CN1678135B - Remote control of phantom power supplied microphones - Google Patents

Abstract

The present invention relates to a method for remote control of a microphone, comprising an audio amplifier (10), a power supply circuit (11), a processor, control electronics (39), A/D and D/A converters (44 , 46), at least one microphone capsule (9) selected in groups such as LED displays (25), and at least one other power supply receiver, and by a phantom power supply unit (31) through the cable conductor (1) of the audio cable , 2) power supply, the so-called phantom power supply. The invention is characterized in that a FM voltage is applied as a control signal to at least one of the two cable conductors (1, 2) carrying out the phantom power supply, and wherein the FM voltage on the microphone side is applied to a control signal Electronics (39), such as a microcontroller or a CPLD, control the electronics to send commands to the individual power receivers in response to frequency-modulated control signals.

Description

How to Remotely Control Phantom Powered Microphones

technical field

The present invention relates to a method for remotely controlling a microphone comprising at least one microphone selected from the group of audio amplifiers, power supply circuits, processors, control electronics, A/D and D/A converters, LED displays, etc. The capsule, and at least one further power receiver, are powered from a phantom power unit via the cable leads of the audio cable, so-called "phantom power supply". the

Background technique

Power supply for microphones is traditionally provided by a power supply, for example, by means of a mixer. During phantom power supply, the positive side of the feed voltage is applied through two equal feeder residences of the two cable conductors of the audio cable. The return current flows from the third wire connected to electrical connector 1 of the XLR plug. To be able to efficiently use the voltage provided by the phantom power supply for condenser microphones, the current consumption of the microphone should be as small as possible to prevent excessive voltage drops across the feed resistors. The maximum current draw for a 48-V condenser microphone is 10mA. Phantom power is standardized here according to DIN EN61938 (formerly IEC268). the

To generate a polarization voltage on the microphone membrane, which typically has a value in the range of 20-100 V DC, mainly combinational circuit components or voltage converters can be used. The rest of the microphone electronics are typically powered by linear regulation, which maintains the supply feed voltage or supply current at a predetermined value. This type of power supply is suitable for microphones with small power consumption. This linearity regulation can become a problem when the power consumption in the microphone is increased eg by using a processor, A/D converter, LED display etc. In this case, most of the energy available from the phantom power supply is lost in the linear regulator. However, according to the standard, since the phantom power supply is current limited by the feed resistor, the maximum supply voltage for the audio amplifier is immediately reduced due to the linear regulation in the microphone, which results in a reduction of the maximum audio output voltage of the microphone. the

Additional issues include the generation of polarization voltages. Usually this voltage is applied to the microphone membrane through a high ohmic resistor. Here, the required power is very low. Efficient regulators for generating this virtually power-free polarizing voltage are also difficult to construct. the

Another question is about the remote control of the microphone. With microphones, there is a growing need to be able to adjust or change important microphone parameters via remote control. These parameters include the polarization voltage on the membrane and the relative sensitivity of the condenser microphone, the directivity of the microphone, the type of phantom power (12V, 24V or 48V), serial number, calibration data from the manufacturer, and signal attenuation level and a connectable filter for audio signals. the

Document DE 3 933 870 A1 discloses a method for remote control of microphone parameters such as directivity, step sound filter or initial damping. In this method, the supply voltage delivered to the cable conductors is regulated by a remote control unit, for example, in a hybrid meter, in such a way that the magnitude of the voltage represents control information for the microphone. On the microphone side, the supply voltage is uncoupled and applied to an evaluation circuit which generates a control signal as a function of the magnitude of the supply voltage. With this method of data transfer, only a small amount of control information can be transmitted to the microphone, and therefore only a few parameters can be remotely controlled from the microphone. the

The document US 6 028 946 A (and the corresponding EP 0 794 686 A2) discloses a digital microphone. The audio signal is digitized by an analog-to-digital converter, and the resulting two-channel digital sound signal is transmitted through a symmetrical two-wire conductor or an associated amplifier. Power to the microphone is provided through this symmetrical two-wire conductor. Incidentally, in an associated amplifier, pulses can be modulated onto the supply voltage of the microphone, which serves as a remote control of the speaker settings. In this context it must be pointed out that the concept of a digital microphone and the subsequent routing of the digital signal is quite different from an analog microphone where the analog signal is routed through the phantom power line. The transmission of a further modulated signal on a line which simultaneously transmits a digital signal does not cause any problems, since a digital audio signal can be easily separated from a further modulated signal. the

A further problem which has not been optimally solved so far concerns the generation of polarization voltages on the membranes of condenser microphones. The level of polarization voltage is directly contained in the sensitivity level of the microphone capsule. As a result, it is also possible to adjust the sensitivity of the capacitive capsule with the help of the polarization voltage. In the case of separate powering of a single membrane with polarization voltage, this is particularly advantageous in combination with double-membrane capsules, since these capsules allow adjustment not only of sensitivity but also of directivity. the

It is known how to adjust the polarization voltage with the help of fixed or trimmed resistors. In this process, in the assembly of the microphone, a one-time adjustment of the polarization voltage takes place. Here, the directivity can once be predetermined with a fixed resistance ratio. With this method, tolerance compensation of sensitivities caused by the assembly of the microphone capsule, as well as by aging processes, may be difficult. For this purpose, a compensation of the polarization voltage will be required during the audio measurement of the sensitivity in the assembled state of the microphone. Tolerance compensation of the sensitivity at different directivities is also not possible. the

US 4,541,112 A (and corresponding EP 0 096 778 B1) discloses an electro-acoustic transducer system with an adjustable pulse generator to convert current DC to AC. A transformer connected to the pulse generator allows inductive decoupling of individual power receivers. The power supply circuit is inductively coupled to the alternating current generated by the pulse generator through the split coil on the transformer. This document is included in the description herein by reference. the

Contents of the invention

Regarding the power supply of microphones, a solution is needed in which the power obtained from phantom power is optimally used and converted into components such as audio amplifiers, microphone capsules, processors, controllers, A/D converters, LED displays etc. The operating voltage required by the separate output receiver. Here, the goal will be to utilize as much as possible of the portion of the power obtained through phantom power to power the audio amplifier. the

These objectives are achieved by a microphone comprising a power supply circuit for a separate power receiver, the microphone being characterized in that the power supply circuit comprises a control unit for converting the direct current transmitted through the cable conductors of the audio cable into alternating current, A transformer connected to the control unit, and power circuits for separate power receivers, wherein the power circuits are inductively coupled to the alternating current generated by the control unit through separate coils on the transformer, and these power circuits are coupled to each other. the

In this process, all the voltages required by the above-mentioned power supply receiver are generated by a power supply circuit, such as a DC/DC converter, which has the following characteristics. The power supply circuit is regulated or operated in such a way that there is a power adaptation to the phantom power unit. Therefore, the maximum possible power achievable by the phantom power unit can always be consumed by the microphone's power supply circuit. The source current consumption of the power supply circuit is constant. Therefore, the power supply circuit acts like a constant current sink relative to the phantom power unit. The individual power supply circuits of the individual power receivers are decoupled in the power supply circuit via transformers in order to meet the different requirements of the individual power receivers with as little power loss as possible: high voltage and low current for polarization voltage , medium voltage and medium current consumption for audio amplifiers, and low voltage and high current for digital electronics. the

The advantageous effect of the condenser microphone according to the invention is evident: with the proposed power supply concept, the electrical energy achieved by the phantom power unit is optimally applied. As a result, the microphone can be provided with new functions (eg remote control, new operating concepts, possibility of automatic compensation, etc.), while the maximum audio output voltage of the microphone remains unchanged. The generation of the essentially power-free polarizing voltage actually occurs as a by-product generated by a simple additional coil on the transformer. the

An additional advantage is that, as a result of the use of an ohm level as high as possible, with a constant power supply at the input of the mains supply circuit, switching fluctuations of the mains supply circuit or of the DC/DC converter can be very easily is filtered out. the

Take advantage of the increased adaptation possibilities in the microphone, such as changing the polarization voltage and its sensitivity, the continuous change of the directivity of the double-membrane capsule and the change of the control signal of the microprocessor storing the calibration data, as well as the modification of the frequency range , the modification of the maximum audio output voltage, or the modification of the THD of the audio amplifier, so there is a need to basically transmit data to the microphone at a higher rate through a remote control. the

According to the invention, these objects can be achieved by means of a method for remotely controlling a microphone, characterized in that a frequency-modulated voltage is applied as a control signal to at least one of the two cable conductors, via which phantom power can also take place, and in The FM voltage on the microphone side is applied to a control electronics such as a microcontroller or a CPLD (Complex Programmable Logic Device) which can send commands to the individual power receivers according to the FM control signal. the

In this method, a frequency modulated voltage is superimposed on the phantom power supply voltage. Data transmission is from a transmitter via the audio line to the microphone, for example, the transmitter is configured in a mixing table or in a device preceding the mixing table. The carrier frequency of the FSK modulation is here above the audio frequency range transmitted by the microphone. the

By using frequency modulated signal transmission, a substantially higher data transmission rate can be obtained compared to transmission using direct current. As a result, a large number of parameters can be transmitted using a specific protocol. The carrier frequencies used for modulation are preferably around 100 kHz, which can be separated from the audio signal by means of filters. the

To meet this requirement for a low tolerance in the polarization voltage of a condenser microphone, for example, to reach a tolerance of ±0.5dB in consideration of sensitivity, a solution is required that allows Flexible adjustment of the polarization voltage is also possible. the

According to the invention, this is obtained by means of a condenser microphone, characterized in that the condenser microphone comprises at least one circuit for regulating the polarization voltage, wherein the circuit for regulating the polarization voltage comprises an analog regulation loop provided with an unregulated voltage , and a digital regulation loop, wherein the digital regulation loop includes a control electronics, such as a microprocessor or a CPLD, providing to the analog regulation loop a desired value for the polarization voltage, which is calculated using the correction factor , and for feedback purposes, the output of the analog regulation loop is connected with the control electronics. the

In this process, the polarization voltage is regulated via a voltage regulation loop integrated in the microphone. The desired value of the polarization voltage is pre-established in the circuit by the control electronics via the D/A converter. As a result, graded fine-tuning of the polarization voltage can be performed. The desired value of the polarization voltage can also be transmitted to the control electronics via remote control. The tolerance of the obtained polarization voltage now depends on the tolerance and thermal response of the reference voltage source. the

The adjustment of the polarization voltage in the microphone by means of a digitally controlled regulation loop allows a very precise, interference-resistant and remotely controllable adjustment of the polarization voltage of the condenser microphone. As a result, very narrow tolerance requirements regarding sensitivity and directivity may be obtained during the manufacture and verification of measurement techniques of condenser microphones. The remotely controllable adjustment of the polarization voltage has the advantage that readjustment by means of fixed resistors or trimmer resistors is no longer necessary; this fact has a favorable effect in terms of costs. Compared to existing solutions with a fixed polarization voltage, the following additional possibilities arise with regard to the condenser microphone according to the invention. the

As a function of the individual features of the double-membrane capsule, different microphone sensitivities can be compensated for in differently adjusted directivity situations, and the required correction factors needed to compensate for the polarization voltage can be stored. the

For example, together with the remote control as described above, the polarization voltage can be calibrated during the audio measurement with the microphone turned off and the correction factor can be stored again. the

It is particularly advantageous to be able to change the polarization voltage of the remote control microphone and its pointing effect during operation. For example, a microphone may audioally follow a moving actor as in a performance in a theater. the

The condenser microphone according to the invention allows aging-induced recalibration of the microphone sensitivity without having to disassemble the microphone, which in turn means cost savings for the consumer. During the replacement of the microphone capsule, the original sensitivity of the microphone can thus be readjusted later, that is to say after integration, by remote control. the

Description of drawings

Hereinafter, the present invention is further explained with reference to the accompanying drawings. In the picture:

Fig. 1 represents the block diagram of a condenser microphone with power supply circuit according to the present invention;

Figure 2 represents a block diagram of an embodiment of a condenser microphone with a power supply circuit according to the present invention;

Fig. 3 represents the circuit diagram of a transistor-LED constant-power supply according to the current state of the art;

Figure 4 represents a circuit diagram of a constant power supply with reverse coupled transistors according to the state of the art;

Figure 5 represents a block diagram of a condenser microphone connected to a remote control unit;

Figure 6 shows a block diagram of a condenser microphone with an integrated circuit for adjusting the polarization voltage; and

Figure 7 shows a circuit for regulating the polarization voltage, including an analog and a digital regulation loop. the

Detailed ways

Fig. 1 is a block diagram showing the main parts of a microphone according to the present invention. The phantom power supply of the microphone shown in FIG. 5 is performed by the phantom power supply unit 31 through the feeding resistors 32, 33 of the same magnitude, which are arranged in a mixing table or a mixing table Before the rear of the three-pole socket 4 for example an XLR socket. Such phantom power is shown in Figure 5. According to the standard, three phantom power supplies are possible: the relevant values of the feed resistors for 12V, 24V or 48V supplies are 680Ω, 1.2KΩ, or 6.8KΩ, respectively. Here lines 1 and 2 represent the cable leads supplied by the phantom power unit; line 3 represents the ground wire of the cable shield which is normally connected to ground. Via an audio cable, ie via lines 1, 2 and resistors 5, 6, the phantom power unit 31 is connected to the input of the power supply circuit 11 according to the invention. Capacitor 7 smoothes the supply voltage with respect to ground. Resistors 5 and 6 are the feed resistors in the microphone. They are used to decouple the power supply of the microphone from the output of the audio amplifier 10 . The feed resistors 5 and 6 of the microphone are assigned as additional internal resistors for the phantom power supply 31 . Power adaptation exists when the internal resistance of the phantom power unit is equal to the internal resistance of the power supply circuit 11 in the microphone. Thus, half of the phantom power supply voltage is the supply voltage for the power supply circuit 11 in the case of power regulation. The maximum of this electrical energy that can be generated by the phantom power supply unit 31 is now distributed via the mains supply circuit 11 in the form of a DC/DC converter to all energy-consuming components in the microphone. The remaining power is used here by the audio amplifier 10 to obtain the highest possible maximum audio output voltage of the microphone. With regard to different supply voltages (12V, 24V or 48V according to the standard), the circuit can be designed in such a way that the power adaptation to the different phantom power supplies occurs automatically. This task is then undertaken by the control unit 12 described below. the

The power supply circuit 11 includes a power supply 13 , a control unit 12 and a transformer 14 connected to the control unit 12 . The control unit 12 with the transformer 14 forms a circuit unit in which the DC voltage is converted into an AC voltage. In this case, the transformer is part of the oscillation generating circuit. In general, alternating current can also be generated by the control unit 12 independently of the transformer. The control unit 12 then includes an oscillating cycle independent of the transformer to generate an alternating current. The transformer only performs the function of converting the alternating current into a single output voltage. the

In a preferred embodiment, the AC signal has a frequency in the range 100-130 kHz. AC signals are also free to oscillate; this represents the possibility for the simplest embodiment of such a circuit. The only important factor is that the frequency range of the AC signal has to be outside the audio frequency range so as not to create any interference with the audio signal which cannot be removed by simple filtering. On the other hand, the frequency should not be too high, because otherwise the efficiency of the circuit is reduced and there may be transmission interference. the

Another advantage of using a frequency of 100-130 kHz is that this frequency can also be used as a periodic pulse for the control electronics 39 provided in the microphone. As a result, disturbing signals generated by digital techniques are minimized, since no additional mixing products are generated between the digital cycle time and the oscillation frequency of the DC/DC converter. the

The resulting AC signal is applied to a transformer 14 . As a result of the separate separate coils on the transformer, separate current loops 15, 16, 17 are formed to feed separate energy consuming components. This decoupling makes it possible to simultaneously power consumers requiring high voltage and low current, as well as consumers requiring high current consumption and low voltage, with as little power loss as possible. Diodes 18, 19, 20 and capacitors 21, 22, 23 in the individual supply circuits 15, 16, 17 represent a rectifier circuit which converts the AC voltage into a DC voltage. Of course, more complex and more efficient rectifiers from the current state of the art can be provided in a separate supply loop. The power supply circuit 16 is used to supply the microphone capsule 9 with a polarization voltage, which is applied to the microphone capsule 9 via the resistor 8 . the

Of course the invention is not limited to condenser microphones, since any kind of microphone, especially dynamic microphones, can be connected to the phantom power supply. The separate power receivers are powered by the phantom power unit in the same manner as shown in Figures 1 and 2. In the case of dynamic microphones, however, no polarization voltage is necessary, so the supply circuit 16 is not required. the

The use of a constant current generator 13 at the input of the DC/DC converter ensures the sinking of a constant source current. Compared with the phantom power supply unit 31 , the constant current generator 13 is like a constant current sink, which represents a constant current generator of the power supply circuit 11 . The constant current generator 13 with the highest possible ohmic rating, among other effects, simplifies the filtering of the switching fluctuations generated during the DC/AC conversion, so that it simultaneously prevents the superimposition of disturbances on the audio signal. Electronic assemblies of this type are well known to those skilled in the art who are familiar with the state of the art. A circuit example of a constant current generator from the state of the art is schematically shown in FIGS. 3 and 4 . Figure 3 shows a "transistor LED" constant current generator with bipolar transistors. Regarding this current generator, the LED is operated in the current direction. As a result, a constant voltage is applied to the LED, and such voltage is also applied to the series connection of the base-emitter diodes of the transistors with emitter resistors. Therefore, the current drawn by the current generator is I=(U _LED -U _bc )/Re, where U _LED is the voltage drop across the LED, U _bc is the base-emitter voltage, and Re is the emitter resistance.

The circuit in FIG. 4 includes a constant current generator with two reverse coupled degenerate transistors 28 , 29 and a further integrated constant current generator 30 . This circuit is preferred because it has better characteristics in terms of constant current and higher initial resistance, so it is preferred. The current generator 30 generates a voltage drop across the initial resistor R _C which is equal to the voltage drop U _RC across the emitter resistor Re of the transistor 28 . Here the current of the constant current generator is I=U _Rc /Re. Transistor 29 forms, together with transistor 28, a reverse coupled degenerative system to ensure the same voltage drop across resistors Rc and Re. As a result, the current I of the current generator also remains constant. The current of the current generator 30 is thus constant 1/100 of the current that finally flows into the DC/DC converter 11 .

Of course, other types of constant current generators may also be provided, for example, a current generator with an inverting operational amplifier, a Howland current generator, and the like. the

The supply voltage for the audio amplifier 10 generated by the power supply circuit 11 is not regulated in the preferred embodiment. In the power supply circuit 16 of the microphone carbon cartridge 9, a regulation circuit 47, 48 is provided between the diode 18 and the resistor 8, comprising a digital regulation circuit 47 and an analog regulation circuit 48, provided for applying to the microphone carbon Polarization voltage of box 9. FIG. 6 together with FIG. 7 shows such a preferably remotely controllable regulation circuit 47 , 48 . The control signals required for the adjustment of the polarization voltage can be transmitted via at least one of the two cable conductors 1 and 2 . The detailed structure and method of operation of such regulating circuits 47, 48 are described below. If the current and voltage limits provided are not the limits already provided in the digital circuit part, in the rest of the power supply circuit, the regulation circuit can also be provided. In the preferred embodiment of FIGS. 1 and 2, no conditioning circuitry is provided in the power supply circuit 15 of the audio amplifier 10. As shown in FIG. As a result, the full power (not used in other circuit parts, such as processor, control electronics 39, polarization voltage of microphone capsule 9, A/D or D/A converter 44, 46, LED display 25) is available in the audio amplifier 10. As a result, a high maximum audio output voltage can be obtained in the current saving design of the audio amplifier 10 to obtain a high maximum audio output voltage. In principle, the resulting supply voltage of the audio amplifier 10 can also exceed the voltage achieved by the phantom power supply. Due to the way the power supply circuit 11 operates, it is also possible to generate very simple positive and negative supply voltages for the audio amplifier 10 . As a result, the audio amplifier 10 can also use ground as a resting potential. The feed voltage of the audio amplifier (10) can thus be symmetrical about ground. the

In a more advantageous embodiment, a DC/DC converter 11 of the type described above operates with an efficiency of about 82%. Since, even in the most favorable cases, there are power losses in the DC/DC converter, it is advantageous, if possible, to connect the dissipative devices in series to the DC/DC converter. As a result of utilizing the constant current generator 13, it is possible to easily connect consumer devices with constant current consumption, such as the logic power supply 24, for example the control electronics 39, or the LED display 25 connected in series to the DC/DC converter 11 , A/D or D/A converters 44, 46 etc. to achieve a fixed direct current. the

A corresponding embodiment of the power supply circuit 11 is shown in FIG. 2 . Compared with Fig. 1, the difference is that only the polarizing voltage and the voltage for the audio amplifier 10 are generated by a DC/DC converter. Other consumers, like the logic power supply 24 which obtains a fixed predetermined DC for the control electronics 39 or the LED display 25, are serially connected to the DC/DC converter. The serially connected DC/DC converter 11 of the digital power supply acts as an active load resistor, wherein the electricity used in this resistor is not converted into heat energy, but is converted in a considerable proportion into the audio amplifier 10 and the microphone capsule 9 Polarization voltage on the available power supply. the

As shown in FIG. 2, together with a logic power supply 24 or other digital electronics implementing the reference voltage, a Zener diode 27 is provided which is particularly well suited for stabilizing this voltage. Through this diode 27 any current not consumed but delivered by the constant current generator 13 is discharged to earth. In principle, any other constant current generator or shunt regulator can be used instead of Zener diode 27 . the

The released power is the product of the current of the constant current generator 13 and the voltage applied to the power supply circuit 11 . In the block diagram of Fig. 1, the entire voltage is applied to the DC/DC converter 11, and all voltages are generated by the DC/DC converter. In the block diagram of FIG. 2, the voltage is divided into a part applied to the DC/DC converter 11 and a second part applied to the LED 25 and the digital power supply. The DC/DC converter represents an effective initial resistance for the LED25 or digital power supply. Since the current consumption of the digital power supply is not constant, but the current I is kept constant by the current generator 13 , excess current which is present depending on the operating state of the digital electronics has to be discharged via the Zener diode 27 . For the power supply of the audio amplifier 10, a power P=I×voltage of the DC/DC converter×efficiency of the DC/DC converter is available. For LEDs and digital electronics, the available power P = I x the voltage that the digital electronics and LEDs have. the

To illustrate, an example is given: in the uncontrolled state, the current consumption of the audio amplifier 10 is about 0.8 mA, and the current consumption of the digital electronics is about 4.2 mA. The current generator 13 delivers a constant current of approximately 4.7mA. Thus in this particular condition it would be more advantageous to have the voltage of the digital electronics not pass through the DC/DC converter, but to utilize a serial connection to the DC/DC converter. Even, in a further study, it can be found that it is more advantageous with regard to energy, to direct all the required voltages through the DC/DC converter as shown in the block diagram of FIG. 1 . the

The switching of the supply voltage of the audio amplifier 10 in this case can result in a maximum usable power of the amplifier: P = 4.7mA x 18V x 0.82 = 69mW. Thus the voltage at the audio amplifier 10 is U=P/I=69mW/0.8mA=55V. This voltage is much higher than the 24V voltage delivered by the phantom power supply unit 31 during the power adaptation process. But since the polarizing voltage is also generated on the membrane of the carbon capsule 9, the actual obtained power supply voltage value of the audio amplifier 10 is slightly lower than this value, but still much higher than the available 24V voltage without a DC/DC converter. the

FIG. 5 shows a microphone 54 connected to a transmitter or a remote control unit 55 . Remote control of important microphone parameters takes place here directly via the audio cable, ie via lines 1,2. The control unit 55 is preferably on the mixer, or arranged in front of it. A microcontroller 35 with a parameter control input 34 controls a frequency modulator 36 which inputs a frequency modulation signal with the same level to the two cable conductors 1, 2 of the audio cable. The FM signal is then rejected in input differential amplifier 42 as a common mode signal. At the same time, the supply voltage of the phantom power supply unit 31 is supplied to the two cable conductors 1 , 2 via feed resistors 32 , 33 . In a preferred embodiment, the FM signal is supplied to the only conductor of the audio cable, ie conductor 2 which is not used for the audio signal. the

In a preferred embodiment, the FM signal is generated by FSK (Frequency Shift Keying) or CPFSK (Continuous Phase FSK). Both modulations are methods known in digital data transmission art. In principle, it is also possible to use ASK (amplitude shift keying) or PSK (phase shift keying) modulation. However, ASK is more likely to be disturbed, and PSK modulation is difficult to perform from a circuit technology point of view. In contrast to the known application of the above methods, in the case of use in microphones, the key factor is that the modulating signal has to be separated from an analog signal, the audio signal. Even if the FM signal is only fed into the conductor 2 which is not intended for the audio signal, capacitive coupling between the two conductors 1, 2 of the audio cable causes interference of the audio signal. Capacitive coupling depends on the construction and length of the audio cable. Therefore, although the control signal is known, filtering interference is difficult. the

In the microphone, the FM voltage is separated from the audio signal by passing through a filter 37, such as a bandpass filter, and the control information contained therein is passed through control electronics 39, such as a microcontroller or a CPLD (complex programmable logic equipment) to evaluate. The cable conductor 2 eliminates the coupling effect with the ground through the capacitor 43 . Control electronics 39 are connected in front of a comparator 38 which functions as a voltage comparator. For example, the command through the output of the control electronics 39 reaches the power supply circuit 11, audio amplifier 10, processor, control electronics 39, A/D or D/A converter 44, 46 and so on. the

The frequency modulation on the two audio lines 1, 2 is performed in the remote control unit 55, which is preferably located in the vicinity of the mixing meter. In the remote control unit 55, on the one hand, the load rate must be applied in the direction towards the microphone 54, and on the other hand, in the direction of the mixing meter, all frequency modulations must be suppressed. Only the audio signal from the microphone 54 has to be transmitted. To make the suppression of FM easier, the modulation is performed on both audio lines 1, 2 with the same level. In the remote control unit 55, as a result, the FM signal appears as a common mode signal to the input differential amplifier 42 and is thus suitably rejected as a common mode signal. In the second variant of the remote control, the FM takes place only in the line that does not transmit the audio signal, line 2. In the direction towards the mixing table, in this variant the FM signal can be eliminated by filtering through the low-pass filter 41 . The phantom supply unit 31 including the feed resistors 32 , 33 as well as the differential amplifier 42 and the low-pass filter is not necessarily integrated in the remote control unit as shown in FIG. 5 . They are also available in mixed tables, for example. the

During transmission of the control signal from the remote control unit 55 to the microphone 54, to ensure that the control signal has actually reached the control electronics 39, the latter sends a data acknowledgment message to the remote control unit 55 in response to the control signal. The data acknowledgment message can also be a frequency modulation signal. Data acknowledgment messages for remote control functions are not strictly necessary; but this increases the reliability of the system at the expense of additional electronics. the

The remote control method described above is of course not limited to condenser microphones, since single power receivers of any kind like microphones, especially dynamic microphones, can be operated with phantom power. the

The microphone according to the invention can be connected to any standard phantom power without affecting the microphone function. The microphone is remotely controllable if the phantom power includes a device for remote control. In any other case, the microphone may be operated by a switch mounted directly on the microphone. the

FIG. 6 shows a condenser microphone according to the invention, in which the regulation of the polarization voltage is performed by means of a two-stage control regulation loop. Here, the second digital control loop 47 is above the internal analog control loop 48 . As a result, a suitably regulated, interference-free polarization voltage can be generated at the microphone capsule 9 . the

A preferably frequency-modulated signal with control information, transmitted via the cable conductor and also connected to the phantom supply unit 31 , passes through a filter 37 and a comparator 38 to the control electronics 39 . A detailed description of the remote control of the microphone according to the present invention has been provided above. See also FIG. 5 in particular. The control of the control electronics 39 can also take place via an adjustment device or operating device in the microphone itself. It is also possible for the control electronics to be connected to a radio or infrared interface for wireless transmission, or to a cable interface. The desired value obtained in the control signal of the polarization voltage is transmitted by the control electronics 39 to the analog regulator 48 via the D/A converter 46. Instead of a D/A converter, a pulse width modulation circuit (PWM) can also be used. Although PWM circuits have low slew rates, they are inexpensive and therefore well suited for regulating a constant level in these converters. FIG. 7 shows an embodiment example showing how control electronics 39 , such as a microcontroller or a CPLD, together with a D/A converter or PWM 46 act on an analog control loop 48 . Many analog control loops are known in the state of the art, and a person skilled in the invention can easily select the elements of such a control loop. As schematically shown in FIG. 6 , the analog regulation loop 48 includes a regulation circuit 56 and a voltage divider 49 , 50 . The details of the regulation circuit 56 or the overall analog regulation loop 48 are shown in FIG. 7 . the

The analog regulation loop 48 is preferably provided by a power supply circuit 11 having an unregulated voltage of about 100-120V. The DC/DC converter may be of the same type as described above, or as shown in Figures 1 and 2 . Resistors 5 and 6 are the feed resistors in the microphone. They are used to decouple the power supply of the microphone and the output of the audio amplifier 10 . Resistors 5 and 6 are the same in size to keep lines 1 and 2 symmetrical. the

Of course the invention is not limited to phantom power supply for condenser microphones. For example, power for a single power receiver of a condenser microphone could also be provided by a battery located in the microphone. the

The desired value provided by the D/A converter or PWM 46, or more precisely, the corrected value of the polarization voltage, is compared with the actual value via the operational amplifier 52. The desired value is calculated from calibration data measured during the manufacture of the microphone and programmed into the control electronics. As a reference value for this calculation, an exact reference voltage 45 on the wires can be used or a reference voltage programmed into the control electronics during the print measurement. For example, the reference voltage 45 can be implemented by the logic power supply 24 . Such a logic power supply 24, preferably fed by a DC/DC converter 11, is not shown in FIG. 7 but is shown in FIGS. 1 and 2. the

In order to suppress the interference effect of high-frequency interference on the analog control loop 48, a preferred embodiment provides a low-pass filter 51 between the D/A converter or PWM 46 and the input of the analog control loop 48, as shown in FIG. 7 shown in . The actual value generated by the analog control loop 48 is absorbed via a voltage divider 49 , 50 and applied via an impedance converter 53 to the inverting input of an operational amplifier 52 . The feedback circuit plus the impedance converter is not included in the schematic diagram of Figure 6. At the same time, this voltage is also applied to the input of the A/C converter 44 of the digital regulation circuit 47 . The resulting digital signal is applied as feedback to the control electronics 39. As a result, the outer digital regulation loop 47 is closed. In FIG. 7, a voltage divider is represented by resistors 49, 50, through which the actual value can be absorbed. As shown in Figure 7, the A/D converter 44, the control electronics 39, and the D/A converter 46 may also be integrated in a single component. the

As an output of the analog adjustment 48 , an adjusted polarization voltage is available, which is applied to the microphone capsule 9 via a high-resistance resistor 8 . The correction voltages or corresponding correction factors required to calculate an adjusted and interference-free polarization voltage can correspond to different settings, which reflect specific sensitivity, steering characteristics, and aging parameters; they can also be stored in the control In the memory provided by the electronic device 39, it can be accessed at any time. the

These correction factors can be changed later by a remote control with the microphone turned off (for example, at the service department or by the seller, and possibly also by the customer). In addition to possible corrections of the microphone characteristics which may result from aging or from replacement of the microphone capsule, customer-specific microphone tuning on site is thus also possible. the

The invention is not limited to these examples of embodiment alone. Of course, it is also conceivable to utilize a microphone in which all or at least some of the circuitry described above is incorporated. For example, remote control of all remotely controllable components can be provided in the microphone; likewise, the power supply circuit 11 can provide power for all power receivers conceivable in the microphone. the

Claims (9)

1. A method for the remote control of a microphone, wherein a microphone (54) is connected to a remote control unit (55), said microphone (54) comprises at least one microphone capsule (9), and a slave audio amplifier (10), at least one component selected from the group of power supply circuit (11), processor, control electronics (39), A/D and D/A converters (44, 46), LED display (25), And by a phantom power supply unit (31) in the remote control unit (55), power is supplied to the microphone by two cable conductors (1, 2) of the audio frequency cable, the so-called phantom power supply is characterized in that an FM voltage is used as a A control signal is applied from the remote control unit (55) to at least one of the two cable conductors (1, 2) conducting the phantom power supply and subsequently to one of the microphones (54) Control electronics (39) which send instructions to the individual said at least one component in dependence on said control signal. 2. The method of claim 1, wherein the carrier frequency for the control signal is 100 kHz. 3. The method as claimed in one of claims 1 to 2, characterized in that an audio signal is transmitted via one of the two cable conductors (1, 2) to which the FM voltage is fed. Another one of the cable conductors (1, 2). 4. Method according to one of claims 1 to 2, characterized in that the frequency-modulated voltage is applied to both cable conductors (1, 2) at the same level as a common-mode signal. 5. A method as claimed in claim 3, characterized in that said frequency modulated voltage is separated from said audio signal by an input differential amplifier (42). 6. A method as claimed in claim 3, characterized in that said frequency modulated voltage is separated from said audio signal by a low pass filter (41). 7. Method according to one of claims 1 to 2, characterized in that, in response to said control signal from said remote control unit (55) to said microphone (54), a data acknowledgment message is sent to the remote control unit. 8. The remote control method according to claim 7, wherein the data confirmation message is also a frequency modulation signal. 9. The remote control method of claim 1, wherein the control electronics is a microcontroller or a CPLD.

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