JPS5925522B2 - Circuit for changing the dynamic range of the input signal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit device for changing the dynamic range of an input signal. The first impedance device is composed of at least one impedance and generates an r-shaped characteristic in the dynamo range at an arbitrary frequency S′j, and the second impedance device acts as a variable impedance as it varies depending on the signal level in the circuit, and the output signal corresponds to the current flowing through the circuit in the case of voltage drive or the circuit in case of current drive. and an output device that obtains an output signal corresponding to a voltage across the range.

Such a circuit configuration is well known from Japanese Patent Application Laid-Open No. 47-26058 (Japanese Patent Publication No. 56-2333).

In these known circuit configurations, only a single transmission path is required. This ,゛ consists of two paths: a substantially linear signal path and a separate path that changes the dynamic range in parallel.
This basically achieves the same effect as the well-known input signal dynamic range changing circuit (Japanese Patent Publication No. 48-41044) in which two parallel signal paths are provided. However, the well-known circuit configuration according to Japanese Patent Application Laid-Open No. 47-26058 constitutes a circuit arrangement that allows dynamic range changes within a single band by narrowing the band so that it does not include large amplitude signals. It can be so.

Furthermore, in a well-known circuit configuration for changing the dynamic range of an input signal (Japanese Patent Publication No. 48-41044), dynamic changes can be obtained in one or more frequency bands independently of other frequency bands.

This is particularly important in noise reduction systems that have to meet stringent requirements, such as in the professional domain. It is therefore an object of the present invention to develop the known circuit arrangement so that one or more frequency bands of an input signal can be processed independently of other frequency bands even when the operation is carried out on a single transmission channel. It is possible to change the dynamic range.

The present invention will be explained below with reference to the drawings.

The frequency selective network shown in Fig. 1 is based on the simple band narrowing principle first explained in JP-A No. 47-26058 when it is desired to obtain a noise reduction device that satisfies strict (professional) conditions. should be used instead of a frequency selective network according to the following.

A frequency selective network formed by four parallel channels 20 to 23 is supplied with a voltage corresponding to the current 1 flowing through the circuit.

Each channel includes a frequency selective filter 24 followed by a low threshold limiter circuit 25. From all of these limiters, the output signals are superimposed in circuit 26; is handled.

When a signal with high amplitude and a certain frequency appears, a limiter corresponding to that frequency band attenuates the signal.
The frequency band is thereby affected and a dynamic range change occurs. The resulting frequency-selective impedance Zs is approximately 10
Typically used to achieve dB noise reduction. 1st
In the figure, the detection of l and the combination of s are shown symbolically.

In practice, for example, the technique according to FIG. 2 can be used. Second
The figure shows an impedance network Zs with an impedance equal to the quotient by VsO)l. In this case, Zs
Although shown floating between terminals 1 and 2, in some cases one of the terminals may be at a reference potential without any significant disadvantage. In the illustrated embodiment, a small value resistor 35 is provided to detect the current. The resulting signal is provided by a transformer 36 and an amplifier 37 and processed accordingly in a noise reduction circuit 38. This noise reduction circuit is as described above and is shown in detail in FIG. The resulting noise-reduced signal s is coupled into the circuit between terminals 1 and 2 by a transformer 40 with a polarity determined by an amplifier 39. This amplifier 39 thus determines whether compression or expansion of the dynamic range occurs. In one modification of the circuit configuration according to FIG. 1, all of the multiple frequency ranges can be controlled individually and independently of each other and can be individually coupled into a series circuit depending on the current 1 and the output signal formed as described above. can.

This series arrangement, ie the superposition of the individual voltages thus carried out, forms the voltage Vs and constitutes the overall frequency-selective impedance Zs. Figures 3 and 4 show the complete noise reduction system, with the compressor on the left and the expander on the right, respectively. The impedance Zs mentioned above is connected in series to the fixed impedance Z1. In the compressor of FIG. 3, the input voltage,
appears across Z1 and Zs. The extender input voltage is Z
, and Zs, and the resulting current 12 provides an output voltage 4 via a current-to-voltage converter 17.
The opposite configuration is used in FIG. 4, in which the input voltage V, is applied across Z and Zs at the compressor, and the resulting current 1, is transferred by converter 17 to the compressor output voltage 2. converted.

In the stretcher, input voltage 3 is converted to drive current 12 by converter 16, whose output voltage V4 appears across Z and Zs.

[Brief explanation of the drawing]

FIG. 1 shows a frequency selective network for a noise reduction device that satisfies industrial requirements. FIG. 2 shows the connection of the network according to FIG. 1 in a noise reduction device. Figures 3 and 4 show the complete noise reduction device. Code explanation, 24: Frequency selection filter, 25:
Limita, 38: Noise reduction circuit.

Claims (1)

[Claims] 1. A circuit for changing the dynamic range of an input signal, comprising: (a) first and second impedance devices connected in series between input terminals connected to a voltage drive source; , the first impedance device comprises at least one impedance that provides a linear characteristic with respect to dynamic range at any given frequency, and the second impedance device is dependent on the signal level in the input signal dynamic range modification circuit. and (b) an output device that obtains an output signal according to a current passing through the input signal dynamic range modification circuit. The second impedance device connects two terminals 1 and 2.
a current path extending between the two terminals, and a frequency selective circuit for introducing a voltage into the current path between the two terminals in response to a current flowing through the current path, the frequency selective circuit comprising: a current path extending between the two terminals; a plurality of signal paths 20-23 configured to provide a plurality of path output signals and a device 26 for combining said plurality of path output signals to provide said introduced voltage; A circuit for changing the dynamic range of an input signal, characterized in that said signal path consists of a filter 24 for defining the frequency band of the individual signal path and a limiting device 25. 2. In a circuit for changing the dynamic range of an input signal, a) first and second impedance devices connected in series between input terminals to which a current drive source is connected, wherein the first impedance The device comprises at least one impedance providing a linear characteristic with respect to dynamic range at any given frequency, the second impedance device being configured to vary depending on the signal level within the input signal dynamic range modification circuit. and (b) an output device that obtains an output signal according to a voltage across the input signal dynamic range changing circuit, the input signal dynamic range changing circuit comprising: The impedance device has two terminals 1
, 2, a current path extending between the two terminals, and a frequency selective circuit for introducing a voltage into the current path between the two terminals in response to the current flowing through the current path, A frequency selective circuit comprises a plurality of signal paths 20-23 configured to provide a plurality of path output signals and a device 26 for combining said plurality of path output signals to provide said introduced voltage. A circuit for changing the dynamic range of an input signal, characterized in that each said signal path consists of a filter 24 defining the frequency band of the individual signal path, and a limiting device 25.