LM3886 output impedance

The datasheet doesn't tell this but it is hinted that it is 0.45 ohms plus the output transistor, so it will never go under 0.45 ohms in open-loop but when you apply feedback you will get this:

100 Hz 0.15 mohms
1 kHz 1.5 mohms
10 kHz 15 milliohms

Notice this is in theory but I think we can conclude this with saying : pretty low and nothing to worry about.

Notice also that in many cases you will need some sort of output filter which add at least a couple of millihohms. My filter has 5 mohms.