Debugging distortion

If there is no distortion meter, the following method can be used for debugging : Temporarily connect a test circuit as shown in Figure 2-9, input a 20kH,
0.7V sine wave signal, and record the indicated value of table PA. If the value is larger, adjust the RP keeps the instructions moderate.
Then move the switch SA to the other side, adjust Wei) l and RP4 to minimize the indicated value, and adjust repeatedly until satisfied.
    The component model can be selected according to the requirements in the figure, and its technical parameters should be selected according to the power supply voltage and output power requirements by referring to the previous
circuit selection method. Although this circuit does not have high requirements for component pairing, tubes of the same grade should be used as much as possible
. Resistors ‰~R52 can be 2 to 3W wirewound resistors, and try to use non-inductive resistors. The rest can be metal film
resistors orRPi~. RP4 uses solid core carbon film potentiometer.