JPS5824841B2 - Enban Records Niokeru Tracing Hisumi Hosesouchi - Google Patents

Description

[Detailed Description of the Invention] The sound groove of a disc record (hereinafter referred to as record) is
The cross section is cut by the cutting blade of the cutter, which is V-shaped.On the other hand, the tip of the playback stylus of the pickup used when playing records has a hemispherical shape, so the trajectory of the tip of the playback stylus Since the trajectory differs from the trajectory of the tip of the cutting blade of the cutter, so-called tracing distortion occurs when playing records, and the quality of the reproduced sound deteriorates.

In particular, signals based on angularly modulated waves in the ultra-audio frequency range (FM waves and PM
(hereinafter sometimes referred to as FM wave signal)
However, if the signal in the form of a signal that is superimposed on the signal in the audio frequency range (hereinafter referred to as the baseband signal) is the original signal to be recorded and reproduced,
The presence of tracing distortion that occurs during playback not only deteriorates the sound quality of the reproduced sound, but also causes the baseband signal to leak into the demodulated output of the FM wave signal due to cross modulation caused by the tracing distortion. Alternatively, distortion of the baseband signal may interfere with the FM wave signal, causing abnormal noise during demodulation and output of the FM wave signal.

In order to remove the above-mentioned tracing distortion that occurs during record playback, it is necessary to apply distortion that is opposite to the tracing distortion that occurs during record playback to the recording signal used for cutting the record in advance. , traditionally,
For example, attempts have been made to remove tracing distortion using a so-called correlator method or a so-called skew sampling method.

However, among the conventional methods described above, the former correlator method requires large-scale delay circuits and gate circuits, and the latter requires special sampling, so the so-called CD-4 method described above It is difficult to apply the conventional method when the record contains FM waves and requires sufficiently flat amplitude characteristics and linear phase characteristics up to the high frequency range.

In other words, when applying the above-mentioned conventional method to cutting CD-4 (registered trademark) type records, sufficient precision is required for each configuration; The transmission characteristics of the delay circuit itself must be sufficiently good, and at the same time, it is necessary to sufficiently increase the number of unit delay circuits, and for the latter, it is necessary to increase the sampling frequency. There are many difficulties in its implementation, and even if it were to be realized, it would require a significant increase in costs.

Furthermore, even if we look at generally known conventional tracing distortion removal methods other than the conventional tracing distortion removal methods exemplified above, the equipment configuration is complicated and the cost is high. There were drawbacks such as.

The applicant company has conducted various research and development efforts in order to obtain a tracing distortion correction device for disc records that can eliminate the above-mentioned drawbacks of conventional tracing distortion removal methods, and has previously filed a patent application filed in 1973. -76935, the original signal of the signal to be recorded on a disc record is f (t
), the playback signal played from the disc record is f(
t), the recording signal waveform to be actually recorded on the disc record is transformed in advance to be different from the original signal waveform,
A signal processing circuit (
(tracing distortion correction device), the input signal is f (t
), where r is the needle tip radius of the playback needle, ■ is the sound groove linear velocity, θ is the cutting angle of the cutter, and is composed of an electric circuit that can be made as shown in the above formula. We proposed this, and by implementing it, we were able to achieve some results.

The present invention was obtained as a result of practical research on the above-mentioned already proposed tracing distortion correction device, and the details thereof will be explained below with reference to the accompanying drawings.

FIG. 1 is a block diagram of one embodiment of the tracing distortion correction device for disc records of the present invention,
In this Figure 1, 1 is the input terminal of the original signal f (t) to be recorded on a disc record (the input terminals 1 and 2 of the tracing distortion correction device are the output terminals of the tracing distortion correction device, and BA is the buffer amplifier, DL is a delay circuit, EQ is an equalizer (frequency weighting circuit with predetermined frequency characteristics), D is a differentiation circuit (differentiator), LPF is a low-pass filter, S is a square circuit (squarer), M is a multiplier, ATT is a variable attenuator, LS is a level setter, ADD is an adder (mixer), INV is a polarity inverter (inverter, phase inverter),
Hatata v is a changeover switch, and 11 to 124 are connection wires (sometimes also referred to as conducting wires or simply wires).

In addition, in the figure, EQl in equalizer EQ,
Items with a subscript 1.degree.2, such as EQ2, are referred to as EQI as a first equalizer, EQ2 as a second equalizer, and so on.

This subscript is used as a code to indicate other components. M.A.T.
The same applies to T, LS, and ADD.

The original signal f(t) to be recorded on the disc record supplied to the input terminal 1 is amplified by the buffer amplifier BA, and then is supplied to the delay circuit DL via the line 11, and also via the line 13. It is applied to the first equalizer EQ1.

The delay circuit DL is output from the buffer amplifier BA and is connected to the line 11.
, 12 to the second adder ADD2 as one input thereof, a predetermined time delay is applied to the original signal.

The delay time to be given to the original signal by the delay circuit DL is determined by the tracing distortion correction signal (hereinafter also referred to as distortion correction signal) applied from the line 123 to the second adder ADD2. A line to the second adder ADD2 is set equal to the amount of time delay caused by passing through the circuit arrangement between line 13 and line 123 for the original signal used to obtain the signal. The original signal given through line 12 and the distorted persimmon signal given through line 123 are inputted as having the correct time relationship with each other, or due to the characteristics of the cutter used, the original signal If the cutting operation of the cutter caused by the distortion correction signal that has a signal component in a higher frequency range than the original signal is delayed in time with respect to the cutting operation of the cutter caused by A second addition is performed via line 123 so that the time delay due to the cutting operation of the Gero cutter is added to the correction signal, and the time delay due to the cutting operation of the Gero cutter can be compensated for in advance to the distortion correction signal. A delay time that allows the distortion correction signal applied to the adder ADD2 to precede the original signal applied to the second adder ADD2 via the line 12 by the time delay caused in the operation of the cutter. set to the amount.

It is desirable to use a delay circuit whose delay time can be variably adjusted as the above-mentioned delay circuit.

By the way, the recording signal waveform recorded on a disc record is reproduced from the original signal so that the tracing distortion that occurs when the pickup's reproduction stylus traces it is completely canceled out during reproduction. It is necessary to add a distortion correction signal that is completely opposite in phase to the tracing distortion that sometimes occurs, but in the actual configuration, for example, low frequency Filter LPF
For example, a cutter may contain circuit elements that cause a time delay to the signal, or a cutter may be used that causes a time delay in its operation for signals in a high frequency range rather than signals in a low frequency range. , a time difference (phase difference) occurs between the distortion correction signal that occupies a high frequency region and the original signal, and the existence of this time difference reduces the expected amount of correction for tracing distortion. like,
A delay circuit DL is provided in the path of the original signal to provide a predetermined delay time to the original signal.

Regarding the operating characteristics of the cutter, a time delay occurs in the operation of the cutter relative to signals in a high frequency range because the cutting blade and movable portion of the cutter have mass.

If a cutter is obtained in which the operational time delay does not pose a problem over the entire frequency band of the recording signal, the operational time delay of the cutter should be considered when determining the delay time of the delay circuit DL. Of course, there is no need to take this into account.

The distortion correction signal applied to the second adder ADD via the line 123 is obtained by converting the original signal sent from the buffer amplifier BA via the line 13 to a number of signal processing circuits as described below. The problem here is that the recording signal recorded in the sound groove of a disc record is generally created by processing the original signal with specific recording characteristics (for example, RIAA%). The recording signal waveform cut into the sound groove by the cutter was given to the cutter by constant-speed recording.

The point is that the waveform of the drive signal (which may be the same as the waveform of the input signal to the cutter drive amplifier) is integrated.

In other words, the distortion correction signal to be created in the tracing distortion correction device satisfactorily cancels out the tracing distortion that occurs in the playback signal from the pickup when the playback needle traces the recording signal waveform cut into the sound groove of the disc record. Therefore, if there is an element between the output terminal 2 of the tracing distortion correction device and the sound groove of the disc record that deforms the signal waveform,
The original signal to be processed in order to create a distortion correction signal in the tracing distortion correction device is also the waveform that the signal receives between the output terminal 2 of the tracing distortion correction device and the sound groove of the disc record. The original signal must undergo a transformation similar to that of the original signal.

The first equalizer EQI is provided to give the above-mentioned waveform modification to the original signal.
The frequency characteristic of the first equalizer EQ1 is such that the waveform deformation similar to the waveform deformation that occurs in the signal waveform between the output terminal 2 of the tracing distortion correction device and the recording signal waveform of the sound groove of a disc record occurs in the original signal. An example of this is shown in FIG. 2.

Furthermore, since the signal sent from the output terminal 2 of the tracing distortion correction device must not be frequency-weighted according to the frequency characteristics in the first equalizer EQ1, it is passed through the first equalizer EQ1. The signal is transmitted to the output terminal 2 after passing through the second equalizer EQ2, which has frequency characteristics opposite to or complementary to the frequency characteristics of the first equalizer EQI.

FIG. 3 shows an example of the frequency characteristics of the second equalizer EQ2.

Note that in the example shown in the first diagram, the first equalizer EQ
1 is provided on the input side of the first differentiating circuit D1, and a second equalizer EQ2 is provided between the lines 123 and 122 on the input side of the second adder ADD2. , the first equalizer EQ1 may be provided on the output side of the first differentiating circuit D1, or the second equalizer EQ2 may be provided on the output side of the first to third differentiating circuit D1.
It may be provided on the input side or output side of each of the level setters LS1 to LS3.

Also, the first and second equalizers EQ1. When EQ2 is arranged in the circuit as in the example shown in the first diagram, the original signal passing through the delay circuit DL also goes through the first and second circuits as shown in the fourth diagram.
The second equalizers EQ1 and EQ2 can be passed through, but when the configuration shown in the fourth figure is adopted, the first and second equalizers EQ1. If the characteristics of EQ2 are not completely opposite to each other, distortion will occur in the signal, so the circuit arrangement as shown in Figure 1 is a preferred embodiment.

Note that the block X in FIG. 4 corresponds to the component shown surrounded by a broken line frame X in FIG.

In FIG. 1, an original signal subjected to predetermined frequency weighting by a first equalizer EQ1 is applied via a line 14 to a first differentiating circuit D1.

Due to the differentiation operation of the original signal by the first differentiating circuit D1 described above, the original signal f (t)...The signal given to the first differentiating circuit as described above is converted to the original signal f ( t), and the processed signal is later passed through a second equalizer EQ2, which has a frequency characteristic opposite to that of the first equalizer EQ1. Assume that the original signal to be subjected to the arithmetic processing in the various paths after the first differentiating circuit is f(t)... is used as the differentiated original signal f'(t).

The equation (1) becomes the following equation (2).

f(t)-A[f'(f))2(1+Bf'(t)-
Cf mold)]...(2) The above-mentioned first differentiating circuit D1
The following calculation circuits perform calculations according to the above equation (2), and include variable attenuators ATT1, ATT2 and level setters LSI, LS2 . For LS3 etc., the above (
2) Set the coefficients of each term in the equation, and the first differentiator D1 creates a differential signal f'(t) of the original signal f(t) as described above, and this differential signal is converted from line 15 to variable Attenuator ATT1 →
The second differentiation circuit D2, which is supplied via line 16→low-pass filter LPF→line 17→line 18, produces a second-order differential signal f''(1) of the original signal f(t).

Further, the differential signal f'(t
) is also supplied via line 17 to the square circuit S (multiplier S with the same multiplier and multiplicand) and via line 19 to the second multiplier M2.

An output signal of (f'(t))2 is output from the above square circuit S to the line 110, which is transmitted to the first level setter LS.
I, and via line 114 to the second multiplier M2, and via lines 114 and 115 to the first multiplier M1.

The first multiplier M1 receives a line 11 from the second differentiating circuit D2.
2→second variable attenuator ATT2→via line 113, the second differential signal f''(1) of the original signal f(t) is also given, so the first multiplier M1 calculates the second differential signal f(t). Output signal f''(1) from circuit D2 and output signal from square circuit S (
f'(t))2, and the output signal (f'(t))"f is sent to the second level setter LS2 via line 116.
"(1), and the second multiplier M2 multiplies the signal f'(t) given via the line 19 by the signal (f'(t))2 given via the line 114. conduct, line 1
The output signal (f
'(t))3.

The output signal given from the first level setter LSI to the first adder ADD1 via line 111 is the first distortion correction signal, and the output signal given from the second level setter LS2 to the first adder ADD1 via line 117 is the first distortion correction signal.
The output signal applied to the first adder ADD1 via line 119 is a second distortion correction signal, and is further applied from the third level setter LS3 to the first adder ADD1 via line 119.
The output signal given to is a third distortion correction signal,
By applying each of these correction signals to the first adder ADD1 with appropriate polarity, the line 120 from the first adder ADD1 receives A (f'(t)F C1+Bf'(t)-Cf “(t
)] is sent out.

The coefficients A, B, and C in the formula representing the output signal described above are the first
-1 is determined by the settings of the second variable attenuators ATT1 and ATT2 and each level setter LS1 to LS3.

In other words, the first and second variable attenuators ATT1 and ATT2 and each level setter LS1 to LS3 are set to a predetermined value determined by the tip radius r of the playback needle, the sound groove linear velocity V of the disc record, etc. For example, the first and second variable attenuators ATT1 and ATT are set so that each distortion correction signal with a signal level of
2 sets the signal level determined by the needle tip radius r of the regenerating needle, and each level setter LS1 to
Depending on the LS3, the signal level is set so that the signal level is changed in a predetermined manner in relation to the sound groove linear velocity.

The first and second variable attenuators ATTI described above.

The connection positions of ATT2 and each of the level setters LS1 to LS3 in the circuit are not limited to the connection positions as shown in Figure 1, but the predetermined level setting to be applied to the signal may be performed using a square circuit or the like. It is advantageous in terms of S/H if it is performed after the operation by the multiplier is completed, and such an implementation mode can be said to be desirable.

The output signal from the first adder ADD 1 is on line 120
is applied to the polarity inverter INV and also applied to one fixed contact a of the changeover switch 8v.

The output of the polarity inverter INV is applied to the other fixed contact of the changeover switch SW through a line 121, and the line 122 and the second equalizer EQ2 are connected to the movable contact C of the changeover switch Hatake v, and via line 123
The polarity of the distortion correction signal given to the adder ADD2 is
They are mutually reversed in accordance with the switching of the movable contact C of the changeover switch 8v described above.

The above-mentioned component consisting of the polarity inverter INV and the changeover switch history is provided to ensure that the distortion correction signal output from the tracing distortion correction device is always used as having an appropriate polarity. By having this component, it becomes possible to selectively use the tracing distortion correction device for both the right channel and the left channel, as well as the cutter drive amplifier and other packing equipment. To make it possible to always supply a signal to a cutter with the correct polarity even if the polarity of the signal is correct.

In this way, in the second adder ADD2,
The original signal and the distortion correction signal are added with appropriate polarity, and the signal sent to the output terminal 2 via the line 124 becomes a recorded signal that does not generate tracing distortion during playback. .

By the way, the above-mentioned tracing distortion correction signal is recorded by an arithmetic circuit consisting of a differentiating circuit, a multiplier (including a square circuit), a coefficient setting circuit (variable attenuator and level setting device), an adder, etc. The original signal to be reproduced, that is, a signal in the form of a signal in which an FM wave signal is superimposed on a baseband signal (in the case of a CD-4 (registered trademark) signal, an occupied frequency band of 20 Hz to 45 KHz) However, if there is noise in the signal to be processed, the problem is that the S/N ratio, especially in the high frequency range, deteriorates extremely. becomes.

In other words, when there is noise in the original signal for some reason, or when noise is generated in various paths before the arithmetic circuit (for example, so-called f2 noise generated in the semiconductor elements that make up the circuit). , etc.), due to the differential action of the differential circuit installed in the arithmetic circuit,
The above-mentioned noise will also be amplified at a rate of 6 dB per octave for calculation processing, but since the multiplier used in the calculation circuit naturally has non-linear input/output characteristics, When noise with enhanced high frequency components is added to the multiplier, a high level beat signal will be generated at the output of the multiplier.

Since the beat signal due to the above-mentioned noise also appears within the FM wave signal region, the S/N of the FM wave signal, which is originally considered to have a lower signal level than the baseband signal, is due to the presence of the above-mentioned noise. This is significantly exacerbated by the beat signal generated based on this.

To solve the above problem, for example, a squaring circuit or a multiplier must be connected to the occupied frequency band of the original signal (if the original signal is CD-4
(registered trademark) system signal, 15Hz to 45Hz
It is conceivable to cut off the high frequency range by setting the operating conditions so that it operates only within a frequency range approximately equal to KHz), but if this solution is adopted, the phase of the signal will change even within the operating range. This method cannot be used because the deviation becomes large and accurate calculation results cannot be obtained.

Therefore, in the tracing distortion correction device of the present invention, the low-pass filter LPF shown following the variable attenuator ATT 1 in FIG. 1 is provided in order to solve the above-mentioned problems. and this low-pass filter LPE
It is preferable to use one whose pass band is the occupied frequency band of the original signal.

In the example shown in the first diagram, the low-pass filter LPF is provided in the circuit following the first differentiating circuit D1, but since the differentiating circuit does not cause cross-modulation, this low-pass filter LPF
may be provided on the input side of the first differentiating circuit D10 (also,
If the circuits in the previous stage were configured so as not to generate much noise, this low-pass filter LFF would be connected to the input side of the square circuit S, the input side of the second differentiating circuit D2, and the second differential circuit D2. It may be provided at any part of the signal path up to the connection point to which one input side of the multiplier M2 is connected.

However, when the low-pass filter LPF is connected to the output side of the first differentiating circuit D1 as in the example shown in the first diagram, the noise generated in the path to the output side of the first differentiating circuit D1 The circuit arrangement as shown in the first diagram is desirable because it is the most efficient in that it can remove all the high-frequency parts of the signal.

In this way, by providing a low-pass filter LPF with a pass band corresponding to the occupied frequency band of the original signal before the multiplier (including the squaring circuit), it is possible to prevent a phase shift from occurring in the signal. A multiplier with a sufficiently wide operating range (for example, an operating range approximately 10 times the occupied frequency band of the original signal) is used in the arithmetic circuit to perform faithful computation without causing a phase shift in the signal. However, since the beat signal due to noise does not appear in the FM wave signal region containing important information, the FM signal in the FM wave signal band where the signal level is -20 dB lower than the standard level is originally
The S/N ratio of the wave signal can be made sufficiently good, and a distortion correction signal with an accurate phase can be obtained.

As is clear from the detailed explanation above, in the tracing distortion correction device of the present invention, the occupied frequency bandwidth of the original signal is set as the passband width at a stage before the multiplier (including the square circuit). By providing a low-pass filter such as this, the noise in the input signal to the multiplier is removed, thereby having a sufficiently wide operating range (frequency band) so as not to introduce phase shifts in the signal. Even if a multiplier is used to perform faithful calculations, the beat signal due to noise does not appear in the FM wave signal region that contains important information, so the FM wave whose signal level is originally -20 dB lower than the reference level. The S/N ratio of the FM wave signal in the signal band can be made sufficiently good, and a distortion correction signal with accurate phase can be obtained.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the tracing distortion correction device of the present invention, Figure 2 is a frequency characteristic curve diagram of the first equalizer, and Figure 3 is a diagram of the frequency characteristic curve of the first equalizer.
The figure is a frequency characteristic curve diagram of the second equalizer, and FIG. 4 is a block diagram of a modified version of the tracing distortion correction device. 1...Input terminal, 2...Output terminal, E
Ql...First equalizer, EQ2...
・Second equalizer, Dl...first differentiating circuit, D2...second differentiating circuit, S...square circuit, Ml......th 1 multiplier, M2...
...Second multiplier, ATT1...First variable attenuator, ATT2...Second variable attenuator, L
SI...First level setter, LS2...
...Second level setter, LS3...Third level setter, ADDl...First adder, AD
D 2... Second adder, 8v... Changeover switch, INV... Polarity anti-private interest, 11-1
24... line.

Claims (1)

[Claims] 1 Differentiating the original signal to be recorded and reproduced by a first differentiating circuit, adding the output signal from the first differentiating circuit to a square circuit, a second differentiating circuit, and a second multiplier, Further, the output of the square circuit is added to the first level setter and the first and second multipliers;
The output from the differentiator is applied to the first multiplier, and the output of the first multiplier is applied to the second level setter,
The outputs of the multipliers are applied to the third level setter, and the first distortion correction signal obtained from the first level setter and the second distortion correction signal obtained from the second level setter are respectively applied. In the tracing distortion correction device for a disc record, wherein the signal, the third distortion correction signal obtained from the third level setter, and the original signal are added to an adder as having respective required polarities. The signal to be given to the connection point to which the input side of the squared circuit, the input side of the second differentiating circuit, one input side of the second multiplier, etc. is connected is mainly within the frequency band occupied by the original signal. In the signal path to the connection point to which the input side of the square circuit, the input side of the second differentiating circuit, one input side of the second multiplier, etc. are connected so that the signal consists of frequency components. A low-pass filter capable of passing a signal in the occupied frequency band of the original signal is provided, and each of the multipliers described above has an operating area wider than the occupied frequency band of the original signal. A tracing distortion correction device for disc records that uses