JPS6031319B2 - Multi-channel record playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-channel record playback device, which is used to demodulate an angle-modulated wave signal reproduced from a multi-channel record in which a direct wave signal and an angle-modulated wave signal are multiplexed and recorded. is connected to a phase locked loop (hereinafter referred to as PLL) having a predetermined lock range, and outputs an output according to the phase difference between the output of a voltage controlled oscillator (hereinafter referred to as VOO) that constitutes this PLL and the input signal of the PLL. Provided is a distortion detection device that can easily and accurately distinguish distortion that may occur in a demodulated signal from a musical tone based on the degree of distortion by detecting a predetermined frequency domain component of the generated output of a synchronous detector. The purpose is to

When demodulating an angle-modulated wave signal played from a multi-channel record in which a direct wave signal and an angle-modulated wave signal are multiplexed and recorded, distortion that adversely affects musical tones may occur in the demodulated signal. .

Possible causes of this distortion include wear and tear on the chopper cord, needle skipping, jumping from the direct wave signal band to the angle modulated wave signal band, and carrier drop caused by these factors. From an auditory perspective, the distortion that occurs in the demodulated signal due to these factors can be classified into the following two types.

{1- Relatively mild distortion such as cracking, hoarseness, and chittering. {2) Distortion that causes abnormal sounds and significantly deteriorates musicality.

The above distortion (■) can be considered to be an evolution of the distortion {1}. In order to reduce the distortion that occurs in the demodulated signal in a strict sense without impairing the musicality, it is necessary to clearly distinguish between the two types of distortion mentioned above, and to try to reduce it in the most appropriate way for each type of distortion. There must be.

However, although various attempts have been made to detect distortion occurring in a demodulated signal in the past, no detection of distortion has been carried out focusing on the above-mentioned viewpoint.

In other words, in the past, in order not to distinguish between the two types of distortion described above, the music signal that is reproduced under the control of the distortion detection signal can be expressed from an intellectual point of view, although abnormal sounds have been removed, the sound Although some slight distortions such as cracks and cracks have occurred, or not only abnormal sounds but also slight distortions have been removed and the distortion in the music signal has been reduced, there may have been some slight distortion in the playback sound field, such as a moderate sound image shift, etc. There were drawbacks such as having undesirable effects. The present invention eliminates the above drawbacks by clearly distinguishing and detecting the two types of distortion, and will be explained below with reference to the drawings.

First, before explaining the operation of the method of the present invention, we will first explain the causes of distortion in multi-channel records, the distortion produced by the PLL for each of the causes of distortion, and the optimal means for understanding the distortion caused by the PLL. I will explain about it.

Due to the characteristics of the recording medium, the signals recorded on multi-channel records have a direct wave signal band 1 as shown in FIG.
It is arranged close to the angle modulated wave signal band 0 of carrier angular frequency c.

Therefore, interference in the angle-modulated wave signal band of distortion generated from the direct wave signal band becomes a problem. That is, the interference of the harmonic distortion plate generated from the direct wave signal band 1 with the angle-modulated wave signal band D and the cross-modulation distortion W between the direct wave signal and the carrier pose problems. Of these, the Tsuru modulation distortion W can be classified into an amplitude variation component and a phase variation component when focusing on the phase relationship with the carrier. Since the carrier frequency of the angle-modulated wave signal recorded in this multi-channel record is set low, the frequency deviation with respect to the carrier is relatively large, and the double modulator has linearity over a wide range. need to be.

Based on the above, the causes of distortion in multi-channel records can be classified into the following four types.
{a} Distortion due to nonlinearity of the transmission system {b- Interference of harmonic distortion generated from the direct wave signal band with the angle-modulated wave signal band'c} Amplitude fluctuation of cross-modulation distortion between the direct wave signal and the carrier {d} phase variation of intermodulation distortion between the direct wave signal and the carrier The demodulator of a multi-channel record is preferably configured in a manner that reduces the amount of distortion caused by these distortion factors.

Generally, one of the following methods is used to measure the amount of strain generated above. '1} Harmonic distortion method ■ Cross-modulation distortion method [3} TIM method '4) Dynamic distortion method It may be difficult to correspond to the amount of distortion.

The measurement method (3) uses a square wave and a sine wave as measurement signals, and the measurement method {4) uses a music signal or a random signal.
This method uses noise as a measurement signal, and is said to have good correspondence with intelligence. On the other hand, in the measurement methods {3} and '4}, since the frequency band width of the measurement signal is wide, it is relatively difficult to determine the frequency band that causes distortion from the obtained results. Therefore, the present applicant first applied for patent application No. 50-8286.
No. 7 (Japanese Unexamined Patent Publication No. 52-657), we proposed a ``dynamic distortion measurement method'' using narrow band noise as the measurement signal source.

In other words, this proposed method uses multiple narrow band noises (excluding the frequency band for measuring dynamic distortion) obtained from white noise with a constant frequency bandwidth and different center frequencies as measurement signals. By using this method, even if the band noise of any frequency band is used as the measurement signal and is transmitted through a transmission system with discontinuous input-to-output characteristics, the noise generated based on the band noise transmitted in this transmission system can be transmitted. Dynamic distortion (also simply referred to as distortion in this specification) can be measured under substantially the same conditions, and therefore, it is possible to measure dynamic distortion in which frequency band and how much dynamic distortion is generated by each band//is measurement signal. This method has the advantage that it is extremely easy to find out what is going on. Next, using this proposed method, we will examine what kind of distortion and amount the four types of distortion generating factors in the multi-channel record cause to the angle modulated signal demodulation PLL.

Fig. 2 is a block system diagram of an example of a method for measuring distortion generated in a PLL.The signal generator 1 shown in the figure generates band noise called single band noise as shown in Fig. 3, which is a distortion generating factor. A signal obtained by processing the signal according to the signal is output. That is, the signal generator 1 has different configurations as will be described later in response to the distortion generation factors. In FIG. 2, reference numeral 2 denotes a PLL, which is configured to have a variable lock range, and the distortion characteristic force is determined according to each lock range. Here, the PLL when the rock range is one dish
(hereinafter referred to as A-PLL) and P in the case of 5kHz
The results obtained for LL (hereinafter referred to as B-PLL) are shown. Reference numeral 3 denotes a band filter that passes only the frequency band components whose dynamic distortion is to be measured from the output signal of the PLL 2.

Here, the band filter 3 is configured to pass the frequency band components at and around 1 kHz, which are recognized to have a high degree of correlation with the distortion measurement results of multi-channel records by Soikan. The signal taken out from this filter 3 is supplied to a measuring meter 4, which causes
The amount of dynamic distortion, etc. appearing in a frequency band of Hz and its vicinity (frequency band for measurement) is measured. Among the causes of distortion in a multi-channel record, when measuring the distortion caused by nonlinearity of the transmission system (a), the signal generator 1 shown in FIG. 2 is configured as shown in FIG. 4. Ru.

In Fig. 4, 5 is a single band noise generator that generates multiple single band noises obtained from white noise with a constant frequency band width and different center frequencies; As for the band noise, only the above-mentioned 1kHz and its neighboring frequency components, which are preset in the measurement frequency band, are blocked by the obijo blocking filter 6.
Other frequency components are supplied to a frequency modulator 8 through a band rejection filter 6 and an equalizer circuit 7, respectively. Angle-modulated band noise similar to the angle-modulated wave signal of a multi-channel record is output from the frequency modulator 8, and is supplied from an output terminal 9 to the PLL 2 shown in FIG. The results of measuring distortion due to nonlinearity of the transmission system itself using the above method are as shown in Figure 8A for A-PLL with a wide lock range, and as shown in Figure 8B for B-PLL with a narrow lock range. It becomes like this.

In other words, regarding distortion due to nonlinearity of the transmission system itself,
The A-PLL shows better characteristics than the B-PLL. In addition, in Figures 8A and B, and in Figure 9A, which will be described later.
, B to FIGS. 11A and 11B, the vertical axis indicates the level of band noise when a predetermined lkHz distortion amount is applied, and the axis indicates the center frequency of the band noise (fc in FIG. 3). Next, to explain the measurement of distortion generated as a result of interference of harmonic distortion generated from the direct wave signal band b with the angle modulated wave signal band, an example of the configuration of the signal generator 1 in this case is as follows. The result will be as shown in FIG.

In this figure, the same parts as in FIG. 4 are given the same reference numerals, and their explanations will be omitted. The single band noise is enhanced in the high range from the differentiator 1, and the output (Y) relative to the input (X) is Y=1. Nonlinear circuit 11 with sphere 0.5lXI
The signal is converted into a direct wave signal equivalently containing distortion, mixed with a carrier from a carrier generator 13 in a mixer 12, and then outputted from an output terminal 114 to the PLL 2.
The distortion caused by the harmonics of the measured direct wave signal band on the angle-modulated wave signal is as shown in Figure 9A in A-PLL, where the N/C (noise to carrier ratio) is 0.6 and the distortion caused by the harmonics of the direct wave signal band is It generates distortion 4WB lower than the standard level of the channel record, but in the B-PLL, as shown in Figure B, the N/C
is approximately 1, generating 4MB lower distortion.

Furthermore, even for input signals that cause the A-PLL to generate large distortion, the B-PLL generates only small distortion. Therefore, the B-PLL is clearly superior to the A-PLL in terms of distortion caused by interference of harmonic distortion in the direct wave signal band with the angle-modulated wave signal. Further, the configuration of the signal generator 1 when measuring the distortion caused by the amplitude variation of cross-modulation distortion between the C direct wave signal and the carrier is as shown in FIG.

In the figure, the same parts as in FIG. 5 are designated by the same reference numerals, and the explanation thereof will be omitted. In FIG. 6, 15 is an amplitude modulator;
A balanced modulator is used, and Takagi-enhanced single-band noise is added to provide an offset to the circuit for carrier injection. Amplitude modulator 1
The output signal of 5 is applied to the PLL 2 from the output terminal 16. As a result of measuring the distortion of the PLL input to the above signal, the B-PLL has a frequency of 10kHz as shown in Figure 10B.
A slight distortion is generated for a signal with a modulation depth of 300%.

However, in the distortion characteristics of the A-PLL shown in A of the same figure,
Distortion occurs for a modulation degree of 100% or more, and a considerable amount of distortion occurs for a modulation degree of 200%. That is,
As is clear from Figures 10A and 10B, regarding PLL distortion caused by amplitude fluctuations of cross-modulation distortion between the immediate wave signal and the carrier, the B-PLL has better distortion characteristics than the A-PLL. Are better. Furthermore, when measuring the PLL distortion caused by the phase variation of cross-modulation distortion between the direct wave signal d and the carrier, the signal generator 1 is configured as shown in FIG.

In this figure, the same parts as in FIGS. 4 and 6 are designated by the same reference numerals, and their explanations are omitted. The single band noise is amplified and frequency modulated by the frequency modulator 8. The output of the frequency modulator 8 is output from the output terminal 17 to the PLL
2. As a result of measuring the distortion of the PLLO that inputs the signal from the output terminal 17, the distortion characteristics are A-PLL.
In the case of B-PLL, it becomes as shown in FIG. 11A, and in the case of B-PLL, it becomes as shown in FIG. 11B.

That is, the distortion characteristic of the A-PLL shown in FIG. 11A is 5k.
5 shows that distortion occurs when the frequency is shifted by 5 kHz or more due to band noise of Hz or more. On the other hand, in the B-PLL, no distortion occurs as shown in FIG. Therefore, with respect to PLL distortion caused by the phase variation of distortion modulation between the direct wave signal and the carrier, the B-PLL has better distortion characteristics than the A-PLL. 0 From the above, if the carrier input to the PLL is a good signal that is not interfered with by the direct wave signal, then the PLL.

The lock range is set wide, and when harmonic distortion due to the direct wave signal band or deep modulation distortion with the carrier occurs, the PLL lock retangance can be narrowed.
To do this, it is sufficient to accurately detect the amount of distortion contained in the input signal of the PLL and control the lock range to an optimum value. FIG. 12 shows a block system diagram of an example of a synchronous detector used as means for grasping the state of the input signal of the PLL. 19, low-pass filter (loop filter) 20, second PLL (hereinafter PLL) consisting of VC021
LL22), where it is demodulated and output from the output terminal 23.

When this PLL 22 is locked to the angle modulated wave signal from the input terminal 18, the phase difference between both input signals of the phase comparator 19 is within the range of oo to 180o with 900 as the center, and the lock is established. In this state, normal demodulation operation is performed. The locked state of this PLL22, that is, the state of the input angle-modulated wave signal, is such that the output signal of VC021 is
It can be detected by the output signal of a synchronous detector 25 that performs synchronous detection (phase comparison) of the signal obtained by shifting the phase by 90° by the o phase shifter 24 and the input angle modulated wave signal from the input terminal 18.

Here, the level of the input angle modulated wave signal is large, and P
A case will be described in which the synchronous detector 25 is configured so that when the LL 22 is locked to the input angle modulated wave signal, a 4.5-min output voltage is taken out from the output terminal 26. A-PLL has a relatively wide lock range
FIG. 13A shows the output voltage of the synchronous detector connected to the A-PLL when the signal generated by the signal generator shown in FIGS. 4 to 7 is applied.

That is, when the PLL 22 in FIG. 12 is changed to an A-PLL and the input terminal 18 and the output terminal 9 in FIG. 4 are connected, the output voltage of the output terminal 26 is as shown by a in FIG. 13A. The center frequency of the band noise at this time is set to z today. When the output signals shown in Fig. 5 and Fig. 6 and Fig. 7 are applied to the input terminal 18 of the same machine, the output voltages obtained from the synchronous detector 25 are shown in Fig. 13A at b, c, and d, respectively. The center frequency of the band noise when obtaining the characteristics shown in b to d is set to 10k song.On the other hand, for B-PLL which has a relatively narrow lock range,
The output voltages of the synchronous detector obtained when the signal from the signal generator shown in FIG. 7 is applied are shown as a to d in FIG. 13B, respectively.

The center frequency of the band noise is 2 kHz for the characteristic a in FIG. 13B, and 10 kHz for the characteristics b to d. In both Figures 13A and 13B, the output voltage of the synchronous detector also increases as the distortion amount, N/C, modulation degree, and frequency deviation increase, and in the case of B-PLL, Figure 13B shows However, the A-PLL has similar output characteristics compared to the B-PLL. As shown in FIG. 13A, a and b to d all have different characteristics, and it is possible to grasp the distortion component contained in the carrier.

From the above, the following was clarified.

In other words, the distortion that may occur in the demodulated signal of the angle-modulated wave signal is reduced by the PLL, which has a relatively wide lock range.
By using the output voltage of the synchronous detector connected to the synchronous detector, it is possible to easily synchronize with the musical tone in half order. FIG. 14 shows the waveform of the output voltage of the synchronous detector when an angle-modulated wave signal reproduced from a multi-channel record is applied to a PLU having a predetermined lock range to which the synchronous detector is connected.

In the figure, the region indicated by V is the case where no distortion occurs in the demodulated signal, and since the excessive distortion described above is an evolved form of the mild distortion indicated by '1', W The region shown is a case where mild distortion occurs, and the region indicated by W is a case where excessive distortion occurs. As described above, it is possible to detect the occurrence of distortion based on the output voltage of the synchronous detector.

However, it is difficult to clearly distinguish between the above two types of distortion. The device of the present invention is capable of distinguishing and detecting these two types of distortion. Note that the waveform of the output voltage of the synchronous detector shown in FIG. 14 is an example, and its shape naturally takes various forms depending on the state of the angle-modulated wave signal.

However, there are significant level differences between when the demodulated signal of the angle-modulated wave signal is normal and when slight distortion has occurred as shown by , and when the pulse has excessive distortion as shown by the skin. The form always holds true. FIG. 15 is a block system diagram of an embodiment of the apparatus of the present invention, in which the same parts as in FIG. 12 are given the same reference numerals, and their explanation will be omitted.

The voltage taken out from the synchronous detector 25 via the output terminal 26 is passed through the Obishiro filter 27 which passes the Nakagusuku frequency component.
, and to a bandpass filter 28 that passes the Takagi frequency components. Note that a Takagi filter may be used instead of the band filter 28. The output signal of the Obishiro filter 27 is waveform-shaped by the control signal processing circuit 29 and output from the output terminal 31.

Further, the output signal of the bandpass filter 28 is waveform-shaped by the control signal processing circuit 30' and outputted from the output terminal 32. When the demodulated signal is normal, the output voltage of the synchronous detector 25 and the output voltage waveforms of the bandpass filters 27 and 28 are as shown in FIGS. 16A, B and C, respectively.

That is, when an angle-modulated wave signal that provides a normal demodulated signal is input to the input terminal 18, no output voltage is generated from the synchronous detector 25 as shown in FIG. As a matter of course, no distortion detection signal is output. . However, when an angle-modulated wave signal that provides a demodulated signal containing relatively mild distortion enters the input terminal 18, the synchronous detector 25 outputs a voltage with a waveform as shown in FIG. It is applied on evenings 27 and 28. Since its passband is the Nakagusuku frequency band in the audio frequency band, the Obishiro filter 27 outputs a vertically symmetrical signal with a relatively high level as shown in FIG. 17B as a distortion detection signal. . Also, Obijo Philharmonic 28,
Since the pass band is the Takagi frequency band in the audio frequency band, a signal as shown in FIG. 17C is output,
A large level distortion detection signal is not generated. In addition, when an angle-modulated wave signal that provides a demodulated signal that includes abnormal noise and distortion that significantly deteriorates musicality is input to the input terminal 18, the synchronous detector 25 outputs a pulse as shown in FIG. 18A. A voltage of 1 is taken out and applied to the band filters 27 and 28. Therefore, at this time, the obijo filter 27 outputs a signal with dulled pulses as shown in FIG. 18B, but a distortion detection signal of a large level is not generated. On the other hand, since the band pass filter 28 has a high frequency band, it outputs the input signal shown in FIG. 18A as a pulse with a sharp rise and a large peak value as shown in FIG. 18C. Therefore, this pulse is applied to the control signal processing circuit 30' as a distortion detection signal. Figure 19 shows Obijo Philharmonic 27,
28, a specific circuit of one embodiment of the control signal processing circuits 29 and 30 is shown.

Obijo filter 27 includes resistors R, o to R, 2, and capacitor C.
, -C3, and has a pass band of, for example, kHz to 3kHz, and the output voltage of the synchronous detector 25 is applied to the input terminal 26. The control signal processing circuit 29 includes an operational amplifier 33 and resistors R, 4 to R, 5, an NPN transistor Q to which EO is applied based on the output of the operational amplifier 33, and an emitter output of this transistor Q to the input terminal 26. A circuit consisting of resistors R, 6, R, 7, a capacitor C4, and a Zener diode D3, which outputs a positive DC voltage of a predetermined level as a control signal to the output terminal 31 only when a signal of a predetermined level or higher is received. It consists of In addition, the Obijo filter 28 includes a resistor R, 8 to R2o, and a capacitor C5.
-C7, and has a passband of, for example, 8kHb to 13kHz, and the output voltage of the synchronous detector 25 is applied to the input terminal 26.

The control signal processing circuit 30 supplies an output from the operational amplifier 34 through a circuit consisting of an operational amplifier 34, resistors R2, to R23, and a capacitor C8 forming a feedback circuit thereof, a resistor R, and a diode D4. 1”・Triggerable monostable multipipulator 35 and capacitor C
9, a resistor 25, and a Zener diode D5, and when a pulse of a predetermined level or higher enters the input terminal 26, a positive DC voltage is guided to the output terminal 32 as a control signal for a predetermined period of time. As described above, according to the device of the present invention, when the demodulated signal is normal, when the demodulated signal has relatively mild distortion, that is, cracking, crackling, etc., abnormal sound is generated in the demodulated signal. It is possible to clearly distinguish and detect a total of three cases in which
By selecting a relatively wide lock range of the LL 22, it is possible to easily distinguish between a music signal and distortion, as explained in FIGS. 13A and 13B.

Therefore, the above two types of distortion detection signals are transmitted to the control signal processing circuit 2.
9 and 30 are used as control signals, and for example, the lock range of a PLL for demodulating the angle-modulated wave signal (first PLL) provided separately from the PLL 22 is narrowed by the output control signal of the output terminal 31, and the high-frequency components of the demodulated signal are By reducing the level of
By effectively reducing mild distortion and narrowing the lock range of the first PLL for distortion accompanied by abnormal noise, abnormal noise cannot be sufficiently reduced, so the output terminal 32
When a circuit that mutes the demodulated signal is operated using the output control signal of It is possible to obtain a demodulated signal.

As described above, the multi-channel record playback device according to the present invention reproduces the reproduced angle-modulated wave signal obtained from the multi-channel record code in which the direct wave signal and the angle-modulated wave signal are multiplexed and recorded. A second phase-locked loop; and a second phase-locked loop applied to the second phase-locked loop in an apparatus for reproducing a multichannel audio signal together with a reproduced direct wave signal after demodulation using a phase-locked loop. The reproduced angle modulated wave signal and the second
A synchronous detector receives the output signal of the voltage controlled oscillator in the phase-locked loop and generates an output according to the phase difference between the two signals, and from the output signal of this glue detector, the During the demodulation signal of the angle modulation signal,
The first frequency component in the audible frequency band, which causes a significant level difference between when there is relatively mild distortion that causes mild noise that can be distinguished from musical sounds, and when it is normal, is resonated. Since it is equipped with a filter circuit and a control signal generation circuit that generates a control signal that variably controls the lock range of the first phase-locked loop according to the output signal level of the filter circuit, carrier drop and direct Among the distortions that may occur in the demodulated signal due to interference waves jumping from the wave signal band to the angle-modulated wave signal band, or due to record wear, etc., sound cracking, hoarseness, or crackling occurs. Therefore, by variable control of the lock range of the first phase-locked loop,
It is possible to eliminate crackling, hoarseness, tingling, etc. in the sound without causing excessive sound image movement in the reproduced sound field, and by selecting a relatively wide lock range of the PLL, it is possible to eliminate the difference between musical sounds and distortion. It can be almost completely identified, and the demodulated signal of the angle-modulated wave signal from the output signal of the above-mentioned synchronous detector contains distortion (abnormal sound) that may cause significant noise. A filter circuit that filters the Takagi frequency component in the audible frequency band, which causes a significant level difference between normal and normal cases, and a circuit that mutes the demodulated signal when the output signal level of this filter circuit exceeds a predetermined level. Since it is equipped with a control signal generation circuit that generates a control signal to operate, only the distortion that may occur in the demodulated signal, which causes abnormal sounds and significantly deteriorates musicality, can be easily converted into musical sounds, and almost completely eliminated. can be identified and detected,
Furthermore, since the degree of distortion that has occurred can be identified, abnormal sounds can be removed, and a demodulated signal without distortion can be obtained depending on the state of distortion without adversely affecting the musical tone. It is something that you have.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the frequency spectrum of signals recorded on a multi-channel record and the resulting distortion.
Fig. 2 is a block diagram of an example of a method for measuring the amount of distortion generated in a multi-channel record, Fig. 3 is a diagram showing a frequency spectrum of an example of single band noise used in Fig. 2, and Figs. Figure 7 is a block system diagram of each example of the main part of Figure 2, Figures 8A and B to Figure 11A.
, B are diagrams showing each characteristic of PLL distortion generated by the signals obtained in FIGS. 4 to 7, respectively.
Figure 2 is an example block system diagram for explaining a synchronous detector, Figures 13A and B are diagrams showing the relationship between various distortions and the output voltage of the synchronous detector, and Figure 14 is a diagram of the synchronous detector. A diagram showing an example of an output voltage waveform, FIG. 15 is a block system diagram of an embodiment of the device of the present invention, and FIGS. 16A to 18C to 18A to
C is a signal waveform diagram for explaining the operation of FIG. 15, and FIG. 19 is a specific circuit diagram of an embodiment of the main part of FIG. 15. 1... Signal generator, 2, 22... Phase locked loop (PLL), 18... Angle modulated wave signal input terminal, 23... Demodulated signal output terminal, 25... Synchronous detection 27 Nakagi frequency component reactor wave band filter 28 Takagi frequency component reactor wave band filter 31
, 32... Control signal output terminal. Figure 1 Figure 2 Figure 4 Figure 3 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 13 Figure 12 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19

Claims (1)

[Claims] 1. After demodulating a reproduced angle-modulated wave signal obtained from a multi-channel record in which a direct wave signal and an angle-modulated wave signal are multiplexed and recorded using a first phase locked loop. An apparatus for reproducing a multi-channel audio signal together with a reproduced direct wave signal, comprising a second phase locked loop, a reproduced angle modulated wave signal applied to the second phase locked loop, and a reproduced angle modulated wave signal applied to the second phase locked loop. A synchronous detector which receives the output signal of the voltage controlled oscillator in the phase locked loop and generates an output according to the phase difference between the two signals, and the output signal of the synchronous detector,
There is a significant level difference between the case where the demodulated signal of the above-mentioned angle-modulated wave signal contains relatively mild distortion that causes mild noise that is audibly distinguishable from musical tones, and the case where it is normal. a filter circuit that filters the generated middle frequency component of the audible frequency band; and a control signal generation circuit that generates a control signal that variably controls the lock range of the first phase locked loop according to the output signal level of the filter circuit. A multi-channel record playback device characterized by comprising: 2. The multi-channel record reproducing apparatus according to claim 1, wherein the second phase locked loop has a lock range of about 10 kHz. 3 The reproduced angle-modulated wave signal obtained from a multi-channel record in which the direct wave signal and the angle-modulated wave signal are multiplexed and recorded is demodulated by the first phase locked loop, and then the reproduced angle-modulated wave signal is multiplexed with the reproduced direct wave signal. An apparatus for reproducing a channel audio signal, comprising: a second phase locked loop; a reproduced angle modulated wave signal applied to the second phase locked loop; a synchronous detector that receives the output signal of the voltage controlled oscillator of the voltage controlled oscillator and generates an output according to the phase difference between the two signals, and the output signal of the synchronous detector;
The high range of the audible frequency band that causes a significant level difference between when the demodulated signal of the angle-modulated wave signal contains distortion (abnormal sound) that causes significant audible noise and when it is normal. It is characterized by comprising a filter circuit that filters a frequency component, and a control signal generation circuit that generates a control signal that operates a circuit that mutes a demodulated signal when the output signal level of the filter circuit exceeds a predetermined level. A multi-channel record playback device. 4. The multi-channel record reproducing apparatus according to claim 3, wherein the second phase locked loop has a lock range of approximately 10 kHz.