A test device and method for audio converter

Abstract

The present invention provides a test device and a test method for an audio converter with low cost, small size and strong anti-interference ability. The present invention comprises a host computer (1), an electronic load (3), an audio feedback circuit (4) and a power supply circuit (5); the method of the present invention comprises the following steps: a. the power supply circuit supplies power to the audio converter to be tested (2), the electronic load and the audio feedback circuit, and the audio converter to be tested is connected to the host computer for communication; b. the host computer controls the audio converter to be tested to play a set audio signal, and the audio converter to be tested outputs an analog audio signal after passing through the electronic load; c. the audio converter to be tested feeds the analog audio signal back to the input end of the audio converter to be tested, and then converts it into a digital audio signal and transmits it to the host computer; d. the host computer collects the digital audio signal, processes and analyzes the signal, and obtains various measurement parameters of the audio converter to be tested. The present invention is used in the field of audio testing.

Description

Technical Field

[0001] The present invention relates to the field of audio testing, and in particular to a testing device and a testing method for an audio converter. Background Art

[0002] With the rapid development of science and technology, people have higher and higher requirements for the communication speed of digital products. With this pursuit, high-speed communication interfaces such as USB and Type-C have emerged, and their application fields are becoming increasingly extensive. In particular, the Type-C communication interface shows a trend of gradually replacing the USB2.0 interface. With the changes in the communication interfaces of electronic products, the Audio interface has also undergone tremendous changes. Many electronic products (mobile phones, tablets, laptops, wearable devices) have even cancelled the Audio interface and replaced it with audio converters such as USB to Audio. However, the quality of various audio adapters produced by different manufacturers varies, so it is imperative to conduct professional testing on such products, mainly to ensure the quality of the products.

[0003] In response to this demand, the industry has proposed many testing methods, which can be roughly divided into two categories:

[0004] 1. Use professional audio test equipment to output the audio signal of the audio converter to the test equipment, then process and analyze the data to calculate the parameters required for the test;

[0005] 2. Design an audio test card to collect audio signals from the audio converter for processing and analysis.

[0006] However, the existing testing methods have the following main shortcomings: 1. High cost: It is necessary to use external standard instruments or design audio acquisition and test board cards, and the cost of this part of hardware is very high; 2. Low test accuracy: There are phenomena such as audio signal attenuation in the acquisition process, which makes it difficult for the test accuracy to meet the product standards; 3. Poor anti-interference: It is easily affected by the test environment and easily interfered by other signals during the transmission of audio signals; 4. The test equipment is large: Due to the use of test equipment and boards, the size of the entire test equipment is large, which is not conducive to production and operation; 5. Low test efficiency: It is difficult to test multiple products at the same time due to the volume limitations of the test boards and equipment. Summary of the invention

[0007] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a testing device and a testing method for an audio converter with low cost, small size and strong anti-interference ability. The testing method has a simple process and has high testing efficiency and testing accuracy.

[0008] The technical solution adopted by the test device of the audio converter of the present invention is: the present invention comprises

[0009] The host computer is used to send an audio output control signal to the audio converter under test, receive the digital audio signal uploaded by the audio converter under test, process and analyze the received signal, and output the test parameters of the audio converter under test;

[0010] An electronic load, used to carry the audio signal output by the audio converter under test;

[0011] an audio feedback circuit, used to connect to the electronic load and feed the audio signal back to the audio converter under test, and

[0012] The power supply circuit is used to supply power to the audio converter, electronic load and audio return circuit under test.

[0013] Further, the audio return circuit includes a coupling circuit connected to the input port of the audio converter to be tested, a left channel return channel and a right channel return channel, the left channel return channel includes a seventh relay, a ninth relay and a tenth relay, one side of the seventh relay is connected to the left channel output port of the audio converter to be tested, and the other side is connected to the electronic load, one side of the ninth relay is connected between the left channel output port and the seventh relay, and the other end is connected to the coupling circuit, the other end of the electronic load is connected to one side of the tenth relay, and the other side of the tenth relay is connected to the coupling circuit, the right channel return channel includes an eighth relay, an eleventh relay and a twelfth relay, one side of the eighth relay is connected to the right channel output port of the audio converter to be tested, and the other side is connected to the electronic load, one side of the eleventh relay is connected between the right channel output port and the eighth relay, and the other end is connected to the coupling circuit, the other end of the electronic load is connected to one side of the twelfth relay, and the other side of the twelfth relay is connected to the coupling circuit.

[0014] Furthermore, a resistor is connected between the fifth pin of the seventh relay and the fifth pin of the eighth relay.

[0015] In addition, the electronic load includes a fifth resistor, a sixth resistor, a seventh resistor and an eighth resistor, the fifth resistor and the seventh resistor are connected in parallel between the seventh relay and the tenth relay, and the sixth resistor and the eighth resistor are connected in parallel between the eighth relay and the twelfth relay.

[0016] Further, the power supply circuit includes a power supply, a four-wire power output and a four-wire power feedback, the four-wire power output includes a positive output line and a negative output line, the four-wire power feedback includes a positive feedback line and a negative feedback line, a four-wire sampling resistor and a fourth relay are arranged on the positive output line, both ends of the four-wire sampling resistor are connected to the multimeter through a first relay, the negative output line and the negative feedback line share a fifth relay, a third relay is arranged on the positive feedback line, a second relay and a first resistor are connected between the positive output line and the positive feedback line, and a second resistor is connected between the negative output line and the negative feedback line.

[0017] Furthermore, a USB connection circuit is also arranged between the audio converter to be tested and the host computer, and the USB connection circuit includes a USB communication chip, a sixth relay, a USB connector and a USB protection chip, the USB protection chip is connected to the USB communication chip, the USB communication chip and the sixth relay are both connected to the USB connector, and the other end of the USB connector is connected to the host computer.

[0018] More specifically, the host computer is a computer.

[0019] The method for testing an audio converter using the above-mentioned audio converter testing device comprises the following steps:

[0020] a. The power supply circuit is used to power the audio converter to be tested, the electronic load and the audio return circuit, and the audio converter to be tested is connected to the host computer for communication;

[0021] b. The host computer controls the audio converter to be tested to play a set audio signal, and the audio converter to be tested outputs an analog audio signal after passing through the electronic load;

[0022] c. The audio converter under test transmits the analog audio signal back to the input terminal of the audio converter under test, and then converts it into a digital audio signal and transmits it to the host computer;

[0023] d. After the host computer collects the digital audio signal, it processes and analyzes the signal to obtain various measurement parameters of the audio converter to be tested.

[0024] Specifically, in step d, the process of processing and analyzing the digital audio signal after the host computer collects it is as follows: the host computer obtains an audio digital signal of a set length through a set sampling rate, and then converts the audio signal from the time domain to the frequency domain through a window function and Fourier transform, and obtains various parameters of the audio signal through signal calculation in the frequency domain, thereby obtaining various parameters of the audio converter to be tested.

[0025] In step d, the various measurement parameters of the audio converter to be tested include but are not limited to the amplitude of the single-frequency audio signal, the frequency of the single-frequency audio signal, the THD of the single-frequency audio signal, the noise, the amplitude of the mixed-frequency audio signal and / or the frequency of the mixed-frequency audio signal.

[0026] The beneficial effects of the present invention are as follows: first, in the present invention, the audio signal output by the audio converter to be tested is input to the input end of the audio converter to be tested through the audio return circuit nearby, and is shielded by ground, thereby reducing the interference of the external environment audio signal; by playing the audio signal with the same amplitude and 180 degrees phase difference through the left and right channels, the zero point of the output signal of the audio converter to be tested is adjusted to eliminate the influence of line resistance on the test; after the host computer collects the audio data, the frequency domain information of the audio signal is obtained through the window function and FFT transformation, the non-audio segment information is filtered out, and then the calculation is performed, which greatly improves the test accuracy, stability and anti-interference. Secondly, under the condition of meeting all audio parameter tests, the present invention only uses an electronic load (composed of resistors), an audio return circuit and a power supply circuit, and does not use any external test board or equipment. The acquisition function is realized by the internal circuit of the audio converter to be tested, and the data processing and analysis are completed by the host computer, which greatly reduces the cost. Again, the present invention does not use an audio test board or device, so the device is small in size, which greatly reduces the requirements for the application environment. At the same time, parallel testing of multiple audio converters to be tested can be achieved, and the data processing of the present invention is completed by the host computer, so the test time is short, which greatly improves the test efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a principle structure diagram of the present invention;

[0028] Figure 2 is a schematic diagram of the power supply circuit;

[0029] Figure 3 is a schematic diagram of the USB connection circuit;

[0030] Figure 4 is a schematic diagram of the audio return circuit;

[0031] Figure 5 It is a schematic diagram of an audio return circuit with the function of eliminating the influence of line resistance;

[0032] Figure 6 is a graph of the amplitudes of the left and right channels output by the audio converter under test;

[0033] Figure 7 It is the frequency domain waveform of the audio signal output by the audio converter under test;

[0034] Figure 8 This is another schematic diagram of an audio return circuit. DETAILED DESCRIPTION

[0035] like Figures 1 to 7 As shown, the present invention includes a host computer 1, an electronic load 3, an audio feedback circuit 4 and a power supply circuit 5. The host computer 1 is used to send an audio output control signal to the audio converter 2 to be tested, receive the digital audio signal uploaded by the audio converter 2 to be tested, process and analyze the received signal, and output the test parameters of the audio converter to be tested; in this embodiment, the host computer 1 is a computer. The electronic load 3 is used to carry the audio signal output by the audio converter 2 to be tested. The audio feedback circuit 4 is used to connect the electronic load 3 and feedback the audio signal to the audio converter 2 to be tested. The power supply circuit 5 is used to supply power to the audio converter 2 to be tested, the electronic load 3 and the audio feedback circuit 4.

[0036] The power supply circuit 5 includes a power supply 51, a four-wire power output and a four-wire power feedback. The four-wire power output includes a positive output line 52 and a negative output line 53. The four-wire power feedback includes a positive feedback line 54 and a negative feedback line 55. A four-wire sampling resistor R3 and a fourth relay K4B are provided on the positive output line 52. Both ends of the four-wire sampling resistor R3 are connected to a multimeter through a first relay K1B. A fifth relay K5B is shared by the negative output line 53 and the negative feedback line 55. A third relay K3B is provided on the positive feedback line 54. A second relay K2B and a first resistor R1 are connected between the positive output line 52 and the positive feedback line 54. A second resistor R2 is connected between the negative output line 53 and the negative feedback line 55.

[0037] The present invention adopts a four-wire power supply mode to power the audio converter to be tested, which can provide an accurate and stable working voltage for the audio converter test, and can also measure the working current and power of the audio converter. Figure 2 It is a schematic diagram of the power supply circuit, wherein PS1_V+ / PS1_V- is a four-wire power output terminal; PS1_S+ / PS1_S- is a four-wire power feedback terminal; the first resistor R1 and the second resistor R2 are used to prevent the four-wire power supply from being overcharged due to an open circuit and burning the audio converter to be tested; the second relay K2B and the third relay K3B are used to switch the four-wire power supply to a two-wire power supply to prevent leakage current on the detection circuit during current testing; the third resistor R3 is a four-wire sampling resistor, which is connected to a multimeter through the first relay K1B and is used to measure the working current of the audio converter; the fourth relay K4 and the fifth relay K5 connect the four-wire power supply to the audio converter to be tested.

[0038] The audio return circuit 4 includes a coupling circuit connected to the input port of the audio converter 2 to be tested, a left channel return channel and a right channel return channel. The coupling circuit is composed of a third capacitor C3 and a fourth capacitor C4 in parallel, and the third capacitor C3 and the fourth capacitor C4 are non-polar capacitors. The left channel return channel includes a seventh relay K7B, a ninth relay K9B and a tenth relay K10B, one side of the seventh relay K7B is connected to the left channel output port D-HP_OUT_L of the audio converter 2 to be tested, and the other side is connected to the electronic load 3, one side of the ninth relay K9B is connected between the left channel output port D-HP_OUT_L and the seventh relay K7B, and the other end is connected to the coupling circuit, the other end of the electronic load 3 is connected to one side of the tenth relay K10B, the other side of the tenth relay K10B is connected to the coupling circuit, and the right The channel return channel includes an eighth relay K8B, an eleventh relay K11B and a twelfth relay K12B, one side of the eighth relay K8B is connected to the right channel output port D-HP_OUT_R of the audio converter 2 to be tested, and the other side is connected to the electronic load 3, one side of the eleventh relay K11B is connected between the right channel output port D-HP_OUT_R and the eighth relay K8B, and the other end is connected to the coupling circuit, the other end of the electronic load 3 is connected to one side of the twelfth relay K12B, and the other side of the twelfth relay K12B is connected to the coupling circuit.

[0039] The audio output signal of the audio converter to be tested passes through the electronic load and then is transmitted back to the input end of the audio converter to be tested through the coupling capacitor. The signal point to be transmitted back can be the audio output signal or the signal point after attenuation. Because there is a gain circuit in the input part of the audio converter, if the output audio signal amplitude is too large, when the output audio signal is directly transmitted back to the input end, the signal collected by the computer end will be saturated and distorted.

[0040] Figure 4It is a schematic diagram of an audio feedback circuit, wherein R5-R8 are load resistors of audio output signals, the electronic load 3 comprises a fifth resistor R5, a sixth resistor R6, a seventh resistor R7 and an eighth resistor R8, the fifth resistor R5 and the seventh resistor R7 are connected in parallel between the seventh relay K7B and the tenth relay K10B, the sixth resistor R6 and the eighth resistor R8 are connected in parallel between the eighth relay K8B and the twelfth relay K12B. The functions of K7 and K8 are to connect the load resistor to the output end of the audio converter, the functions of K9 and K11 are to respectively transmit the audio signals of the left and right channels back to the input end of the audio converter, the functions of K10 and K12 are to respectively divide the audio signals of the left and right channels and transmit them back to the input end of the audio converter, and the functions of C3 and C4 are to couple the output signal of the audio converter to the input end.

[0041] In the audio feedback circuit, when the audio signal is divided by the load resistor and then fed back to the input of the audio converter, the voltage division multiple is determined by the hardware circuit (i.e., the voltage division resistor). However, since the resistance of this voltage division resistor is small (the resistance of the load resistor is already determined), the line resistance in the circuit will also affect the voltage division multiple.

[0042] Figure 5 This is a circuit for eliminating the influence of line resistance. A resistor R9 is connected between the 5th pin of the seventh relay K7B and the 5th pin of the eighth relay K8B. The resistor R9 is added to eliminate the influence of line resistance on the voltage division multiple. If there is no resistor R9, the actual voltage division multiple is:

[0043] Left channel: (R7+RAC) / (R5+R7+RAC);

[0044] Right channel: (R8+RBC) / (R6+R8+RBC).

[0045] The voltage division multiples required for the left and right channel designs are R7 / (R5+R7) and R8 / (R6+R8) respectively. The actual voltage division multiples will be greater than the designed values.

[0046] according to Figure 5 After adding resistor R9, R7, R8 and R9 are placed as close together as possible during design. During the test, load resistors are connected to the left and right channels, and audio signals with the same amplitude and 180 degrees phase difference are played at the same time. Then the zero point of the audio signal will move from point C to the center of A and B. Since R7, R8 and R9 are closely arranged, the distance between R7 and R8 and the zero point of the audio signal is close enough, and their line resistance can be ignored, thereby eliminating the influence of line resistance on the voltage divider multiple. Figure 6As shown, when the left and right channel output audio signals have the same amplitude and a phase difference of 180 degrees, when the left and right channel signals reach R9, their amplitudes are exactly superimposed (the amplitudes are added at the same time point) to 0, so the zero point of the audio signal in the circuit is adjusted to R9.

[0047] A USB connection circuit 6 is also provided between the audio converter 2 to be tested and the host computer 1. The USB connection circuit 6 includes a USB communication chip U1, a sixth relay K6B, a USB connector USB Conn and a USB protection chip U2. The USB protection chip U2 is connected to the USB communication chip U1. The USB communication chip U1 and the sixth relay K6B are both connected to the USB connector USB Conn. The other end of the USB connector USB Conn is connected to the host computer 1.

[0048] The audio converter to be tested is connected to the USB connector via a USB switch and a relay, and then connected to the computer via a USB cable. The audio converter can be connected to the computer during the test and disconnected after the test is completed to avoid direct plugging and unplugging of the audio converter. Figure 3 It is a USB connection circuit, in which U1 and K6 are used to connect or disconnect the USB line; USB Conn is a connector on the circuit board, which is connected to the computer via a USB cable; U2 is an ESD protection IC to prevent problems such as static electricity on the USB line.

[0049] The method for testing the audio converter of the present invention comprises the following steps:

[0050] a. The power supply circuit 5 supplies power to the audio converter 2 to be tested, the electronic load 3 and the audio return circuit 4, and the audio converter 2 to be tested is communicatively connected to the host computer 1;

[0051] b. The host computer 1 controls the audio converter 2 to be tested to play a set audio signal, and the audio converter 2 to be tested outputs an analog audio signal after passing through the electronic load 3;

[0052] c. The audio converter 2 to be tested transmits the analog audio signal back to the input end of the audio converter 2 to be tested, and then converts it into a digital audio signal and transmits it to the host computer 1;

[0053] d. After the host computer 1 collects the digital audio signal, it processes and analyzes the signal to obtain various measurement parameters of the audio converter 2 to be tested. The various measurement parameters of the audio converter 2 to be tested include but are not limited to the amplitude of the single-frequency audio signal, the frequency of the single-frequency audio signal, the THD of the single-frequency audio signal, the noise, the amplitude of the mixed-frequency audio signal and / or the frequency of the mixed-frequency audio signal.

[0054] In the step d, the process of processing and analyzing the digital audio signal after the host computer 1 collects the digital audio signal is as follows: the host computer 1 obtains the audio digital signal of the set length through the set sampling rate, and then processes it through the Blackman_Harris window function and Fourier transform (here, the Blackman_Harris window function and Fourier transform are both universal and standard formulas and calculation methods. The present invention utilizes the functions of window function processing and Fourier transform, which can be obtained from existing technical literature and are not repeated here), converts the audio signal from the time domain to the frequency domain, and calculates the various parameters of the audio signal through the signal in the frequency domain, thereby obtaining the various parameters of the audio converter to be tested.

[0055] If the computer sets the sampling rate to 48000 during the sampling process, and the Fourier transform uses 8192 points, then the frequency resolution in the frequency domain is 48000 / 8192=5.86Hz. If the audio converter outputs an audio signal with a frequency of 1000Hz, then the frequency points reflected in the frequency domain are between 5.86*169=990.34Hz and 5.86*171=1002.06Hz, resulting in the loss of energy at the 1000Hz frequency when calculating the test results. If the audio converter outputs an audio signal with a frequency of 996Hz (5.86*170=996.2Hz), the calculated test results will be closer to the true value.

[0056] Figure 7 This is the time domain waveform of the 1000Hz audio signal after the window function and Fourier transform. Since the sampled audio signal is not a complete periodic signal, after the window function and Fourier transform processing, in addition to the amplitude at the 1000Hz frequency point, there will also be amplitudes at several surrounding frequency points. Therefore, when calculating the test results, the amplitudes of the surrounding frequency points need to be calculated on the amplitude of 1000Hz.

[0057] In this embodiment, the method and process for calculating the parameters of the audio signal are as follows.

[0058] Conditions: The sampling rate is Fs=48000 (i.e. 48000 data are sampled in 1 second), the sampling N=8192 data (sampling time: 8192 / 48000=170.7 milliseconds), the frequency resolution after Fourier transform is 48000 / 8192=5.86Hz, let the frequency domain function be F(n), n is the nth frequency point.

[0059] (1) Amplitude calculation of single-frequency audio signal:

[0060] Find the frequency point x where F(n) is the largest in the frequency domain range of 20Hz-20KHz, then the signal amplitude (reference voltage is 1V) is:

[0061] .

[0062] (2) Frequency calculation of single-frequency audio signal:

[0063] Just find the maximum F(n) in the frequency domain range of 20Hz-20KHz, and the corresponding frequency point is the frequency of the audio signal:

[0064] f=x*48000 / 8192 Hz.

[0065] (3) THD calculation of single frequency audio signal:

[0066] Find the frequency point x where F(n) is the largest in the frequency domain range of 20Hz-20KHz, and then the THD of the single-frequency audio signal is:

[0067] .

[0068] That is, the ratio of the invalid frequency response result to the valid frequency response result, expressed in dB.

[0069] (4) Noise calculation:

[0070] At this time, the audio converter has no output signal or outputs white noise. The noise of the audio converter is calculated as follows (this formula is also applicable to crosstalk calculation):

[0071] .

[0072] (5) Calculation of the amplitude and frequency of the mixed frequency audio signal:

[0073] Set a threshold and find F(n) greater than the threshold in the frequency domain range of 20Hz-20KHz. If these frequency points are adjacent, then select the largest F(n) among them. This method will find all frequency points greater than the threshold, which are the frequency points of the corresponding mixed audio signal.

[0074] like Figure 8 As shown, for the audio converter output load circuit, the following solution can be used instead:

[0075] The audio output signal realizes the voltage division function through the load resistor. Since the resistance value is small, it is easily affected by the resistance accuracy and circuit. Therefore, a large voltage division resistor can be selected to be connected in parallel at both ends of the load resistor. In this way, the voltage division circuit is less affected by the external circuit and the resistance value while the load resistor value has little effect. Among them, R5-R8 is used as the load resistor, and R10-R13 is used as the voltage division resistor.

Claims

1. A test device for an audio converter, characterized in that: It includes The host computer (1) is used to send an audio output control signal to the audio converter under test (2), receive a digital audio signal uploaded by the audio converter under test (2), process and analyze the received signal, and output test parameters of the audio converter under test; An electronic load (3) for carrying the audio signal output by the audio converter (2) to be tested; an audio feedback circuit (4), used for connecting to the electronic load (3) and transmitting the audio signal back to the audio converter (2) to be tested, and The power supply circuit (5) is used to supply power to the audio converter (2) to be tested, the electronic load (3) and the audio feedback circuit (4).

2. The audio converter test device according to claim 1, characterized in that: The audio return circuit (4) comprises a coupling circuit connected to the input port of the audio converter (2) to be tested, a left channel return channel and a right channel return channel, the left channel return channel comprises a seventh relay (K7B), a ninth relay (K9B) and a tenth relay (K10B), one side of the seventh relay (K7B) is connected to the left channel output port (D-HP_OUT_L) of the audio converter (2) to be tested, and the other side is connected to the electronic load (3), one side of the ninth relay (K9B) is connected between the left channel output port (D-HP_OUT_L) and the seventh relay (K7B), and the other side is connected to the coupling circuit, the other end of the electronic load (3) is connected to one side of the tenth relay (K10B), and the The other side of the tenth relay (K10B) is connected to the coupling circuit. The right channel return channel includes an eighth relay (K8B), an eleventh relay (K11B) and a twelfth relay (K12B). One side of the eighth relay (K8B) is connected to the right channel output port (D-HP_OUT_R) of the audio converter (2) to be tested, and the other side is connected to the electronic load (3). One side of the eleventh relay (K11B) is connected between the right channel output port (D-HP_OUT_R) and the eighth relay (K8B), and the other end is connected to the coupling circuit. The other end of the electronic load (3) is connected to one side of the twelfth relay (K12B), and the other side of the twelfth relay (K12B) is connected to the coupling circuit.

3. The test device for an audio converter according to claim 2, characterized in that: A resistor (R9) is connected between the fifth pin of the seventh relay (K7B) and the fifth pin of the eighth relay (K8B).

4. A test device for an audio converter according to claim 2 or 3, characterized in that: The electronic load (3) comprises a fifth resistor (R5), a sixth resistor (R6), a seventh resistor (R7) and an eighth resistor (R8); the fifth resistor (R5) and the seventh resistor (R7) are connected in parallel between the seventh relay (K7B) and the tenth relay (K10B); the sixth resistor (R6) and the eighth resistor (R8) are connected in parallel between the eighth relay (K8B) and the twelfth relay (K12B).

5. The audio converter test device according to claim 1, characterized in that: The power supply circuit (5) comprises a power supply (51), a four-wire power supply output and a four-wire power supply feedback. The four-wire power supply output comprises a positive output line (52) and a negative output line (53). The four-wire power supply feedback comprises a positive feedback line (54) and a negative feedback line (55). A four-wire sampling resistor (R3) and a fourth relay (K4B) are provided on the positive output line (52). Both ends of the four-wire sampling resistor (R3) are connected to a multimeter via a first relay (K1B). The negative output line (53) and the negative feedback line (55) share a fifth relay (K5B). The positive feedback line (54) is provided with a third relay (K3B). A second relay (K2B) and a first resistor (R1) are connected between the positive output line (52) and the positive feedback line (54). A second resistor (R2) is connected between the negative output line (53) and the negative feedback line (55).

6. The audio converter test device according to claim 1, characterized in that: A USB connection circuit (6) is also provided between the audio converter to be tested (2) and the host computer (1). The USB connection circuit (6) comprises a USB communication chip (U1), a sixth relay (K6B), a USB connector (USB Conn) and a USB protection chip (U2). The USB protection chip (U2) is connected to the USB communication chip (U1), the USB communication chip (U1) and the sixth relay (K6B) are both connected to the USB connector (USB Conn), and the other end of the USB connector (USB Conn) is connected to the host computer (1).

7. The audio converter test device according to claim 1, characterized in that: The host computer (1) is a computer.

8. A method for testing an audio converter using the audio converter testing device as claimed in claim 1, characterized in that: The method comprises the following steps: a. The power supply circuit (5) supplies power to the audio converter to be tested (2), the electronic load (3) and the audio return circuit (4), and the audio converter to be tested (2) is communicatively connected to the host computer (1); b. The host computer (1) controls the audio converter to be tested (2) to play a set audio signal, and the audio converter to be tested (2) outputs an analog audio signal after passing through the electronic load (3); c. The audio converter under test (2) transmits the analog audio signal back to the input end of the audio converter under test (2), and then converts it into a digital audio signal and transmits it to the host computer (1); d. After the host computer (1) collects the digital audio signal, it processes and analyzes the signal to obtain various measurement parameters of the audio converter (2) to be tested.

9. The method according to claim 8, characterized in that In the step d, the process of processing and analyzing the digital audio signal after the host computer (1) collects the digital audio signal is as follows: the host computer (1) obtains an audio digital signal of a set length through a set sampling rate, and then converts the audio signal from the time domain to the frequency domain through a window function and Fourier transform, and obtains various parameters of the audio signal through signal calculation in the frequency domain, thereby obtaining various parameters of the audio converter to be tested.

10. The method according to claim 8, characterized in that: The various measurement parameters of the audio converter (2) to be tested include but are not limited to the amplitude of a single-frequency audio signal, the frequency of a single-frequency audio signal, the THD of a single-frequency audio signal, noise, the amplitude of a mixed-frequency audio signal and / or the frequency of a mixed-frequency audio signal.

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