Regulating circuit for eliminating howling of wireless microphone

Abstract

The utility model relates to the technical field of microphones, in particular to an adjusting circuit for eliminating howling of a wireless microphone, which comprises a microphone, a microphone howling suppression circuit, an audio amplification circuit, a high-frequency oscillation circuit and a power supply circuit, the microphone, the microphone howling suppression circuit, the audio amplification circuit, the high-frequency oscillation circuit and the power supply circuit are electrically connected in sequence; the microphone is used for receiving an external sound wave signal to generate an audio signal; the microphone howling suppression circuit performs howling feedback suppression on the audio signal; the audio amplifying circuit receives an audio signal to generate an amplified audio signal; the high-frequency oscillation circuit receives the amplified audio signal to generate an amplified audio signal with oscillation frequency; the power supply circuit supplies power. According to the utility model, the problems of high cost and high complexity when howling elimination is realized by using a DSP module and a control algorithm in the prior art are solved.

Description

Technical Field

[0001] This utility model relates to the field of microphone technology, and in particular to an adjustment circuit for eliminating feedback in wireless microphones. Background Technology

[0002] A multifunctional studio is a modern audiovisual space that integrates multiple uses such as program recording, live broadcasting, virtual production, conferences, and teaching; it is widely used in radio and television stations, new media organizations, and other scenarios.

[0003] Wireless microphones are used in program recording, live broadcasting and other scenarios. When the microphone and the speaker are too close, a sharp interference sound may sometimes be produced, which is called acoustic feedback, commonly known as "howling".

[0004] "Whistle" is caused by the wireless microphone picking up the sound output from the speaker → the signal being amplified by the mixing console → played back through the speaker → picked up again by the microphone → amplified repeatedly, eventually forming a sharp whistling sound at a specific frequency (resonance frequency).

[0005] Feedback can affect the recording and live broadcasting of programs. Existing methods include increasing the distance, i.e., increasing the distance between the microphone and the speaker to disrupt the feedback loop; or adjusting the directivity, i.e., using a cardioid or supercardioid microphone to reduce the pickup of speaker sound. However, the position of wireless microphones in program recording scenarios is random, and increasing the distance and using a cardioid microphone lacks flexibility.

[0006] A control circuit and speaker for anti-feedback of a wireless microphone, disclosed in publication number CN222089747U, is equipped with a DSP module for anti-feedback. The microphone channel in the DSP module is also equipped with an equalizer. By adjusting the equalizer, the frequency points that are prone to feedback can be found, effectively preventing feedback. However, this method requires a DSP module and an equalizer, which is costly. In addition, the DSP module needs to start a frequency shifting algorithm to move the peak frequency higher or lower, thereby destroying the conditions that constitute acoustic feedback and achieving the purpose of anti-feedback. That is, it requires algorithm design in conjunction with the controller, making the control method complex. Summary of the Invention

[0007] To overcome the problems existing in the prior art, this utility model uses an oscillating tube to frequency-modulate the microphone signal. When whistling feedback occurs, the modulation depth is adjusted using a modulation potentiometer to eliminate the whistling.

[0008] The technical solution adopted in this utility model is as follows: a wireless microphone feedback cancellation adjustment circuit, comprising:

[0009] Includes: a microphone, a microphone feedback suppression circuit, an audio amplifier circuit, a high-frequency oscillation circuit, and a power supply circuit; the microphone, microphone feedback suppression circuit, audio amplifier circuit, high-frequency oscillation circuit, and power supply circuit are electrically connected in sequence;

[0010] in,

[0011] A microphone is used to receive external sound wave signals in order to generate audio signals;

[0012] The microphone feedback suppression circuit suppresses feedback noise in the audio signal;

[0013] An audio amplifier circuit receives an audio signal and generates an amplified audio signal.

[0014] A high-frequency oscillation circuit receives amplified audio signals to generate amplified audio signals with an oscillation frequency.

[0015] The power supply circuit is used to supply power.

[0016] Furthermore, it also includes: an antenna for outputting audio signals to the speakers.

[0017] Furthermore, the microphone feedback suppression circuit includes: a modulation potentiometer RP1, resistors R1 and R2, capacitors C1, C2, and C3, and a microphone MIC; wherein, the upper end of C1 is connected to the common terminal of R1 and R2; the lower end of R1 is connected to the common terminal of C2 and MIC; the lower end of MIC is connected to the common terminal of C1 and RP1; the right end of C2 is connected to the upper end of RP1; the right end of RP1 is connected to the left end of C3; and the lower end of C1 is connected to the common terminal of MIC and RP1.

[0018] Furthermore, the audio amplifier circuit includes: oscillator VT1, resistors R3, R4, R5, and capacitor C4; wherein, the base of VT1 is connected to the common terminal of C3 and R3, R3 is connected in parallel with the base and collector of VT1, the collector of VT1 is connected to the common terminal of R4, C4, and R3, the right end of C4 is connected to the lower end of R5, the upper common terminal of R4 and R5 is connected to the right end of R2, and the emitter of VT1 is connected to the common terminal of RP1, MIC, and C1.

[0019] Furthermore, the high-frequency oscillation circuit includes: oscillator VT2, capacitors C5 and C7, trimmer capacitor C6, inductor L1, and resistor R6; wherein, the upper end of C5 is connected to the common terminal of VT2, C4, and R5 respectively, and C7 is connected in parallel with the emitter and collector of VT2; the upper end of R6 is connected to the common terminal of VT2 and C7; the lower end of R6 is connected to the lower end of C5, the lower end of C6 connected in parallel with L1 is connected to the collector of VT2, and the upper end of C6 connected in parallel with L1 is connected to the common terminal of R5, R4, and R2.

[0020] Furthermore, the power supply circuit includes: capacitor C8, switch S1, and battery E; wherein, the positive terminal of E is connected to the lower end of S1, the upper end of S1 is connected to the common terminal of C8, L1, C6, R4, R5, and R2, the lower end of C8 is connected to the common terminal of R6, C5, VT1, RP1, MIC, and C1, and the negative terminal of E is connected to the antenna.

[0021] Furthermore, the VT1 model includes: 9011 and 3DG201NPN transistors.

[0022] Furthermore, the VT2 model includes: 9018NPN transistor.

[0023] Furthermore, the resistors include: carbon film resistors.

[0024] Furthermore, capacitors include: electrolytic capacitors, ceramic trimmer capacitors, high-frequency ceramic capacitors, and ceramic chip capacitors.

[0025] The beneficial effects of this utility model are:

[0026] 1. The circuit structure of this utility model is simple, which solves the problems of high cost and complexity in the existing technology of using DSP modules and control algorithms to achieve whistling noise cancellation;

[0027] 2. This utility model utilizes a modulation potentiometer for whistling suppression adjustment, quickly eliminating whistling noise;

[0028] 3. This utility model utilizes an oscillating tube to achieve audio amplification and oscillation frequency adjustment;

[0029] 4. Use a fine-tuning capacitor to set the frequency modulation band of the center frequency;

[0030] 5. It can be widely used in the functional studios of radio and television stations to improve the effect of program recording, performance and other activities. Attached Figure Description

[0031] Figure 1 This is a block diagram of the adjustment circuit system for eliminating feedback in a wireless microphone according to this utility model.

[0032] Figure 2 Detailed circuit diagram of the wireless microphone feedback cancellation adjustment circuit of this utility model. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings.

[0034] A wireless microphone feedback cancellation adjustment circuit includes: a microphone, a microphone feedback suppression circuit, an audio amplifier circuit, a high-frequency oscillation circuit, and a power supply circuit; wherein the microphone is electrically connected to the microphone feedback suppression circuit, the microphone feedback suppression circuit is electrically connected to the audio amplifier circuit, the audio amplifier circuit is electrically connected to the high-frequency oscillation circuit, and the power supply circuit is electrically connected to the high-frequency oscillation circuit, the microphone feedback suppression circuit, the audio amplifier circuit, and the high-frequency oscillation circuit.

[0035] Microphones are used to receive external sound wave signals, such as people speaking or performing during program recordings or live broadcasts.

[0036] Microphone feedback suppression circuit is used to suppress feedback noise.

[0037] Audio amplifier circuits are used to amplify sound wave signals (i.e., audio signals);

[0038] High-frequency oscillation circuits are used to adjust the oscillation frequency of sound wave signals;

[0039] The power supply circuit is used to provide the power supply voltage.

[0040] It also includes: antenna A1, which is used to send sound wave signals to the speaker;

[0041] In addition to antennas, Bluetooth modules and wired communication modules can also be used as sound wave signal transmission media to play sound from external speakers.

[0042] The microphone is a MIC;

[0043] The microphone feedback suppression circuit includes: modulation potentiometer RP1, resistors R1, R2, C1, C2, and C3. The upper end of C1 is connected to the upper end of R1 and the left end of R2. The lower end of R1 is connected to the left end of C2 and the upper end of the microphone. The lower end of the microphone is connected to the lower end of C1 and the lower end of RP1. The right end of C2 is connected to the upper end of RP1, and the right end of RP1 is connected to the left end of C3. C1 is used for filtering the microphone.

[0044] The audio amplifier circuit includes: oscillator VT1, resistors R3, R4, R5 and capacitor C4; the base of VT1 is connected to the right end of C3, R3 is connected in parallel with the base and collector of VT1, the collector of VT1 is connected to the lower end of R4 and the left end of C4, the right end of C4 is connected to the lower end of R5, the upper ends of R4 and R5 are connected to the right end of R2, and the emitter of VT1 is connected to the common terminal of RP1, MIC and C1.

[0045] The high-frequency oscillation circuit includes: oscillator VT2, capacitors C5 and C7, trimmer capacitor C6, inductor L1, and resistor R6. The upper end of C5 is connected to the common terminal of the base-collector junction of C4, R5, and VT2. C7 is connected in parallel with the emitter and collector of VT2. The upper end of R6 is connected to the common terminal of VT2 and C6. The lower end of R6 is connected to the common lower terminal of C5, VT1, RP1, MIC, and C1. The lower end of the parallel connection between C6 and L1 is connected to the collector of VT2. The upper end of the parallel connection between C6 and L1 is connected to the common terminal of R5, R4, and R2.

[0046] The power supply circuit includes: capacitor C8, switch S1, and battery E. The positive terminal of the battery is connected to the lower end of S1, the upper end of S1 is connected to the common terminal of C8, L1, C6, R4, R5, and R2, the lower end of C8 is connected to the common terminal of R6, C5, VT1, RP1, MIC, and C1, and the negative terminal of the battery is connected to A1. Due to high-frequency interference in the circuit, voltage fluctuations may occur, so C8 is used to filter out high-frequency noise. S1 is turned on or off to control the connection between the wireless microphone and the speaker.

[0047] Component selection and fabrication:

[0048] VT1 can be a 9011 or 3DG201 type silicon NPN transistor, requiring β to be greater than 100;

[0049] VT2 can be a 9018 type silicon NPN transistor with β greater than 100;

[0050] RP1 uses a small potentiometer with a switch;

[0051] R1 to R6 are all RTX type 1 / 8W carbon film resistors;

[0052] C1, C2, C3, and C4 are CD11-6.3V type electrolytic capacitors; C6 is a 5 / 20pF ceramic trimmer capacitor; C7 is a CC1 type high-frequency ceramic capacitor; C5 and C8 are ordinary ceramic capacitors.

[0053] Inductor L1 is made by winding 1mm diameter enameled wire around a round rod with a diameter of 8-10mm for 5 turns, and then stretching it to 12mm.

[0054] Working principle:

[0055] The transducer is an electret condenser microphone (MIC). After receiving the sound wave signal, the MIC outputs the corresponding audio signal, which is output through C2 and the right end of RP1.

[0056] VT1 is an audio amplifier. VT1 outputs the amplified audio voltage to C4, which is then applied between the base and emitter of the oscillator transistor VT2. This causes the junction capacitance of VT2 to change with the audio voltage, resulting in a slight change in the oscillation frequency, thus achieving frequency modulation. R3 is a voltage negative feedback bias resistor, which helps stabilize the operating point of VT1. Adjusting RP1 changes the strength of the audio signal output by the audio amplifier VT1, thereby changing the modulation depth. When the wireless microphone is close to the speaker, if a whistling feedback phenomenon occurs, simply reduce the value of RP1 to decrease the modulation depth and eliminate the whistling. VT2 is an ultra-high frequency oscillator. The oscillation is mainly maintained by the positive feedback of C7. The center frequency of the oscillation is determined by the frequency selection circuit L1 and C6. Adjusting the fine-tuning capacitor C6 keeps the center frequency in the 88-108MHz frequency modulation band.

[0057] During debugging, select the value of R3 so that the collector voltage of VT1 is between 1.5 and 1.8V; the collector current of VT2 is around 1.0 to 1.8mA. If the difference is too large, the value of R5 can be adjusted to meet the requirements. Then, touch the collector of VT2 with a metal tool (such as a screwdriver) to see if there is a change in the collector current of VT2. If the current increases, it means that VT2 has started oscillating and the circuit is normal. If the current does not change, it means that VT2 is not oscillating. The circuit should be carefully checked until the fault is eliminated.

[0058] Using a metal tool to introduce a human body induction signal, the metal tool and the human body form an antenna + capacitive coupling system, which will introduce 50Hz power frequency interference or high-frequency spurious signals from the environment. When the collector is touched, the interference signal is injected into the circuit, which is equivalent to applying an external excitation signal to VT2. If the circuit oscillates normally, the injected small signal will be amplified by the oscillation circuit, resulting in a significant increase in collector current (because the oscillator enters the working state, the power consumption increases). The current rise can be observed with a multimeter or the oscillation waveform can be seen with an oscilloscope. If the circuit does not oscillate (the current does not change significantly), it means that the oscillation conditions are not met (such as bias error, feedback failure, component damage, etc.).

[0059] Connect a plastic wire about 0.5m long to the negative terminal of battery E as a transmitting antenna; use the antenna to transmit sound waves to an external playback device.

[0060] Based on the above-described preferred embodiments of this utility model, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the technical concept of this utility model. The technical scope of this utility model is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A wireless microphone feedback cancellation adjustment circuit, characterized in that, include: Microphone, microphone feedback suppression circuit, audio amplifier circuit, high-frequency oscillation circuit, and power supply circuit; The microphone, microphone feedback suppression circuit, audio amplification circuit, high-frequency oscillation circuit, and power supply circuit are connected in sequence. in, A microphone is used to receive external sound wave signals in order to generate audio signals; The microphone feedback suppression circuit suppresses feedback noise in the audio signal; An audio amplifier circuit receives an audio signal to generate an amplified audio signal. A high-frequency oscillation circuit receives amplified audio signals to generate amplified audio signals with an oscillation frequency. The power supply circuit is used to supply power.

2. The wireless microphone feedback cancellation adjustment circuit as described in claim 1, characterized in that, The microphone feedback suppression circuit includes: modulation potentiometer RP1, resistors R1 and R2, capacitors C1, C2, and C3, and a microphone MIC; the upper end of C1 is connected to the common terminal of R1 and R2; the lower end of R1 is connected to the common terminal of C2 and MIC; the lower end of MIC is connected to the common terminal of C1 and RP1; the right end of C2 is connected to the upper end of RP1; the right end of RP1 is connected to the left end of C3; and the lower end of C1 is connected to the common terminal of MIC and RP1.

3. The adjustment circuit for eliminating wireless microphone feedback as described in claim 2, characterized in that, The audio amplifier circuit includes: oscillator VT1, resistors R3, R4, R5 and capacitor C4; the base of VT1 is connected to the common terminal of C3 and R3, R3 is connected in parallel with the base and collector of VT1, the collector of VT1 is connected to the common terminal of R4, C4 and R3, the right end of C4 is connected to the lower end of R5, the upper common terminal of R4 and R5 is connected to the right end of R2, and the emitter of VT1 is connected to the common terminal of RP1, MIC and C1.

4. The wireless microphone feedback cancellation adjustment circuit as described in claim 3, characterized in that, The high-frequency oscillation circuit includes: oscillator VT2, capacitors C5 and C7, trimmer capacitor C6, inductor L1, and resistor R6; the upper end of C5 is connected to the common terminal of VT2, C4, and R5 respectively; C7 is connected in parallel with the emitter and collector of VT2; the upper end of R6 is connected to the common terminal of VT2 and C7; the lower end of R6 is connected to the lower end of C5; the lower end of C6 connected in parallel with L1 is connected to the collector of VT2; and the upper end of C6 connected in parallel with L1 is connected to the common terminal of R5, R4, and R2.

5. The wireless microphone feedback cancellation adjustment circuit as described in claim 4, characterized in that, The power supply circuit includes: capacitor C8, switch S1, and battery E; the positive terminal of E is connected to the lower end of S1, the upper end of S1 is connected to the common terminal of C8, L1, C6, R4, R5, and R2, the lower end of C8 is connected to the common terminal of R6, C5, VT1, RP1, MIC, and C1, and the negative terminal of E is connected to the antenna.

6. The adjustment circuit for eliminating wireless microphone feedback as described in claim 5, characterized in that, The antenna is used to output audio signals to the speaker.

7. The wireless microphone feedback cancellation adjustment circuit as described in any one of claims 2 to 5, characterized in that, The VT1 model includes: 9011 and 3DG201NPN transistors.

8. The wireless microphone feedback cancellation adjustment circuit as described in any one of claims 2 to 5, characterized in that, The VT2 model includes: 9018NPN transistor.

9. The wireless microphone feedback cancellation adjustment circuit as described in any one of claims 2 to 5, characterized in that, Resistors include: Carbon film resistor.

10. The wireless microphone feedback cancellation adjustment circuit as described in any one of claims 2 to 5, characterized in that, Capacitors include: electrolytic capacitors, ceramic trimmer capacitors, high-frequency ceramic capacitors, and ceramic chip capacitors.

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