CN107968976A - A kind of low distortion audio frequency broadcast system - Google Patents
A kind of low distortion audio frequency broadcast system Download PDFInfo
- Publication number
- CN107968976A CN107968976A CN201810007531.1A CN201810007531A CN107968976A CN 107968976 A CN107968976 A CN 107968976A CN 201810007531 A CN201810007531 A CN 201810007531A CN 107968976 A CN107968976 A CN 107968976A
- Authority
- CN
- China
- Prior art keywords
- resistance
- triode
- circuit
- capacitance
- operational amplifier
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R3/00—Circuits for transducers, loudspeakers or microphones
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2420/00—Details of connection covered by H04R, not provided for in its groups
- H04R2420/05—Detection of connection of loudspeakers or headphones to amplifiers
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Acoustics & Sound (AREA)
- Signal Processing (AREA)
- Amplifiers (AREA)
Abstract
The invention discloses a kind of low distortion audio frequency broadcast system, it is characterised in that：Including audio receiving module, the bandwidth-limited circuit being connected with audio receiving module, the low distortion audio amplifier circuit being connected with bandwidth-limited circuit, and the loudspeaker BT being connected with low distortion audio amplifier circuit.The present invention can be isolated the interfering noise outside setting range, effectively eliminate interfering noise, improve communication effect.The present invention can reduce the amplified distortion factor of audio signal, so as to improve communication effect.
Description
Technical field
The present invention relates to a kind of audio system, in particular to a kind of low distortion audio frequency broadcast system.
Background technology
With the continuous development of electronic technology, electronics has been popularized, to bringing great convenience.But
The audio output system that existing electronics uses also existing defects, i.e. the sound noise of its output is more, and call is not
It is enough clear, it largely have impact on speech quality.
The content of the invention
It is an object of the invention to overcome the sound noise that audio output system exports more, call not enough clearly lacks
Fall into, there is provided a kind of low distortion audio frequency broadcast system.
The purpose of the present invention is achieved through the following technical solutions：A kind of low distortion audio frequency broadcast system, including audio receive
Module, the bandwidth-limited circuit being connected with audio receiving module, the low distortion audio amplification being connected with bandwidth-limited circuit
Circuit, and the loudspeaker BT being connected with low distortion audio amplifier circuit；The bandwidth-limited circuit includes receiving with audio
The second order high-pass filtering circuit that module is connected, the second order being serially connected between second order high-pass filtering circuit and audio amplifier circuit are low
Bandpass filter circuit；The low distortion audio amplifier circuit includes amplification chip U1, and the distortion being connected with amplification chip U1 is adjusted
Circuit, cathode is connected with 3 pins of amplification chip U1, the polar capacitor C5 of anode ground connection, and one end and polar capacitor C5 are just
Pole is connected, the resistance R11 of another termination power；The amplification chip U1 is connected with second-order low-pass filter circuit, distortion tune
Economize on electricity Lu Zeyu loudspeakers BT connections.
Further, the distortion, which adjusts circuit, includes triode Q1, triode Q2, the emitter of cathode and triode Q2
It is connected, polar capacitor C7, the P pole of anode and loudspeaker BT connections is connected with the anode of polar capacitor C7, N poles are through resistance
The diode D3 being connected after R14 with the collector of triode Q2, one end is connected with 2 pins of amplification chip U1, the other end
The resistance R12 being connected after potentiometer R13 with the emitter of triode Q2, be serially connected in triode Q1 base stage and emitter it
Between capacitance C6, the resistance R15 being serially connected between the collector and emitter of triode Q1, the collector of cathode and triode Q1
It is connected, the polar capacitor C8 of anode ground connection, and N poles are connected with the collector of triode Q1, two pole of voltage stabilizing of P poles ground connection
Pipe D2；The collector of the triode Q1 connects power supply, and emitter is connected with the emitter of triode Q2, base stage and triode Q2
Base stage be connected；7 pins of the amplification chip U1 are connected with the collector of triode Q1, and 6 pins are with triode Q1's
Base stage is connected, and 4 pins ground connection, 2 pins are connected with second-order low-pass filter circuit；The grounded collector of the triode Q2, its
Emitter is connected with the control terminal of potentiometer R13.
The second order high-pass filtering circuit includes operational amplifier A 1, and one end is connected with audio receiving module, the other end
Capacitance C1, the P pole being connected after capacitance C2 with the cathode of operational amplifier A 1 is grounded after resistance R3, N poles and capacitance C1 and
The diode D1 that the tie point of capacitance C2 is connected, is serially connected between the N poles of diode D1 and the output terminal of operational amplifier A 1
Resistance R2, the resistance R4 being serially connected between the output terminal of operational amplifier A 1 and the P poles of diode D1, and one end and computing
The cathode of amplifier A1 is connected, the resistance R1 of other end ground connection；The output terminal of the operational amplifier A 1 is filtered with step low-pass
Wave circuit is connected, its anode is connected with the P poles of diode D1.
The second-order low-pass filter circuit includes operational amplifier A 2, and one end is connected with the output terminal of operational amplifier A 1
Connect, the resistance R5 that the other end is connected after resistance R7 with the cathode of operational amplifier A 2, one end is with resistance R5's and resistance R7
The capacitance C4 that tie point is connected, the other end is connected with the output terminal of operational amplifier A 2, the resistance being in parallel with capacitance C4
R8, one end is connected with the cathode of operational amplifier A 2, capacitance C3, the resistance R6 being in parallel with capacitance C3 of other end ground connection,
And the resistance R9 that one end is connected with the output terminal of operational amplifier A 2, the other end is grounded after resistance R10；The computing is put
The anode of big device A2 is connected with the tie point of resistance R9 and resistance R10, its output terminal is then connected with 2 pins of amplification chip U1
Connect.
The centre frequency of the second order high-pass filtering circuit isThe second-order low-pass filter
The centre frequency of circuit is
The gain A of the second order high-pass filtering circuitF1Equal to the gain A of second-order low-pass filter circuitF2, i.e.,：The gain A of the bandwidth-limited circuitF=AF1AF2。
The cutoff frequency of the bandwidth-limited circuit is 300~3000Hz.
The present invention compared with the prior art, has the following advantages and beneficial effect：
(1) present invention can be isolated the interfering noise outside setting range, effectively eliminate interfering noise, be improved
Communication effect.
(2) present invention can reduce the amplified distortion factor of audio signal, so as to improve communication effect.
Brief description of the drawings
Fig. 1 is the overall structure diagram of the present invention.
Embodiment
The present invention is described in further detail with reference to embodiment, but embodiments of the present invention are not limited to
This.
Embodiment
As shown in Figure 1, the low distortion audio frequency broadcast system of the present invention, including audio receiving module, with audio receiving module
The bandwidth-limited circuit being connected, the low distortion audio amplifier circuit being connected with bandwidth-limited circuit, and with low distortion sound
The loudspeaker BT that frequency amplifying circuit is connected.
Specifically, the audio receiving module is used to receive audio signal, it can be realized using existing antenna.The band logical
The frequency filtering of filter circuit is 300~3000Hz, it effectively can filter interfering noise and retain the audio signal spoken,
So that the sound that the present invention exports becomes apparent from.
In order to filter interference signal, as shown in Figure 1, the bandwidth-limited circuit includes two to be connected with audio receiving module
Rank high-pass filtering circuit, the second-order low-pass filter circuit being serially connected between second order high-pass filtering circuit and audio amplifier circuit.
Specifically, the second order high-pass filtering circuit includes operational amplifier A 1, capacitance C1, capacitance C2, resistance R1, resistance
R2, resistance R3, resistance R4 and diode D1.
During connection, one end of capacitance C1 is connected with audio receiving module, the other end after capacitance C2 with operation amplifier
The cathode of device A1 is connected.The P poles of diode D1 are grounded after resistance R3, N poles are connected with the tie point of capacitance C1 and capacitance C2
Connect.Resistance R2 is serially connected between the N poles of diode D1 and the output terminal of operational amplifier A 1.Resistance R4 is serially connected in operational amplifier
Between the output terminal of A1 and the P poles of diode D1.One end of resistance R1 is connected with the cathode of operational amplifier A 1, another termination
Ground.The output terminal of the operational amplifier A 1 is connected with second-order low-pass filter circuit, its anode is extremely connected with the P of diode D1
Connect.
The audio signal of audio receiving module output inputs to operational amplifier A 1 after capacitance C1 and capacitance C2 are filtered,
The operational amplifier A 1, capacitance C1, capacitance C2, resistance R4 and resistance R3 are collectively forming high-pass filter；The operational amplifier A 1 is
Negative-feedback, it can be with the gain of stabilizing circuit.The centre frequency of the second order high-pass filtering circuit is
In the present embodiment, the capacitance of capacitance C1 and capacitance C2 are that the resistance value of 0.068 μ F, resistance R1 and resistance R2 is 8.2K
Ω；It can be drawn by above-mentioned formula, the centre frequency f of second order high-pass filtering circuit in the present embodiment1=286Hz.In addition, diode
The model 14001 of D1, the resistance value of resistance R4 are 27K Ω, and the resistance value of resistance R3 is 47K Ω, the model of operational amplifier A 1
OP07.The audio signal that operational amplifier A 1 exports is input to second-order low-pass filter circuit.
As shown in Figure 1, the second-order low-pass filter circuit includes operational amplifier A 2, resistance R5, resistance R7, resistance R6, electricity
Hinder R8, resistance R9, resistance R10, capacitance C3 and capacitance C4.During specific connection, one end and the operational amplifier A 1 of resistance R5
Output terminal be connected, cathode of the other end with operational amplifier A 2 after resistance R7 is connected.One end of capacitance C4 and resistance
The tie point of R5 and resistance R7 are connected, the other end is connected with the output terminal of operational amplifier A 2.Resistance R8 and capacitance C4 phases
It is in parallel.One end of capacitance C3 is connected with the cathode of operational amplifier A 2, other end ground connection.Resistance R6 is in parallel with capacitance C3.
One end of resistance R9 is connected with the output terminal of operational amplifier A 2, the other end is grounded after resistance R10.The operational amplifier
The anode of A2 is connected with the tie point of resistance R9 and resistance R10, its output terminal is then connected with audio amplifier circuit.
The audio signal that operational amplifier A 1 exports inputs to operational amplifier A 2, while electricity after resistance R5 and resistance R7
Audio signal can be filtered by holding C3 and capacitance C4；The operational amplifier A 2, resistance R5, resistance R7, capacitance C3, resistance R6,
Capacitance C4 and resistance R8 are collectively forming low-pass filter.Operational amplifier A 2 is also negative-feedback, it can be with the increasing of stabilizing circuit
Benefit.The centre frequency of the second-order low-pass filter circuit isIn the present embodiment, resistance R5 and
The resistance value of resistance R7 is that the capacitance of 8.2K Ω, capacitance C3 and capacitance C4 are 0.0068 μ F；It can be drawn by above-mentioned formula, this reality
Apply the centre frequency f of second-order low-pass filter circuit in example2=2856Hz.In addition, the resistance value of resistance R6 is 10K Ω, resistance R8
Resistance value be 1K Ω, the resistance value of resistance R9 is 27K Ω, and the resistance value of resistance R10 is 47K Ω, the model of operational amplifier A 2
OP07。
Obtained by above-mentioned, the cutoff frequency of the bandwidth-limited circuit of the present embodiment is 286Hz~2856Hz, so that effectively
Interference signal beyond one's voice in speech frequency signal is isolated, improves speech quality.
In addition, the gain A of the second order high-pass filtering circuitF1Equal to the gain A of second-order low-pass filter circuitF2, i.e.,：The gain A of the bandwidth-limited circuitF=AF1AF2。
The low distortion audio amplifier circuit includes amplification chip U1, and the distortion being connected with amplification chip U1 adjusts circuit,
Cathode is connected with 3 pins of amplification chip U1, the polar capacitor C5 of anode ground connection, and one end is connected with the cathode of polar capacitor C5
Connect, the resistance R11 of another termination power.2 pins of the amplification chip U1 are connected with the output terminal of operational amplifier A 2, lose
The true circuit that adjusts then is connected with loudspeaker BT.
Polar capacitor C5 can be filtered input voltage processing, amplification chip U1 work is more stablized；The electricity
Resistance R11 plays partial pressure, and the resistance value of resistance R11 is 10K Ω, and the capacitance of polar capacitor C5 is 0.1 μ F,
In addition, the distortion, which adjusts circuit, includes triode Q1, triode Q2, resistance R12, potentiometer R13, zener diode
D2, capacitance C6, resistance R15, polar capacitor C8, polar capacitor C7, resistance R14 and diode D3.
Wherein, the cathode of polar capacitor C7 is connected with the emitter of triode Q2, anode and loudspeaker BT are connected.Two
The P poles of pole pipe D3 are connected with the anode of polar capacitor C7, collector of the N poles with triode Q2 after resistance R14 is connected.Electricity
One end of resistance R12 is connected with 2 pins of amplification chip U1, emitter phase of the other end after potentiometer R13 with triode Q2
Connection.Capacitance C6 is serially connected between base stage and the emitter of triode Q1.Resistance R15 is serially connected in the collector and hair of triode Q1
Between emitter-base bandgap grading.The cathode of polar capacitor C8 is connected with the collector of triode Q1, anode ground connection.The N poles of zener diode D2
It is connected with the collector of triode Q1, P poles ground connection.
The collector of the triode Q1 connects power supply, and emitter is connected with the emitter of triode Q2, base stage and three poles
The base stage of pipe Q2 is connected.7 pins of the amplification chip U1 are connected with the collector of triode Q1,6 pins and triode
The base stage of Q1 is connected, and 4 pins ground connection, 2 pins are connected with second-order low-pass filter circuit.The collector of the triode Q2 connects
Ground, its emitter are connected with the control terminal of potentiometer R13.
Triode Q1 and triode Q2 forms complementary structure, and amplification chip is then formed with reference to potentiometer R13 and resistance R12
The backfeed loop of U1, this structure can reduce the distortion that signal occurs in transmitting procedure.Capacitance C6 can be played a filtering role,
Its capacitance is 0.1 μ F.The gain ranging that the distortion adjusts circuit can be adjusted by adjusting potentiometer R13.Polar capacitor C8 can be to defeated
Enter voltage to be filtered, zener diode D2 can carry out voltage stabilizing to voltage, to improve the stability of amplification chip U1.The resistance
The resistance value of R12 is 1K Ω, and the resistance value of potentiometer R13 is 20K Ω, and the resistance value of resistance R14 is 10K Ω, and the resistance value of resistance R15 is
The capacitance of 100K Ω, capacitance C6 are 0.1 μ F, and the capacitance of polar capacitor C7 is 4.7 μ F, and the capacitance of polar capacitor C8 is 470 μ F, two
The model LM74 of the model 1N4742 of the model 1N4003 of pole pipe D3, zener diode D2, amplification chip U1.
The audio signal of second order high-pass filtering circuit output is input to after amplification chip U1 is amplified processing, from amplification core
The 6 pins output of piece U1, and drive after the complementary triode Q1 and triode Q2 set drive the speaker BT sounding again.
As described above, the present invention can be realized well.
Claims (7)
- A kind of 1. low distortion audio frequency broadcast system, it is characterised in that：Including audio receiving module, it is connected with audio receiving module Bandwidth-limited circuit, the low distortion audio amplifier circuit being connected with bandwidth-limited circuit, and with low distortion audio amplify The loudspeaker BT that circuit is connected；The bandwidth-limited circuit includes the second order high-pass filtering electricity being connected with audio receiving module Road, the second-order low-pass filter circuit being serially connected between second order high-pass filtering circuit and audio amplifier circuit；The low distortion audio Amplifying circuit includes amplification chip U1, and the distortion being connected with amplification chip U1 adjusts circuit, 3 pipes of cathode and amplification chip U1 Foot is connected, the polar capacitor C5 of anode ground connection, and one end is connected with the cathode of polar capacitor C5, the resistance of another termination power R11；The amplification chip U1 is connected with second-order low-pass filter circuit, and distortion adjusts circuit and is then connected with loudspeaker BT.
- A kind of 2. low distortion audio frequency broadcast system according to claim 1, it is characterised in that：The distortion adjusts circuit bag Triode Q1, triode Q2 are included, the polar capacitor that cathode is connected with the emitter of triode Q2, anode and loudspeaker BT are connected The diode that C7, P pole are connected with the anode of polar capacitor C7, N poles are connected after resistance R14 with the collector of triode Q2 D3, one end is connected with 2 pins of amplification chip U1, emitter of the other end with triode Q2 after potentiometer R13 is connected Resistance R12, the capacitance C6 being serially connected between the base stage of triode Q1 and emitter, be serially connected in the collector and hair of triode Q1 Resistance R15 between emitter-base bandgap grading, cathode is connected with the collector of triode Q1, anode ground connection polar capacitor C8, and N poles with The collector of triode Q1 is connected, the zener diode D2 of P poles ground connection；The collector of the triode Q1 connects power supply, transmitting Pole is connected with the emitter of triode Q2, and base stage is connected with the base stage of triode Q2；7 pins of the amplification chip U1 with The collector of triode Q1 is connected, and 6 pins are connected with the base stage of triode Q1,4 pins ground connection, 2 pins and step low-pass Filter circuit connects；The grounded collector of the triode Q2, its emitter are connected with the control terminal of potentiometer R13.
- A kind of 3. low distortion audio frequency broadcast system according to claim 2, it is characterised in that：The second order high-pass filtering electricity Road includes operational amplifier A 1, one end is connected with audio receiving module, the other end after capacitance C2 with operational amplifier A 1 Capacitance C1, the P pole that cathode is connected is grounded after resistance R3, two poles that N poles are connected with the tie point of capacitance C1 and capacitance C2 Pipe D1, the resistance R2 being serially connected between the N poles of diode D1 and the output terminal of operational amplifier A 1, is serially connected in operational amplifier A 1 Output terminal and diode D1 P poles between resistance R4, and one end is connected with the cathode of operational amplifier A 1, the other end The resistance R1 of ground connection；The output terminal of the operational amplifier A 1 is connected with second-order low-pass filter circuit, its anode and diode The P poles of D1 are connected.
- A kind of 4. low distortion audio frequency broadcast system according to claim 3, it is characterised in that：The second-order low-pass filter electricity Road includes operational amplifier A 2, and one end is connected with the output terminal of operational amplifier A 1, the other end is put after resistance R7 with computing The resistance R5 that the cathode of big device A2 is connected, one end is connected with the tie point of resistance R5 and resistance R7, the other end and computing are put The capacitance C4 that the output terminal of big device A2 is connected, the resistance R8 being in parallel with capacitance C4, one end and the cathode of operational amplifier A 2 It is connected, capacitance C3, the resistance R6 being in parallel with capacitance C3 of other end ground connection, and one end and the output of operational amplifier A 2 End is connected, the resistance R9 that the other end is grounded after resistance R10；The anode of the operational amplifier A 2 and resistance R9 and resistance The tie point of R10 is connected, its output terminal is then connected with 2 pins of amplification chip U1.
- A kind of 5. low distortion audio frequency broadcast system according to claim 4, it is characterised in that：The second order high-pass filtering circuit Centre frequency isThe centre frequency of the second-order low-pass filter circuit is
- A kind of 6. low distortion audio frequency broadcast system according to claim 5, it is characterised in that：The second order high-pass filtering electricity The gain A on roadF1Equal to the gain A of second-order low-pass filter circuitF2, i.e.,：The bandpass filtering electricity The gain A on roadF=AF1AF2。
- A kind of 7. low distortion audio frequency broadcast system according to claim 6, it is characterised in that：The bandwidth-limited circuit Cutoff frequency is 300~3000Hz.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810007531.1A CN107968976A (en) | 2018-01-04 | 2018-01-04 | A kind of low distortion audio frequency broadcast system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810007531.1A CN107968976A (en) | 2018-01-04 | 2018-01-04 | A kind of low distortion audio frequency broadcast system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN107968976A true CN107968976A (en) | 2018-04-27 |
Family
ID=61993999
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201810007531.1A Pending CN107968976A (en) | 2018-01-04 | 2018-01-04 | A kind of low distortion audio frequency broadcast system |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN107968976A (en) |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN203800893U (en) * | 2014-03-18 | 2014-08-27 | 王丰硕 | Current-mode audio frequency amplifier |
| CN204104105U (en) * | 2014-09-04 | 2015-01-14 | 清华大学 | A kind of circuit of Earphone Amplifier |
| CN204290889U (en) * | 2014-12-05 | 2015-04-22 | 杭州海康威视数字技术股份有限公司 | A kind of filtering and amplifying circuit |
| CN105232040A (en) * | 2015-09-29 | 2016-01-13 | 武汉工程大学 | Muscle fatigue detection system and method |
| CN107301029A (en) * | 2017-06-19 | 2017-10-27 | 北京小米移动软件有限公司 | Dio Output Modules, method and terminal device |
| CN208015983U (en) * | 2018-01-04 | 2018-10-26 | 成都威邦科技有限公司 | A kind of low distortion audio frequency broadcast system |
-
2018
- 2018-01-04 CN CN201810007531.1A patent/CN107968976A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN203800893U (en) * | 2014-03-18 | 2014-08-27 | 王丰硕 | Current-mode audio frequency amplifier |
| CN204104105U (en) * | 2014-09-04 | 2015-01-14 | 清华大学 | A kind of circuit of Earphone Amplifier |
| CN204290889U (en) * | 2014-12-05 | 2015-04-22 | 杭州海康威视数字技术股份有限公司 | A kind of filtering and amplifying circuit |
| CN105232040A (en) * | 2015-09-29 | 2016-01-13 | 武汉工程大学 | Muscle fatigue detection system and method |
| CN107301029A (en) * | 2017-06-19 | 2017-10-27 | 北京小米移动软件有限公司 | Dio Output Modules, method and terminal device |
| CN208015983U (en) * | 2018-01-04 | 2018-10-26 | 成都威邦科技有限公司 | A kind of low distortion audio frequency broadcast system |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN104935742B (en) | Communication terminal and the method for improving its tonequality under handset mode | |
| CN101641965A (en) | Acoustic processing system and method for electronic device and mobile telephone terminal | |
| CN103428607A (en) | Audio signal playing system and electronic device | |
| CN105208494B (en) | A kind of three-in-one audio devices | |
| CN208015983U (en) | A kind of low distortion audio frequency broadcast system | |
| CN106373603A (en) | Device and method for controlling recording according to sound volume | |
| CN107968975A (en) | Audio frequency broadcast system based on bandpass filter | |
| CN208402103U (en) | A kind of feedback interference low distortion audio frequency broadcast system | |
| CN208061666U (en) | A kind of voltage follow low distortion audio frequency broadcast system | |
| CN107948866A (en) | A kind of feedback interference low distortion audio frequency broadcast system | |
| CN208402102U (en) | Bandpass filtering audio frequency broadcast system based on feedback interference | |
| CN108010543A (en) | A kind of voltage follow low distortion audio frequency broadcast system | |
| CN208015982U (en) | Audio frequency broadcast system based on bandpass filter | |
| CN207895428U (en) | Audio frequency broadcast system based on voltage follow | |
| CN107968976A (en) | A kind of low distortion audio frequency broadcast system | |
| CN201717940U (en) | Mobile phone provided with hand-free music playing function | |
| CN209517434U (en) | A kind of noise reduction folder neck microphone | |
| CN204721585U (en) | Receiver amplifier | |
| CN107948867A (en) | Bandpass filtering audio frequency broadcast system based on feedback interference | |
| CN107809693B (en) | Double-voice-coil earphone | |
| CN203563181U (en) | Mobile terminal having KTS sound effect | |
| CN107911097A (en) | A kind of bandpass filter | |
| CN108021352A (en) | Audio frequency broadcast system based on voltage follow | |
| CN102340563A (en) | Method for eliminating TDD (time division duplex) noise of FM (frequency modulation)-GSM (global system for mobile communications) mobile phone | |
| CN208299760U (en) | A kind of low distortion signal amplifier based on LM4766 |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |