JP2676555B2 - Analog delay circuit - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analog delay circuit, and more particularly to an analog delay circuit suitable for correcting a time difference due to a mounting position of each unit in a speaker system.

[Prior Art] In the three-way speaker system as shown in FIG. 5, since the baffle surfaces of the squawker 2, the tweeter 4, and the woofer 6 are the same, the positions of the respective diaphragms are as shown in FIG. They are different, and there is a time difference of ta between the squawker 2 and the woofer 6, and similarly, a time difference of tb occurs between the squawker 2 and the tweeter 4. Further, in order to supply the midrange sound signal to the squawker 2, as shown in FIG. 6, a high pass filter 8 and a low pass filter 10 are provided.
Although the audio signal passed through is supplied to the squawker 2, the filters 8 and 10 cause a delay of tc shown in FIG. Conventionally, as shown in FIG. 5, in order to match the time axis shift caused by the time difference and the delay due to the filter, that is, the voice signals are amplified in-phase from the squawker 2, tweeter 4 and woofer 6 simultaneously. Woofer 6
The digital delay circuits 14 and 14 are inserted after the low-pass filter 11 for extracting the low-frequency audio signal supplied to the tweeter and for the high-pass filter 12 for extracting the high-frequency audio signal supplied to the tweeter 4, respectively. It was
Reference numerals 16, 16 and 16 are amplifiers for amplifying audio signals supplied to the squawker 2, the tweeter 4, and the woofer 6, respectively.

[Problems to be Solved by the Invention] However, the digital delay circuits 14, 14 currently have a 16-bit configuration, the number of components is large, the configuration is complicated, and the theoretical S There was a problem that the / N ratio was only about 98 dB.

Also, in the case of digital delay, in order to separate the audio signal band from the sampling frequency band, D / A conversion and D
A filter that sharply cuts during A / A conversion is required. A high-order (multistage) filter is used for this filter. There is also a problem that the higher the order of the filter, the more easily the phase rotation and the ramp up of the delay signal occur, and the sound quality deteriorates.

It is an object of the present invention 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 for blocking or attenuating an input signal input over a period in which a control signal is supplied, and a leading edge of the input signal. And edge detection means for generating a detection signal and control signal generation means for generating the control signal in response to the detection signal for a predetermined period.

[Operation] According to the present invention, when the input signal is supplied, the leading edge is detected by the edge detection means, the detection signal is generated, and in response to this, the control signal generation means outputs the control signal for a predetermined period. 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 that of delaying the input signal for the predetermined period is obtained.

[Embodiment] FIG. 1 shows a delay circuit 18 according to the present invention for delaying a high frequency sound signal supplied to a tweeter 4 of a speaker system. It is provided between an analog high-pass filter 12 for extracting a signal and an amplifier 16 for amplifying the audio signal in the high frequency range.

The delay circuit 18 receives the output of the analog high-pass filter 12 as shown in FIG. 2 (a), and as shown in FIG. 2 (b), an edge detection circuit 20 for generating a signal whose leading edge is detected. have. This edge detection signal is
It 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 the attenuator 24 supplies the treble sound signal supplied from the analog high-pass filter 12 through the analog delay circuit 23 during the period in which the control signal is supplied as shown in FIG. Block or dampen as shown in d). An analog delay circuit
23 is provided by compensating for the delay caused when the control signal is generated by the edge detection circuit 20 and the control signal generation circuit 22, and the head part of the high frequency sound signal is set at the time of generation of the control signal. This is so that it is supplied to the attenuator 24.

For example, the time for cutting off or attenuating the head portion of the audio signal in the high frequency range can be set to 0.7 msec. Usually, in the case of a music signal, it has a duration of at least tens of milliseconds, so
Blocking or attenuating short music signals at best 1 /
Since it is about 100, it is inaudibly indistinguishable, has no influence, does not cause problems such as sound quality deterioration in practical use, and is equivalent to delaying a high-frequency audio signal by 0.7 msec.

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 sound signal from the analog filter 12 by the voltage control amplifier 25 and outputs the amplified output. Rectify by the rectifier circuit 26. The rectified output is smoothed by the time constant circuit 28 and supplied to the control circuit 30. This control circuit 30
The gain of the voltage controlled amplifier 25 is controlled based on the smoothed signal from the time constant circuit 28 so that the voltage controlled amplifier 25 always supplies a high-range signal of a constant level to the rectifier circuit 26. The reason why the treble range signal is automatically controlled in this way is to widen the range of the edge detection level.

The rectified output of the rectifier circuit 26 is supplied to the time constant circuit 32, smoothed, and then supplied to the comparison circuit 34. The rectified output of the rectifier circuit 26 is also directly supplied to the comparison circuit 34. Generally, a high-frequency range signal, especially a music signal, has a very short rise time, and is, for example, 0.2 to 0.3 msec.
That is, even if the leading edge portion rises, it cannot follow it quickly, and the level of the treble range signal is constant in the time constant circuit.
It becomes larger than the output of 32, and the comparison circuit 34 generates an output (edge detection signal) as shown in FIG.
Eventually, the output of the time constant circuit 32 also rises, the treble range 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 treble range signal can be detected.

The edge detection signal generated by the comparison circuit 34 of the edge detection circuit 20 is output to the fourth by the smoothing circuit 36 of the control signal generation circuit 22.
The waveform is smoothed as shown in FIG. The waveform shaping circuit 38 rises as shown in FIG. 4C when the smoothed signal becomes equal to or higher than the threshold level TH shown in FIG. 4B, and when the smoothed signal becomes equal to or lower than the threshold level TH, as shown in FIG. Generate a falling pulse signal.

This pulse signal is supplied to the pulse generation circuit 40 configured by, for example, a one-shot multivibrator. The pulse generation 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) for a period of, for example, 100 msec. This pulse signal is supplied to the pulse generation circuit 42 formed of, for example, a one-shot multivibrator. The pulse generation circuit 42 responds to the rising edge of the pulse signal from the pulse generation circuit 40 and generates a pulse signal for a period of, for example, 0.7 msec. This pulse signal is supplied to the attenuator 24 as a control signal. Therefore, the delay time can be adjusted by adjusting the pulse generation period of the pulse generation circuit 42. The pulse generating circuit 40 is provided so that when the high-frequency range signal is repeatedly supplied at short intervals, the high-frequency range signal is delayed only at the very beginning and is not delayed thereafter. That is, even if the comparison circuit 34 generates the edge detection signal and the waveform shaping circuit 38 generates the pulse signal while the pulse generation circuit 40 is generating the pulse signal, the pulse generation circuit 40 already outputs the pulse signal. Since the pulse signal is generated, the pulse signal does not rise newly, so the pulse generation circuit 42 does not generate the pulse signal, and the attenuator 24 passes the treble signal without attenuating or blocking it.

In the above embodiment, the case where the high range signal supplied to the tweeter is delayed has been described, but this delay circuit can also be used when delaying the low range signal supplied to the woofer. Further, in the above-described embodiment, the period in which the pulse generation circuit 40 generates the pulse signal is set to 100 msec, but the length of this period can be arbitrarily changed according to the situation.

EFFECTS OF THE INVENTION As described above, according to the present invention, the leading edge of the audio signal is detected, and in response to this, the audio signal is cut off or attenuated for a predetermined time from the beginning of the audio signal from the beginning. Therefore, it is equivalent to delaying the audio signal for a predetermined time from the beginning. Moreover, when making such a delay, since it is composed entirely of analog elements,
The S / N ratio does not deteriorate and time correction can be performed. By the way, in the above example, an S / N ratio of about 110 dB was obtained. Further, since the phase rotation and the rampage phenomenon of the delay due to the high-order filter as in the conventional digital delay circuit do not occur, the reproduced sound quality is not deteriorated. Moreover, the circuit configuration is simple and can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a delay circuit according to the present invention, FIG. 2 is a waveform diagram of each part of the circuit of FIG. 1, and FIG. 3 is a detailed block diagram of a main part of the delay circuit of FIG. 4, FIG. 4 is a waveform diagram of each part of the circuit of FIG. 3, 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.

Claims (1)

(57) [Claims] 1. An attenuator for blocking or attenuating an input signal input over a period in which a control signal is supplied, an edge detecting means for detecting a leading edge of the input signal and generating a detection signal, and the detection signal. An analog delay circuit comprising: a control signal generating means that responds to generate a control signal for a predetermined period.