How to measure voltage on the power amplifier board? What is the use of measuring voltage?

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Measuring voltage on the power amplifier board refers to detecting the voltage of key nodes such as input, output, bias, etc. of the power amplifier board through a multimeter or other measuring tools to determine whether the working state of the power amplifier board is normal.

The role of measuring voltage on the power amplifier board

Determine whether the power amplifier board is working normally: By measuring the input and output voltages, it can be determined whether the power amplifier board can amplify the signal normally.

Detect bias voltage: Measuring the bias voltage of the power amplifier board can determine whether the static operating point of the power amplifier board is correct.

Troubleshooting: If the measured voltage value is abnormal, the fault point can be located, whether it is a power supply problem, an input signal problem, or an internal fault of the power amplifier board.

Evaluate the performance of the power amplifier: By measuring the size and stability of the output voltage, evaluate the performance of the power amplifier, such as distortion, frequency response, etc.

Specific content of measuring voltage on the power amplifier board

Input voltage measurement:

Use the DC voltage range of the multimeter, connect the red probe to the positive input terminal of the power amplifier board, and the black probe to the ground wire to measure whether the input voltage is normal.

The input voltage must match the rated voltage of the device. If it does not meet the specifications, there may be a problem with the power supply or input terminal.

Output voltage measurement:

Switch the multimeter to the AC voltage range, connect the red probe to the output terminal of the power amplifier board, and the black probe to the ground wire to measure the output voltage.

Theoretically, the DC voltage of the power amplifier output should be zero, but it is generally around 0.2V or higher in practice. The lower this voltage, the better.

The output voltage value fluctuates with the size of the music and can be measured by the AC range of the multimeter.

Bias voltage measurement:

Bias voltage refers to the average value of the positive half-cycle and negative half-cycle of the power amplifier output electrical signal. By measuring, the working state of the power amplifier output circuit and the bias voltage value of the circuit can be reflected.

For OCL power amplifiers, the midpoint voltage is the voltage of the speaker output to the ground; for OTL power amplifiers, it is before the large capacitor of the speaker output.

Midpoint voltage measurement:

Turn on the power supply of the power amplifier to put it in working state, then connect the probe of the multimeter between the output terminal of the power amplifier and the ground, and read the midpoint voltage.

Precautions during measurement

Safety first: Before connecting or disconnecting the multimeter, make sure the amplifier is powered off to avoid electric shock.

Select the range correctly: Select the appropriate range according to the expected voltage value to avoid damaging the multimeter.

Avoid short circuit: During the measurement process, avoid short circuiting the probe.

Use the appropriate test instrument: For high-frequency signals, ordinary multimeters may produce errors. It is recommended to use a millivolt meter with higher accuracy.