Dear forum members;

We are building a number of stereo amplifiers based on the LM386 chip. The amps are using electret microphones with a bias resistor (+5v), and are based on the standard 200x amplification circuit from the National 386 datasheet. We are driving (pretty mediocre) 8-ohm, 1/4-watt speakers.

Unfortunately, we are experiencing substantial crosstalk; signals from the microphones are being picked up by both amplifiers at near-equal volume levels. We seem to be having leakage through the grounds. My suspicion is that we need to do power supply filtering, as it seems highly plausible that the current draw from one speaker is leaking through the circuit and being perceived as an audio signal by the other amplifier chip.

Does anyone have experience in successfully building stereo LM386 circuits? Any knowledge to share? Your expertise is gratefully welcomed! I will post a schematic of our circuit shortly; I'll need to draw it up.

Best regards,

men_with_ties

 

Post a picture of how you have built it as well.

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A filter capacitor from pin 7 to ground improves the power supply rejection a lot. If your supply is an old 9V battery then it should have a 1000uF bypass capacitor in addition to adding capacitors to the pins 7.

The datasheet for the LM386 shows that power supply rejection is pretty good above 500Hz with a 10uF capacitor and good above 100Hz with a 50uF capacitor.
Without the capacitor then a signal on the supply voltage is amplified and produced by the LM386.

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Uncle $crooge