JPH0345099A - Analog delay circuit - Google Patents

Abstract

PURPOSE:To obtain an analog delay circuit inexpensively by detecting a head edge of an audio signal and interrupting or attenuating the audio signal for a prescribed time from the head of the audio signal in response thereto. CONSTITUTION:A delay circuit 18 is provided with an analog high pass filter 12 extracting a high compass audio signal and an edge detection circuit 20 provided in pre-stage to an amplifier 16 amplifying the high frequency audio signal, receiving an output of the analog high pass filter 12 and generating a signal detecting its head edge. The edge detection signal is fed to a control signal generating circuit 22, which generates a control signal for a prescribed period. The control signal is given to an attenuator 24, which interrupts or attenuate the high compass audio signal supplied from the analog high pass filter 12 via the analog delay circuit 23 while the control signal is supplied. Thus, the circuit constitution is simplified, the S/N is not deteriorated and the time is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an analog delay circuit, and particularly to one suitable for use in correcting time differences due to position of each unit in a speaker system.

[Prior Art] In a three-way speaker system as shown in Fig. 5, the squawker 2, tweeter 4, and woofer 6 have the same baffle surface, so the positions of their respective diaphragms are as shown in the figure. There is a time difference ta between the squawker 2 and the woofer 6, and similarly there is a time difference tb between the squawker 2 and the tweeter 4. In addition, in order to supply the squawker 2 with a midrange audio signal, the audio signal that has passed through the bypass filter 8 and the low-pass filter 10 is supplied to the squawker 2 as shown in FIG.
This filter 8.10 produces a delay tc shown in FIG. In order to adjust the time axis shift caused by such time differences and delays caused by filters, conventionally, as shown in FIG. Digital delay circuits 14 and 14 are inserted after the low-pass filter 11 for extracting the low-frequency sound signal to be supplied to the woofer 6 and after the bypass filter 12 for extracting the high-frequency sound signal to be supplied to the tweeter 4, respectively. was being carried out. In addition, 16.16.16 is Squawka 2
, the tweeter 4, and the woofer 6, respectively.

[Invention or Problem 8] However, the digital delay circuit 14.14 is currently
The mainstream is a 6-bit configuration, which has a large number of components, is complex, and has a theoretical S/N ratio of 98d.
There was a problem that it was only about B grade.

Furthermore, in the case of digital delay, in order to separate the audio signal band and the sampling frequency band, a filter is required that cuts sharply at the time of A/D conversion and D/A conversion. This filter uses a high-order (multi-stage) filter. The higher the order of the filter, the more likely it is that phase rotation or delayed signal fluctuations will occur, resulting in a problem of deterioration in sound quality.

An object of the present invention is to provide an analog delay circuit that solves the above problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an attenuator that cuts off or attenuates an input signal input during a period in which a control signal is supplied, and a leading edge of the input signal. edge detection means for detecting and generating a detection signal;
and control signal generating means for generating the control signal over a predetermined period in response to the detection signal.

[Operation] According to the present invention, when an input signal is supplied, the leading edge is detected by the edge detection means, a detection signal is generated, and in response to this, the control signal generation means generates a control signal for a predetermined period of time. occurs, and the attenuator attenuates or blocks the input signal.

That is, the input signal is blocked or attenuated for a predetermined period from the beginning of the input signal, and an effect equivalent to delaying the input signal for a predetermined period can be obtained.

[Embodiment] FIG. 1 shows a delay circuit 18 according to the present invention implemented in order to delay a high-frequency sound signal supplied to a tweeter 4 of a speaker system. An analog bypass filter 12 for extracting a signal, and an amplifier 1 for amplifying this high-frequency audio signal.
It is provided between 6 and 6.

This delay circuit 18 receives the output of the analog bypass filter 12 as shown in FIG. 2(a), and receives the output as shown in FIG. 2(b).
As shown in FIG. 2, an edge detection circuit 20 is provided which generates a signal that detects the leading edge. This edge detection signal is supplied to the control signal generation circuit 22, and the control signal generation circuit 22 generates a control signal for a predetermined period as shown in FIG. 2(C). This control signal is supplied to the attenuator 24, and this attenuator 24 receives the high-frequency audio signal supplied from the analog bypass filter 12 via the analog delay circuit 23, while the control signal is being supplied.
It is blocked or attenuated as shown in Figure (d). The reason why the analog delay circuit 23 is provided is to compensate for the delay that occurs when the edge detection circuit 20 and the control signal generation circuit 22 generate the control signal, and to adjust the high-frequency sound at the time when the control signal is generated. This is to ensure that the leading portion of the signal is supplied to the attenuator 24.

For example, the time for blocking or attenuating the leading portion of a high-frequency audio signal can be set to 0.7 msec. Normally, music signals have a duration of several tens of seconds at the shortest, so what is cut off or attenuated is about 1/100th of the short music signal, so it cannot be discerned audibly. ,
There is no effect, no problems such as deterioration of sound quality occur in practice, and it is equivalent to delaying the high-frequency audio signal by 0.7 seconds.

FIG. 3 is a detailed block diagram of the edge detection circuit 20 and the control signal generation circuit 22. The edge detection circuit 20 amplifies the high-frequency audio signal from the analog filter 12 with the voltage control amplifier 25, and outputs the amplified output. It is rectified by a rectifier circuit 26. This rectified output is smoothed by a time constant circuit 28 and supplied to a control circuit 30. This control circuit 30 controls the gain of the voltage control amplifier based on the smoothing signal from the time constant circuit 28, so that a high frequency signal at a constant level is always supplied to the rectification circuit 26 from the voltage control amplifier 25. do it like this.

The reason why the high frequency signal is automatically gain controlled in this way is to widen the range of edge detection levels.

The rectified output of the rectifier circuit 26 is supplied to a time constant circuit 32, smoothed, and supplied to a comparison circuit 34. The comparator circuit 34 is also directly supplied with the rectified output of the rectifier circuit 26 . Generally, high-frequency signals, especially music signals, have a very short rise time, for example, 0.2 to 0.
3 ms, the output of the time constant circuit 32 is, even if the high frequency signal rises, that is, even if the leading edge part rises, the output of the time constant circuit 32 is
Unable to quickly follow this, the level of the high frequency signal becomes higher than the output of the time constant circuit 32, and as shown in FIG. 4(a), the comparison circuit 34 generates an output (edge detection signal). do. Eventually, the output of the time constant circuit 32 also increases, the high frequency signal and the output of the time constant circuit 32 become equal, and the output of the comparison circuit 34 disappears. Therefore, the leading edge of the high frequency signal can be detected.

The edge detection signal generated by the comparison circuit 34 of the edge detection circuit 20 is smoothed by the smoothing circuit 36 of the control signal generation circuit 22 as shown in FIG. 4(b), and is supplied to the waveform shaping circuit 38. This waveform shaping circuit 38 is shown in FIG.
) A pulse signal is generated that rises when the smoothed signal reaches the threshold level 78 or higher as shown in FIG.

This pulse signal is supplied to a pulse generation circuit 40 composed of, for example, a one-shot multivibrator. This pulse generating circuit 40 responds to the rise of the pulse signal from the waveform shaping circuit 38 and generates a pulse signal as shown in FIG. 4(d) over a period of, for example, 100+s seconds. This pulse signal is supplied to a pulse generation circuit 42 configured as, for example, a one-shot multivibrator. The pulse generating circuit 42 generates a pulse signal over a period of, for example, 0.7+w seconds in response to the rise of the pulse signal from the pulse generating circuit 40. This pulse signal is supplied to the attenuator 24 as a control signal. Therefore, by adjusting the pulse generation period of the pulse generation circuit 42, the delay time can be adjusted. In addition,
The reason why the pulse generating circuit 40 is provided is that when high-frequency signals are repeatedly supplied at short intervals, only the first signal is delayed, and the subsequent signals are not delayed. That is, even if the comparator circuit 34 generates an edge detection signal and the waveform shaping circuit 38 generates a pulse signal while the pulse generation circuit 40 is generating a pulse signal, the pulse generation circuit 40 has already generated a pulse signal. Since the pulse signal is generated, no new pulse signal will rise, so the pulse generation circuit 42 does not generate a pulse signal, and the attenuator 24 allows the high frequency signal to pass through without attenuating or blocking it.

In the above embodiment, a case has been described in which a high-frequency range signal supplied to a tweeter is delayed, but this delay circuit can also be used when a low-frequency range signal supplied to a woofer is delayed. Further, in the above embodiment, the period during which the pulse generating circuit 40 generates the pulse signal is set to 10 h seconds, but the length of this period can be arbitrarily changed depending on the situation.

[Effects of the Invention] As described above, according to the present invention, the leading edge of an audio signal is detected, and in response to this, the audio signal is blocked or attenuated for a predetermined period of time from the beginning of the audio signal. Therefore, this is equivalent to delaying the audio signal for a predetermined period of time from the beginning. Moreover, when creating such a delay, since it is composed entirely of analog elements, the S
/N ratio does not deteriorate, and time correction can be made. By the way, in the above example, the S
/N ratio was obtained. In addition, since phase rotation and delay fluctuations caused by high-order filters that occur in conventional digital delay circuits do not occur, there is no deterioration in reproduced sound quality. Furthermore, the circuit configuration is simple and can be manufactured at low cost.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the delay circuit according to the present invention, FIG. 2 is a waveform diagram of each part of the circuit of FIG. 1, and FIG.
A detailed block diagram of the main parts of the delay circuit shown in the figure.
FIG. 5 is a waveform diagram of each part of the circuit shown in the figure, FIG. 5 is a layout diagram of a speaker system, and FIG. 6 is a block diagram of a conventional speaker system. 20... Edge detection circuit, 22... Control signal generation circuit, 24... Attenuator. Figure 1 - M2 Figure 3 Figure 2 Figure 2 31'14

Claims (1)

[Claims] (1) an attenuator that blocks or attenuates the input signal input during the period in which the control signal is supplied;
An analog delay circuit comprising edge detection means for detecting a leading edge of the input signal and generating a detection signal, and control signal generation means for generating the control signal over a predetermined period in response to the detection signal.