Electronic – LM386 amp circuit lag

amplifierlm386

I'm building a motorcycle intercom and am using the LM368 IC for my amp. My circuit works well (surprisingly, I'm new to this).

I've got a button which I use as a push to talk switch. This works for the most part, however when I press the button it takes a good 5 seconds before I hear any output.

Below is my very rough schematic.

enter image description here

Any ideas what might be causing this lag?

Thanks all.

Best Answer

It is probably charge time of C5. C5 must reach full charge before the DC level of the amplifier is settled down. But C5 is charging through some large resistances, so it takes some time.

C5 is charging through about 70k of resistance. Resistors add in series, so R2 is in series with the input resistance of the LM386 (about 50k) and R3 is 10K series resistance on the other side.

The charge time is proportional to the RC product. Input RC is (70k * 10μ) or 0.7 seconds.

If C5 is too low a value, the amplifier sound will be tinny. If it is too large, you will get the long turn-on transient that you are seeing.

All to say, try reducing C5 to 0.1μF or 0.047μF.

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