KE7GKP:
the output of the amp isn't the real reflection of the input signal (+ gain) for short period of time around zero input signal. It causes a 'notching effect' at zero crossing that is easily seen on a scope and can be heard if one knows what to listen for. Again
Absolutely true. However, if s3n4te is only listening to square waves out of an Arduino, he probably won't even notice it.
I told him that.
Not clear why one would string all those discrete components together to make a low-power amplifier when you can get an LM386 for less than the price of a pack of chewing gum?
Maybe he is trying to learn how to design audio circuits, it's still an honorable task. The 'golden ear' audiophiles still frown on using opamps or ICs in general in their megabucks systems, go figure.
PS: In his circuit he is taking the feedback signal not from the opamp output, but rather right from the speaker output tap, which is common for such audio amps.