I am using an LM386 to generate white noise. The circuit also has a second 386 for an on-board audio amplifier. Both chips are powered by the same 9V battery.
The audio amp won't pass the white noise signal and I can't figure out why, is there an impedance-matching issue? I have tried different value capacitors to buffer between the two ICs, resistors, resistors-to-ground, and an op-amp with 1:1 ratio.
When I turn the noise generator on and off, I can hear like a DC 'pop' on the speaker, but I can't hear the noise. When I tap the signal at C3 (between the two 386's) and plug that into a commercial amp, I can hear the signal fine. There's just something about that second amp that won't pass the white noise.
https://www.circuitlab.com/circuit/g85pxv/white-noise-and-lm386-amp/
Best Answer
Pin 3 (final stage) might need a resistor to ground - try 1kohm. All the application circuits I've seen do have a lowish value.
Also I have reservations about it working correctly without a low impedance on the 1st stage speaker output (after the capacitor) so try a resistor on pin 3 (2nd stage) that is more like 10 ohms.