JPS5814613A - Expanding circuit of signal level - Google Patents

Abstract

PURPOSE:To increase the dynamic range of a music source, by setting a noninversion type saturated amplifying circuit consisting of an operational amplifer, the resistances and Zener diodes at the input side of a level detecting circuit of an expanding circuit. CONSTITUTION:A noninversion type saturated amplifying circuit comprising an operational amplifier 8, the resistances 9 and 10, and the Zener diodes 11 and 12 is set at the input side of a level detecting circuit 3 of an expanding circuit. This saturated amplifying circuit gives a linear amplification to an input signal having its output voltage set lower than the Zener voltage of the diodes 11 and 12. When the output voltage reaches the Zener voltage, the level of the output voltage is constant although the level of the input signal increases. When the input signal level increases to exceed the Zener voltage, a linear amplifying action is carried out againg. Thus the expanding action is performed at both a low and high level since the output of the circuit 3, i.e. the control signal of a voltage variable gain amplifying circuit 2 follows the characteristics of the saturated amplifier.

Description

[Detailed description of the invention] The present invention detects the level P/ of an input signal, and
The present invention relates to a so-called signal expansion circuit that increases the dynamic range tm of a signal, and particularly relates to an expansion circuit used for the purpose of expanding the dynamic range of a music source.

As this type of signal expansion circuit, one having the configuration shown in FIG. 181 is known. In other words, the signal (vl) input from the terminal (1) is detected by level detection [VCA (voltage variable gain amplifier) (2) whose gain is controlled by g1 (3)
A level operation is performed by this method, and it is polished out from the terminal (4). Here, V OA (2) has a characteristic that the gain is proportional to the control signal of the level detection circuit (3), and therefore,
As shown in Figure 2 characteristic (1), the Kugata signal level A/(Vi
)K, the output signal level (VO) is 2 in logarithmic input scale.
The elongation properties are doubled. This is used when reproducing music sources such as magnetic tapes, disk records, or FM broadcasts, and is intended to further expand the original dynamic range of these sources. In the music source creation process, extensive editing and recording is performed, which not only destroys the peak components of the original sound source but also increases the noise level μ, resulting in a narrow dynamic range. . Therefore,
As shown in the first factor, the dynamic range V is recovered by passing the expansion circuit during playback using the rotation W&. This is the principle, but in reality, as shown in characteristic (1) K in Figure 112 above, if the expansion is performed uniformly across all levels, the reproduced sound will become unnatural, and therefore the second characteristic (8) As shown, height A/(
It is necessary to have the characteristic that the expansion is carried out only in the (to) and low V (A/#) regions. Moreover, this characteristic cannot be obtained only with the nine expansion circuits shown in the first section above, and therefore, conventionally, this has been achieved using the configuration shown in FIG. That is, vCA(@
) and the V-beta detection circuit (7) are connected in series with the compression circuit inner tube () of the expansion circuit shown in @1@ above.

This compression 1% is the input signal dynamic v >
sF has characteristics that compress f to 172 on a logarithmic scale, and basically has complementary characteristics to the expansion circuit characteristics, but the compression circuit in Figure 3) has the characteristics (3) in Figure 4.
φ to the low level trunk) and high Vbe A't1) as shown in
The characteristic is that the compression operation stops (becomes linear amplification). Therefore, after being compressed by the circuit that grows this characteristic Yt, when the expansion shown by the fourth characteristic (1) is performed,
Fourth y: The desired characteristic shown by J characteristic (2) is obtained. However, since two circuits, the EEi11 circuit and the expansion circuit, are required, the circuit scale becomes large and the cost increases.

The present invention provides an entire circuit that obtains the necessary stretching characteristics using only a stretching circuit, and the present invention will be described in conjunction with the following description. That is, the level detection circuit input fllK of the above-mentioned expansion circuit, the calculation increase #(S)% resistance (9), (2
), a Zener diode (2), and a non-y-rotated saturated amplifier circuit. This saturation amplifier performs linear amplification for input signals whose output W voltage is lower than the Zener voltage of the Zener diode (2), and when the output voltage reaches the Zener voltage, the input signal level increases. However, the voltage remains constant, and when the input signal level increases further and exceeds the Zener voltage, linear amplification operation resumes. That is, the sixth
As shown in the above, a linear amplification characteristic @) is obtained at a low level, a saturation characteristic C) is obtained at a medium level, and a linear amplification characteristic is obtained again at a high level. Characteristic (4) is an ideal characteristic, and characteristic (5) is an actual characteristic. Therefore, since the control signal of the level detection circuit output, ie, V OA (2), follows this saturation amplifier characteristic, the above-mentioned second plane or I! An elongation characteristic approximately equal to the characteristic shown by characteristic (2) in FIG. 4 can be obtained. Here 1g5a
The saturation characteristics of the amplifier are expressed as Zener diode an,
Although this is obtained by an anti-series circuit of oa, this may be achieved by, for example, a nine-inverse parallel circuit in which diodes are connected in parallel with each other with opposite polarities. In addition, by slightly modifying the circuit, the non-inverting saturated amplifier circuit (8) can be inserted between the level A/19 output circuit (3) and the V (3A circuit (2)), that is, at the P point. According to the present invention, the necessary expansion characteristics can be obtained with an extremely simple circuit configuration, and the dynamic Kuffi source can be realized at a much lower cost than the conventional one, and which also has high performance. An expansion circuit that can sufficiently expand the range can be obtained.

[Brief explanation of drawings]

The first factor is the block circuit diagram showing the basic configuration of the expansion circuit.
Figure g2 is a drawing showing the basic characteristics of an expansion circuit and the characteristics necessary for an expansion circuit used for the purpose of expanding the dynamic range. Figure 5 and @4 (2) are respectively the expansion surfaces used for the purpose of expanding the dynamic range. The fifth factor is a circuit diagram showing the signal level expansion circuit of the present invention, and FIG. 6 is a drawing showing the characteristics of the circuit.

Claims (2)

[Claims] (1) A level detection circuit for detecting the input signal level, and the output control of the level detection circuit - variable gain for controlling the signal and linearly extending the dynamic range V of the input signal on a logarithmic scale. A signal level expansion circuit comprising: an amplifier circuit; and a non-y-rotation amplifier circuit connected in series with the level detection circuit and having an amplitude limiting means in a feedback path. (2)' ~ The rear width limiting means of the feedback path of the non-rotating amplifier circuit is a circuit in which diodes of opposite polarity are connected in parallel, or a circuit in which Zener diodes are connected in series and in a row. A signal level expansion circuit according to claim 1g1.