Mad Scientist Jr wrote:
If this amp powered by a battery?

A 9V battery, although I plugged a 200 mA 9V AC adapter into it and it
worked also, though I didn't leave it plugged in that long - maybe if
it was in longer it would have fried it. I'm not sure how many mA
would be unsafe for this circuit - I looked up 9V batteries to see
what the current typically is, but it seems this depends on the
circuit.
(snip)

The current with the adapter is also controlled by the
attached circuit. The 200 mA rating is the maximum current
the load can draw, before the adapter risks over heating.
The only real risk with the adapter is that, under no load
conditions, its voltage will rise above its 9 volt, full
load rating, enough to damage the chip. All versions of
LM386 can handle a 12 volt supply and are not usually
damaged by 15 volts if little sound is being produced. I
would check the adapter with no load and make sure it does
not produce more than 15 volts.