KR940003920Y1 - Click noise preventing apparatus of digital audio device - Google Patents

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Description

Glitch Noise Reduction Devices for Digital Sound Equipment

1 is a circuit diagram of a glitch noise preventing device of the digital sound device of the present invention.

2 is a signal waveform diagram in each part of the circuit for explaining the operation of the present invention.

3 is a block diagram of a general digital audio device.

4 is a circuit diagram of a conventional resample hold device.

* Explanation of symbols for main parts of the drawings

10: first resample and hold means 11: buffer amplifier

12 analog switch 13 operational amplifier

14 second resample and hold means 15 subtraction means

16: analog switch 17: operational amplifier

18: differential amplifier

The present invention digitally converts an audio signal to a recording medium, and reproduces the digital audio signal recorded on the recording medium as an analog signal, and then outputs the analog signal after converting the digital signal into an analog signal. The present invention relates to a glitch noise preventing device of a digital sound device that removes glitch noise generated when sampling.

First, referring to the configuration of a general digital audio device, as shown in FIG. 3, a recording unit (a) for digitally converting an analog audio signal to be recorded on a recording medium, and reproducing an analog signal by reproducing the signal recorded on the recording medium. And a reproducing section (b) for converting and outputting the signal into a reproducing section, the recording section (a) shows a sample holding section (1) for sampling and holding an input analog audio signal, and the sampled and held analog signal. An analog digital converter 2 for converting to a digital signal, a recording digital signal processor 3 for signal processing the digitally converted audio signal into a recording format, and amplifying the signal-processed digital audio signal to a recording medium 5 And a recording amplifier (4) for recording in the recording medium. The configuration of the reproducing section (b) reproduces a digital audio signal from the recording medium (5). A reproducing amplifier 6, a reproducing digital signal processor 7 for signal processing the reproduced digital audio signal in a reproducing format, a digital analog converter 8 for converting the reproduced digital signal into an analog signal; And a resample and hold section 9 for resampling and holding the analog audio signal to produce and output the original analog audio waveform.

Referring to the operation of the digital sound device having the above configuration, the analog audio signal to be recorded is sampled and held in the sample holding unit 1 and input to the digital analog converter 2, and the digital analog converter 2 is sampled and held. The audio signal is digitally converted to a predetermined sampling frequency and supplied to the digital signal processor 3, and the digital signal processor 3 processes the input digital audio signal according to a recording format and amplifies it through the recording amplifier 4. After that, recording is performed on the recording medium 5.

In this way, the signal recorded in the recording medium 5 in the recording section a is reproduced in the playback section b as follows.

That is, the digital audio signal reproduced from the recording medium 5 to the reproduction amplifier 6 is subjected to the digital signal processing appropriate for the reproduction format in the reproduction digital signal processor 7, and then converts the digital audio signal into the digital analog converter 8. The digital analog converter 8 converts the input digital audio signal into an analog signal according to a sampling frequency, and supplies it to the resample and hold unit 9.

Since the analog signal output from the digital analog converter 8 has a quantitative value for each sampling period, it is output as a waveform as shown in (a) of FIG. 2, and makes the output waveform a smooth analog signal. In order to input to the resample and hold section 9, the resample and hold section 9 performs resampling and hold processing of the input signal, and as a result, outputs the low pass filtered (integrated) analog audio signal with a sampling period. You will.

The conventional circuit configuration of such a resample and hold section 9 is shown in FIG.

As shown in FIG. 4, the conventional resample and hold section 9 includes a buffer amplifier 11 for buffering and amplifying an audio signal input from the digital analog converter 8, and an output from the buffer amplifier 11; An analog switch 12 for switching the signal to a sampling signal SF period, an operational amplifier 13 for holding a signal sampled and input from the analog switch 12, and a signal together with the operational amplifier 13 It consists of a capacitor (C1) and a resistor (R2) forming an integrator for the hold, where R1 represents a resistor, T0 represents a switch control stage, IN represents an input stage, and OUT represents an output stage.

The resampling and holding operation of the analog signal by the conventional resampling and holding unit 9 configured as described above is performed as follows.

When the output signal of the digital analog converter 8 is input to the input terminal IN, the buffer amplifier 11 buffers the input signal and inputs it to the analog switch 12 through the resistor R1.

The analog switch 12 receives the sampling signal SF of the timing and frequency as shown in (b) of FIG. 2 into the control terminal T0 and calculates the input signal during the period in which the sampling signal SF is high. It is supplied to the input terminal (-) of the amplifier 13, and the input signal is bypassed to the ground terminal during the low-in period.

Accordingly, an input signal is sampled and input to the input terminal (−) of the operational amplifier 13 at the period of the sampling signal SF, and the input signal charges the capacitor C1, and the charged signal of the operational amplifier 13 An analog audio signal held by the output terminal high impedance and sampled and held as shown in (c) of FIG. 2 is output to the output terminal OUT.

This operation is continued and the waveform as shown in (a) of FIG. 2 is smoothly shaped and output as shown in (c). When the resampling and hold operations are executed, the analog switch 12 performs the sampling signal SF. Glitch noise, as shown in (c) of FIG. 2, is generated at the rising edge fling edge of the sampling signal SF, and the glitch noise is reflected in the resampled and held output signal OUT. As a result, there is a problem that the sound quality of the reproduced audio signal is deteriorated.

Even when the input terminal IN of such a phenomenon is no signal, the sampling signal SF actually input to the control terminal T0 may be weighted due to the leakage of the capacitor C1 by the capacitance of the analog switch 12. It may also occur in the sample and hold section 1.

That is, the sample and hold section 1 also has the same configuration as that of FIG. 4 and samples and holds the input analog audio signal (holding the sampled value of the analog signal for the time required for the analog digital converter 2 to convert it). To do so). Waveforms during sampling are not affected by undesired voltages, but the hold value can be affected by the glitch noise that occurs when moving from the sample state to the hold state, and this effect is recorded on the recording medium 5. The quality of the audio signal is reduced, and the sound quality of the reproduced audio signal is also deteriorated.

The present invention implements a second resample and hold for a no-signal input at the same timing as the first resample and hold, and solves the conventional problem as described above, and occurs at the first resample and hold. Prevents glitches in digital sound equipment by subtracting the glitches from the glitches generated during the second resample and hold, resulting in a clean waveform audio signal with glitches removed. It is an object to provide a device.

1 is a view showing a circuit configuration of the present invention for achieving the above object.

As shown in FIG. 1, the glitch noise preventing device of the digital sound device according to the present invention comprises: a first resample and hold means 10 for sample and hold an input analog audio signal at a predetermined sampling period; Glitch noise of the same waveform and timing as the glitch noise of the first resample and hold means 10 is sampled and held at the same sampling period as the first resample and hold means 10 in the no signal input state. A second resample and hold means 14 output from the second resample and hold means 14 and an audio signal including glitch noise output from the first resample and hold means 10. And subtracting means 15 for subtracting the glitch noise and outputting the audio signal from which the glitch noise has been removed.

The first resample and hold means 10 includes a buffer amplifier 11 for buffering and amplifying the input audio signal, and an analog switch for switching the signal output from the buffer amplifier 11 at a sampling signal SF period. A switch 12, an operational amplifier 13 for holding a signal sampled from the analog switch 12, and a capacitor C1 and a resistor which together with the operational amplifier 13 form an integrator for signal holding; And a second resample and hold means (14) comprising: an analog switch (16) switched at a sampling signal (SF) cycle in a no signal input state, and no signal input to the analog switch (16); Integrator for holding a glitch noise signal together with a resistor (R3) for applying a signal, an operational amplifier (17) for holding a glitch noise signal sampled from the analog switch (16), and the operational amplifier (17). And a subtracting means (15), wherein the subtracting means (15) comprises an audio signal including glitch noise output from the first resample and hold means (10) and the second resample and hold. A differential amplifier 18 for calculating a glitch noise signal output from the means 14 to remove glitch noise components, and inputting the output signal of the first resample and hold means 10 to the differential amplifier 18 The main portion comprises resistors R6 and R7 and resistors R5 and R8 for inputting the output signal of the second resample and hold means 14 to the differential amplifier 18. In FIG. A symbol R1 is a resistor, T0, T1 is a control terminal of the analog switches 12 and 16, IN is an input terminal, OUT is an output terminal, a is an unsignal input terminal, and b is an output terminal.

The glitch noise canceling operation by the glitch noise preventing device of the digital sound device of the present invention configured as described above will be described with reference to the circuit configuration of FIG. 1 and the waveform diagram of FIG.

When the output signal of the digital analog converter 8 in FIG. 3 is input to the input terminal IN, the buffer amplifier 11 buffers the input signal to the analog switch 12 through the resistor R1. Will be entered.

The analog switch 12 receives the sampling signal SF of the timing and frequency as shown in (b) of FIG. 2 into the control terminal T0 and calculates the input signal during the period in which the sampling signal SF is high. It is supplied to the input terminal (-) of the amplifier 13, and the input signal is bypassed to the ground terminal during the low-in period.

Accordingly, an input signal is sampled and input to the input terminal (−) of the operational amplifier 13 at the period of the sampling signal SF, and the input signal charges the capacitor C1, and the charged signal of the operational amplifier 13 As a result, the first resample and hold means 10 outputs the sampled and held analog audio signal to the output terminal as shown in FIG.

This operation is continued and the waveform as shown in (a) of FIG. 2 is smoothly shaped and output as shown in (c). When the resampling and hold operations are performed, the analog switch 12 performs the sampling signal SF. Glitch noise as shown in (c) of FIG. 2 is generated at the rising edge and the pulling edge of the sampling signal SF, and the glitch noise is resampled and held at the rising edge of the sampling signal SF. It is reflected on the output signal and output.

That is, the signal output from the first resample and hold means 10 includes glitch noise as shown in (c) of FIG. 2, and this signal is a resistor (R6) (R7) of the subtraction means 15. It is input to the non-inverting input terminal (+) of the differential amplifier 18 via the channel.

Meanwhile, the second resample and hold means 14 are operated at the same timing as the sample and hold timing of the first resample and hold means 10 to generate glitch noise.

That is, the input terminal a of the analog switch 16 is grounded through the resistor R3 to be in a no-signal input state, and the analog switch 12 samples the timing and frequency as shown in FIG. The signal SF is input to the control terminal T1, and the signal applied by the resistor R3 is supplied to the input terminal (−) of the operational amplifier 17 during the period in which the sampling signal SF is high, and low. During in period, the input signal is bypassed to ground.

Accordingly, the glitch noise signal input in the period of the sampling signal SF is sampled and input to the input terminal (−) of the operational amplifier 17, the input signal charges the capacitor C1, and the charged signal is an operational amplifier ( The second resample and hold means 14 output the sampled and held glitch noise signal to the output terminal as shown in (d) of FIG.

This operation is continued to output the glitch noise waveform at the same timing as the audio signal including the glitch noise as shown in (c) of FIG. 2 as shown in (d). In this way, the second resample and hold means 14 The output signal is input to the inverting input terminal (−) of the differential amplifier 18 via the resistors R5 and R8 of the subtraction means 15.

Accordingly, the differential amplifier 18 differentially amplifies the signal of FIG. 2 (d) input to the inverting input terminal (−) from the signal of FIG. 2 (c) input to the non-inverting input terminal (+). Since the result of the differential amplification corresponds to the subtraction processing of the two signals, the output OUT signal of the subtracting means 15 eventually removes the glitch noise component from the audio signal of the waveform as shown in FIG. It is output as a clean waveform audio signal.

The circuit configuration and operation as described above are similarly applied to the sample and hold unit 1 provided in the recording unit a in FIG. 3 to remove the glitch noise of the recorded audio signal. To analog digital converters (2).

As described above, according to the present invention, since the glitch noise generated at the sample and hold of the digital sound device can be eliminated, the audio signal recorded on the recording medium in the digital sound device or the audio signal reproduced on the recording medium. It is possible to increase the sound quality of, and to implement a high-fidelity digital sound device is effective.

Claims (1)

A first resample and hold means 10 for sample and hold an input analog audio signal at a predetermined sampling period, and a no-signal input is sampled at the same sampling period as the first resample and hold means 10 in a no-signal input state. A second resample and hold means 14 for end-and-hold to output glitch noise having the same waveform and timing as the glitch noise of the first resample and hold means 10, and the first resample and hold means 10; And subtracting means 15 for outputting the audio signal from which the glitch noise is removed by subtracting the glitch noise output from the second resample and hold means 14 from the audio signal including the glitch noise output from Characterized by glitch noise suppression in digital sound equipment.