KR950006183Y1 - Sound frequely characteristics automatic control circuit of vcr - Google Patents

Abstract

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Description

Automatic frequency control circuit for audio signal recording and playback in VCR

1 is a circuit diagram of a voice frequency characteristic automatic adjustment circuit of the present invention.

2A and 2B are a recording state and a head state of the tape by the inventive circuit.

3 is an output frequency characteristic diagram of a regenerative equalization amplifier in the inventive design.

* Explanation of symbols for main parts of the drawings

1: recording amplifier 2: reproducing system

3: amplifier 4: low pass filter

5: integrator 6: frequency characteristic variable amplifier

7, 8: comparator 9: device on controller

10 NOR gate 11: DC level converter

12: frequency characteristic control means H1: recording and playback head

H2: Playhead EQ1-EQ3: Equalizer

The present invention relates to a circuit for automatically adjusting frequency characteristics of voice in VCR, and in particular, by automatically converting frequency characteristics according to the state of a tape, that is, high quality or low quality, it is possible to always listen to high quality sound signals. The present invention relates to a circuit for automatically adjusting the voice frequency characteristics of a V-C.

The conventional VCR is not equipped with a frequency characteristic automatic control circuit as in the present invention, and thus has a constant frequency characteristic regardless of a high quality tape or a low quality tape, so that a beautiful sound signal cannot be heard on a low quality tape. There was this.

The present invention has been made to solve such a conventional problem, and has a variable variable equalization means capable of varying frequency characteristics by a predetermined control signal between a recording and playback head of a VCR and a reproduction system, and reproducing. A frequency characteristic control means is provided at the rear end of the head to output a control signal from the frequency characteristic control means to enable the variable-variable equalization means to operate at different frequency characteristics depending on the state of the tape, that is, the quality or the quality. In this case, the frequency characteristic (equal amplification frequency bandwidth) is automatically maximized on high quality tape, and the frequency characteristic is automatically lowered on low quality tape, so that the user can always listen to high quality sound signal. To provide a circuit for automatically adjusting the voice frequency characteristics in a seed Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

As shown in Fig. 1, the constitution of the present invention is a first head for reproducing a portion in which a voice signal is carried on a video tape, which records a voice signal on a VCR tape or reproduces a recorded voice signal. A circuit for varying and amplifying a frequency characteristic of a reproduction head H1 and an audio signal reproduced from the first head, wherein the frequency signal controlling means 12 controls the audio signal output from the recording and reproduction head H1. A frequency characteristic variable amplifier 6 for equalizing and amplifying and outputting the audio signal reproduced from the recording and reproduction head H1 to another frequency characteristic (EQ characteristic), and a portion where no signal is carried on the video tape. A second head for reproducing, the reproducing head (H2) for reproducing a non-recorded portion on said VCR tape; A circuit for converting a noise component signal out of a signal reproduced from the second head to a DC level, the DC level conversion for level converting a noise signal component appearing in accordance with the state of a tape in a signalless output from the reproduction head H2. A control circuit which compares the output section of the DC level converting section 11 with a predetermined reference level and varies the frequency characteristic of the frequency characteristic variable amplifying section 6 according to the comparison value. A frequency characteristic for comparing the noise signal level output from the DC level converter 11 with a reference level, and outputting a switching control signal for changing the EQ characteristic of the frequency characteristic variable amplifier 6 according to the comparison result Control means 12.

The variable frequency characteristic amplifying unit 6 includes an amplifier 61 for amplifying an input voice signal and a first voice signal fed back from an output terminal of the amplifier 61 to an input terminal. Means for controlling the feedback characteristics of the equalizer EQ1, the second equalizer EQ2, the third equalizer EQ3 and the first to third equalizers EQ1, EQ2 and EQ3. It consists of a 1st switching means SW1, a 2nd switching means SW2, and a 3rd switching means SW3 which turn on or off by the switching control signal of (12), respectively.

The DC level converting unit 11 includes an amplifier 3 for amplifying a noise signal of a non-recorded portion output from the reproduction head H2, and a low pass for filtering a voice frequency band component of the amplified noise signal. A filter 4 and an integrator 5 for integrating the low pass filtered noise signal and converting the signal into a direct current signal corresponding to the noise level. The frequency characteristic control means 12 includes the direct current level converting unit ( A first comparator for outputting a switching control signal for reducing the EQ characteristic of the frequency characteristic variable amplifier 6 to a minimum bandwidth by comparing the signal level input at 11) with the S / N ratio lower limit level which is a predetermined low potential level. (7) and comparing the signal level input from the DC level converting section 11 with the S / N ratio upper limit level, which is a predetermined high potential level, to make the EQ characteristic of the frequency characteristic variable amplifying section 6 the maximum bandwidth. Widening The second comparator 8 for outputting the switching control signal and the output signals of the first comparator 7 and the second comparator 8 are logically combined to adjust the EQ characteristics of the frequency characteristic variable amplifier 6 to an intermediate value. NOR gate 10 for outputting a switching control signal to adjust the bandwidth, the first equalizer (EQ1), resistor (R1) (R2) and capacitor (C1) for setting the equalization amplifier frequency characteristics to the maximum bandwidth The second equalizer EQ2 comprises a resistor R3, R4 and a capacitor C2 for setting equalization amplification frequency characteristics to a median bandwidth, and the third equalizer EQ3 is And resistors R5 and R6 and capacitor C3 for setting equalization amplification frequency characteristics to minimum bandwidths.

In addition, the present invention, the fourth switching means (SW4) for supplying or blocking the output signal of the first comparator 7 to the variable frequency characteristic amplifier 6 and the output signal of the second comparator 8 A fifth switching means SW5 for supplying or cutting off to the frequency characteristic variable amplifier 6, and an apparatus on controller 9 for controlling the fourth switching means SW4 and the fifth switching means SW5 on or off. It includes a configuration.

In FIG. 1, reference numeral R7 denotes a resistor, C4 denotes a capacitor, 1 denotes a recording amplifier, and SW6 denotes a recording / playback selection switch.

Referring to the effects of the present invention configured as described above with reference to Figure 2 (a), (b) and 3 as follows.

First, when the recording / playback selection switch SW6 is turned off, that is, the recording mode is switched and a predetermined audio signal is input to the recording amplifier 1, the audio signal is recorded by the recording and playback head H1. The amplifier 1 is amplified and recorded on the tape with the second degree.

In order to play the tape recorded in this way, the switch SW6 is turned on to switch to the playback mode, and when the device on controller 9 is operated, the audio signal is reproduced by the recording and playback head H1. The fourth switching means SW4 and the fifth switching SW5 are turned on, and the playback signal H2 reproduces the noise signal of the non-recorded portion of the tape.

That is, as shown in FIG. 2B, the playback head H2 provided above the recording and playback head H1 reproduces the non-recorded portion at the top of the portion where the audio signal is recorded as shown in FIG.

Therefore, the noise signal of the non-recording part on the tape read through the reproduction head H2 is level-converted by the DC level converting part 11 into the DC signal.

That is, the reproduced noise is amplified by the amplifier 3, and then only the noise component corresponding to the voice frequency signal band is filtered through the low pass filter 4, and integrated through the integrator 5, thereby reducing the noise signal level. The DC signal is integrated and output at a DC level corresponding to the non-inverting input terminal (+) and the inverting input terminal (-) of the first and second comparators 7 and 8 of the frequency characteristic control means 12. Is applied to.

At this time, in the case of a high-quality tape, since the magnetic material is constantly arranged in the recording area, no signal including the noise signal is recorded, but when the magnetic material ages with the use of a long time, the noise signal is recorded in the recording area in FIG. Since remains, this noise signal is read through the reproduction head H2, and the DC signal corresponding to the noise level is output.

In addition, the reference voltage V1 applied to the inverting input terminal (-) of the first comparator 7 is set to the lowest value based on the normal S / N level, and the ratio of the second comparator 8 is lower. The reference voltage V2 applied to the inverting input terminal is set to the highest value [V1 < V2].

On the other hand, in the case of low quality tape, the DC level (assuming = V3) of the noise signal output from the integrator 5 is output at high potential to be higher than the reference voltage V1, so that the output of the first comparator 7 On the contrary, when the tape is of good quality, the signal voltage output from the integrator 5 is lower than the reference voltage V2 so that the output of the second comparator 8 is in a high state.

[1] the control operation of the EQ characteristic according to the magnitude relationship between the noise signal level V3 and the reference voltages V1 and V2. Good quality tape playback [2]. Poor quality tape playback, [3]. Heavy tape playback, [4]. The following description will be made for each case, such as when the switching means SW4 and SW5 are turned off by the device on controller 9.

[One]. When playing good quality tapes; In the case of reproducing a good quality tape, the DC level V3 output from the integrator 5 becomes a signal level near zero.

Therefore, in this case, the output of the first comparator 7 becomes 'low' by V3 < V1, and the output of the second comparator 8 becomes V < V3 < Becomes high, the reference voltage V1 of the first comparator 7 is applied to the inverting input terminal (+), and the reference voltage V2 of the second comparator 8 is the non-inverting input terminal. Because it is added to (-).

The output of the NOR gate 10 for ORing and inverting the outputs of the first and second comparators 7 and 8 becomes 'low'.

Therefore, the 'high' signal is applied only to the control terminal Co1 of the first switching means SW1 so that only the first switching means SW1 is turned on, so that the first equalizer EQ1 is on the feedback line of the amplifier 61. Therefore, in this case, the frequency characteristic variable amplifier 6 operates with equalization characteristics of the minimum bandwidth (solid line characteristic in FIG. 3) determined by the resistors R1 and R2 and the capacitor C1.

[2]. When playing poor quality tapes; In the case of reproducing a very low quality tape, the DC level V3 output from the integrator 5 is greatly increased to exceed the level of the reference voltage V1 as well as the reference voltage V2.

In this case, therefore, the magnitude of V1 < V2 < V3 is in a large and small relationship, and the output of the first comparator 7 becomes 'high' by V1 < V3, and the output of the second comparator 8 is V2 < 'Low', and the output of the NOR gate 10 is 'low'.

Therefore, the 'high' signal is applied only to the control terminal Co3 of the third switching means SW3 so that only the third switching means SW3 is turned on, so that the third equalizer EQ3 is on the feedback line of the amplifier 61. Therefore, in this case, the frequency characteristic variable amplifier 6 operates with the equalization characteristic of the minimum bandwidth (dotted dashed line characteristic in FIG. 3) determined by the resistors R5 and R6 and the capacitor C3. .

[3]. When playing heavy tape; In the case of playing a heavy tape, the DC level V3 output from the integrator 5 is not large but is placed at a level larger than the reference voltage V1 and smaller than the reference voltage V2.

In this case, therefore, the magnitude of V1 < V3 < V2 is placed in a large and small relationship. Therefore, the output of the first comparator 7 also becomes 'high' by V1 < V3, and the output of the second comparator 8 by V3 < Is also 'high', and the output of the NOR gate 10 is 'low'.

Therefore, the 'high' signal is applied only to the control terminal Co1 of the first switching means SW1 and the control terminal Co3 of the third switching means SW3, so that the first and third switching means SW1 (SW3) Only the first and third equalizers EQ1 and EQ3 are intervened on the feedback line of the amplifier 61, so that in this case it is determined by resistors R1 and R2 and capacitor C1. Variable frequency amplification unit with equalization characteristics in a range smaller than the maximum bandwidth (solid line characteristic of FIG. 3) and larger than the minimum bandwidth (dotted dashed line characteristic of FIG. 3) determined by resistors R5 (R6) and capacitor C3. (6) is operated.

[4]. When the switching means SW4 and SW5 are all off; Since the output signals of the first comparator 7 and the second comparator 8 are not supplied to the variable frequency characteristic amplifier 6, a 'low' signal is input to both input terminals of the NOR gate 10, so that the NOR gate The output of (10) becomes 'high', and this 'high' signal is applied to the control terminal Co2 of the second switching means SW2 to turn on the second switching means SW2.

Therefore, the second equalizer EQ2 is intervened on the feedback line of the amplifier 61, so in this case the intermediate normal bandwidth determined by the resistors R3 and R4 and the capacitor C2 The frequency characteristic variable amplifier 6 is operated by the equalization characteristic of FIG. 3.

As described above, according to the present invention, when reproducing the audio signal recorded on the magnetic tape, the state of the tape is decoded by a separate playhead, and in the case of a good quality tape, the frequency characteristics of the sound signal are maximized. It is possible to listen to a good sound signal, and in the case of a low quality tape, it is possible to listen to a beautiful sound signal at all times regardless of the aging state of the tape by lowering the frequency characteristic to a minimum.

Claims (6)

A first head which reproduces a portion on which the audio signal is carried on the video tape; A second head for reproducing a portion where no signal is carried on the video tape; A variable frequency characteristic amplifier for varying and amplifying the frequency characteristic of the speech signal reproduced from the first head; A DC level converting unit converting a noise component signal of the non-signal reproduced from the second head into a DC level; Frequency characteristic control means for comparing the output level of the DC level converting section with a predetermined reference level and varying the frequency characteristic of the frequency characteristic variable amplifier according to the comparison value; Voice frequency characteristics automatic control circuit in the VRC comprising a configuration, including. The variable frequency amplifier of claim 1, wherein the frequency characteristic variable amplifying unit expands and converts the frequency characteristic of the audio signal fed back from the output terminal of the amplifier 61 to the input terminal and a predetermined bandwidth. A first equalizer (EQ1), a first switching means (SW1) for turning on or off a feedback path of the first equalizer (EQ1) under the control of the frequency characteristic selection control means, and the amplifier A second equalizer EQ2 for converting the frequency characteristic of the voice signal fed back from the output terminal 61 to an intermediate bandwidth, and under the control of the frequency characteristic selection control means; The second switching means (SW2) for turning on or off the feedback path of the EQ2), and the frequency characteristics of the audio signal fed back from the output terminal of the amplifier 61 to the input terminal in a predetermined bandwidth A third equalizer EQ3 for reducing and converting, and a third switching means SW3 for turning on or off the feedback path of the third equalizer EQ3 under the control of the frequency characteristic selection control means. Automatic frequency control circuit for voice frequency characteristics in V.al. The DC level converting means according to claim 1, wherein the DC level converting means includes: an amplifier 3 for amplifying the noise signal output from the second head, and a low band for filtering audio frequency band components of the noise signal amplified by the amplifier 3; Voice frequency characteristics in VCC comprising a pass filter 4 and an integrator 5 for integrating the noise signal passing through the low pass filter 4 into a DC signal corresponding to the noise level. Automatic control circuit. The tape playback apparatus of claim 1, wherein the frequency characteristic control means compares the signal level output from the DC level converting unit with a predetermined reference voltage V1 and compares the frequency characteristic of the frequency characteristic variable amplifying unit with a low quality tape. Comparing the first comparator 7 for outputting a switching control signal for converting the reduced band characteristics, and the signal level output from the DC level converter with a predetermined reference voltage (V2), A second comparator 8 and a first comparator 7 and a second comparator for outputting a switching control signal for converting the frequency characteristic of the frequency characteristic variable amplifier into an extended band characteristic corresponding to a high quality tape reproduction; By the logical combination of the output signal of (8), the characteristic variable amplifying section is characterized by the normal bandwidth characteristic, which is a case where the expansion or contraction of the frequency characteristic is not required. Automatic audio-frequency characteristic in the V CR, characterized in that consists of a coined word gate 10 for outputting a switching control signal for converting the frequency characteristics control circuit. 3. The resistor (R1) (R2) of claim 2, wherein the first equalizer (EQ1) is set to a resistance value for converting the characteristic of the frequency characteristic variable amplifier into an extended bandwidth corresponding to a good tape. The second equalizer EQ2 comprises a resistor R3 (R4) which sets the characteristic of the frequency characteristic variable amplifier to a resistance value for converting the characteristic of the frequency characteristic variable amplifier into a normal bandwidth. And the capacitor C3 set to the capacitance value, and the third equalizer EQ3 is a resistance value for converting the characteristic of the frequency characteristic variable amplifier into a reduced bandwidth corresponding to a low quality tape. A voice frequency characteristic automatic adjustment circuit in a VR, comprising a resistor (R5) and a capacitor (C3) set to a corresponding capacitance value. 5. The fourth comparator (SW4) according to claim 4, wherein the output signal of the first comparator (7) is supplied or interrupted to the frequency characteristic variable amplifier and the NOR gate (10), and the second comparator (8). On or off control of the fifth switching means (SW5) and the fourth switching means (SW4) and the fifth switching means (SW5) for supplying or blocking the output signal of the frequency variable amplifier and the NOR gate (10) And a device on controller (9).