JPH08249603A - Sound quality improving circuit of magnetic recording/ reproducing device - Google Patents

Abstract

PURPOSE: To reduce the distortion of a magnetic recording/reproducing signal and to improve sound quality by inserting a distortion generation circuit into the feedback loop of a reproduction equalizer amplifier in a magnetic recording/reproduction device. CONSTITUTION: A sound quality improving circuit consists of a reproduction equalizer amplifier 2 and a distortion generation circuit. The reproduction equalizer amplifier 2 consists of an operational amplifier E with a noninverting terminal 1 where a reproducing signal from a reproduction head enters and an inverting input terminal for inputting a feedback signal via the reproduction equalizer circuit E including a parallel circuit of a resistor R1 and a capacitor. A distortion generating circuit 4 is constituted of a series connection of an inductor L and a capacitor C2 and a parallel connection with a resistor R3 and at the same time is inserted and is installed between the inverting input terminal and the ground of the operational amplifier A, thus canceling out odd-harmonic distortion constituents included in the magnetic reproducing signal using odd-harmonic distortion constituents generated by the distortion generation circuit 4 and hence obtaining an audio signal output with less distortion and improving sound quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound quality improving circuit for a magnetic recording / reproducing apparatus.

[0002]

2. Description of the Related Art Conventionally, as an audio signal recording / reproducing apparatus,
A magnetic recording / reproducing apparatus using a magnetic reproducing head (coil with a core) and a magnetic reproducing medium such as a magnetic tape is generally used. FIG. 5 is a circuit diagram of an example of such a magnetic recording / reproducing apparatus. A reproduction output signal from a magnetic reproduction head (not shown) input to an input terminal 1 is amplified by a reproduction equalizer amplifier 2 to produce an audio output signal. Is output to the output terminal 3.

[0003]

However, in the above-mentioned conventional magnetic recording / reproducing apparatus, when the audio signal recorded on the magnetic tape is reproduced by the magnetic reproducing head, it is caused by the electromagnetic conversion by the magnetic tape and the reproducing head. Then, the odd-order distortion is generated in the reproduced signal reproduced from the magnetic tape. Distortion caused by such a magnetic tape and a reproducing head is generated by the hysteresis loop, as shown in FIG.
FIG. 7B shows the basic waveform of the reproduction signal shown in FIG.
The odd harmonics mainly consist of the third harmonic as shown in FIG. Therefore, the actual waveform of the reproduced signal reproduced by the reproducing head from the magnetic medium, that is, the magnetic tape is as shown in FIG.
There is a problem that the combined waveforms of (A) and (B) result in a waveform in which the head of the wave is crushed, as shown in FIG. 7C, and the sound quality deteriorates. FIG. 8 is a frequency spectrum diagram of the conventional magnetic recording / reproducing apparatus.
As an example, the spectra of the 3rd and 5th harmonics for a fundamental frequency of 330 Hz are shown. In view of the above problems, an object of the present invention is to provide a sound quality improving circuit of a magnetic recording / reproducing apparatus capable of improving distortion by reducing distortion (odd order distortion, total harmonic distortion) of a magnetic recording / reproducing signal. Especially.

[0004]

A sound quality improving circuit of a magnetic recording / reproducing apparatus according to the present invention is
A distortion generation circuit for generating odd-order distortion components of the feedback signal of the amplifier is inserted in the feedback loop of the reproduction equalizer amplifier. The reproduction equalizer amplifier has a non-inverting input terminal to which a reproduction signal from the reproduction head is input, and a first
And an inverting input terminal to which a feedback signal is input via a reproduction equalizer circuit including a parallel connection of a resistor and a first capacitor, and the distortion generating circuit includes an inductor and a second capacitor connected in series. And a second resistor connected in parallel, and inserted between the inverting input terminal of the operational amplifier and the ground.

The reproducing equalizer amplifier has a non-inverting input terminal to which a reproducing signal from the reproducing head is input, and a first
And an inverting input terminal to which a feedback signal is input via a reproduction equalizer circuit including a parallel connection of a resistor and a first capacitor, and the distortion generating circuit includes an inductor and a second capacitor connected in series. A parallel connection of a plurality of resistors and a series connection of switches, and the distortion generating circuit is inserted between the inverting input terminal of the operational amplifier and the ground. Further, the second resistor may be a variable resistor. Further, the values of the plurality of resistors are selected according to the type of magnetic tape.

[0006]

A distortion generating circuit for generating an odd-order distortion component of a feedback signal is inserted in a feedback loop of a reproduction equalizer amplifier, and an odd-order distortion component included in a magnetic reproduction signal is generated by the odd-order distortion component generated by this distortion generation circuit. By canceling the components, a voice output signal with less distortion can be obtained and the sound quality can be improved.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a sound quality improving circuit according to the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a first embodiment of the present invention. In FIG. 1, 1 is an input terminal, 2 is a reproduction equalizer amplifier, and 3 is an output terminal. The reproduction equalizer amplifier 2 includes an operational amplifier A having a non-inverting input terminal connected to an input terminal 1, and a parallel connection of a resistor R1 and a capacitor C1 connected to a feedback loop between the output terminal and the inverting input terminal of the amplifier A. The regenerative equalizer circuit E and the resistor R2 connected between the inverting input terminal of the amplifier A and the ground. The audio signal recorded on the magnetic tape (not shown) is reproduced by a magnetic reproducing head (not shown) and supplied to the input terminal 1, amplified by the reproduction equalizer amplifier 2 and supplied to the output terminal 3. At this time, the reproduced audio signal of the magnetic reproducing head input to the input terminal 1 is
It contains odd-order distortion (particularly third-order distortion) components that are generated due to electromagnetic conversion by the magnetic tape and the magnetic reproducing head. FIG. 3 (A) is the basic waveform of the reproduced audio signal, FIG. 3 (B)
Shows the actual waveform of the reproduced audio signal.

Therefore, in the present invention, the distortion generating circuit 4 is inserted in the feedback loop of the reproduction equalizer amplifier 2. That is,
The distortion generating circuit 4 is composed of a series connection of an inductor L and a capacitor C2 and a parallel connection of a resistor R3, one end of which is connected to the inverting input terminal of the operational amplifier A via the resistor R2,
The other end is grounded. In the above configuration, when the feedback signal of the reproduction equalizer amplifier 2 is supplied to the distortion generating circuit 4,
An odd-order distortion component of the feedback signal is generated in the inductor L. The waveform of, for example, the third-order distortion component of this odd-order distortion component is shown in FIG. The magnitude of the odd-order distortion component generated in the inductor L is the same as the magnitude of the odd-order distortion component included in the reproduction signal of the magnetic reproducing head supplied to the non-inverting input terminal of the operational amplifier A. Select the value of resistor R3. By doing so, the odd-order distortion component included in the reproduction signal of the magnetic reproducing head supplied to the non-inverting input terminal of the operational amplifier A is the same as the odd-order distortion component generated in the inductor L supplied to the inverting input terminal. Reverse phase, ie 180
Since the phases are out of phase with each other, they cancel each other out, and the above-mentioned odd-order distortion component is greatly reduced on the output side of the operational amplifier A and the output terminal 3 to improve the distortion, as shown in FIG. Thus, a voice output signal that is close to the basic waveform shown in FIG. 3A is obtained.

FIG. 4A shows a frequency distribution diagram of a reproduced audio signal before distortion improvement, and FIG. 4B shows a frequency distribution diagram of a reproduced audio signal after distortion improvement. As an example, distribution up to the seventh harmonic component. Indicates. FIG. 5 is a frequency spectrum diagram of the circuit of FIG.
The spectrum of the 2nd and 5th harmonic is shown. Comparing the amplitudes of the third-order harmonic components in FIG. 5 according to the present invention and FIG. 8 according to the conventional example, it is −38.83 dBV in FIG. 8 whereas −41.73 dBV is 2.9 dB in FIG.
It can be seen that the amplitude is reduced by V and the harmonic component is reduced. This is converted into the distortion factor as shown in FIG.
Since the third harmonic distortion of (1) corresponds to 1.6% and the third harmonic distortion of FIG. 5 corresponds to 1.1%, it means that the distortion rate improvement of 0.5% is obtained.

Since the amount of the odd-order distortion component contained in the reproduction signal of the magnetic reproducing head changes depending on the type of magnetic tape, the resistance R3 is made a variable resistance and the distortion generated at the inverting input terminal of the operational amplifier A is generated. The amount of odd-order distortion components generated in the inductor L of the circuit 4 is varied according to the magnetic tape, for example, in the case of 120us tape, the amount of odd-order distortion components is small, and in the case of 70us tape, the resistance R3 is varied so that the odd-order distortion components become Cancel. Further, by appropriately selecting the inductance of the inductor L and the capacitance of the capacitor C2, it is possible to provide appropriate frequency characteristics. In the above configuration, the circuit network for canceling the odd-order distortion component is inserted in the feedback loop of the reproduction equalizer amplifier, so that there is an advantage that the main transmission system of the audio signal is not adversely affected. However, as another embodiment different from the above configuration, the distortion generating circuit 4 may be inserted in series with the reproduction equalizer amplifier 2.

Next, FIG. 2 is a circuit diagram showing a second embodiment of the present invention. In FIG. 2, the distortion generation circuit 4 includes an inductor L and a capacitor C2 connected in series, and resistors R4 and R5.
And the parallel connection of the switches S in series. In this embodiment, the resistance values of the resistors R4 and R5 are selected according to the type of magnetic tape, and the inverting input terminal of the operational amplifier A is switched by switching the switch S according to the type of magnetic tape used. The amount of the odd-order distortion component generated in the inductor L of the distortion generating circuit 4 supplied to the above is canceled in accordance with the amount of the odd-order distortion component included in the reproduction signal of the magnetic reproducing head. The number of resistors that can be switched by the switch S may be two or more depending on the number of types of magnetic tape.

[0012]

According to the sound quality improving circuit of the present invention, the following effects can be obtained. (1) The sound quality can be improved by reducing the odd-order distortion of the audio signal. (2) The circuit scale is small. (3) The number of parts is small and the cost is low. (4) Parts are inexpensive.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a sound quality improving circuit of a magnetic recording / reproducing apparatus of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the sound quality improving circuit of the magnetic recording / reproducing apparatus of the present invention.

FIG. 3 is a signal waveform diagram of each part of the sound quality improvement circuit of the magnetic recording / reproducing apparatus of the present invention.

FIG. 4 is a frequency distribution diagram of reproduced audio signals.

5 is a frequency spectrum diagram of the circuit of FIG.

FIG. 6 is a circuit diagram showing an example of a conventional magnetic recording / reproducing apparatus.

7 is a waveform chart of each part of the circuit of FIG.

FIG. 8 is a frequency spectrum diagram of the circuit of FIG.

[Explanation of symbols]

 1 Input Terminal 2 Reproduction Equalizer Amplifier 3 Output Terminal 4 Distortion Generation Circuit A Operational Amplifier E Regeneration Equalizer Circuit

Claims (5)

[Claims] 1. A magnetic recording / reproducing apparatus, wherein a distortion generating circuit for generating an odd-order distortion component of a feedback signal of the reproducing equalizer amplifier is inserted in a feedback loop of the reproducing equalizer amplifier. circuit. 2. The sound quality improvement circuit according to claim 1,
The reproduction equalizer amplifier has a non-inverting input terminal to which a reproduction signal from the reproduction head is input and an inverting input terminal to which a feedback signal is input via a reproduction equalizer circuit including a parallel connection of a first resistor and a first capacitor. The distortion generating circuit is configured by connecting an inductor and a second capacitor in series and a second resistor in parallel, and is inserted between the inverting input terminal of the operational amplifier and ground. A sound quality improving circuit for a magnetic recording / reproducing apparatus characterized in that: 3. The sound quality improvement circuit according to claim 1, wherein
The reproduction equalizer amplifier has a non-inverting input terminal to which a reproduction signal from the reproduction head is input and an inverting input terminal to which a feedback signal is input via a reproduction equalizer circuit including a parallel connection of a first resistor and a first capacitor. The distortion generating circuit comprises a series connection of an inductor and a second capacitor, a parallel connection of a plurality of resistors and a series connection of switches, and the distortion generation circuit is A sound quality improving circuit for a magnetic recording / reproducing apparatus, which is inserted between an inverting input terminal of an operational amplifier and ground. 4. The sound quality improvement circuit according to claim 2,
A sound quality improvement circuit of a magnetic recording / reproducing apparatus in which the second resistance is a variable resistance. 5. The sound quality improvement circuit according to claim 3,
A plurality of resistance values are selected according to the type of magnetic tape.