JP3099302B2 - Sound device and magnetic information reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio device such as a cassette tape player used for a vehicle and a magnetic information reproducing device.

[0002]

2. Description of the Related Art Generally, when a transceiver is used near a cassette tape deck, radio waves of the transceiver are picked up by a head of the cassette tape. In order to prevent the picked-up radio wave from being output from the speaker as noise, a high frequency cut capacitor for removing a frequency higher than a frequency band in an audible range is provided as a noise removing device.

FIG. 7 is an explanatory diagram showing a cassette tape player as the above-described conventional audio device and magnetic information reproducing device, FIG. 8 is a waveform diagram showing the output of a deck equalizer amplifier, and FIG. 8B is a waveform chart when the input to the deck equalizer amplifier exceeds the allowable input level.

In these figures, reference numeral 1 denotes a deck head as a magnetic information reading head unit for reading magnetic information of a cassette tape as a magnetic information holding member. The deck head 1 is a deck head as an input signal from an input unit. Output the output 2. Reference numeral 3 denotes a deck equalizer amplifier (hereinafter, referred to as deck EQ) as a detection unit that detects and amplifies the deck head output 2 and outputs a deck equalizer amplifier output (hereinafter, referred to as deck EQ output) 4 as a detection signal. Reference numeral 5 denotes a Dolby circuit for reducing the high-frequency portion previously increased by the Dolby method when the magnetic information of the cassette tape is recorded in the Dolby method. The Dolby circuit 5 outputs a Dolby circuit output 6.

[0005] Reference numeral 7 denotes an electronic volume controller for continuously adjusting the volume of the Dolby circuit output 6. The electronic volume controller 7 outputs an electronic volume controller output 8. Reference numeral 9 denotes an audio mute unit serving as an attenuation unit and an adjustment unit for temporarily attenuating the electronic volume control unit output 8. The audio mute unit output 10 output from the audio mute unit 9 is an amplifier 1
The signal is amplified by 1 and becomes an amplifier output 12, which is output from the speaker unit 13 as sound. 14 is the deck head 1
Is a high-frequency removing capacitor connected between the deck EQ3 and the deck EQ3, and 15 is a high-frequency removing capacitor connected between the deck EQ3 and the Dolby circuit 5. 1
Reference numeral 6 denotes a transceiver that emits a radio wave near the deck head 1.

Next, the operation will be described. The deck head 1 reads magnetic information from the cassette tape and receives radio waves from the transceiver 16 as noise. This noise is included in the deck head output 2. Therefore, the capacitor 14 cuts a higher frequency component than the predetermined frequency of the entire deck head output 2, converts the deck head output 2 into an audio frequency band by the deck EQ 3, and then converts the deck head output 2 to an audio frequency band higher by the capacitor 15. Is removed to remove noise.

Here, when the signal level of the deck head output 2 input to the deck EQ3 is within the allowable input level of the deck EQ3, the signal is normally output near a reference bias voltage of generally about 3 volts as shown in FIG. , Operate as described above. However, when the level of the deck head output 2 input to the deck EQ3 is larger than the allowable input level of the deck EQ3, the deck EQ3 becomes saturated and greatly fluctuates from the reference bias voltage, and as shown in FIG. The noise having the low frequency component is included in the deck EQ output 4. This noise cannot be removed by the capacitor 15 for removing high-frequency components, but is amplified by the Dolby circuit 5, passes through the electronic volume control unit 7 and the audio mute unit 9, is amplified by the amplifier 11, and is amplified by the speaker unit 1.
3 is output.

[0008]

Since the conventional audio apparatus is constructed as described above, if the level of the deck head output 2 input to the deck EQ3 is larger than the allowable level of the deck EQ3, the deck EQ3 becomes saturated. Thus, a low-frequency noise is included in the deck EQ output 4.
This noise cannot be removed by the capacitor 15 and is output from the speaker 13 to generate an unpleasant sound, and there is a problem that the speaker 13 may break down in a severe case.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an audio device and a magnetic information reproducing device which do not output a noise which causes a breakage of a speaker from a speaker. And

[0010]

An audio apparatus and a magnetic information reproducing apparatus according to the present invention include a signal level comparing section for outputting an operation signal when a signal level of a detected input signal deviates from a predetermined range, And an attenuating section for attenuating the detected input signal by the operation signal output from the level comparing section.

A low-frequency pass filter for extracting a frequency component lower than a predetermined frequency value from the detected input signal, a low-frequency component comparison unit for comparing the output of the low-frequency filter with a predetermined value, and a low-frequency component comparison unit A phase conversion unit that changes the phase of the output of the low-frequency pass filter according to the comparison result output from the unit, and a synthesis circuit that synthesizes the output of the phase conversion unit with the input signal after detection.

Further, there are provided a DC signal level comparing section for comparing the signal level of the DC component of the input signal with a predetermined value, and an adjusting section for adjusting the signal level of the input signal based on the comparison result output from the DC signal level comparing section. It is a thing.

A DC signal level comparing section for comparing the signal level of the DC component of the input signal with a predetermined value and an AC signal level comparing section for comparing the signal level of the AC component of the input signal with a predetermined value are provided. An adjustment unit is provided for adjusting the signal level of the input signal based on the comparison results output from the level comparison unit and the AC signal level comparison unit.

Further, a detector for detecting an input signal output from a magnetic information reading head for reading magnetic information from a magnetic holding member, and operates when a signal level of the detection signal output from the detector is larger than a predetermined value. A signal level comparing section for outputting a signal and an attenuating section for attenuating a detection signal by an operation signal output from the signal level comparing section are provided.

[0015]

According to the present invention, a signal level comparing section for outputting an operation signal when the signal level of a detected input signal deviates from a predetermined range, and an operation signal output from the signal level comparing section is used to detect an operation signal after the detection. An attenuator for attenuating the input signal is provided, and the detected input signal attenuated by the attenuator is input to the speaker.

Also, a low-frequency pass filter for extracting a frequency component lower than a predetermined frequency value from the detected input signal, a low-frequency component comparing section for comparing the output of the low-frequency pass filter with a predetermined value, and a low-frequency component comparing section A phase conversion unit that changes the phase of the output of the low-frequency pass filter according to the comparison result output from the comparison unit; and a synthesis unit combines the output of the phase conversion unit with the input signal after detection, and the input signal after detection. This cancels the low frequency components of

Further, there are provided a DC signal level comparing section for comparing the signal level of the DC component of the input signal with a predetermined value, and an adjusting section for adjusting the signal level of the input signal based on the comparison result output from the DC signal level comparing section. The signal level of the input signal is adjusted by the adjusting section based on the signal level of the DC component of the input signal, and the adjusted input signal is input to the speaker section.

A DC signal level comparing section for comparing the signal level of the DC component of the input signal with a predetermined value and an AC signal level comparing section for comparing the signal level of the AC component of the input signal with a predetermined value are provided. An adjusting unit that adjusts the signal level of the input signal based on the comparison result output from the level comparing unit and the AC signal level comparing unit is provided. The signal level of the input signal is adjusted by the adjusting unit, and the adjusted input signal is input to the speaker unit.

Further, a detector for detecting an input signal output from a magnetic information reading head for reading magnetic information from a magnetic holding member, and operates when a signal level of a detection signal output from the detector is larger than a predetermined value. A signal level comparing section for outputting a signal and an attenuating section for attenuating a detection signal by an operation signal output from the signal level comparing section are provided, and the detection signal attenuated by the attenuating section is input to a speaker section. Things.

[0020]

[Embodiment 1] FIG. 1 is a block diagram showing a cassette tape reproducing device as an audio device and a magnetic information reproducing device according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a detector and a level detecting circuit. In these figures, 1 is a magnetic information carrier and
Information reading to read magnetic information of cassette tape
This is the deck head as the
Head 1 is a deck head as an input signal from the input section.
Output 2 is output. 3 detects deck head output 2
Amplified and output from the deck equalizer amplifier as a detection signal.
A detector for outputting a force (hereinafter referred to as a deck EQ output) 4
Deck equalizer amplifier (hereinafter referred to as Deck EQ)
). 5 is Dolby magnetic information on cassette tape
Dolby format when recorded in
A Dolby circuit that reduces the high-frequency part
You. This Dolby circuit 5 outputs a Dolby circuit output 6.
You. 7 can continuously output the volume of this Dolby circuit output 6.
It is an electronic volume control unit that adjusts strangely.
The unit 7 outputs an electronic volume control unit output 8. 9 is this electron
Attenuator and adjustment for temporarily attenuating volume controller output 8
The audio mute unit as a unit
9 is an audio mute unit output 10
, And becomes the amplifier output 12 from the speaker unit 13
Output as audio. 16 is the electric power near deck head 1.
It is a transceiver making waves. Further, a detector 21 is connected between the deck EQ 3 and the Dolby circuit 5. The detector 21 detects the magnitude of the potential of the DC component of the deck EQ output 4 and outputs a detection signal 22. 2
Reference numeral 3 compares the detection signal 22 with an upper limit level or a lower limit level which is set in advance in correspondence with the audible range. When the detection signal 22 is larger than the upper limit level or smaller than the lower limit level, the operation signal 24 is sound-mute unit. 9 is a level detection circuit serving as a signal level comparison unit and a DC signal level comparison unit for outputting to the DC signal level comparison unit 9.

The detector 21 comprises a detecting transistor 25 and a smoothing capacitor 26, as shown in FIG. As shown in FIG. 2, the level detecting circuit 23 includes an upper limit Zener diode 27, a lower limit Zener diode 28, control transistors 29, 30, and 31, discharge resistors 32 and 33, and bias resistors 34 and 35. Be composed. A is a power supply terminal for supplying a voltage between the transistor 29 and the transistor 30 via the resistor 34, and B is a power supply terminal for supplying a voltage between the transistor 30 and the transistor 31 and the audio mute unit 9 via the resistor 35. Terminal.

Next, the operation will be described. When the signal level of the deck head output 2 including noise due to the radio wave from the transceiver 16 becomes higher than the allowable input level of the deck EQ3, the deck EQ3 saturates, and the noise due to the radio wave from the transceiver 16 is converted into a signal in the frequency band of the voice band. And is included in the deck EQ output 4. This deck EQ
The detection signal 22 is detected from the output 4 by the detector 21, and the DC potential of the detection signal 22 is previously detected by the level detection circuit 23.
Is compared with the upper limit level and the lower limit level which are set in the. When it is larger than the upper limit level or smaller than the lower limit level, the operation signal 24 is sent to the audio mute unit 9.
Is output. The audio mute unit 9 is activated by the operation signal 24, attenuates the electronic volume control unit output 8, and outputs the attenuated audio mute unit output 10. Then, the audio mute section output 10 is input to the speaker section 13 via the amplifier 11.

Further, in FIG.
The low-frequency noise detected at 5 is applied to the smoothing capacitor 2
6, the noise voltage is compared with the upper limit voltage and the lower limit voltage by the upper limit Zener diode 27 and the lower limit Zener diode 28, and the voltage detected by the transistors 29, 30, and 31 is used as an audio mute unit. 9 is controlled. Further, the upper limit Zener diode 27 and the lower limit Zener diode 28 are set so as not to operate on a normal signal as shown in FIG. 8A but to operate on an abnormal signal as shown in FIG. 8B. Other configurations and operations are the same as those of the conventional example shown in FIG .

Embodiment 2 FIG. FIG. 3 is a block diagram showing a cassette tape reproducing device as an audio device according to Embodiment 2 of the present invention. In this figure, the deck EQ output 4 becomes a low-pass filter output 42 of only a low frequency band by a low-pass filter 41,
The signals are output to a level detection circuit 43 as a low frequency component comparison unit and a phase conversion circuit 44 as a phase conversion unit. The level detection circuit 43 has the same configuration as the level detection circuit 23 in the first embodiment, and outputs an operation signal 45 when the DC potential of the low-pass filter output 42 is out of a preset potential range. I do. When the operation signal 45 is input, the phase conversion circuit 44 outputs the low-pass filter output 42
Is output to a synthesizing circuit 47 as a synthesizing unit. This combining circuit 47
In the above, the output 46 of the phase conversion circuit and the output 6 of the Dolby circuit are combined, and the low frequency components cancel each other. A composite circuit output 48 from which the low frequency component has been canceled is output. The synthesis circuit output 48 is input to the speaker unit 13 via the electronic volume control unit 7, the audio mute unit 9, and the amplifier 11.

FIG. 4 is a circuit diagram showing a low-pass filter, a phase conversion circuit, and a synthesis circuit according to the second embodiment. In this figure, a low-pass filter 41 is composed of an operational amplifier 49, a high-frequency cut capacitor 50, and attenuating resistors 51 and 52. Phase conversion circuit 44
Is composed of an inverting amplifier 53 and resistors 54 and 55. A power supply 56 for an inverting amplifier 53 is connected between the level detection circuit 43 and the phase conversion circuit 44 via a transistor 57 and resistors 58 and 59. The combining circuit 47 is composed of combining diodes 60 and 61. Also,
The attenuation amount is determined by the attenuation resistors 51 and 52, the cutoff frequency is determined by the high frequency cut capacitor 50, and the frequency components lower than this cutoff frequency are output as the low-pass filter output 42. The level detection circuit 43 compares the voltage of the low-pass filter output 42 with a predetermined value. When the voltage of the low-pass filter output 42 is higher than the predetermined value, the power supply transistor 57 is operated, and the power is supplied to the inverting amplifier 53. Supplied,
The phase of the low-pass filter output 42 is inverted and input to the synthesis circuit 47. Other configurations and operations are the same as those of the first embodiment shown in FIGS.

Embodiment 3 FIG. Further, in the first embodiment, the DC potential of the deck EQ output 4 is compared with the upper limit level or the lower limit level by the level detection circuit 23. However, as shown in FIG. , And converts the AC detector output 72 detected by the AC detector 71 into DC by the converter 73, and converts the converter output 74 output from the converter 73 into the DC signal level comparing unit and the AC By inputting the signal to the level detection circuit 23 as a signal level comparison unit, the level detection circuit 23 can compare the upper limit level and the lower limit level of the DC potential of the deck EQ output 4 and the potential of the AC component.

FIG. 6 is a circuit diagram showing an AC detector and a converter according to the third embodiment. In this figure, an AC detector 71 is composed of the capacitor 75 and the full wave integer diversion of diodes 76 and 77 for the alternating-current detection. The converter 73 includes resistors 78 and 79 for smoothing and capacitors 80 and 81 for smoothing. Signal detected by the alternating-current detection capacitor 75 is flowed full wave integer diode 76 and 77, is smoothed by the resistor 78 and 79 and a capacitor 80 and 81, is outputted as a DC voltage. Other configurations and operations are the same as those of the first embodiment shown in FIGS.

In the first embodiment, the magnitude of the potential of the DC component is compared with a predetermined value in the signal level comparing section. However, it is also possible to compare a value such as the amount of change in the potential with the predetermined value.

In each of the above embodiments, the cassette tape reproducing apparatus has been described.
It can also be used for audio equipment such as players and radio tuners.

In each of the above embodiments, the case where the radio wave of the transceiver is mixed as noise is shown, but it is also possible to use the case where other noise such as the noise generated from the plug of the car is mixed.

[0031]

As described above, according to the present invention, a signal level comparing section for outputting an operation signal when the signal level of a detected input signal deviates from a predetermined range, and an output from the signal level comparing section. An attenuator for attenuating the input signal after detection by the operation signal; and the input signal after detection attenuated by the attenuator is input to the speaker. When the signal level of the input signal after detection is high, damage to the speaker unit can be prevented.

Also, a low-frequency pass filter for extracting a frequency component lower than a predetermined frequency value from the detected input signal, a low-frequency component comparison unit for comparing the output of the low-frequency pass filter with a predetermined value, A phase converter for phase-converting the output of the low-pass filter based on the comparison result output from the component comparator; and a combining unit combining the output of the phase converter with the input signal after detection, and Since the low-frequency component of the signal is canceled, it is possible to prevent an unpleasant output from the loudspeaker unit which occurs when the signal level of the low-frequency component of the detected input signal is high.

Further, a DC signal level comparing section for comparing the signal level of the DC component of the input signal with a predetermined value and an adjusting section for adjusting the signal level of the input signal based on the comparison result output from the DC signal level comparing section are provided. The signal level of the input signal is adjusted by the adjusting section based on the signal level of the DC component of the input signal, and the adjusted input signal is input to the speaker section. Damage to the speaker due to the high signal level of the DC component of the signal can be prevented.

A DC signal level comparing section for comparing the signal level of the DC component of the input signal with a predetermined value and an AC signal level comparing section for comparing the signal level of the AC component of the input signal with a predetermined value are provided. An adjusting unit that adjusts the signal level of the input signal based on the comparison result output from the level comparing unit and the AC signal level comparing unit is provided. Since the input signal adjusted by the adjusting unit for adjusting the signal level is input to the speaker unit,
Damage to the speaker due to the high signal level of the DC component of the input signal or the signal level of the AC component of the input signal can be prevented.

Further, a detector for detecting an input signal output from a magnetic information reading head for reading magnetic information from a magnetic holder, and operates when a signal level of a detection signal output from the detector is larger than a predetermined value. A signal level comparing section for outputting a signal and an attenuating section for attenuating a detection signal by an operation signal output from the signal level comparing section are provided, and the detection signal attenuated by the attenuating section is input to a speaker section. Therefore, it is possible to prevent damage to the speaker unit when the signal level of the detection signal is high.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a cassette tape reproducing apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a circuit diagram showing a cassette tape reproducing device according to Embodiment 1 of the present invention.

FIG. 3 is a block diagram showing a cassette tape reproducing device according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram illustrating a low-pass filter, a phase conversion circuit, and a synthesis circuit according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing a cassette tape reproducing device according to Embodiment 3 of the present invention.

FIG. 6 is a circuit diagram illustrating an AC detector and a converter according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a conventional cassette tape reproducing device.

8A and 8B show the output of a deck equalizer amplifier in a conventional cassette tape reproducing apparatus. FIG. 8A is a waveform chart at a normal time, and FIG. 8B is a waveform chart at an input exceeding an allowable input level. .

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Head deck 3 Deck equalizer amplifier 9 Audio mute part 13 Speaker part 21 Detector 23 Level detection circuit 41 Low-pass filter 43 Level detection circuit 44 Phase conversion circuit 47 Synthesis circuit 71 AC detection circuit 73 Converter

Claims (5)

(57) [Claims] 1. A detection unit for detecting an input signal inputted from the input unit, the signal level comparing section for outputting an operation signal when the signal level of the detection signal output from the detection unit deviates a predetermined range, the operation An acoustic apparatus comprising: an attenuation unit that attenuates the detection signal by a signal; and a speaker unit to which an output of the attenuation unit is input. 2. A detection unit for detecting an input signal input from the input unit retrieves frequency components lower than a predetermined frequency value from the signal level of the detection signal output from the detection unit, a low-pass filter for outputting, A low-frequency component comparison unit that compares the output of the low-frequency pass filter with a predetermined value and outputs a comparison result; a phase conversion unit that changes the phase of the output of the low-frequency pass filter based on the comparison result; An acoustic device comprising: a combining unit that combines an output of a conversion unit with the detection signal; and a speaker unit to which an output of the combining unit is input. 3. A DC signal level comparing section for comparing a signal level of a DC component of an input signal inputted from an input section with a predetermined value, and outputting a comparison result, based on a comparison result output from the DC signal level comparing section. An audio device, comprising: an adjusting unit that adjusts a signal level of the input signal; and a speaker unit connected to the adjusting unit. 4. A DC signal level comparing section for comparing a signal level of a DC component of an input signal inputted from an input section with a first predetermined value, and outputting a comparison result. compared to the second predetermined value, comparing the AC signal level comparing section for outputting a result, the comparison result output comparison result and the AC signal level comparator or et al., which is output from the DC signal level comparator < An audio apparatus, comprising: an adjustment unit for adjusting the signal level of the input signal; and a speaker unit to which an output of the adjustment unit is input. 5. A magnetic information reading head unit for reading magnetic information from a magnetic information holding body holding magnetic information, a detecting unit for detecting an input signal output from the magnetic information reading head unit, and an output from the detecting unit. A signal level comparing section for comparing the signal level of the detected signal with a predetermined value and outputting a comparison result; an attenuating section for attenuating the detected signal based on the comparison result; A magnetic information reproducing apparatus comprising: