three layers as described above are transferred to the video head (
4), PCM head (19) and FMA head (11)
) The signal spectrum reproduced by
C). As is clear from the figure, FM
There is almost no direct interference with the C(L) signal (31) of the A-L/R signal (50), and furthermore, there is also no interference with the QDPSK signal (34) than with the FMA-R@ signal (
This is a significant decrease compared to 33).

Also, the FM audio signal is originally an FM audio signal (32) and an FM audio signal (32).
Although frequency multiplex recording was performed for two types of signals, the A-R signal (33), according to this embodiment, the FMA-L/R signal (
50), there is a margin in the recording capacity.

Therefore, it is possible to increase the recording level with less distortion. This means that the recording level of FMA-L/R@ (50) can be set to a level that can compensate for S/N deterioration due to erasure associated with recording of the QDPSK signal (30).

Note that the FMA-R signal (33) is not output in the three-layer recording mode due to the operation of the switching circuit (58);
The operation of the VCO (57b) may be stopped under the control of the control circuit (55).

Next, the reproduction operation of the FM audio signal will be described.

The signal with the spectrum shown in Fig. 4(C) is from the FMA head (
11), is amplified to approximately a predetermined level by the FM audio signal reproducing amplification circuit (12), and is then output to the BPF-L (13a).
), BPF-R (13b) and BPF-L
/R (13c) separates each signal component. In three-layer recording mode, B P F -L (13a)
The output level of BPF-L/R (13c) is higher than the output level of BPF-L/R (13c), and conversely becomes lower in the dual-layer recording mode. Therefore, B P F −L (13a) and BPF
-L/R (13c) output level comparison circuit (59
), and if the output of BPF-L (13a) is large, set the switching circuit (60) to the NC side and switch BPF-L/R.
(13c) (1) If the output is large, the switching circuit (60)
If connected to the No side, the FM audio signal reproduction processing circuit (1
4), the FMA-L signal (32
).

FMA-R signal (33) or FMA-L/R signal (
50) is input.

The above FM audio signal reproduction processing circuit (10 frequency demodulation is
For example, demodulation is performed with V CO (5?a) and P , D (81a) and V CO (57b) and P , D (Blb), respectively, but the frequency range that can be demodulated is generally wide.

Any of the FMA-L signal (32), FMA-R signal (33), or FMA-L/R signal (50) can be demodulated.

Then, the demodulated audio signal is N, C(5fia)
After being subjected to noise reduction processing by N and C (58b), the signals are output as L-CH and R-OH audio signals.

On the other hand, a magnetic tape with three-layer recording is converted into a two-layer recording method V.
When playing with TR, FM audio signal reproduction amplifier (12)
Since the output level of B P F -L (13
The output levels of a) and B P F -R (13b) become sufficiently low. Therefore, the dual-layer recording system VTR has F
In order to determine that the tape has no M audio signal recorded on it, the operation of the FM audio signal reproduction processing circuit (10) is stopped and no abnormal noise is output. It is compatible with layer recording type VTRs to the extent that no major problems occur, and high-quality audio can be achieved.

Note that the above embodiment is based on a 5-VH5 system VTR, and the carrier wave of the FM audio signal during three-layer recording is 1.5 MHz.
Although the carrier wave of the PCM audio signal (QD PSK signal) was set to 2.5 MHz, other frequencies may be used as long as the purpose and effect are the same.

It may be applied to any one of the mode, 5-VH3H2O3P mode, and EP%-mode.

Further, in the above embodiment, the present invention is applied to a 5-VH3H2O3TR, but the same effect can be obtained even if the present invention is applied to other VTRs.

[Effects of the Invention] As described above, according to the present invention, in the three-layer recording mode, the carrier wave of the FM audio signal is converted into a PCM audio signal (QDP
Since only one type is used that does not directly interfere with the FM audio signal (SK signal), it is possible to increase the recording level of the FM audio signal without causing mutual interference. Therefore, it is possible to compensate for the S/N deterioration of the FM audio signal due to partial erasure of the FM audio signal due to the recording of the PCM audio signal, and it is possible to obtain a magnetic tape recording and reproducing device with high sound quality.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an FM audio signal recording system of a magnetic tape recording/reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of an FM audio signal reproducing system, and FIG. RF video signal, QDP according to an embodiment of the invention
A diagram showing the spectra of the SK signal (PCM audio signal) and FMA signal, and Figure 4 explains the effect of reducing mutual interference of the low-pass conversion color signal (C (L) signal), QD PS K signal, and FMA signal. FIG. 5 is a block diagram showing the configuration of a conventional magnetic tape recording and reproducing apparatus for recording video signals, FM audio signals and PCM audio signals, and FIG. 6 is a block diagram showing the configuration of a conventional magnetic tape recording and reproducing apparatus for recording video signals, Figure 7 shows the spectra of FM audio signals and PCM audio signals; Figure 7 is a cross-sectional view of a magnetic tape to explain dual-layer recording; Figure 8
The figure shows an example of the azimuth angle of the magnetic head for video and FM audio in two-layer recording, Figure 9 is a cross-sectional view of a magnetic tape to explain three-layer recording, and Figure 10 shows the image in three-layer recording. , a diagram showing an example of the azimuth angle of a magnetic head for FM audio and PCM audio, FIG.
FIG. 12, which is a diagram for explaining mutual interference between an M audio signal and an FM audio signal, is a diagram showing an example of distortion during recording of a conventional FM audio signal and erasure characteristics due to recording of a PCM signal. (8)...FM audio signal recording processing circuit, (8)...
Addition circuit, (12) - FM audio signal reproduction amplification circuit, (1
3a)...BPF-L, (13b)...BPF
-R, (13c)...BPF-L/R, (14)
...FM audio signal reproduction processing circuit, (53)...addition circuit, (54), (5B), (80)--switching circuit,
(55)...control circuit, (59)...signal amplitude detection circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] (1) An audio phase modulation signal obtained by converting an audio signal into digital data corresponding to a video field and phase modulating this digital data, an audio frequency modulation signal and a luminance signal obtained by frequency modulating the above audio signal or another audio signal. A magnetic tape recording and reproducing device configured to record and reproduce a video signal synthesized by frequency modulating and low frequency conversion of a color signal on a magnetic tape, the audio frequency being recorded in a deep layer of a magnetic layer of the magnetic tape. The modulated signal has a two-layer recording mode in which the video signal is recorded on a surface layer, and a three-layer recording mode in which the audio phase modulation signal is recorded in an intermediate layer between the deep layer and the surface layer, and in the two-layer recording mode, A second carrier wave in which the audio frequency modulated signal shares a signal band with a first carrier wave that does not share a signal band with the audio phase modulated signal.
two channels of audio are recorded using a carrier wave of
and audio 1 with a third carrier wave different from the second carrier wave.
control means for channel recording; and means for making the third carrier wave recording level in the three-layer recording mode higher than in the two-layer recording mode; A magnetic tape recording and reproducing device characterized in that it is configured to reduce mutual interference between phase modulated signals and to compensate for deterioration in signal-to-noise ratio due to partial erasure of the audio frequency modulated signal accompanying recording of the audio phase modulated signal. .