Bill said:
One end of the pot is at ground and the wiper connects directly to the
LM386 input. The other end of the pot connects to a capacitor which is
tied to the signal riding on a DC offset. So there is no DC voltage
across the pot. My concern was when power is applied and the wioer of
the pot is set at maximum (connected to the cap), a DC voltage will be
momentarially applied to the input as the capacitor charges during
power-on. It would just be a short spike of a few milliseconds.
Yes. There will be a power up transient. If you use a
capacitor on the bypass terminal, it will also produce an
output transient at power up. If you couple the speaker to
the output with a capacitor, and the other end of the
speaker connects to one side of the supply, you will get a
power up transient. (You can eliminate most of that by
putting two equal capacitors in series across the supply,
and tie the speaker between the middle node and the output)
You might get the combination of these transients to
partially cancel if you work at it.
The gain is 20, and I need 5 volts p-p out, so the normal input should
not exceed 150mV peak.
Do you think a Schottky diode could be used from ground to the input
to limit the signal to around 300mV? Or is that necessary?
Since the +-0.4 input volts is the absolute maximum, this is
probably a good idea. I can see how the -0.4 volts might
cause problems, but I can't understand how exceeding +0.4
volts does anything except saturate the output.