1. Solder the resistance capacitor first, and the chip will not be soldered temporarily, then carefully check to ensure that the position and polarity are correct, and the tin points on the back can not be connected; 2. Power-on test 78L09 output 9V and voltage regulator tube 5V are normal, it is very important to ensure that the power supply is normal; 3. At this time, 5532 and PT23399 can be welded for overall testing; 4. In order to be compatible with low-sensitivity microphones, the circuit magnification is relatively high. When using, the microphone volume can be adjusted to match the external signal, and the maximum volume is not necessarily required; 5. When choosing the correct directional microphone and keeping a proper distance from the speakers, howling can be avoided. Please novices should not consult this question repeatedly; 6. If there is noise, please disconnect all pre-amplifiers, etc., power the microphone board separately, and use headphones to connect to the output terminal for trial listening. If there is noise, it means that there may be a problem with the simple board, otherwise it means that the noise comes from other equipment or lines. Interference, please treat it differently; 7. It is normal for the Kara 0K mode to have a certain noise floor. Many advanced power amplifiers are designed with a music pass-through mode. The principle is to disconnect the power of the microphone board when not in use to avoid noise; 8. The magnification of the chip is relatively large, and it may not be used up in actual use. This is also one of the sources of noise. Reduce the 47K resistance across 5532's 1-2 pins and 6-7 pins, and change the 2.2K of the output terminal. The resistance of the mixing resistor can change the mixing ratio of the speech signal and the music signal, and to a certain extent can control the noise to an acceptable level.
