KR100206750B1 - Time-based error noise reducing system - Google Patents

Abstract

The present invention relates to a time-based error noise reduction device of V-Cal. In the related art, the switching unit is not smooth when selecting two signals by selecting two signals in a state where a phase difference exists between the A and B head signals during reproduction. In the audio output side, there is a problem of degrading the sound quality because it exists as an unwanted voice signal, that is, noise.

Accordingly, the present invention determines the time base error (TIME-BASE-ERROR), that is, the phase difference Δt between the two head signals based on the digital data which is the output of the digital FM demodulator, thereby controlling the output of the RAM, thereby controlling the time base error. In enabling noise reduction, the time base error [Delta] t can be effectively determined by using digital data, which is the output of the digital FM demodulator, in the playback of the high-fidelity audio of V-Cal.

Description

Time Base Error Noise Reduction Device

1 is a block diagram of a conventional HI-FI audio reproduction system.

FIG. 2 is a cross-sectional view of FIG. 1 showing a hi-fi audio head on a drum.

3A and 3B are waveform diagrams showing overlapping regions of an audio signal in FIG.

4 is a circuit diagram of a time base error noise reduction device of the present invention.

5a and b are digital pulse count demodulator waveform diagrams in FIG.

* Explanation of symbols for main parts of the drawings

1, 2: first and second preamplifiers 3, 4: first and second left channel band filter units

5, 6: 1st, 2nd right channel band filter unit 7-10: 1st-4th digital FM demodulator

11, 12: head switching switch 13, 14: first, second digital / analog converter

15-18: 1st-4th RAM 19: Head signal phase difference detector

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a high-fidelity audio reproduction system of V-Cal, and more particularly, to a time base error noise reduction device suitable for reducing time base error noise by effectively discriminating time base error (TIME-BASE-ERROR)? T. .

In the conventional V-Cal hi-fi audio reproduction system, as shown in FIG. 1, two heads AH and BH mounted on a drum and fine audio detected through the heads AH and BH are illustrated. First and second preamplifiers (1) and (2) for amplifying a high frequency signal, and audio RF signals amplified by the first preamplifier (1) by filtering a left channel (L-CH) having a carrier frequency of 1.3 MHz Audio frequency amplified by the first left / right channel band filter unit 3 (5) and the second preamplifier 2, respectively, separated by a signal and a right channel (R-CH) signal having a carrier frequency of 1.7 MHz. A second left / right channel band filter unit 2 for filtering the signal into a left channel (L-CH) signal having a carrier frequency of 1.3 MHz and a right channel (R-CH) signal having a carrier frequency of 1.7 MHz, respectively; 4), first to fourth digital FM demodulators 7-10 for demodulating the signal separated by the band filter unit 3-5, and A, B heads ( First and second head switching switches 11 and 12 for generating one continuous signal according to the head switching pulse HSP, and the first and second head switching switches 11; A first and second digital / analog converters 13 and 14 for converting a digital signal through an analog (12) into an analog signal to be input to the left channel (L-CH) and the right channel (R-CH). do.

Looking at the prior art configured as described above is as follows.

When the A and B heads AH and BH mounted on the drum detect the very fine audio high frequency signals recorded on the magnetic tape and provide them to the first and second preamplifiers 1 and 2, The second preamplifier 1 is amplified to several tens of dB.

The signal amplified by the first preamplifier 1 is band filtered by the first left and right channel band filter units 3 and 5.

Accordingly, the left channel signal L-CH having a carrier frequency of 1.3 MHz is separated through the first left channel band filter unit 3, and the left channel signal L-CH having a carrier frequency of 1.7 MHz is separated from the first right channel band filter unit 5. The right channel signal R-CH is separated.

Similarly, the second left and right channel band filter units 4 and 6 perform band filtering on the output signals of the second preamplifier 2, respectively. L-CH) (R-CH) is separated.

The separated signal is demodulated and output as a voice signal (BASE BAMD SIGNAL) from the first to fourth digital FM demodulators 7-10.

At this time, the head switching switches 11 and 12 select the output of the digital FM demodulator 7-10 by the head switching pulse HSP to the first and second digital / analog converters 13 and 14. If provided, the first and second analog / digital converters 13 and 14 convert the analog signal into an analog signal and output the analog signal.

However, this conventional V-Hi hi-fi reproducing system records the FM audio signal on a tape in a form of disconnection of a certain period through two heads as shown in FIG. The signal detected through the head is also alternately selected by the head switch in the state of being disconnected in time, thereby becoming one continuous signal. When the head switching switches 11 and 12 linking these two signals are closely examined, the signal is reproduced as shown in FIG. There is a phase difference between the time A and B head signals.

When the two signals are selected to extract one continuous signal in the state where the phase difference exists, the head switching switches 11 and 12 are not smooth, which is an unwanted voice signal, that is, noise as seen from the audio output side. There was a problem that is lowering.

The present invention can eliminate the time base error noise by controlling the output of the RAM by determining the time base error [Delta] t at the time of head switching in the digital FM demodulation system during Hi-Fi playback of V-Cal to solve such a conventional problem. Invented a time base error noise reduction device, which will be described with reference to the accompanying drawings.

4 is a block diagram of a time base error noise reduction device according to the present invention. As shown in FIG. 4, two heads AH BH mounted on a drum and the heads AH BH are detected. The first and second preamplifiers (1) and (2) for amplifying the fine signal, and the audio high frequency signals amplified by the first and second preamplifiers (1) and (2) have a carrier frequency of 1.3 MHz and First and second left channel band filter units 3 (4) and first and second right channel band filter units for separating the left channel signal L-CH and the right channel signal R-CH of 1.7 MHz. (5) (6), the first and second left channel band filter sections 3 and 4 and the first and second right channel band filter sections 5 and 6 separate the signals through the FM. Demodulating the output of the first-fourth digital FM demodulator (7-10) and the first-fourth digital FM demodulator (7-10) according to the head switching pulse (HSP) into one continuous signal. First and second head switching switches 11 and 12, and the first and second head switching First and second digital / analog converters 13 for converting the digital signals through the switch 11 and 12 into analog signals and inputting them to the left channel L-CH and the right channel R-CH. A V-Hi hi-fi audio reproduction system consisting of (14), wherein the outputs of the first to fourth digital FM demodulators (7-10) are stored respectively, and when a control signal is inputted, the first and second head switches. Head-switching pulse (HSP) by receiving the outputs of the first to fourth rams 15-18 and the first and second digital FM demodulators 7 and 8 to be input to the switches 11 and 12. The first to fourth rams 15-18 are controlled by the control output according to the present invention, and a head signal phase difference detector 19 for detecting the phase difference between the A and B heads AH and BH is added.

The operation and effect of the present invention configured as described above will be described with reference to the waveform diagram of the digital pulse count demodulator of FIG.

When the A and B heads AH and BH mounted on the drum detect the very fine audio high frequency signals recorded on the magnetic tape and provide them to the first and second preamplifiers 1 and 2, , The second preamplifier (1) (2) is amplified and output to several tens of dB level.

The high frequency audio signal amplified by the first preamplifier 1 is filtered by the first left and right channel band filter units 3 and 5, and the left channel signal L-CH having a carrier frequency of 1.3 MHz is filtered. The audio signal is amplified by the second preamplifier 2 and provided to the first and third digital FM demodulators 7 and 9 by separating the right channel signal R-CH having a carrier frequency of 1.7 MHz. Filtered by the second left and right channel band filter units 4 and 6, the left channel signal L-CH having a carrier frequency of 1.3 MHz and the right channel signal R-CH having a carrier frequency of 1.7 MHz are filtered. It is separated and provided to the second and fourth digital FM demodulators 8 and 10.

Then, the first-fourth digital FM demodulator 7-10 demodulates the input signal into a voice signal (BASE BAND SIGNAL).

At this time, the first-fourth digital FM demodulator 7-10, as shown in a of FIG. 5, has a baseband as the number of times the FM signal crosses the zero axis during a certain period of N. CLOCK. A pulse-counting method is used which indicates the magnitude of the signal level is large and small.

Accordingly, the outputs of the first to fourth digital FM demodulators 7-10 are digital data and are represented in the form of demodulation signals (1-5) as shown in b of FIG.

That is, if the output of the first digital FM demodulator 7 of the A head AH is in the form of a demodulation signal (1-5) as shown in b of FIG. 5, the second digital FM demodulator 7 of the B head BH ) Output in the same form with the difference of Δt (number × yen clock) in time.

When the head switching is performed at the head switching switches 11 and 12, the head signal phase difference detector 19 receives the head switch pulse HSP from the head switching phases based on the overlap period signal before and after the head switch. By obtaining the phase difference? T between the head signals and controlling the output of each of the first to fourth RAMs 11-14 using this? T as information, the signal after the head switching is eliminated by the phase difference, i.e., no time base error noise. Since the left channel L-CH and the right channel R-CH from the first and second digital / analog converters 13 and 14 are output, hi-fi audio reproduction output is obtained.

As described in detail above, the present invention reduces the time base error noise of the head switching unit by using the output of the digital FM demodulator, thereby improving the reproduction sound quality of hi-fi audio.

Claims (2)

In an audio playback apparatus of V-Cal, a preamplifier for amplifying a signal detected from the heads A and B mounted on a drum and separating the signals into left and right channels, and the signals separated into the left and right channels according to predetermined bands. A band filter unit for filtering, a digital FM demodulator for demodulating the signal filtered by the band filter unit, a RAM for storing the digital FM demodulated signal and outputting the signal to a head switching switch, and the digital FM demodulated signal and And a head signal phase difference detector for detecting a phase difference between the A and B heads by a head switching pulse and controlling the output of the RAM using the detected phase difference. The apparatus of claim 1, wherein the head signal phase difference detector receives a digital FM demodulation signal and a head switching pulse to detect a difference between overlapping sections of the A and B head signals.