JPH09246899A - Circuit eliminating noise giving disturbance onto audio frequency of audible frequency amplifier due to external high frequency and/or internal high frequency signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure reproduction of a clear sound by connecting a simple filter to an externally connected part including audio frequency amplifier input output terminals and AC power supply directly or externally. SOLUTION: A filter 3 to eliminate the entire frequency band of a disturbing high frequency signal RF is connected electrically to a radio transmitter-receiver or an electronic device 1 such as an audio equipment represented only by an audible frequency amplifier 2 for audio signal conversion. For example, the filter 3 consisting of a capacitor C and a choke coil L is directly connected to an amplifier 2 on a common chassis of the small sized electronic device 1. Thus, external or internally generated disturbing high frequency RF masking an audible audio frequency is excluded, that is, filtered over the entire audio frequency to secure the clearness of the audible tone AF to the utmost. Furthermore, a distortion component included in the audible tone that cannot measure by an audible frequency measurement device is also eliminated and a balanced tone with high clearness is obtained without a complicated operation required for a negative feedback amplifier.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conventionally known radio / broadcast frequency transmitter / receiver, magnetic tape / CD player,
It is applied to audio amplifiers of electronic devices including audio equipment such as tuners, and the interference noise is caused by an electronic circuit built in the electronic device as an internal source or free space through input / output lines of the electronic device. More specifically, the present invention relates to an arrangement of a wave breaker that substantially eliminates the cause of turbidity that is caused by incoming high-frequency disturbances and harmonics and that gives a audible disturbance to the audio frequency output from an audio amplifier.

[0002]

2. Description of the Related Art Generally, the purest waveform of sound is represented by a sinusoidal voltage signal, but a newly generated unnecessary component, that is, a signal containing harmonic distortion is transmitted for a while. This unnecessary component pollutes the original beautiful sound, that is, deteriorates the sound quality due to the presence of an element whose input and output of the electronic device are completely unproportional. In particular, it is known that the odd harmonics of the original signal wave become anharmonic sounds, and when there are a lot of them, the sounds become very muddy. Therefore, the harmonic distortion refers to an unnecessary component generated in one signal, while the intermodulation distortion interferes with each other when a plurality of signals having different frequencies are simultaneously input to the electronic device and has a proportional relationship with the output. Disintegrate to produce a distorted waveform.

By the way, an actual music waveform is composed of a combination of various frequency signals, and when input to the electronic device, it causes intermodulation distortion as described above, and contains many complicated unnecessary components. Therefore, the sound quality is significantly deteriorated.

The above-mentioned noise is caused even if the volume adjustment is minimized.
There are two noises, one coming from an amplifier at the end of the electronic device and one that grows as the volume control is maximized, usually at audio frequencies (20Hz to 20KHz).
White noise is the most perceptible to the ears over the entire area, and is a built-in circuit component in the electronic device.
A transistor is a noise source. The pulsating noise having a sharp waveform is generated by the power supply rectifier and the spark discharge / ignition circuit.

Therefore, a high-frequency interfering wave containing a harmonic component of the audio frequency is output together with the audio frequency in the path from the electronic circuit built in the electronic device to the speaker output line via the audio frequency amplifier. In addition, such an interfering noise is generated depending on the output level of the electronic device, for example, a wireless transmitter / receiver for a telephone or an audio device for home.
Its size also varies from region to region.

On the other hand, an interfering high-frequency noise radio wave (propagation noise) coming from the outside world may pass or propagate through the introduction input line and the derivation output line of the electronic device. For example, by using an aerial power line corona or general radio wave interference (high frequency noise) as a source, it is directly coupled to the input / output lines of the electronic device, enters the front stage of the amplifier of the built-in electronic circuit, interferes, and causes radio interference. The transparency of the sound is spoiled.

Therefore, in order to prevent the propagation noise from leaking out a high-frequency interfering wave which is a noise source inside the electronic device, noise reduction means, for example, for each application,
Measures such as providing a frequency band leaker (bandpass / noise filter) for each output capacity are taken.

Therefore, the propagation noise is a high-frequency interference wave caused by general electric equipment such as digital processing equipment, vacuum cleaners, microwave ovens, mobile phones, etc. as a noise source. In order to prevent these from leaking to the outside, As a noise reduction means for an electric device, although measures such as provision of a capacitor and a filter are taken, it is hard to say that the audible sound output from the audio device is completely harmless.

Since noise is generated from a self-contained electronic circuit itself, such as a laser beam printer, in the disturbance given by the externally transmitted high frequency, for example, a house or an electromagnetic shield of a case is used to transmit the noise to the outside. This prevents high frequency leaks. Even when steep pulse noise generated in the self-circuit may cause a malfunction in the IC circuit, it is general to locally shield the noise generation source.

[0010]

However, in any of the measures taken for the conduction noise radiated from the electronic device itself and the propagation noise existing in free space, the frequency and level of the noise source vary. However, the unpleasant sound and the turbid sound cannot be completely removed from the reproduced sound of the audible frequency, and the spread of the sound frequency characteristic and the speed / rise of the sound are significantly hindered.

In the audio field, it is a hobby world that cannot be theoretically solved in the past, and it is believed that the disturbance of the audible audio frequency is caused by the high frequency and the harmonic of the audio frequency. However, because it was not accepted, for a serious music maniac, it has a delicate god diameter that pursues a clear sound until it gets tired, and on top of that, against the noise that can not be captured because there is no measuring instrument itself He has acquired a sharp and sensitive hearing ability.

FIG. 1 and FIG. 2 show the input limit and dynamic range (variable voice signal or variation amount of sound) of an amplifier incorporated in the electronic device such as a radio device or an audio device. in the present embodiment represents a graph illustrating the relationship between approximately 90db) and interference frequency, Figure 1 is disturbing high frequency RF is considerably larger than the potential noise level NL _a of the amplifier, FIG. 2 is relatively disturbance frequency The case where is small is illustrated respectively.

In both of the figures, the audio signal wave AF is masked by the interference high frequency RF. Therefore, the clean range (clarity of sound) CR of the audio signal wave AF becomes wider or narrower than the output characteristic A of the audio amplifier depending on the degree of the disturbance.

Therefore, the present invention eliminates or leaks the internally generated or externally disturbing high frequency RF in which the audible voice frequency is masked, that is, leaks the wave over the entire voice frequency to make the audible sound AF.
The objective is to ensure the transparency of

[0015]

In order to achieve the above-mentioned object, the circuit arrangement for canceling the noise which disturbs the audio frequency of the audio amplifier due to the internally generated and / or external high frequency of the present invention is a signal in the audio frequency band. Receive and / or play
Provide a wave breaker that eliminates only the high frequency noise component that obscures the clarity of audible sound at the external input part including the amplifier input and / or output terminal of the electronic device that amplifies and converts to audio output and the AC power line. Is characterized by.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments will be described below with reference to the drawings. FIG. 3 and FIG. 4 show different embodiments, and an electronic device 1 such as a wireless transmitter / receiver or an audio device, which is represented by only an audio amplifier 2 for converting an audio signal.
On the other hand, a wave breaker 3 for electrically eliminating the entire frequency band of the interference high frequency RF is electrically connected.

FIG. 3 shows an example in which a leakage wave device 3 including a capacitor C and a choke coil L is directly attached to an amplifier 2 on a common chassis of a small electronic device 1. t ₁ and t ₂ are input terminals of the wave breaker.

Next, FIG. 4 shows an electronic device 1 such as a large home stereo represented by an amplifier, which has an input terminal t ₅ ,
For an independent output amplifier 2 with t ₆ , input terminal t
_The wave breaker 3 including ₁ and t ₂ and output terminals t ₃ and t ₄ is externally attached.

Although the audio amplifier is targeted in the above-mentioned embodiment, an AC power source is also attached, and therefore, the external connection portion of the amplifier and the power source is also targeted for connecting the noise canceller. Further, in the case of direct mounting on a printed circuit board, a wave breaker may be connected to the audio frequency amplifier, the AC line, a portion corresponding to the input or output terminal thereof, and the external connection portion.

The capacitances of the capacitor C and the choke coil L as the obstruction coil, which constitute the above-mentioned wave breaker, in the case of a CD player as an example, the noise that interferes with the audible frequency is the input analog signal. A digital pulse frequency of the order of several tens of KHz and its harmonics in the process of quantization may be selected. Further, in the LP player, the noise frequency mixed at the same time when the sound groove is cut on the disc, the tracing noise of the sound groove at the time of reproduction, and C of the wave breaker for the harmonics thereof,
The L value may be selected.

The values of L and C are audio amplifier,
When connecting as a wave breaker to the input terminal side of the external connection portion including the AC power source, L is preferably 1 mH and C is 100.
0 pF is suitable. . When connecting to an output terminal or the like, L is preferably 1 to 50 μH and 20 μH, and C is suitably 100 to 500 pF.

[0022]

Since the present invention is constructed as described above, it has the following effects. Interference noise source that muffles audible sound caused by internal or external high frequency that interferes with the audible sound frequency of electronic devices such as communication equipment and audio equipment, including audio amplifiers. Focusing on the frequency of, a simple filter can be directly or externally attached to the external connection portion including the audio amplifier input / output terminals and the AC power source, and thus clear sound can be secured.

Even the distortion contained in the audible sound that cannot be captured by the audio frequency measuring device is erased, and the complicated operation caused by the negative feedback amplifier is wiped out to obtain a well-balanced and transparent sound. It has become possible. The metallic sound of the audio output of the CD player was weakened to give a rounded sound, and the cutting noise of the analog disk, the playback tracing noise, and these high-frequency noises could be completely eliminated.

Further, by eliminating the high frequency interference at the input / output terminal corresponding part of the audio frequency amplifier and the external connection part including the AC power supply line, the immunity (immunity) in audibility to the audio frequency is ensured. Therefore, it is possible to suppress the occurrence of harmonic interference including a high frequency component through the speaker output line and the wiring cable.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a high level interference high frequency and a dynamic range with respect to an input of an audio amplifier.

FIG. 2 is a graph showing a relationship between a small level of interference high frequency and a dynamic range with respect to an input of an audio amplifier.

FIG. 3 is a direct connection wiring diagram of a wave breaker to an electronic device representing an audio amplifier.

FIG. 4 is an external connection diagram of a wave breaker to an electronic device representing an audio amplifier.

[Explanation of symbols]

 1 Electronic Device 2 Audio Amplifier 3 Leaker

Claims (1)

[Claims] 1. A portion corresponding to an audio frequency amplifier input and / or output terminal of an electronic device for receiving and / or reproducing / amplifying a signal in an audio frequency band and converting it into a sound output, and / or an AC.
Noise that interferes with the audio frequency of an audio amplifier due to internally generated and / or external high frequencies, characterized in that a leaker that removes only high-frequency noise components that obscure the clarity of sound is provided at the external connection part including the power supply line. Circuit arrangement to erase.