JP4702307B2 - Meter drive circuit - Google Patents

Description

  The present invention relates to a meter drive circuit that can be used in common when driving a gain meter or a gain reduction meter.

  In order to prevent the output signal from increasing when the input signal exceeds a certain level (threshold level), a compressor is known that decreases the gain as the input signal increases. The gain of the input signal is the amplitude level (volume) of the input signal. The compressor is a kind of effector, and is a circuit (device) that compresses the dynamic range of the audio signal. Then, when the gain of the input audio signal exceeds the threshold level (threshold), the audio signal gain is compressed at a set ratio. In this way, the compressor is designed so that the amount by which the gain of the input signal is reduced can be adjusted by the ratio setting value, and the difference between the maximum and minimum gains is compressed, so that the protrusion of sound in the ensemble can be suppressed. It becomes like this.

  In an audio device including a compressor, a gain meter that displays a gain of an input signal and a gain reduction meter that displays a gain reduction level of the compressor are often provided. The user checks the gain of the input signal with a gain meter and adjusts the gain of the input signal. Further, the user confirms the gain reduction level with a gain reduction meter, and adjusts the gain reduction level so as to be in an optimum state (a state where compression is not excessively applied). The gain reduction level is the amount of compression (compression ratio) when the input signal gain is compressed by the compressor. The compression ratio represents the relationship between the volume before the compressor is applied and the volume after the compressor is applied. It is. The compression rate is expressed as (gain of output signal) / (gain of input signal). This compression rate takes a value of 0 to 1, and the smaller this value, the greater the compression.

FIG. 6A shows an example of the configuration of a gain meter that displays the gain of the input signal. The gain meter shown in this figure has a configuration in which light emitting units with 10 segments are arranged in the vertical direction, and is a gain meter that displays a gain level from −∞ dB to +10 dB. This gain meter has a bar graph-like display mode in which the number of light emitting units that are lit from the bottom to the top increases as the gain of the input signal increases. The lighting color in the second row from the top of the gain meter is, for example, “red”, the lighting color in the lower two rows is, for example, “orange”, and the lighting color in the lower row is “green”. Thus, the outline of the gain of the input signal can be grasped.
FIG. 6B shows an example of the configuration of a gain reduction meter that displays the gain reduction level of the compressor. The gain reduction meter shown in this figure has a configuration in which light emitting sections with 10 segments are arranged in the vertical direction, and is a gain reduction meter that displays a gain reduction level from 0 dB to +20 dB. This gain reduction meter has a bar graph-like display mode in which the number of light emitting sections that are lit from top to bottom increases as the gain reduction level of the compressor increases. The two-stage lighting color below the gain meter is, for example, “red”, the upper two-stage lighting color is, for example, “orange”, and the upper-stage lighting color is “green”, and the lighting color is This makes it possible to grasp the outline of the gain reduction level.

An example of a mode in which the dynamic range of the input signal is compressed by the compressor is shown in FIG. The waveform signal shown in the upper part of FIG. 7 is the waveform of the input signal input to the compressor, with the horizontal axis representing time and the vertical axis representing gain [dB]. As shown in the figure, the input signal includes a waveform having a gain exceeding the threshold level. When such an input signal is input to the compressor, the compressor compresses and outputs an input signal having a gain exceeding the threshold level. The waveform of the compressed output signal is indicated by a solid line in the lower part of FIG. 7, and the waveform indicated by a broken line in the lower part of FIG. 7 is a waveform before compression. That is, the gain of the waveform indicated by the broken line is compressed to the gain of the waveform indicated by the solid line, and the amount of compression is used as the gain reduction level (GR). As shown in the figure, the gain reduction level becomes maximum at the peak time tp of the waveform of the input signal, and when the output signal gain is Gout and the input signal gain is Gin, the compression ratio is expressed by the following equation.
Compression rate = Gout / Gin
However, when the unit of the gain Gout of the output signal and the gain Gin of the input signal is [dB],
Compression rate = Gout [dB] −Gin [dB]
It becomes. The gain Gout of the output signal can be adjusted by the ratio, and the gain Gout of the output signal is expressed by the following equation. In the gain reduction meter, the sign of the compression rate is inverted and displayed.
Gout = (Gin−SL) * ratio + SL
However, SL is a threshold level.

  By the way, the gain meter has an envelope follower circuit that detects an envelope signal by holding the peak of the input signal for a predetermined time, and the gain meter displays the envelope level of the input signal output from the envelope follower circuit. ing. The gain reduction meter supplies the compression rate signal determined by the gain adjustment unit of the compressor to the envelope follower circuit, and displays the level of the compression rate envelope signal output from the envelope follower circuit on the gain reduction meter. I have to. As described above, the gain reduction meter and the gain meter both use the envelope follower circuit, and therefore, the meter driving circuit having the same configuration is used for the gain reduction meter and the gain meter in order to reduce the cost and simplify the design. I am doing so. Since the envelope follower circuit allows the user to clearly recognize the maximum value, the peak hold process for holding the display of the maximum value of the gain (amplitude value of the input signal) for a certain time is performed. . Here, in the gain meter, it is important that the maximum value of the gain of the input signal can be confirmed, and it is meaningful to use the peak hold processing. However, in the gain reduction meter, it is important to be able to confirm the minimum value of the compression ratio (the most strongly compressed state), but the peak hold process is to clarify the maximum value and to clarify the minimum value. (Minimum value may not be displayed). Thus, the conventional gain reduction meter has a problem that the minimum value of the compression rate cannot be clearly or accurately recognized.

  Accordingly, the present invention provides a meter driving circuit that can clearly and accurately recognize the minimum value of the compression rate in the gain reduction meter even when the meter driving circuit having the same configuration is used for the gain reduction meter and the gain meter. It is an object.

  In order to achieve the above object, the meter drive circuit of the present invention includes a first selection unit that selects either an input signal or an inverted input signal and inputs the selected signal to the envelope follower unit, and an output of the envelope follower unit or The most important feature is that a second selection means is provided for selecting one of the inverted outputs and supplying the selected output to the meter.

  According to the present invention, the first selection means for selecting either the input signal or the inverted input signal and inputting it to the envelope follower means, and selecting either the output of the envelope follower means or the inverted output The second selection means for supplying to the meter is provided, and the setting of the first selection means and the second selection means is switched so that the minimum value of the compression rate can be clearly and accurately recognized in the gain reduction meter. become.

FIG. 1 is a block diagram showing a configuration of a digital mixer 1 to which a gain meter and a gain reduction meter having a meter driving circuit according to an embodiment of the present invention can be applied.
A digital mixer 1 according to the embodiment of the present invention shown in FIG. 1 controls the overall operation of the digital mixer 1 and generates a control signal in response to the operation of a mixing operator. ) 10, a rewritable nonvolatile flash memory 11 in which operation software such as a mixing control program executed by the CPU 10 is stored, and a RAM (Random Access Memory) 12 in which the work area of the CPU 10 and various data are stored. It has. Thus, by storing the operation software in the flash memory 11, the operation software can be upgraded by rewriting the operation software in the flash memory 11. Other devices such as a digital recorder are connected to the digital mixer 1 via other I / O 13 which is an input / output interface.

  The display 14 is an LCD display composed of a liquid crystal display that displays various setting screens for setting parameters of each channel. The LCD display includes a gain meter and a compressor for displaying the gain of the detection point in the selected channel. A gain reduction meter that displays the compression rate can be displayed. The gain meter and the reduction meter in this case are configured as shown in FIGS. The electric fader 15 is a fader that adjusts the level of the signal of the input channel or the signal of the output channel, and the level can be adjusted manually or electrically. The operation element 16 includes an operation element for performing an operation related to the monitor, a cursor movement key for moving a cursor displayed on the display 14, an increase / decrease key for increasing / decreasing a set value, a rotary encoder for selecting a set value, This is an operator provided on a panel composed of an enter key or the like for confirming the selected value. All inputs and all outputs of the digital mixer 1 are performed by a waveform I / O (waveform data interface) 17. The waveform I / O 17 includes a plurality of A input ports to which analog signals are input, a plurality of A output ports to which analog signals are output, and a bidirectional input of digital signals from outside and output of digital signals to the outside. A plurality of D input / D output ports.

  The waveform I / O 17 is also provided with a monitor port for outputting a monitor signal when the operator of the digital mixer 1 operates the operation element. By supplying the monitor signal from the monitor port to the operator monitor 18 in the operator room, the operator in the operator room can operate the digital mixer 1 while monitoring the output channel signal. Furthermore, it is possible to listen to a signal of a certain input channel or output channel or a signal sent to a performer without changing the mixing state. Further, the signal processing unit 19 is configured using a number of DSPs (Digital Signal Processors), and performs mixing processing, effect processing, and the like under the control of the CPU 10. The mixing signal mixed by the signal processing unit 19 can be supplied to the recorder 20 and recorded, and the mixing signal reproduced from the recorder 20 can be supplied to the signal processing unit 19. In this case, the recorder 20 can compress and record the mixing signal and expand and output the reproduced mixing signal. Each unit is connected to the communication bus 21.

Next, FIG. 2 shows a functional block diagram of an equivalent mixer in which mixing processing is performed in the digital mixer 1 having the configuration shown in FIG. 1 according to the present invention.
In FIG. 2, analog signals input to a plurality of analog input (A input) ports 30 are converted into digital signals by built-in AD converters and input to input patches 32. The digital signals input to the plurality of digital input (D input) ports 31 are input to the input patch 32 as they are. In the input patch 32, any one of a plurality of input ports that are signal input sources is selectively patched (connected) for each input channel of the plurality of input channel sections 33a to 33n, for example, 32 channels. Each input channel is supplied with a signal from an input port patched with an input patch 32.

  Each input channel in the input channel units 33a, 33b,..., 33n includes an attenuator, an equalizer, a compressor, a fader, and a send adjustment unit that adjusts the send level to the MIX buses 34a to 34m. In the input channel, the frequency balance and the level sent to the MIX buses 34a to 34m are controlled. The 32-channel digital signals output from the input channel sections 33a to 33n are selectively output to one or a plurality of 16 MIX buses 34a, 34b,. In the MIX buses 34a to 34m, in each of the 16 buses, one or a plurality of digital signals selectively input from any of the 32 input channels are mixed, and a total of 16 channels of mixing outputs are generated. It is output to MIX output channel sections (MIXch) 35a to 35m. As a result, 16 channels of mixed output can be obtained. In many cases, the output from the MIX buses 34a to 34m is supplied as a final output to a speaker or the like.

Each output channel in the MIX output channel sections 35 a to 35 m is provided with an attenuator, an equalizer, a compressor, and a fader. In these output channels, the frequency balance and the level sent to the output patch 36 are controlled. In the output patch 36, any one of the 16 mixing signals of the MIX output channel portions 35a to 35m, which is the signal input source, is connected to an analog output (A output) port portion 37 or a digital output (D output) port portion. Each of the 38 output ports can be selectively patched (connected), and a signal from a channel patched by the output patch 36 is supplied to each output port.
A digital output signal supplied to an analog output (A output) port unit 37 having a plurality of analog output ports is converted into an analog output signal by a built-in DA converter and output from the analog output port. The analog output signal output from the analog output (A output) port unit 37 is amplified and emitted from the main speaker. Further, the analog output signal is supplied to an in-ear monitor worn by the performer on the ear or reproduced by a stage monitor speaker placed in the vicinity of the performer. A digital audio signal output from a digital output (D output) port unit 38 having a plurality of digital output ports is supplied to the recorder 20 or an externally connected DAT or the like so that it can be digitally recorded. Yes.

  As described above, each input channel of the input channel sections 33a to 33n and each output channel of the MIX output channel sections 35a to 35m are provided with a compressor, and the gain of the input signal exceeds the set threshold level. As shown in FIG. 7, the dynamic range of the signal is compressed. And the gain of the detection point in each input channel of the input channel parts 33a-33n and each output channel of the MIX output channel parts 35a-35m can be selectively displayed by a gain meter, and the input channel parts 33a-33n. The compression rate of the compressor in each input channel and each output channel of the MIX output channel sections 35a to 35m can be selectively displayed on the gain reduction meter. In this case, the user selects a channel to be displayed on the gain meter and the gain reduction meter and a detection point to be displayed on the gain meter. As a result, the user can confirm the maximum value of the gain of the signal displayed on the gain meter, and if the gain is too large, the user can operate the predetermined operation element 16 to reduce the gain of the signal. Further, the ratio and the threshold level can be adjusted so as not to be over-compressed while checking the minimum value of the compression rate displayed on the gain reduction meter. The compression rate takes a value of 0 to 1, and the smaller the value, the larger the compression.

Next, FIG. 3 shows a circuit block diagram showing the configuration of the meter drive circuit according to the embodiment of the present invention.
The meter driving circuit 40 shown in FIG. 3 includes a first signal inversion unit 40a, a first selection unit SWa, an envelope follower unit 40b, a second signal inversion unit 40c, and a second selection unit SWb. I have. The first signal inversion unit 40a inverts the sign of the input signal, and the second signal inversion unit 40c inverts the sign of the envelope signal output from the envelope follower unit 40b. The first selection unit SWa has a movable contact a and two fixed contacts b and c, and selects and outputs either an input signal or an inverted input signal. The second selection unit SWb has a movable contact d and two fixed contacts e and f, and selects and outputs either the envelope signal output from the envelope follower unit 40b or the inverted envelope signal. ing. The envelope follower unit 40b detects the envelope of the signal by performing a peak hold process on the signal selected by the first selection unit SWa.

Here, the peak hold process performed by the envelope follower unit 40b will be described. First, the peak (maximum value) of the input signal is detected, and the peak value is set as the output value for the hold time set from the time of detection. . Next, when the hold time elapses, the output value is gradually attenuated based on the decay setting value. When a match between the input signal value and the output value is detected, the value of the input signal is detected from the detected time point. Is the output value. By repeating such processing, the envelope follower unit 40b outputs the envelope signal of the input signal. In the envelope follower section 40b, when emphasizing and outputting the peak portion of the input signal, the hold time length is set long and the decay slope is set gently to output an accurate envelope. Set the hold time length short and set the slope of the decay steep.
The meter drive circuit 40 shown in FIG. 3 is used in common for the meter drive circuit of the gain meter and the meter drive circuit of the gain reduction meter by switching the selection mode of the first selection unit SWa and the second selection unit SWb. be able to.

Accordingly, a circuit block diagram showing the configuration of the compressor unit 41 is a circuit block diagram showing a configuration in which the meter driving circuit 40 is applied to the meter unit 42 which is a meter driving circuit of the gain meter and the meter unit 43 which is a meter driving circuit of the gain reduction meter. FIG. 4 is shown together with the figure. The compressor unit 41 is one of the compressors provided in the input channels of the input channel units 33a to 33n and the output channels of the MIX output channel units 35a to 35m.
As shown in FIG. 4, the waveform of an input signal that is an audio signal input to the compressor unit 41 of each channel is shown as a waveform S. This input signal is input to the multiplier 41a and the envelope follower 41b. The envelope follower unit 41b of the compressor unit 41 accurately detects the envelope that is the envelope of the input waveform S. The envelope waveform detected by the envelope follower unit 41b is shown as a waveform Ev1. The envelope follower unit 41b of the compressor unit 41 detects the envelope on the positive side of the input signal by performing a peak hold process on the input signal. The envelope follower 41b in the compressor 41 is set so that the hold time length is shortened and the decay slope is steep so as to output an accurate envelope of the input audio signal. Has been.

The envelope signal output from the envelope follower unit 41b of the compressor unit 41 is determined according to the envelope level and the set ratio when the envelope signal is input to the gain adjustment unit 41c and exceeds the set threshold level. Outputs the gain adjustment signal. The gain adjustment signal represents a compression rate for compressing the input signal in the compressor unit 41, and a waveform of the compression rate is illustrated as a waveform Rd1. The gain adjustment unit 41c adjusts the gain from the envelope value by using a table that defines the compression ratio according to the ratio of each value of the envelope, a function that calculates the compression ratio from the envelope and ratio values, and the like. The signal (compression rate) is calculated.
The compression rate is a ratio representing the relationship between the volume before being applied and the volume after being applied, that is, the ratio for compressing the volume of the input audio signal. The gain adjustment signal (compression rate) is a value multiplied by the input audio signal, and takes a value of 0 to 1. In this case, if the compression rate is small, the output signal output from the compressor unit 41 is also small, and the compression is larger as the compression rate is smaller.

Returning to FIG. 4, the gain adjustment signal (compression rate) is supplied to the multiplier 41a as a multiplication coefficient. The multiplier 41a multiplies the supplied gain adjustment signal (compression ratio) by the signal input as a multiplication coefficient, so that when the input signal exceeds the threshold level as shown in FIG. The dynamic range is compressed according to the value of the gain adjustment signal (compression rate). The output of the multiplier 41a becomes the output of the compressor unit 41. The output signal output from the multiplier 41a is supplied to the next stage in the channel section and also input to the meter section.
The meter unit 42 is switched in conjunction with the first signal inversion unit 42a, the first selection unit SWa1, the envelope follower unit 42b, the second signal inversion unit 42c, and the first selection unit SWa1. 2 selection units SWb1. The first signal inversion unit 42a and the second signal inversion unit 42c invert the signal, and the first selection unit SWa1 has a movable contact a1 and fixed contacts b1 and c1. The second selection unit SWb1 has a movable contact d1 and fixed contacts e1 and f1. The movable contact a1 in the first selection unit SWa1 is connected to the fixed contact b1, and the signal input to the meter unit 42 that is not inverted by the first inversion unit 42a is selected, and the envelope follower unit of the meter unit 42 is selected. 42b.

  The waveform of the signal output from the compressor unit 41 (the waveform of the compressed audio signal) input to the envelope follower unit 42b of the meter unit 42 is shown as a waveform S ′, and the envelope of this waveform S ′ is the envelope follower. It is detected in the part 42b. An envelope waveform detected by the envelope follower unit 42b is shown as a waveform Ev. The envelope follower unit 42b detects the positive envelope of the input signal by performing a peak hold process on the input signal. The movable contact d1 in the second selection unit SWb1 is connected to the fixed contact e1, and the envelope signal output from the envelope follower unit 42b that is not inverted by the second signal inversion unit 42c is selected, and FIG. ) To a gain meter (G meter) as shown in FIG. The envelope follower section 42b of the meter section 42 is set so that the hold time length is long and the decay slope is gentle so that the peak portion of the input signal can be emphasized. Is set. As a result, the envelope signal of the waveform Ev with the peak portion emphasized as shown in the figure is output from the envelope follower unit 42b and supplied to the gain meter, and is output from the compressor unit 41 by viewing the gain meter. The peak level of the signal can be easily confirmed.

  Further, the gain adjustment signal (compression rate) having the waveform Rd1 output from the gain adjustment unit 41c is supplied to the multiplier 41a and input to the meter unit 43. The meter unit 43 is switched in conjunction with the first signal inversion unit 43a, the first selection unit SWa2, the envelope follower unit 43b, the second signal inversion unit 43c, and the first selection unit SWa2. 2 selection units SWb2. The first signal inversion unit 43a and the second signal inversion unit 43c invert the signal, and the first selection unit SWa2 has a movable contact a2 and fixed contacts b2 and c2. The second selection unit SWb2 has a movable contact d2 and fixed contacts e2 and f2. The movable contact a2 in the first selection unit SWa2 is connected to the fixed contact c2, and a gain adjustment signal (compression ratio) whose polarity is inverted by the first signal inversion unit 43a is selected, and the envelope follower of the meter unit 43 is selected. It is input to the part 43b.

  The waveform of the gain adjustment signal (compression rate) with the positive / negative inverted input to the envelope follower unit 43b of the meter unit 43 is shown as a waveform Rd2, and the envelope follower unit 43b applies a peak hold process to the waveform Rd2. The peak of the gain adjustment signal (compression ratio) inverted by the above is emphasized and output. An envelope waveform of the inverted gain adjustment signal (compression ratio) output from the envelope follower unit 43b is shown as a waveform Rd3. The movable contact d2 in the second selection unit SWb2 is connected to the fixed contact f2, and the sign of the envelope waveform (waveform Rd3) output from the envelope follower unit 43b is inverted by the second signal inverting unit 43c so that the positive / negative is the original. The envelope waveform of the gain adjustment signal (compression ratio) returned to is selected and supplied to a gain reduction meter (GR meter) as shown in FIG. An envelope waveform of the gain adjustment signal (compression rate) output from the second signal inverting unit 43c output from the second selection unit SWb2 is illustrated as a waveform Rd4. It should be noted that the envelope follower unit 43b in the meter unit 43 is set so that the hold time length is long and the decay time is reduced so that the peak portion of the inverted gain adjustment signal (compression ratio) can be output in an emphasized manner. The inclination is set to be gentle. As a result, an inverted gain adjustment signal (compression ratio) of the waveform Rd3 with the peak portion emphasized as shown in the figure is output from the envelope follower unit 43b, and further inverted to emphasize the minimum value portion. A waveform Rd4 of the gain adjustment signal (compression rate) is supplied to the gain reduction meter. Thereby, the minimum value of the compression rate in the compressor unit 41 can be easily confirmed by visually recognizing the gain reduction meter.

  As shown in FIG. 4, the circuit configuration of the meter unit 42 and the meter unit 43 is the same, and the meter driving circuit (meter meter) of the gain meter depends on which path is selected by the two built-in selection units. Part 42) and a meter driving circuit (meter part 43) of the gain reduction meter. Thus, since a common meter drive circuit can be used for the meter unit 42 and the meter unit 43, cost reduction and design can be facilitated. The selection unit SWa1 (SWa2) and the selection unit SWb1 (SWb2) are switched in conjunction, and the selection unit SWa1 or selection unit SWb2 can be a switch such as a dip switch or an electronic switch, and is assembled on a printed circuit board. In the meter driving circuit, the switches such as dip switches and electronic switches corresponding to the selection units SWa1 and SWb2 are fixedly switched in advance as shown in FIG. It can be.

Next, FIG. 5 shows a circuit block diagram illustrating an example of a circuit configuration of the envelope follower unit 50 used as the envelope follower units 41b, 42b, and 43b.
In the envelope follower unit 50 shown in FIG. 5, the subtractor 51 subtracts the delayed signal (previous output signal) fed back from the input IN. This delay signal (previous output signal) is an output from the delay unit 55. The determination unit 52 to which the output of the subtractor 51 is input determines the magnitude relationship between the amplitude values of the input IN and the delay signal (previous output signal) from the positive / negative sign of the input subtraction signal, and the peak of the input IN The value is detected at the point where the sign of the subtraction signal is reversed. In this case, the portion immediately before the point at which the sign of the subtraction signal switches from positive to negative is the attack portion of the input IN, and the portion immediately after is the hold portion. Further, the decay portion is immediately before the point at which the sign of the subtraction signal switches from negative to positive.

In the control unit 53 to which the output of the subtractor 51 is input, based on the information on the point at which the magnitude relationship between the amplitude values of the input IN and the delay signal (previous output signal) input from the determination unit 52 is switched. In the attack part, the output of the subtractor 51 is outputted as an output value as it is, in the hold part, the value when the hold is started is outputted as the output value, and in the decay part, the hold output value is gradually attenuated along the decay. The value is output as an output value. An output from the control unit 53 is input to an adder 54 and added to a delay signal (previous output signal) to obtain an output OUT which is an envelope signal of the input IN. The output OUT is delayed by one sample time by the delay unit 55 and supplied to the subtractor 51 and the adder 54.
Here, the envelope follower unit 50, in which the holding time in the control unit 53 is set short and the decay slope is set steeply, can be detected as an accurate envelope, and thus is used as the envelope follower unit 41b of the compressor unit 41. The Further, since the envelope follower unit 50 in which the holding time in the control unit 53 is set long and the decay slope is set gently can be output with the peak emphasized, the envelope follower unit 42b in the meter units 42 and 43, 43b is used.

In the present invention described above, the meter driving circuit is a meter driving circuit for a gain meter or gain reduction meter in a digital mixer. However, the meter driving circuit is not limited to this, and the meter driving of a gain meter or gain reduction meter for general audio equipment is used. It can be a circuit.
Note that the signal inverting unit 43c on the output side of the meter unit 43, which is a meter driving circuit of the gain reduction meter, may be omitted, and the output of the envelope follower unit 43b may be offset and output instead. Even in this way, it is possible to display on the gain reduction meter so that the minimum value of the compression rate can be clearly recognized.

It is a block diagram which shows the structure of the digital mixer which can apply the gain meter provided with the meter drive circuit of an Example of this invention, and a gain reduction meter. FIG. 2 is a functional block diagram of an equivalent mixer in which mixing processing is performed in the digital mixer configured as shown in FIG. 1 according to the present invention. It is a circuit block diagram which shows the structure of the meter drive circuit of the Example of this invention. It is a circuit block diagram which shows the meter drive circuit of the gain meter which applied the meter drive circuit concerning this invention, and the meter drive circuit of a gain reduction meter with the structure of a compressor part. It is a circuit block diagram which shows an example of the circuit structure of the envelope follower part applicable to the meter drive circuit concerning this invention. It is a figure which shows an example of a structure of the gain meter which displays the gain of an input signal, and a structure of the gain reduction meter which displays the gain reduction level of a compressor. It is a figure which shows an example of the aspect which compresses the dynamic range of an input signal with a compressor.

Explanation of symbols

1 Digital mixer, 10 CPU, 11 Flash memory, 12 RAM, 13 Other I / O, 14 Display, 15 Electric fader, 16 Operator, 17 Waveform I / O, 18 Monitor for operator, 19 Signal processing unit, 20 Recorder, 21 Communication bus, 30 Analog input (A input) port, 31 Digital input (D input) port, 32 input patch, 33a-33n input channel section, 34a-34m MIX bus, 35a-35m output channel section, 36 output Patch, 37 analog output (A output) port section, 38 digital output (D output) port section, 40 meter drive circuit, 40a multiplier, 40a first signal inversion section, 40b envelope follower section, 40c second signal inversion Part, 41 compressor part, 41a multiplier, 41b Bellow follower unit, 41c gain adjustment unit, 42 meter unit, 42a first signal inversion unit, 42b envelope follower unit, 42c second signal inversion unit, 43 meter unit, 43a first signal inversion unit, 43b envelope follower Unit, 43c second signal inversion unit, 50 envelope follower unit, 51 subtractor, 52 determination unit, 53 control unit, 54 adder, 55 delay unit, SWa first selection unit, SWa1 first selection unit, SWa2 1st selection part, SWb 2nd selection part, SWb1 2nd selection part, SWb2 2nd selection part, a movable contact, a1 movable contact, a2 movable contact, b, c fixed contact, b1, c1 fixed contact , B2, c2 fixed contact, d movable contact, d1 movable contact, d2 movable contact, e, f fixed contact, e1, f1 fixed contact, e2, f2 Fixed contact

Claims (3)

First signal inverting means for inverting the input signal;
A first inversion signal inverted by the first signal inversion means, and a first selection means for selecting one of the input signals;
Envelope follower means for outputting an envelope signal of the first selection signal detected by holding a peak of the first selection signal selected by the first selection means for a predetermined time;
Second signal inverting means for inverting the envelope signal output from the envelope follower means;
A second inversion signal inverted by the second signal inversion means, and a second selection means for selecting one of the envelope signals,
A meter driving circuit characterized in that a second selection signal selected by the second selection means is supplied to a meter.   When the meter is a gain meter, the first selection unit and the first selection unit and the second selection unit select the envelope signal while the first selection unit selects the input signal. 2. The meter driving circuit according to claim 1, wherein the second selecting means is set.   When the meter is a gain reduction meter, the first selection unit selects the first inversion signal, and the second selection unit selects the second inversion signal. 2. The meter driving circuit according to claim 1, wherein the first selection unit and the second selection unit are set.

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